Motor Control Centers
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in Motor Control Centers.
---
title: Motor Control Centers
category: Electrical / Power Distribution Equipment
−toc_depth: 3
description: >
− When to use: Low-voltage motor control centers (MCCs) rated 600V and below for commercial, institutional, and industrial facilities. Covers floor-standing, factory-assembled, NEMA ICS 18 / UL 845 listed assemblies with plug-in vertical bucket construction housing combination motor starters, soft starters, variable frequency drive units, feeder taps, control transformers, metering, and PLC interface compartments. Includes indoor and outdoor configurations and is intended for facilities with multiple motor loads served from a common bus.
+ When to use: Factory-assembled, floor-standing low-voltage motor control centers rated 600 V and below, listed to UL 845 and built to NEMA ICS 18, in which combination motor starter units, reduced-voltage starter units, variable frequency drive units, feeder units, control power units, and metering units plug onto a common vertical bus fed from a common horizontal bus. Covers the assembly ratings, the enclosure and structure, the bus, the wiring class and type, arc-flash mitigation, the unit construction and the devices inside each unit, communications, identification, factory and field testing, installation, warranty, and spares, for indoor and outdoor installations.
− Not intended for: Switchgear without motor starters (see [[sync/low-voltage-switchgear]]), distribution switchboards without plug-in motor control units (see [[sync/low-voltage-switchboards]]), lighting and appliance branch circuit panelboards (see [[sync/panelboards]]), individually mounted enclosed motor controllers feeding a single motor, medium-voltage motor controllers above 600V, intelligent motor control centers using only digital protective relays without conventional starters, or specifications for the variable frequency drives themselves when furnished as bucket contents (drive performance and configuration requirements are covered by [[sync/hvac-variable-frequency-drives]] for HVAC service).
+ Not intended for: Individually enclosed combination and manual motor starters serving one motor ([[sync/combination-motor-starters]]); distribution switchboards and switchgear without plug-in motor control units ([[sync/low-voltage-switchboards]], [[sync/low-voltage-switchgear]]); panelboards ([[sync/panelboards]]); medium-voltage motor controllers above 600 V; the performance, harmonic treatment, and configuration of the variable frequency drives installed as unit contents ([[sync/hvac-variable-frequency-drives]]); the motors served; the short-circuit, coordination, and arc-flash studies that establish the ratings and settings ([[sync/arc-flash-study]]); and the building automation or process control system to which the assembly reports ([[sync/building-automation-system]], [[sync/process-control-networks]]).
---
# Scope {toc}
−## This specification covers low-voltage, metal-enclosed, floor-standing motor control center (MCC) assemblies rated 600V and below. {note}
+## This standard governs the low-voltage motor control center as a listed assembly: its structure, horizontal and vertical bus, wireways, unit compartments, the plug-in and frame-mounted units installed in them, the common control and communications provisions, and the field work that puts the assembly into service. {note}
−## Equipment shall comply with NEMA ICS 18 and shall be listed and labeled to UL 845 by a Nationally Recognized Testing Laboratory (NRTL).
+## A motor control center differs from a switchboard in that its load devices are motor controllers assembled into removable units that plug onto a shared vertical bus, so that a starter can be added, exchanged, or withdrawn for service without disturbing the bus or its neighbors. {note}
−## The assembly shall consist of one or more vertical sections joined to form a continuous assembly with a common horizontal bus and individual plug-in vertical buckets housing combination motor starters, feeder taps, soft starters, variable frequency drive units, control transformers, and metering as required.
+## The assembly is one listed product. Its short-circuit rating, its seismic qualification, and its arc-flash characteristics are properties of the whole, established by the manufacturer for the configuration shipped, and a unit or a bus modification introduced outside that listing removes the assembly from the condition under which it was rated. {note}
−## A motor control center is distinguished from switchgear and switchboards by the integration of motor starting and protection devices into plug-in unit compartments that share a common bus structure. {note}
+## The following are governed elsewhere and are outside this standard: {note}
−## Where a project requires only feeder distribution without motor starters, see [[sync/low-voltage-switchgear]] or [[sync/low-voltage-switchboards]]. {note}
+- individually enclosed combination and manual motor starters serving a single motor, under [[sync/combination-motor-starters]]
+- the drive performance, harmonic treatment, bypass logic, and parameter configuration of variable frequency drive units, under [[sync/hvac-variable-frequency-drives]]
+- the motors served, their nameplate data, and their disconnecting means at the motor
+- the short-circuit, protective device coordination, and arc-flash incident energy studies, under [[sync/arc-flash-study]]
+- the power and control conductors and their terminations, under [[sync/conductors-and-cables]]
+- the raceways serving the assembly, under [[sync/raceways-and-conduit]]
+- the grounding electrode system and the equipment grounding conductors, under [[sync/grounding-and-bonding]]
+- the metering devices themselves and the monitoring system they report to, under [[sync/electrical-power-monitoring]]
+- the sequences of operation, points, and network architecture of the building automation or process control system, under [[sync/building-automation-system]] and [[sync/process-control-networks]]
−## Where a single motor is served by an individually enclosed combination starter rather than a centralized assembly, an enclosed motor controller specification governs and an MCC is not required. {note}
+## Motor control centers shall comply with NEMA ICS 18 and shall be listed and labeled to UL 845 by a Nationally Recognized Testing Laboratory.
−## This standard governs the MCC enclosure, bus structure, unit compartment construction, common control and metering, and field installation. {note}
+## The number of vertical sections, the units installed in each section, and the motor, horsepower, and starter type served by each unit shall be as indicated on [[drawing: the motor control center schedule]].
−## The performance and configuration of variable frequency drive units installed as bucket contents shall comply with [[sync/hvac-variable-frequency-drives]] for HVAC service or with the applicable process control standard for other service.
+## Motor control center locations shall be as indicated on [[drawing: the electrical plans]].
−## Conductors and terminations entering and leaving the MCC shall comply with [[sync/conductors-and-cables]].
+## The requirements of this standard apply to the assembly and to the units as installed in it; a device requirement stated in [[sync/combination-motor-starters]] for a stand-alone starter applies to a motor control center unit only where this standard invokes it.
−## Raceways and conduit serving the MCC shall comply with [[sync/raceways-and-conduit]].
−
−## Grounding and bonding of the MCC and all motor circuits shall comply with [[sync/grounding-and-bonding]].
−
# Referenced Standards {toc}
−## Equipment, materials, and installation shall comply with the latest adopted edition of the following.
+## Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
+## Where the contract documents, the Authority Having Jurisdiction, or two referenced standards impose conflicting requirements, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
+
| Standard | Title |
|----------|-------|
−| UL 845 | Standard for Motor Control Centers |
+| UL 845 | Motor Control Centers |
| UL 489 | Molded-Case Circuit Breakers, Molded-Case Switches, and Circuit-Breaker Enclosures |
| UL 508 | Industrial Control Equipment |
−| UL 61800-5-1 | Adjustable Speed Electrical Power Drive Systems — Safety Requirements |
−| NEMA ICS 18 | Motor Control Centers |
−| NEMA ICS 2 | Industrial Control and Systems: Controllers, Contactors, and Overload Relays Rated Not More Than 2000 Volts AC or 750 Volts DC |
+| UL 60947-4-1 | Low-Voltage Switchgear and Controlgear - Part 4-1: Contactors and Motor-Starters - Electromechanical Contactors and Motor-Starters |
+| UL 61800-5-1 | Adjustable Speed Electrical Power Drive Systems - Part 5-1: Safety Requirements - Electrical, Thermal and Energy |
+| UL 50E | Enclosures for Electrical Equipment, Environmental Considerations |
+| NEMA ICS 1 | Industrial Control and Systems: General Requirements |
+| NEMA ICS 2 | Industrial Control and Systems: Controllers, Contactors, and Overload Relays Rated 600 Volts |
| NEMA ICS 6 | Industrial Control and Systems: Enclosures |
+| NEMA ICS 18 | Motor Control Centers |
| NEMA 250 | Enclosures for Electrical Equipment (1000 Volts Maximum) |
−| NFPA 70 | National Electrical Code (Article 430 — Motors, Motor Circuits, and Controllers; Article 409 — Industrial Control Panels) |
+| NEMA MG 1 | Motors and Generators |
+| NFPA 70 | National Electrical Code (Articles 110, 240, 409, and 430) |
| NFPA 70E | Standard for Electrical Safety in the Workplace |
| IEEE 1584 | Guide for Performing Arc-Flash Hazard Calculations |
| IEEE 519 | Standard for Harmonic Control in Electric Power Systems |
+| IEEE C37.20.7 | Guide for Testing Switchgear Rated Up to 52 kV for Internal Arcing Faults |
| ANSI/NETA ATS | Standard for Acceptance Testing Specifications for Electrical Power Equipment and Systems |
−| IBC | International Building Code (seismic provisions) |
| ASCE 7 | Minimum Design Loads and Associated Criteria for Buildings and Other Structures |
−| ICC ES AC156 | Acceptance Criteria for Seismic Certification by Shake-Table Testing of Nonstructural Components |
−| ASHRAE 90.1 | Energy Standard for Buildings Except Low-Rise Residential Buildings (submetering provisions) |
+| ICC-ES AC156 | Acceptance Criteria for Seismic Certification by Shake-Table Testing of Nonstructural Components |
+| IBC | International Building Code |
+| ANSI/ASHRAE/IES 90.1 | Energy Standard for Buildings Except Low-Rise Residential Buildings |
−## Where the contract documents, the adopted building code, or a referenced standard conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
−
# Submittals {toc}
## Action Submittals {toc}
−### Contractor shall submit the following for the Engineer's review and approval prior to fabrication:
+### The Contractor shall submit the following for review before fabrication begins:
−- Shop drawings showing front, side, and rear elevations, overall dimensions, shipping splits, lifting points, and conduit entry locations
−- Single line diagram showing horizontal and vertical bus configuration, main and feeder devices, and each motor circuit by unit designation
−- Unit elevation drawings showing the arrangement of each bucket including starter type, branch device, control transformer, pilot devices, and nameplate
−- Bill of materials listing every starter, branch circuit protective device, contactor, overload relay, soft starter, VFD unit, and metering device
−- Schematic and wiring diagrams for the common control bus, communications network, and each unit
−- Bus bracing calculations and short-circuit withstand documentation for the horizontal and vertical bus at the specified rating
−- Combination motor controller series rating documentation, where series-rated combinations are proposed, identifying the upstream device required to achieve the marked rating
−- Seismic certification documentation per ICC ES AC156 or analysis per ASCE 7, where required by the building code
−- Harmonic distortion analysis where VFD or soft-start units exceed 25% of the connected MCC load, demonstrating compliance with IEEE 519 at the point of common coupling
+- shop drawings showing front elevations, section widths, depths, and heights, shipping splits, lifting provisions, weight per shipping section, conduit entry areas, and the anchorage pattern
+- a one-line diagram of the assembly showing the incoming connection, the main device, the horizontal and vertical bus, the neutral and ground bus, and each unit by its designation
+- a unit arrangement drawing for each vertical section showing the compartment size and contents of every unit, including spare and space compartments
+- a bill of material for each unit listing the disconnect, the controller, the overload relay, the control power transformer, the pilot devices, the auxiliary contacts, and the network interface
+- schematic and wiring diagrams for each unit type and for the common control and communications wiring
+- the assembly short-circuit current rating and the bus bracing rating, with the basis on which each was established
+- the tested series-rated combinations, where series ratings are the rating basis, identifying the upstream device on which each rating depends
+- the seismic qualification certificate for the assembly as configured, where seismic qualification is required
+- product data for every device installed in a unit, and for the metering and network components
+- the nameplate schedule listing the text to appear on the assembly, section, and unit nameplates
```datasheet
−label: Submittal Documentation
+label: Action Submittal Package
type: checkbox
options:
− - "Shop drawings (front, side, rear elevations, shipping splits)"
− - "Single line diagram with unit designations"
− - "Unit elevation drawings (per bucket)"
− - "Bill of materials with branch device and starter details"
− - "Schematic and wiring diagrams (common control and per unit)"
− - "Bus bracing and short-circuit withstand calculations"
− - "Series-rating documentation (if applicable)"
− - "Seismic certification (ICC ES AC156 or ASCE 7)"
− - "Harmonic distortion analysis (IEEE 519)"
− - "Catalog cut sheets for all branch devices, starters, and metering"
+ - "Shop drawings"
+ - "Assembly one-line diagram"
+ - "Unit arrangement drawings"
+ - "Unit bills of material"
+ - "Schematic and wiring diagrams"
+ - "Short-circuit and bus bracing rating basis"
+ - "Series-rated combination listing"
+ - "Seismic qualification certificate"
+ - "Device product data"
- "Nameplate schedule"
default:
− - "Shop drawings (front, side, rear elevations, shipping splits)"
− - "Single line diagram with unit designations"
− - "Unit elevation drawings (per bucket)"
− - "Bill of materials with branch device and starter details"
− - "Schematic and wiring diagrams (common control and per unit)"
− - "Bus bracing and short-circuit withstand calculations"
− - "Catalog cut sheets for all branch devices, starters, and metering"
+ - "Shop drawings"
+ - "Assembly one-line diagram"
+ - "Unit arrangement drawings"
+ - "Unit bills of material"
+ - "Schematic and wiring diagrams"
+ - "Short-circuit and bus bracing rating basis"
+ - "Device product data"
- "Nameplate schedule"
```
−### Fabrication shall not proceed until submittals are reviewed and returned.
+### Fabrication shall not begin until the action submittals have been reviewed and returned.
+## Informational Submittals {toc}
+
+### The Contractor shall submit the following with or before the action submittals:
+
+- the manufacturer's qualification statement and the UL 845 file reference under which the assembly will be listed
+- the qualifications of the firm and the technicians who will perform field acceptance testing
+- the factory test procedure, where witnessed factory testing is indicated
+- the harmonic analysis required by [[sync/hvac-variable-frequency-drives]], where drive units are installed in the assembly
+- the manufacturer's published derating factors applied for ambient temperature and altitude, where either exceeds the usual service conditions of NEMA ICS 1
+
+```datasheet
+label: Informational Submittal Package
+type: checkbox
+options:
+ - "Manufacturer qualification statement"
+ - "Field testing firm and technician qualifications"
+ - "Factory test procedure"
+ - "Harmonic analysis"
+ - "Ambient and altitude derating factors"
+```
+
## Closeout Submittals {toc}
−### Contractor shall provide at substantial completion:
+### The Contractor shall submit the following before the assembly is accepted:
−- Operation and maintenance manuals, bound, with table of contents and section dividers for each unit type
−- As-built shop drawings reflecting field modifications, including unit relocations and parameter changes
−- Factory and field test reports including NETA acceptance test records and manufacturer startup reports
−- Final programmed parameter settings for each VFD unit and soft-start unit, printed and provided in the manufacturer's electronic configuration file format
−- Warranty documentation listing the MCC assembly serial number, individual unit serial numbers, installation dates, and warranty expiration dates
−- Spare parts inventory with manufacturer part numbers and reorder information
−- Complete set of keys for all locks and one set of breaker racking tools, where applicable
+- operation and maintenance data covering the structure, the bus, each unit type, and each device installed in a unit
+- record drawings reflecting every field change to the unit arrangement, the wiring, and the network addressing
+- the certified factory test report and the field acceptance test report
+- the manufacturer's start-up report, where manufacturer start-up is indicated
+- the final settings of every adjustable device, including overload relay dial and class settings, trip unit settings, soft starter parameters, and the drive parameter files
+- the network address list and the point list for every networked device
+- the arc-flash incident energy labels installed, with the study revision they were taken from
+- the warranty certificate identifying the assembly serial number and the warranty commencement date
+- a signed receipt from the Owner for the spare units and spare parts delivered
```datasheet
−label: Required Closeout Submittals
+label: Closeout Submittal Package
type: checkbox
options:
− - "Operation and maintenance manuals (bound, with section dividers)"
− - "As-built shop drawings reflecting field modifications"
− - "Factory and field test reports (NETA and manufacturer startup)"
− - "Final programmed parameter settings (VFD and soft-start units)"
− - "Warranty documentation (assembly and unit serial numbers)"
− - "Spare parts inventory with part numbers and reorder information"
− - "Complete set of keys and breaker racking tools (where applicable)"
+ - "Operation and maintenance data"
+ - "Record drawings"
+ - "Factory and field test reports"
+ - "Manufacturer start-up report"
+ - "Final device settings and parameter files"
+ - "Network address and point list"
+ - "Arc-flash label record"
+ - "Warranty certificate"
+ - "Spare parts receipt"
default:
− - "Operation and maintenance manuals (bound, with section dividers)"
− - "As-built shop drawings reflecting field modifications"
− - "Factory and field test reports (NETA and manufacturer startup)"
− - "Warranty documentation (assembly and unit serial numbers)"
− - "Spare parts inventory with part numbers and reorder information"
− - "Complete set of keys and breaker racking tools (where applicable)"
+ - "Operation and maintenance data"
+ - "Record drawings"
+ - "Factory and field test reports"
+ - "Final device settings and parameter files"
+ - "Warranty certificate"
+ - "Spare parts receipt"
```
…2 unchanged lines
## Manufacturer Qualifications {toc}
−### MCCs shall be manufactured by a single company responsible for the structural assembly, horizontal and vertical bus, and all integral starter, branch device, and control components installed in factory-furnished units.
+### The assembly shall be produced by a manufacturer who has held a UL 845 listing for motor control centers of the type furnished for not less than the period indicated in the datasheet.
−### The manufacturer shall have a minimum of five years documented experience producing UL 845 listed motor control centers.
+```datasheet
+label: Minimum Manufacturer Listing History
+type: range
+unit: years
+options:
+ min: 0
+ max: 20
+ setpoints: [0, 3, 5, 10, 20]
+default: 5
+```
−### The manufacturer shall maintain an ISO 9001 certified quality management system.
+### The manufacturer shall maintain a factory-trained field service organization able to reach the site, and shall state the location of the nearest such office in the qualification statement.
−### The manufacturer shall maintain a service organization with factory-trained field representatives accessible within the project's geographic region.
+### The manufacturer shall state in the qualification statement the period, measured from the date of manufacture, for which replacement plug-in units and bus components for the assembly platform will remain available.
−### The manufacturer shall commit to providing replacement plug-in units, bus components, and control devices for the MCC platform for a minimum of ten years from the date of manufacture.
−
## Source Limitations {toc}
−### The MCC structure, horizontal bus, vertical bus, plug-in unit chassis, common control bus, and combination starter assemblies shall be furnished by the MCC manufacturer as an integrated assembly.
+### The structure, horizontal bus, vertical bus, unit compartments, unit chassis, and common control provisions shall be furnished by one manufacturer under one UL 845 listing.
−### Third-party plug-in units, control components, or bus modifications assembled by others are not acceptable unless specifically pre-approved by the MCC manufacturer in writing and listed under the same UL 845 file.
+### A unit assembled or modified by a party other than the manufacturer shall be installed in the assembly only where the manufacturer confirms in writing that the unit is covered by the assembly listing and that the assembly short-circuit current rating is unchanged.
−### Where VFD units, soft-start units, or metering devices furnished by others are installed in the MCC, those units shall be mounted in factory-furnished unit compartments meeting UL 845 unit construction requirements, and the assembly shall remain a single listed product.
+### A unit in the listing whose contents come from another maker, such as a drive or a meter, remains covered by the assembly listing only where the manufacturer installed it in a unit of its own construction and evaluated it as part of the assembly. {note}
−## Testing Personnel Qualifications {toc}
+## Field Testing Firm {toc}
−### Field acceptance testing shall be performed by a firm regularly engaged in testing electrical power equipment, employing technicians certified by NETA or equivalent.
+### Field acceptance testing shall be performed by the firm indicated in the datasheet.
−### Testing personnel shall have a minimum of three years documented experience testing low-voltage motor control centers and the specific starter and drive technologies present in the assembly.
+```datasheet
+label: Field Acceptance Testing Firm
+type: radio
+options:
+ - "Independent testing firm accredited to ANSI/NETA ATS"
+ - "Manufacturer's field service organization"
+ - "Installing contractor's own technicians"
+```
−# Environmental and Service Conditions {toc}
+### The technicians who perform field acceptance testing shall hold a current certification for low-voltage equipment testing from NETA or from the manufacturer of the equipment tested, and shall have tested motor control centers of the type furnished.
−## MCCs shall be suitable for continuous operation under the service conditions indicated in the datasheet.
+### An independent firm has no stake in whether the assembly passes and reports against a published acceptance standard; the manufacturer's organization knows the product best and is already on site for start-up; the installing contractor's own technicians cost least and are available on the installer's schedule. Which of these the Owner wants depends on how the results will be used, and on whether a report from the party who built or installed the equipment would satisfy the Owner's insurer and the Authority Having Jurisdiction. {note}
−## Where site conditions exceed these parameters, the Contractor shall notify the manufacturer and the equipment shall be derated accordingly.
+# Environmental and Service Conditions {toc}
−## The design maximum ambient temperature at the installation shall be as indicated in the datasheet.
+## Ambient Temperature {toc}
+### The assembly shall carry its nameplate continuous current ratings at the design ambient temperature of the room indicated in the datasheet.
+
```datasheet
−label: Ambient Temperature (Maximum)
+label: Indoor Design Ambient Temperature
type: range
unit: °C
options:
min: 40
max: 55
− setpoints: [40, 50, 55]
+ setpoints: [40, 45, 50, 55]
default: 40
```
−## The elevated selections apply to specific installations: 50°C to elevated mechanical rooms and 55°C to rooftop or unconditioned spaces. {note}
+### The usual service conditions of NEMA ICS 1 and UL 845 establish the ratings at a 40 °C ambient, so a 40 °C design ambient is the condition at which the nameplate applies without correction; a higher value buys margin for a room whose ventilation cannot hold that ambient at design load, at the cost of a larger bus or a larger unit for the same connected load. {note}
−## The installation altitude shall be as indicated in the datasheet.
+### Where the assembly is installed outdoors and [[parameter: site-ambient-temperature-maximum]] exceeds 40 °C, the manufacturer shall derate the bus and the units in accordance with its published factors and shall state the derated ratings in the action submittals.
−```datasheet
−label: Installation Altitude
−type: select
−options:
− - "Below 6,600 ft (2,000 m) - no derating"
− - "6,600 - 9,900 ft (2,000 - 3,000 m)"
− - "Above 9,900 ft (3,000 m) - consult manufacturer"
−default: "Below 6,600 ft (2,000 m) - no derating"
−```
+### Where the assembly is installed outdoors, the enclosure space heaters shall be sized to hold the interior above the dew point at [[parameter: site-ambient-temperature-minimum]].
−## The corrosion severity classification of the installation environment shall be as indicated in the datasheet.
+## Altitude {toc}
−```datasheet
−label: Corrosion Severity
−type: select
−options:
− - "C2 - Low (indoor, climate-controlled)"
− - "C3 - Medium (indoor, unconditioned mechanical room)"
− - "C4 - High (industrial, coastal, water/wastewater)"
− - "C5 - Very High (chemical, marine, severely corrosive)"
−```
+### The assembly shall be derated for [[parameter: altitude]] in accordance with the manufacturer's published correction factors where the altitude exceeds the 2000 m usual service condition of NEMA ICS 1.
−## The corrosion classification is an assessment of the actual installation environment made by the Engineer; there is no classification that is correct for every project, so the field carries no default. {note}
+### Air thins with altitude, which reduces both the convective cooling that sets the continuous current rating and the dielectric strength of the clearances inside the assembly, so a unit rated at sea level carries less current and less insulation margin at elevation than its nameplate states. {note}
−## Continuous current ratings of the horizontal bus, vertical bus, and individual starter units are established at the standard reference ambient of 40°C and below 6,600 ft altitude per NEMA ICS 18.
+### Ambient temperature derating and altitude derating shall be applied cumulatively where both conditions apply.
−## Where the installed environment exceeds these reference conditions, the manufacturer shall derate the assembly per published tables and confirm bus and unit ratings on the submittal documents.
+## Humidity {toc}
−## For installations classified C3 or higher, vertical and horizontal bus shall be copper, tin-plated as a minimum.
+### The assembly shall be rated for operation at a relative humidity up to 95%, non-condensing.
−## For installations classified C3 or higher, exposed steel surfaces shall receive an enhanced two-coat finish system.
+### Where the installed location is unconditioned, whether indoors or outdoors, thermostatically controlled space heaters shall be furnished in each vertical section and shall be supplied from a circuit that stays energized while the assembly main device is open.
−## For installations classified C3 or higher, plug-in unit stab-on connectors shall be silver-plated.
+## Seismic Qualification {toc}
−## For C5 environments, stainless steel enclosure construction or factory-applied chemical-resistant coatings shall be considered, and the manufacturer's certification of suitability for the specific corrosive exposure shall be submitted with shop drawings.
+### The seismic qualification of the assembly shall be as indicated in the datasheet.
−## Seismic Requirements {toc}
−
−### The seismic certification basis shall be as indicated in the datasheet.
−
```datasheet
−label: Seismic Certification
+label: Seismic Qualification
type: select
−drawing_ref: "structural drawings"
+derived: "[[parameter: seismic-design-category]] and the component importance factor ASCE 7 Chapter 13 assigns to the assembly"
options:
- "Not required"
− - "IBC/ASCE 7 - Importance Factor 1.0"
− - "IBC/ASCE 7 - Importance Factor 1.5 (essential facility)"
− - "OSHPD pre-approval required (California healthcare)"
−default: deferred
+ - "Shake-table qualification per ICC-ES AC156 with component importance factor 1.0"
+ - "Shake-table qualification per ICC-ES AC156 with component importance factor 1.5"
+ - "Qualification by analysis per ASCE 7 Chapter 13"
+default: derived
```
−### The Seismic Design Category and Importance Factor are established by the project's structural design; the electrical scope adopts them rather than setting them. {note}
+### Where seismic qualification is required, it shall be performed in accordance with the seismic provisions of [[parameter: adopted-building-code]] and ASCE 7 Chapter 13.
−### Where required by the applicable building code, MCCs shall be seismically certified by shake-table testing per ICC ES AC156 or by analysis per ASCE 7.
+### Whether the assembly must be qualified follows from the seismic design category, and whether it must remain operable after the design earthquake, rather than merely stay anchored, follows from the component importance factor; neither is decided within this standard. {note}
−### Seismic certification shall be by an independent third-party testing laboratory.
+### Seismic qualification shall cover the complete assembly in the configuration shipped, including every installed unit and the heaviest unit arrangement in any section.
−### Certification shall cover the complete assembly including all plug-in units, bus, and the largest configuration shipped to the site.
+### A certificate covering a single section, an empty structure, or a component tested apart from the assembly shall not be accepted as qualification of the assembly.
−### Certification of individual sections or components in isolation is not acceptable, and field-modified assemblies that depart from the certified configuration shall be re-evaluated.
+### A field change to the unit arrangement that departs from the qualified configuration shall be re-evaluated by the manufacturer against the qualification before the assembly is energized.
−# Electrical Requirements {toc}
+# Electrical Ratings {toc}
−## System Ratings {toc}
+## Service Configuration {toc}
−### Whether the MCC serves as service entrance equipment shall be as indicated in the datasheet.
+### Whether the assembly is service entrance equipment shall be as indicated in the datasheet.
```datasheet
−label: Service Entrance Equipment
+label: Service Configuration
type: radio
−drawing_ref: "one-line diagram"
+drawing_ref: "the one-line diagram"
options:
- "Service entrance equipment"
…2 unchanged lines
```
+### Where the assembly is service entrance equipment, it shall be listed as suitable for use as service equipment and shall comply with NFPA 70 Article 230, including the service disconnect, the available fault current marking, and the grounding electrode conductor termination.
+
+## System Voltage and Frequency {toc}
+
### The system voltage and configuration shall be as indicated in the datasheet.
```datasheet
label: System Voltage
type: select
−drawing_ref: "one-line diagram"
+drawing_ref: "the one-line diagram"
options:
− - "208Y/120V 3Φ 4-wire"
− - "240V 3Φ 3-wire (delta)"
− - "480Y/277V 3Φ 4-wire"
− - "480V 3Φ 3-wire (delta)"
− - "600Y/347V 3Φ 4-wire"
+ - "208Y/120 V 3Φ 4-wire"
+ - "240 V 3Φ 3-wire delta"
+ - "240/120 V 3Φ 4-wire high-leg delta"
+ - "480Y/277 V 3Φ 4-wire"
+ - "480 V 3Φ 3-wire delta"
+ - "600Y/347 V 3Φ 4-wire"
+ - "600 V 3Φ 3-wire delta"
default: deferred
```
…11 unchanged lines
```
−### 60 Hz is the North American norm and is the datasheet default; 50 Hz MCCs and the motors they serve are a distinct product selection, available for systems that operate at that frequency. {note}
+## Main Device {toc}
−### MCCs are typically downstream distribution equipment fed from upstream switchgear or switchboards. {note}
+### The incoming main device shall be as indicated in the datasheet.
−### Where an MCC is configured as service entrance equipment, it shall comply with NFPA 70 Article 230 including provisions for service disconnect, available fault current marking, and ground fault protection as required by Article 230.95 for solidly grounded wye services of more than 150V to ground and 1000A or more.
+```datasheet
+label: Main Device Type
+type: select
+drawing_ref: "the one-line diagram"
+options:
+ - "Main lugs only"
+ - "Main circuit breaker"
+ - "Main fusible switch"
+ - "Main insulated-case circuit breaker"
+default: deferred
+```
−## Bus Rating {toc}
+### The main device frame and trip rating shall be as indicated on [[drawing: the one-line diagram]].
−### Main horizontal bus continuous current rating shall be as indicated in the datasheet.
+### The trip unit of a main circuit breaker shall be as indicated in the datasheet.
```datasheet
+label: Main Circuit Breaker Trip Unit
+type: select
+drawing_ref: "the one-line diagram"
+options:
+ - "Thermal-magnetic"
+ - "Electronic with long-time, short-time, and instantaneous functions"
+ - "Electronic with long-time, short-time, instantaneous, and ground-fault functions"
+default: deferred
+```
+
+### Ground-fault protection of equipment on the main device shall be as indicated in the datasheet.
+
+```datasheet
+label: Ground-Fault Protection of Equipment on the Main Device
+type: radio
+derived: "NFPA 70 230.95 and 215.10 applied to the system voltage, the main device rating, and whether the assembly is service entrance equipment"
+options:
+ - "Not provided"
+ - "Provided"
+default: derived
+```
+
+### Whether the main device must carry ground-fault protection of equipment is fixed by code from the system grounding, the voltage to ground, and the device rating, so the field records the consequence of those inputs rather than a preference; a project may add ground-fault protection where code does not require it. {note}
+
+## Bus Continuous Current {toc}
+
+### The horizontal bus continuous current rating shall be as indicated in the datasheet.
+
+```datasheet
label: Horizontal Bus Continuous Current
type: range
unit: A
−drawing_ref: "one-line diagram"
+drawing_ref: "the one-line diagram"
options:
min: 600
− max: 3000
− setpoints: [600, 800, 1000, 1200, 1600, 2000, 2500, 3000]
+ max: 3200
+ setpoints: [600, 800, 1000, 1200, 1600, 2000, 2500, 3000, 3200]
default: deferred
```
−### Vertical bus continuous current rating shall be as indicated in the datasheet.
+### The vertical bus continuous current rating shall be as indicated in the datasheet.
```datasheet
label: Vertical Bus Continuous Current
type: range
unit: A
+drawing_ref: "the motor control center schedule"
options:
min: 300
− max: 1200
− setpoints: [300, 600, 800, 1200]
+ max: 1600
+ setpoints: [300, 600, 800, 1200, 1600]
+default: deferred
```
−### The marked short-circuit current rating shall be as indicated in the datasheet.
+### The vertical bus in each section shall carry the sum of the full-load currents of the units installed in that section, and the manufacturer shall confirm the loading of each section on the unit arrangement drawings.
+### A section populated with several large starters, soft starters, or drive units can exceed the lowest vertical bus rating before it runs out of compartment space, which is why the vertical bus is confirmed per section against the units actually installed rather than assumed from the horizontal bus. {note}
+
+## Short-Circuit Ratings {toc}
+
+### The assembly short-circuit current rating marked on the nameplate shall equal or exceed the available fault current at the line terminals, and shall be as indicated in the datasheet.
+
```datasheet
−label: Short-Circuit Current Rating (SCCR)
+label: Assembly Short-Circuit Current Rating
type: range
−unit: kAIC
−drawing_ref: "one-line diagram"
+unit: kA
+drawing_ref: "the one-line diagram"
options:
− min: 22
+ min: 10
max: 100
− setpoints: [22, 42, 65, 85, 100]
+ setpoints: [10, 14, 18, 22, 25, 30, 35, 42, 50, 65, 85, 100]
default: deferred
```
−### The combination motor controller coordination type shall be as indicated in the datasheet.
+### The bus short-circuit bracing shall be as indicated in the datasheet.
```datasheet
−label: Combination Motor Controller Coordination
−type: select
+label: Bus Short-Circuit Bracing
+type: range
+unit: kA
+derived: "the assembly short-circuit current rating; the bus is braced to not less than the rating marked on the assembly"
options:
− - "Type 1 - No damage to persons; component replacement acceptable"
− - "Type 2 - No damage permitted except light contact welding"
−default: "Type 1 - No damage to persons; component replacement acceptable"
+ min: 10
+ max: 100
+ setpoints: [10, 14, 18, 22, 25, 30, 35, 42, 50, 65, 85, 100]
+default: derived
```
−### The fault current rating basis shall be as indicated in the datasheet.
+### The marked assembly rating is the lowest of the bus bracing, the interrupting rating of each unit disconnect, and the rating of each combination controller as tested under UL 845, so the bus bracing is a floor beneath the assembly rating rather than a separate choice. {note}
+### The basis on which the assembly rating is established shall be as indicated in the datasheet.
+
```datasheet
−label: Series Rating
+label: Fault Current Rating Basis
type: radio
options:
− - "Fully rated (every device rated for available fault current)"
− - "Series rated (combinations tested per UL 489 / UL 845)"
−default: "Fully rated (every device rated for available fault current)"
+ - "Fully rated"
+ - "Series rated"
+default: "Fully rated"
```
−### Bus shall be braced for the available short-circuit current at the point of installation as determined by a short-circuit analysis.
+### A fully rated assembly carries a rating on every unit that stands on its own; a series-rated assembly reaches its marked rating through tested combinations in which a downstream device is rated only when the specific upstream device it was tested with remains in place, so a later change to the main device or to an upstream breaker can silently void the rating. Series rating lowers the cost of the units where the available fault current is high, and is used where the upstream device is under the same Owner's control and is not expected to change. {note}
−### Coordinate the available fault current with the upstream device and the utility service per [[sync/low-voltage-switchgear]].
+### Where series rating is the basis, every series-rated combination shall be marked on the assembly in accordance with NFPA 70 110.22, and the upstream device on which each rating depends shall be identified in the action submittals.
−### Vertical bus rating shall be sized for the cumulative full-load current of the units installed in each vertical section with allowance for diversity.
+## Neutral and Ground Bus {toc}
−### Where high-density populations of large starters, soft starters, or VFD units are planned in a single vertical section, the 600 A standard rating is often insufficient and 800 A or 1200 A vertical bus shall be specified.
+### The neutral bus shall be as indicated in the datasheet.
−### Verify vertical bus loading on the submittal documents.
+```datasheet
+label: Neutral Bus
+type: select
+derived: "the system voltage configuration (three-wire or four-wire) and the share of nonlinear load served from the assembly"
+options:
+ - "No neutral bus"
+ - "Neutral bus rated 100% of the horizontal bus"
+ - "Neutral bus rated 200% of the horizontal bus"
+default: derived
+```
−### The marked short-circuit current rating of the MCC shall equal or exceed the available fault current at the MCC line terminals.
+### A three-wire system has no neutral to carry, a four-wire system carries one rated with the phase bus, and a four-wire system whose load is predominantly nonlinear carries the triplen harmonic currents that add in the neutral rather than cancel, which is the condition under which the neutral is rated above the phase bus. {note}
−### The SCCR is the lowest of the bus bracing rating, the marked rating of each branch device, and the rating of any combination motor controller as listed in UL 508 / UL 845. {note}
+### Where a neutral bus is furnished, it shall be insulated from the structure, and where the assembly is service entrance equipment the main bonding jumper shall be furnished by the manufacturer.
−### Combination motor controllers using a magnetic-only branch device coordinated with a motor starter and overload relay establish a "Type 2" coordination rating per UL 508 that limits component damage during a fault; specify Type 2 coordination where post-fault uptime is critical. {note}
+### The ground bus shall be as indicated in the datasheet.
−### Series-rated combinations may reduce equipment cost but constrain future modifications because each downstream device is only rated when paired with the specific upstream device listed in the series rating table. {note}
+```datasheet
+label: Ground Bus
+type: radio
+options:
+ - "Full-length ground bus"
+ - "No ground bus"
+default: "Full-length ground bus"
+```
−### Fully rated systems are recommended for facilities expected to undergo future load growth, equipment additions, or upstream source changes. {note}
+### An assembly added to an existing lineup whose ground bus continues through the joined sections is the case in which a ground bus of its own is omitted; every free-standing assembly carries one. {note}
−## Neutral and Ground Bus {toc}
+### Where a ground bus is furnished, it shall be copper, shall extend the full length of the assembly, and shall be accessible from the front of each section without removing a bus barrier.
−### The neutral bus rating shall be as indicated in the datasheet.
+### Each plug-in unit shall make ground continuity to the ground bus through a dedicated ground stab that engages before the line stabs on insertion and releases after them on withdrawal.
+### Grounding and bonding of the assembly shall comply with [[sync/grounding-and-bonding]].
+
+# Enclosure and Structure {toc}
+
+## Enclosure Type {toc}
+
+### The enclosure type shall be as indicated in the datasheet.
+
```datasheet
−label: Neutral Bus Rating
+label: Enclosure Type per NEMA 250
type: select
options:
− - "Not applicable (3-wire system, no neutral)"
− - "100% of main bus rating"
− - "50% of main bus rating (reduced)"
− - "200% of main bus rating (oversized for harmonic loads)"
−default: "100% of main bus rating"
+ - "Type 1"
+ - "Type 1 gasketed"
+ - "Type 12"
+ - "Type 3R"
+ - "Type 4"
+ - "Type 4X"
+default: "Type 1"
```
−### A 3-wire system with no neutral records "Not applicable" rather than leaving the field ambiguous. {note}
+### A dry, conditioned electrical room is the installed location on most projects, and a Type 1 enclosure is the construction rated for it; the gasketed and Type 12 constructions keep out the dust of an unconditioned mechanical or process space, Type 3R is the outdoor construction, and Type 4 and Type 4X are the washdown and corrosive-exposure constructions. {note}
−### Oversized neutral bus is required where nonlinear loads, including VFD units, electronic ballasts, and switched-mode power supplies served from the MCC, exceed 30% of the connected load.
+### Where the assembly is installed outdoors, the enclosure shall be Type 3R at minimum, with rain hoods over ventilation openings and a drip shield over each door.
−### The Engineer shall evaluate harmonic loading per IEEE 519 when selecting neutral bus sizing for MCCs serving substantial VFD populations.
+### Where the assembly is installed outdoors, the outdoor housing arrangement shall be as indicated in the datasheet.
−### Whether a ground bus is furnished with the assembly shall be as indicated in the datasheet.
−
```datasheet
−label: Ground Bus
+label: Outdoor Housing Arrangement
type: radio
options:
− - "Included — full length of the assembly"
− - "Not required"
−default: "Included — full length of the assembly"
+ - "Non-walk-in"
+ - "Walk-in aisle"
```
−### A full-length ground bus is the normal construction and is the datasheet default; "Not required" exists for the rare addition to an existing line-up whose ground bus is carried through from the adjoining sections. {note}
+### A walk-in housing puts the working space inside a weatherproof room so that a unit can be serviced in any weather, at the cost of a larger and heavier structure; a non-walk-in housing is the smaller and lighter structure, and its working space is the outdoor pad in front of it. {note}
−### Where a ground bus is furnished, it shall be bare copper, extending the full length of the assembly, accessible from the front of each vertical section without removing live parts barriers.
+### Where a walk-in housing is furnished, the aisle shall provide the working space required by NFPA 70 110.26 in front of every unit door, and the housing shall have lighting, a convenience receptacle, and a door openable from inside without a key.
−### Every plug-in unit shall make positive ground continuity to the ground bus through a dedicated ground stab independent of the line stabs, engaging before the line stabs make contact during unit insertion.
+## Enclosure Material and Finish {toc}
−### Grounding electrode and equipment grounding conductor terminations shall comply with [[sync/grounding-and-bonding]].
+### The enclosure material shall be as indicated in the datasheet.
−# Physical Construction {toc}
+```datasheet
+label: Enclosure Material
+type: select
+options:
+ - "Painted steel"
+ - "Type 304 stainless steel"
+ - "Type 316 stainless steel"
+default: "Painted steel"
+```
−## Enclosure {toc}
+### Where a Type 4X enclosure is indicated, the enclosure material shall be a stainless steel or another material listed for the Type 4X rating.
−### The enclosure NEMA rating shall be as indicated in the datasheet.
+### Structural members shall be steel of not less than 12 gauge, and doors and covers shall be steel of not less than 14 gauge, formed and reinforced so that a door does not deflect when opened with its devices installed.
+### The finish system applied to a painted steel enclosure shall be as indicated in the datasheet.
+
```datasheet
−label: Enclosure Rating
+label: Painted Steel Finish System
type: select
options:
− - "NEMA 1 - Indoor general purpose"
− - "NEMA 1A - Indoor general purpose, gasketed"
− - "NEMA 12 - Indoor industrial, dust-tight, drip-tight"
− - "NEMA 3R - Outdoor rainproof"
− - "NEMA 4 - Watertight (washdown areas)"
− - "NEMA 4X - Watertight, corrosion-resistant (food processing, water/wastewater)"
−default: "NEMA 1 - Indoor general purpose"
+ - "Polyester powder coat over a phosphate pretreatment"
+ - "Epoxy powder coat over a phosphate pretreatment"
+ - "Two-coat epoxy primer and polyurethane topcoat"
+default: manufacturer
```
−### The NEMA ICS 18 class and wiring type shall be as indicated in the datasheet.
+### The manufacturer shall state the finish system and its dry film thickness in the product data.
+### A polyester powder coat is the finish the assemblies are built with and holds up indoors and in ordinary outdoor exposure; an epoxy powder coat resists chemical splash better and chalks faster in sunlight; a two-coat liquid system is applied where a chemical or marine exposure has already been identified and the enclosure is not being made of stainless steel. {note}
+
+### The finish color shall be as indicated in the datasheet.
+
```datasheet
−label: NEMA Construction Class
+label: Finish Color
type: select
options:
− - "Class I, Type B - Common control, wiring terminated at unit"
− - "Class I, Type C - Common control, wiring terminated at master terminal blocks"
− - "Class II, Type B - Manufacturer wires unit-to-unit per schematic, unit terminations"
− - "Class II, Type C - Manufacturer wires unit-to-unit per schematic, master terminal blocks"
−default: "Class I, Type C - Common control, wiring terminated at master terminal blocks"
+ - "ANSI 61 light gray"
+ - "ANSI 49 medium gray"
+ - "ANSI 70 sky gray"
+ - "Custom color matched to a sample furnished by the Owner"
+default: "ANSI 61 light gray"
```
−### The section accessibility configuration shall be as indicated in the datasheet.
+## Section Arrangement {toc}
+### The section accessibility shall be as indicated in the datasheet.
+
```datasheet
label: Section Accessibility
−type: radio
+type: select
options:
− - "Front accessible (rear against wall)"
− - "Front and rear accessible"
−default: "Front accessible (rear against wall)"
+ - "Front-accessible, single-sided"
+ - "Front-accessible, back-to-back sections"
+ - "Front- and rear-accessible"
+default: "Front-accessible, single-sided"
```
−### Enclosure shall be fabricated from cold-rolled steel with a minimum thickness of 12 gauge (2.66 mm) for structural members and 14 gauge (1.90 mm) for covers and doors.
+### A single-sided assembly stands against a wall and needs working space on one side only; a back-to-back assembly puts two rows of units on a shared horizontal bus in the depth of one, which halves the floor length for the same unit count but needs working space on both faces; a rear-accessible assembly provides rear cable access for large incoming conductors at the cost of a rear working space that a single-sided assembly does not need. {note}
−### All structural members shall be bolted or continuously welded.
+### Section depth and height shall be the manufacturer's standard for the largest unit installed, and shall be shown on the shop drawings.
−### Doors shall be hinged with concealed hinges and equipped with a quarter-turn latch for each non-defeatable interlocked unit and key-lockable latches for instrument and metering compartments.
+### Sections shall be bolted together to form a rigid continuous assembly, with the horizontal bus spliced at every shipping split by a bolted splice plate furnished by the manufacturer.
−### For outdoor installations (NEMA 3R), the enclosure shall include rain hoods over ventilation openings, sun shields where direct solar exposure is expected, and thermostat-controlled condensation heaters in each vertical section sized at a minimum of 250 W per section.
+## Wireways and Conduit Entry {toc}
−### Outdoor enclosures shall be furnished with a walk-in arrangement only where the MCC is large enough to provide working clearances per NFPA 70 Article 110.26 inside the enclosure; otherwise the enclosure shall be a non-walk-in design and working clearances shall be maintained externally.
+### Conduit entry to the assembly shall be as indicated in the datasheet.
−### NEMA ICS 18 defines Class I MCCs as assemblies where the manufacturer makes no electrical interconnections between units beyond the common bus, leaving inter-unit logic wiring to the field installer. {note}
+```datasheet
+label: Conduit Entry
+type: radio
+drawing_ref: "the electrical plans"
+options:
+ - "Top entry"
+ - "Bottom entry"
+ - "Top and bottom entry"
+default: deferred
+```
−### Class II MCCs include factory-installed inter-unit control wiring per a customer-furnished elementary diagram and are appropriate for projects with extensive interlocking, sequencing, or PLC integration. {note}
+### Each vertical section shall have a vertical wireway running the full height of the section, adjacent to the unit compartments, separated from the bus and from the unit compartments by a barrier, and closed by a hinged or removable cover.
−### Type B wiring terminates control conductors at the individual unit's terminal block; Type C extends control conductors to a master terminal block at the top or bottom of each vertical section for simplified field termination. {note}
+### The vertical wireway shall be sized so that the load and control conductors of every unit in the section fit within the fill limits of NFPA 70 Article 312.
−### Class I Type C is the most common configuration in commercial and institutional service. {note}
+### A horizontal wireway shall be furnished at the top and at the bottom of the assembly, continuous through the sections, and isolated from the horizontal bus by a barrier.
−### Rear-accessible configurations require minimum 36 in. working clearance at rear per NFPA 70 Article 110.26 and provide front and rear access to bus, cable, and unit compartments.
+### Conduit shall enter only through the wireway areas designated on the shop drawings; the bus compartments, the unit compartments, and the barriers between them shall not be penetrated.
−### Front-accessible configurations may be installed with the rear of the assembly against a wall and reduce required floor space at the cost of rear maintenance access. {note}
+## Barriers and Unit Doors {toc}
−## Bus Bars {toc}
+### The horizontal bus, the vertical bus, each unit compartment, and each wireway shall be separated from one another by grounded metal barriers.
−### The horizontal bus material and plating shall be as indicated in the datasheet.
+### Each unit compartment shall have its own hinged door, interlocked to the unit disconnect so that the door cannot be opened with the disconnect closed and the disconnect cannot be closed with the door open, with a tool-operable defeat for authorized testing.
+### The unit disconnect operating handle shall be operable from outside the closed door and shall accept not fewer than three padlocks in the open position.
+
+### The disconnect of a unit shall be capable of being padlocked in the open position with the unit in the connected, the test, and the withdrawn positions.
+
+# Bus {toc}
+
+## Horizontal Bus Material {toc}
+
+### The horizontal bus material shall be as indicated in the datasheet.
+
```datasheet
label: Horizontal Bus Material
type: radio
options:
− - "Copper (tin-plated)"
− - "Copper (silver-plated)"
− - "Aluminum (tin-plated)"
+ - "Copper"
+ - "Aluminum"
```
−### The vertical bus plating shall be as indicated in the datasheet.
+### Copper bus carries more current per unit cross-section, needs no special joint preparation, and costs more; aluminum bus is lighter and less expensive for the same rating, and its joints depend on plating and on the joint hardware to hold their resistance through thermal cycling, which is why aluminum is used where the cost difference on a large bus matters and the joint construction is tested as part of the listing. {note}
+### Where aluminum horizontal bus is selected, it shall be an alloy and temper the manufacturer has tested under the assembly listing, and every bolted joint shall be plated through the contact area.
+
+### The vertical bus shall be copper.
+
+### The vertical bus carries the stab contacts of every unit, and each insertion and withdrawal scrapes the plating across the contact surface; copper holds a plated contact surface through that wear, which is why vertical bus is copper regardless of the horizontal bus material. {note}
+
+## Bus Plating {toc}
+
+### The bus plating shall be as indicated in the datasheet.
+
```datasheet
−label: Vertical Bus Material
+label: Bus Plating
type: radio
options:
− - "Copper (tin-plated)"
− - "Copper (silver-plated)"
−default: "Copper (tin-plated)"
+ - "Tin plating"
+ - "Silver plating"
+default: manufacturer
```
−### Provisions for future bus extension shall be as indicated in the datasheet.
+### The manufacturer shall state the plating in the product data.
+### Silver plating has the lower contact resistance and is the historic choice for stab contacts; tin plating resists tarnishing in atmospheres containing sulfur compounds, which blacken silver and raise its contact resistance, and is the plating applied to most assemblies as built. Where the installed environment carries hydrogen sulfide, as in a wastewater facility, tin is the plating that holds its contact resistance. {note}
+
+### Plating shall be continuous over every bolted joint contact surface and over the full length of the vertical bus stab contact area.
+
+## Bus Joints and Bracing {toc}
+
+### Bus joints shall be bolted with hardware that maintains contact pressure through thermal cycling, and the joint hardware and torque shall be those established under the assembly listing.
+
+### The bus shall be braced to withstand the bus short-circuit bracing indicated in the datasheet without damage, and the bracing shall be maintained through every shipping split.
+
+## Bus Protection Provisions {toc}
+
+### The bus protection provisions furnished shall be as indicated in the datasheet.
+
```datasheet
−label: Bus Extension Provisions
−type: radio
+label: Bus Protection Provisions
+type: checkbox
options:
− - "No future extension"
− - "Provision for future extension at one end"
− - "Provision for future extension at both ends"
−default: "Provision for future extension at one end"
+ - "Insulated horizontal bus"
+ - "Insulated and isolated vertical bus"
+ - "Automatic shutters over unused vertical bus stab openings"
+ - "Manual blanking covers over unused vertical bus stab openings"
+ - "Insulated bus splice covers at shipping splits"
```
−### Vertical bus shall be copper regardless of horizontal bus selection because vertical bus is repeatedly stressed by unit insertion and removal.
+### An insulated and isolated vertical bus exposes bare bus only at the stab opening a unit occupies; automatic shutters close the opening the moment a unit is withdrawn, where manual blanking covers depend on the person who withdrew the unit to install them. Each provision reduces the bare bus a worker can reach with a unit out of its compartment, and each adds cost to every section. {note}
−### Aluminum vertical bus is not acceptable.
+### Every unused vertical bus stab opening shall be covered by a shutter or a blanking cover when the assembly is delivered.
−### Bus bar joints shall be bolted with Belleville washers to maintain contact pressure under thermal cycling, and all joint contact surfaces shall be plated to match the bus plating.
+## Bus Extension Provisions {toc}
−### Vertical bus shall be isolated and insulated from the unit compartment interior.
+### The provisions for future extension of the assembly shall be as indicated in the datasheet.
−### Bus shall be covered with a flame-retardant insulating shield that exposes only the stab openings required by the inserted unit at each elevation.
+```datasheet
+label: Bus Extension Provisions
+type: select
+options:
+ - "No extension provisions"
+ - "Extension provisions at one end"
+ - "Extension provisions at both ends"
+```
−### Open stab openings not occupied by a plug-in unit shall be covered with manufacturer-furnished blanking shutters.
+### Extension provisions consist of a removable end closure, horizontal bus ends drilled for a splice, and ground and neutral bus ends drilled to match, so that a section can be added without drilling live bus. {note}
−## Wireway {toc}
+# Wiring Class and Type {toc}
−### The conduit entry direction shall be as indicated in the datasheet.
+## Wiring Class {toc}
+### The NEMA ICS 18 wiring class of the assembly shall be as indicated in the datasheet.
+
```datasheet
−label: Conduit Entry
+label: Wiring Class per NEMA ICS 18
type: radio
−drawing_ref: "electrical plans"
options:
− - "Top entry"
− - "Bottom entry"
− - "Top and bottom entry"
−default: deferred
+ - "Class I"
+ - "Class II"
+default: "Class I"
```
−### Each vertical section shall include a continuous vertical wireway adjacent to the unit compartments with a hinged or removable cover providing access to the full height of the section.
+### A Class I assembly is furnished with no control interconnection between units; each unit is complete in itself and the interlocking and sequencing wiring between units is field work. A Class II assembly is furnished with the inter-unit control wiring installed at the factory from an elementary diagram furnished with the order, so that sequencing, interlocks, and a control-logic interface arrive wired and tested. {note}
−### Vertical wireway shall be sized to accept all load and control conductors entering and leaving the section without exceeding NFPA 70 Article 312 fill limits, and shall be physically separated from the bus compartment by a continuous metal barrier.
+### Class II construction moves the inter-unit wiring and its checkout from the site to the factory, which shortens the site work and produces a tested system when the interlocking between units is extensive, at the cost of an elementary diagram that must be complete before the order is placed and a longer lead time when it changes. {note}
−### A continuous horizontal wireway shall be provided at the top of the assembly, the bottom of the assembly, or both, sized for the cumulative conduit and conductor entries to the assembly.
+### Where Class II wiring is selected, the elementary diagram from which the manufacturer wires the assembly shall be as indicated on [[drawing: the motor control center control diagrams]].
−## Barriers and Compartmentalization {toc}
+## Wiring Type {toc}
−### Metal barriers shall separate the horizontal bus compartment, the vertical bus compartment, the unit compartments, and the wireway.
+### The NEMA ICS 18 wiring type shall be as indicated in the datasheet.
−### Barriers shall prevent propagation of an arcing fault from one compartment to adjacent compartments.
+```datasheet
+label: Wiring Type per NEMA ICS 18
+type: select
+options:
+ - "Type A"
+ - "Type B-D"
+ - "Type B-T"
+ - "Type C"
+```
−### Each plug-in unit shall be installed in an individual compartment with a hinged door interlocked to the unit's branch disconnect such that the door cannot be opened with the disconnect in the ON position unless the interlock is defeated by a tool.
+### Type A furnishes no terminal blocks, so field control and load conductors land directly on the device terminals within the unit; Type B-D furnishes unit terminal blocks for control conductors with load conductors landing on the disconnect or the overload relay inside the unit; Type B-T furnishes unit control terminal blocks and, for the smaller units, load terminal blocks mounted in the vertical wireway so that a load conductor can be landed without opening the unit; Type C extends the control conductors of every unit to master terminal blocks at the top or bottom of each section, with the option of load terminal blocks there as well. {note}
−## Arc Flash Mitigation {toc}
+### Each step from Type A toward Type C moves more of the field termination out of the unit and toward a point the installer can reach without opening a door, at the cost of terminal blocks, wire, and section space; a Type C assembly is also the one in which a unit can be exchanged without disturbing any field-landed control conductor. {note}
−### Where arc energy reduction is required, the method shall be as indicated in the datasheet.
+### Where a wiring type with terminal blocks is selected, every terminal block shall be permanently marked with the conductor designations shown on the schematic diagrams.
+### Control wiring within a unit and between units shall be stranded copper, not smaller than 16 AWG, and the source of every control circuit shall be identified at the unit.
+
+# Arc-Flash Mitigation and Maintenance Safety {toc}
+
+## Arc Energy Reduction {toc}
+
+### Where a circuit breaker in the assembly is rated or can be adjusted to 1200 A or more, arc energy reduction shall be provided in accordance with NFPA 70 240.87 by the method indicated in the datasheet.
+
```datasheet
label: Arc Energy Reduction Method
type: select
+derived: "NFPA 70 240.87 applied to the rating of the main device and of each feeder device shown on the one-line diagram"
options:
− - "Not required — no device rated 1200A or more"
− - "Energy-reducing maintenance switch (ERMS) on main and feeders 1200A and above"
− - "Zone-selective interlocking (ZSI) on electronic trip devices"
− - "Arc-resistant construction tested per IEEE C37.20.7"
+ - "Not applicable, no device rated 1200 A or more"
+ - "Energy-reducing maintenance switching with local status indicator"
+ - "Zone-selective interlocking"
+ - "Differential relaying"
+ - "Energy-reducing active arc-flash mitigation system"
+ - "Instantaneous trip setting below the available arcing current"
+default: derived
```
−### Whether arc energy reduction is required at all is fixed by NFPA 70 Article 240.87 from the breaker rating, so only the means of providing it is a project selection. {note}
+### Whether arc energy reduction is required is fixed by the device rating, so the field carries the consequence of the one-line diagram; only the method is a project selection where the threshold is met. {note}
−### NFPA 70 Article 240.87 requires arc energy reduction on circuit breakers rated 1200A or more. {note}
+### An energy-reducing maintenance switch lowers the instantaneous pickup for the duration of the work and depends on a worker turning it on; zone-selective interlocking and differential relaying act without a worker's intervention but need the downstream devices or the current transformers to be part of the scheme; an active mitigation system detects the arc itself by light and current and clears it faster than any trip unit, at the highest cost. {note}
−### For MCC main breakers and feeder breakers meeting the 1200A threshold, an Energy Reducing Maintenance Switch (ERMS) or equivalent reduction method shall be provided.
+### Where energy-reducing maintenance switching is selected, the switch shall be lockable in the maintenance position and its status shall be indicated at the switch and, where a network is furnished, over the network.
−### Arc flash hazard analysis shall be performed per IEEE 1584 and incidence energy labels shall be applied to every door and access location per NFPA 70 Article 110.16 and NFPA 70E.
+## Arc-Resistant Construction {toc}
−### See [[sync/low-voltage-switchgear]] for arc flash mitigation guidance applicable to upstream equipment. {note}
+### Arc-resistant construction shall be as indicated in the datasheet.
−## Infrared Scanning Provisions {toc}
+```datasheet
+label: Arc-Resistant Construction
+type: select
+options:
+ - "Not required"
+ - "Type 1 accessibility per IEEE C37.20.7"
+ - "Type 2 accessibility per IEEE C37.20.7"
+ - "Type 2B accessibility per IEEE C37.20.7"
+```
−### Enclosure shall include removable infrared inspection windows or cover plates at each main bus joint, each vertical bus stab tier, and the main incoming lugs.
+### Arc-resistant construction directs the products of an internal arcing fault away from the front of the assembly, and Type 2 extends that protection to the sides and rear; Type 2B additionally keeps the protection with a unit door open for the low-voltage control compartment. It protects a worker standing at the assembly during an arcing fault with the doors closed and latched, and it adds a plenum, reinforced doors, and pressure-relief flaps that raise the height and the cost of every section. {note}
−### Windows shall allow thermographic inspection of energized connections without removing live-parts barriers.
+### Where arc-resistant construction is selected, the assembly shall have been tested to IEEE C37.20.7 in the configuration furnished, and the exhaust plenum and its discharge location shall be shown on the shop drawings.
−# Plug-In Unit Construction {toc}
+### Arc-resistant construction does not lower the incident energy at a unit whose door is open, and does not substitute for the arc energy reduction required by NFPA 70 240.87. {note}
−## Unit Sizes {toc}
+## Maintenance Safety Provisions {toc}
−### The unit mounting arrangement shall be as indicated in the datasheet.
+### The maintenance safety provisions furnished shall be as indicated in the datasheet.
```datasheet
−label: Unit Mounting
−type: radio
+label: Maintenance Safety Provisions
+type: checkbox
options:
− - "Plug-in (stab-on) units"
− - "Frame-mounted (bolt-on) units for the largest frames"
− - "Mixed - plug-in below the specified frame, frame-mounted above"
−default: "Plug-in (stab-on) units"
+ - "Infrared inspection windows at bus joints and main terminations"
+ - "Voltage presence indicator at each unit"
+ - "Absence-of-voltage tester at the main device"
+ - "Remote operator for the main device"
+ - "Unit test position with control power available"
```
−### Plug-in unit compartments shall be sized in standard NEMA ICS 18 increments to permit interchange of units of equal size between compartments.
+### Each provision lets a task be performed with less exposure than the alternative: an infrared window lets a bus joint be scanned under load with the cover on, a voltage indicator confirms the state of a unit before its door is opened, an absence-of-voltage tester verifies a de-energized state without a handheld meter, a remote operator lets the main be closed from outside the arc-flash boundary, and a test position lets a unit's control circuit be checked with its power stabs disengaged. {note}
−### Sixth-, quarter-, half-, three-quarter-, and full-section unit heights shall be available.
+### Arc-flash incident energy labels shall be applied to each section in accordance with NFPA 70 110.16 and NFPA 70E, with the values taken from the study performed under [[sync/arc-flash-study]].
−### Each compartment shall be furnished with a separately operable hinged door with a viewing window where pilot devices are mounted.
+# Plug-In Units {toc}
−### Plug-in units engage the vertical bus through self-aligning stab connectors and engage the ground bus through an independent ground stab that makes before and breaks after the line stabs.
+## Unit Construction {toc}
−### Frame-mounted units are used for the largest motor starter frames (typically NEMA Size 5 and above) and for VFD units exceeding the largest plug-in compartment dimension; frame-mounted units are bolted to the assembly structure and field-wired to the bus. {note}
+### Units shall be plug-in units that engage the vertical bus through self-aligning, spring-loaded stab connectors, except where the unit exceeds the largest plug-in frame the manufacturer furnishes.
−## Combination Motor Starters {toc}
+### A unit larger than the largest plug-in frame shall be a frame-mounted unit bolted to the structure and connected to the bus by bolted connections made by the manufacturer.
−### Combination motor starters shall comply with NEMA ICS 2 and UL 845.
+### Units shall be built in the standard NEMA ICS 18 compartment increments so that a unit can be moved to any compartment of the same size in the assembly.
−### The branch disconnect type shall be as indicated in the datasheet.
+### Each plug-in unit shall have a positive latch that holds it in the connected position, and a withdrawal mechanism that disengages the stabs without pulling on the unit door or its devices.
+### Each plug-in unit shall be capable of being withdrawn to a position in which its power stabs are disengaged and the unit remains supported by the structure.
+
+### Each unit compartment shall carry a nameplate on the door and a matching designation inside the compartment, so that a withdrawn unit and its compartment can be matched.
+
+## Combination Starter Units {toc}
+
+### Combination starter units shall comply with NEMA ICS 2 and UL 845, and each shall consist of a unit disconnect, a contactor, an overload relay, a control power source, and the pilot devices, assembled and wired by the manufacturer in one unit.
+
+### The unit disconnect of a combination starter unit shall be as indicated in the datasheet.
+
```datasheet
−label: Branch Disconnect Type
+label: Combination Starter Unit Disconnect Type
type: select
options:
− - "Motor circuit protector (instantaneous-trip circuit breaker)"
− - "Thermal-magnetic molded case circuit breaker"
+ - "Instantaneous-trip circuit breaker"
+ - "Thermal-magnetic circuit breaker"
- "Fusible disconnect switch"
−default: "Motor circuit protector (instantaneous-trip circuit breaker)"
```
−### The predominant starter type in the assembly shall be as indicated in the datasheet.
+### An instantaneous-trip circuit breaker carries no thermal element and is adjusted above the motor inrush so that it clears only faults, leaving running overload protection to the overload relay; it is listed for use only as part of a tested combination and offers the closest coordination with a motor's starting current. A thermal-magnetic breaker adds its own thermal element as a second layer of overload protection, which lets it stand alone but which can trip on a long start unless it is sized above the inrush. A fusible switch provides the highest interrupting rating in the smallest unit and clears a high-magnitude fault fastest, at the cost of a fuse replacement after every fault and a single-phasing exposure that the overload relay must cover. {note}
+### Where an instantaneous-trip circuit breaker is selected, its trip setting shall be set within the range NFPA 70 430.52 permits for the motor served and shall be recorded in the closeout submittals.
+
+### Where a fusible disconnect switch is selected, the fuse class and the rejection feature shall be as indicated on [[drawing: the motor control center schedule]].
+
+### The coordination type of each combination starter unit shall be as indicated in the datasheet.
+
```datasheet
−label: Starter Type
−type: select
+label: Combination Controller Coordination Type
+type: radio
options:
− - "Full-voltage non-reversing (FVNR)"
− - "Full-voltage reversing (FVR)"
− - "Two-speed (constant or variable torque)"
− - "Reduced voltage soft starter (RVSS)"
− - "Variable frequency drive (VFD)"
− - "Wye-delta (closed transition)"
− - "Autotransformer reduced voltage"
−default: "Full-voltage non-reversing (FVNR)"
+ - "Type 1"
+ - "Type 2"
```
−### The largest NEMA starter size in the assembly shall be as indicated in the datasheet.
+### Under UL 60947-4-1, a Type 1 coordinated combination survives a short circuit without hazard to persons or to the installation but may need its contactor or overload relay replaced before it is returned to service; a Type 2 coordinated combination is tested so that the contactor and overload relay remain serviceable after the fault, with light contact welding that can be separated permitted. Type 2 coordination is reached by pairing a specific disconnect with a specific contactor and overload relay, and is used where the time to return a motor to service after a fault matters more than the cost of the tested pairing. {note}
+### The coordination type shall be established by a tested combination published by the manufacturer, and the tested pairing shall be identified in the unit bill of material.
+
+## Reduced-Voltage Starter Units {toc}
+
+### The units that start at reduced voltage shall be as indicated on [[drawing: the motor control center schedule]].
+
+### The reduced-voltage starting method for those units shall be as indicated in the datasheet.
+
```datasheet
−label: NEMA Starter Size (Maximum in Assembly)
+label: Reduced-Voltage Starting Method
type: select
−drawing_ref: "motor schedule"
options:
− - "Size 1 (up to 10 HP at 480V)"
− - "Size 2 (up to 25 HP at 480V)"
− - "Size 3 (up to 50 HP at 480V)"
− - "Size 4 (up to 100 HP at 480V)"
− - "Size 5 (up to 200 HP at 480V)"
− - "Size 6 (up to 400 HP at 480V)"
−default: deferred
+ - "Solid-state soft starter"
+ - "Autotransformer, closed transition"
+ - "Wye-delta, closed transition"
+ - "Wye-delta, open transition"
+ - "Part-winding"
+ - "Primary resistor"
```
−### The overload relay type shall be as indicated in the datasheet.
+### A solid-state soft starter ramps the voltage continuously and can also stop the motor gently, and its starting current is adjustable after installation; an autotransformer starter delivers the highest starting torque per ampere of line current of the electromechanical methods; a wye-delta starter needs a motor wound with both ends of each phase brought out; part-winding needs a motor wound for it; and a primary resistor starter dissipates the starting energy as heat. The electromechanical methods start at a fixed reduction set by their taps or their winding, and an open-transition method draws a second inrush at the transition that a closed-transition method avoids. {note}
+### Where a solid-state soft starter is selected, the bypass arrangement shall be as indicated in the datasheet.
+
```datasheet
−label: Overload Relay Type
+label: Soft Starter Bypass Arrangement
type: radio
options:
− - "Electronic (solid-state) with class selection"
− - "Bimetallic thermal"
−default: "Electronic (solid-state) with class selection"
+ - "No bypass contactor"
+ - "Integral bypass contactor"
+ - "Separate full-rated bypass contactor"
```
−### The unit control voltage shall be as indicated in the datasheet.
+### A soft starter without a bypass carries the running current through its power semiconductors for the whole run and dissipates their conduction loss continuously, so the unit is sized and ventilated for that heat; an integral bypass contactor carries the running current once the motor is at speed, removes the running loss, and lets the unit run cooler, but it is rated to close and carry rather than to start; a separate full-rated bypass contactor can start the motor across the line with the soft starter out of service, at the cost of a contactor of the full starter size. The running loss is what makes a bypass worth its cost on a large motor that runs continuously, and what makes it unnecessary on a small motor that runs briefly. {note}
+### Reduced-voltage starter units shall include a running overload relay that protects the motor through the start as well as during the run.
+
+## Contactors and Overload Relays {toc}
+
+### The contactor rating basis shall be as indicated in the datasheet.
+
```datasheet
−label: Control Voltage
−type: select
+label: Contactor Rating Basis
+type: radio
options:
− - "120V AC from unit-mounted control transformer"
− - "24V DC from common DC control bus"
− - "Line voltage (240V, 480V) - no transformer"
−default: "120V AC from unit-mounted control transformer"
+ - "NEMA-rated per NEMA ICS 2"
+ - "IEC-rated per UL 60947-4-1"
+default: "NEMA-rated per NEMA ICS 2"
```
−### Each combination starter unit shall consist of an integral branch disconnect, a magnetic motor contactor, an overload relay, control transformer (where required), and pilot devices, assembled and wired by the manufacturer in a single plug-in compartment.
+### A NEMA-rated contactor is rated by size for any motor of that horsepower on any duty, with a contact mass sized accordingly; an IEC-rated contactor is rated by utilization category for the specific duty applied, so a smaller and less expensive contactor can serve the same motor where the duty is known and stays within the category, and a larger one is needed where it does not. The difference shows in a high-cycle or plugging duty, where a contactor sized to its rated category has less margin than the NEMA size, and in the space a unit needs. {note}
−### Motor circuit protectors (MCPs) are instantaneous-trip (magnetic) breakers sized for short-circuit and ground-fault protection of the motor branch circuit while the overload relay provides running overload protection per NFPA 70 Article 430. {note}
+### Contactors shall be rated for the horsepower and voltage of the motor served, with the size or utilization category stated in the unit bill of material.
−### MCPs are preferred for combination starters because the magnetic-only design allows trip setting coordination with motor inrush characteristics. {note}
+### The overload relay type shall be as indicated in the datasheet.
−### Thermal-magnetic breakers are acceptable where MCPs are unavailable for the required frame size, and fusible switches are appropriate where high interrupting capacity is required without breaker upgrade. {note}
+```datasheet
+label: Overload Relay Type
+type: select
+options:
+ - "Electronic"
+ - "Bimetallic thermal"
+ - "Eutectic melting-alloy thermal"
+default: "Electronic"
+```
−### Full-voltage non-reversing is the most common configuration for HVAC fans and pumps not requiring reduced-voltage starting or variable speed control. {note}
+### An electronic overload relay measures the motor current directly and adds phase loss, phase unbalance, and ground-fault sensing, a selectable trip class, and a communications interface where one is furnished, which is why it has become the relay the assemblies are built with; a bimetallic relay trips on the heat of a heater element and is adjustable within a range; a melting-alloy relay trips when its solder pot melts and is set by the heater installed, with no adjustment and no additional protection. {note}
−### Reduced voltage soft starters and VFDs are required for motors where in-rush current exceeds utility or generator source capacity, where mechanical shock loading must be reduced, or where variable speed control is required for process or energy conservation.
+### The overload relay trip class shall be as indicated in the datasheet.
−### Selection of soft starter versus VFD shall be based on whether continuous speed control is required (VFD) or only controlled starting and stopping (soft starter).
+```datasheet
+label: Overload Relay Trip Class
+type: range
+options:
+ min: 5
+ max: 30
+ setpoints: [5, 10, 15, 20, 30]
+default: 20
+```
−### Individual starter sizes for each motor shall be selected by the manufacturer based on the connected motor horsepower and service factor with no derating below NEMA ICS 2 published ratings.
+### Where a different trip class is indicated for a unit on [[drawing: the motor control center schedule]], that class shall govern for that unit.
−### IEC-rated contactors shall not be substituted for NEMA-rated contactors except where specifically approved by the Engineer.
+### The trip class is the number of seconds within which the relay trips at 600% of its setting; Class 20 is the class NEMA ICS 2 establishes for general-purpose motors, Class 10 protects a motor that reaches temperature quickly, and Class 30 rides through the long start of a high-inertia load that a lower class would trip on. {note}
−### IEC contactors generally have lower thermal mass and shorter expected mechanical life under high-cycle service. {note}
+### Each overload relay shall be selected and set for the full-load current and the service factor of the motor served, in accordance with NFPA 70 430.32.
−### Electronic overload relays provide selectable trip class (Class 10, 20, or 30) to match motor starting characteristics, ground fault sensing, phase loss and phase imbalance protection, and communications interfaces for status and trip reporting. {note}
+### Each overload relay shall have a manual reset accessible from the front of the closed unit door, and the reset provisions for remote or automatic reset shall be furnished only where indicated on [[drawing: the motor control center schedule]].
−### Bimetallic thermal overloads are acceptable for small simple FVNR starters where the additional functionality of electronic relays is not required. {note}
+## Control Power {toc}
−### Unit-mounted control transformers shall be sized for the connected pilot device load plus 50% spare capacity, with primary and secondary fusing per NFPA 70 Article 450.
+### The control voltage for starter units shall be as indicated in the datasheet.
−### Common 24V DC control buses are preferred where the MCC integrates with a PLC or DCS using 24V DC field devices; coordinate the control voltage selection with [[sync/building-automation-system]] or the process control standard.
+```datasheet
+label: Control Voltage
+type: select
+options:
+ - "120 V AC from a control power transformer in each unit"
+ - "120 V AC from a common control power transformer with a control power bus"
+ - "24 V DC from a common control power supply with a control power bus"
+ - "24 V AC from a control power transformer in each unit"
+ - "Line voltage without a transformer"
+default: "120 V AC from a control power transformer in each unit"
+```
−## Variable Frequency Drive Units {toc}
+### A transformer in each unit keeps every unit self-contained and lets it be tested and exchanged without a common control source; a common control power source removes a transformer from every unit and reduces heat and unit size, at the cost of a single source whose loss stops every motor it controls. A 24 V DC control source is the arrangement used where the unit control circuits interface directly with a programmable controller's field wiring, and a line-voltage control circuit is the arrangement a small assembly uses where no pilot device is touched by an operator. {note}
−### VFD bypass provisions shall be as indicated in the datasheet.
+### Where a control power transformer is furnished in a unit, it shall be sized for the connected control load, including the contactor coil inrush, with primary and secondary overcurrent protection in accordance with NFPA 70 Article 430 Part VI.
+### Where a common control power source is furnished, its loss shall be alarmed, and its distribution to the units shall be through a control power bus furnished by the manufacturer.
+
+## Pilot Devices {toc}
+
+### Each starter unit shall be furnished with the door-mounted devices indicated in the datasheet.
+
```datasheet
−label: VFD Bypass Requirement
−type: radio
+label: Starter Unit Door Devices
+type: checkbox
options:
− - "No bypass"
− - "Manual bypass (across-the-line, manual transfer)"
− - "Automatic bypass on drive fault (across-the-line, automatic transfer)"
−default: "No bypass"
+ - "Hand-off-automatic selector switch"
+ - "Start and stop pushbuttons"
+ - "Run pilot light"
+ - "Stopped pilot light"
+ - "Overload trip pilot light"
+ - "Elapsed time meter"
+ - "Ammeter"
+ - "Overload reset button"
+default:
+ - "Hand-off-automatic selector switch"
+ - "Run pilot light"
+ - "Overload reset button"
```
−### VFD units installed in MCC plug-in compartments shall comply with UL 61800-5-1 and shall be mounted, wired, and cooled within the compartment per the drive manufacturer's published requirements.
+### Where different door-mounted devices are indicated for a unit on [[drawing: the motor control center schedule]], those devices shall be furnished on that unit in place of the datasheet selection.
−### Compartment ventilation shall accommodate the drive's continuous heat dissipation at full load and ambient.
+### The run pilot light color shall be as indicated in the datasheet.
−### Where the drive heat dissipation exceeds the compartment's natural ventilation capacity, a forced-air cooled compartment or a frame-mounted drive shall be specified.
+```datasheet
+label: Run Pilot Light Color
+type: radio
+options:
+ - "Red"
+ - "Green"
+```
−### For HVAC service VFD units, the drive performance, harmonic mitigation, and configuration requirements of [[sync/hvac-variable-frequency-drives]] shall govern in addition to the MCC unit compartment requirements of this standard.
+### Two conventions are in use and each is coherent on its own terms: one uses red for running because a running motor is the energized and hazardous state, and green for stopped; the other uses green for running and red for stopped or tripped, following the traffic convention. The colors need to match the convention already used in the facility and in the control system graphics, which is why the field asserts no default. {note}
−### VFD bypass adds an across-the-line starter and contactor arrangement that can run the motor at full speed if the drive fails. {note}
+### The pilot light type shall be as indicated in the datasheet.
−### Bypass is recommended for life-safety and essential service motors (smoke control fans, critical pumps) but is not necessary for general HVAC service where temporary motor outages during drive repair are acceptable. {note}
+```datasheet
+label: Pilot Light Type
+type: radio
+options:
+ - "LED, push-to-test"
+ - "Incandescent, transformer type"
+default: "LED, push-to-test"
+```
−### Bypass increases the unit size by approximately one size and adds cost; coordinate the requirement with the building operations plan. {note}
+### Each starter unit shall be furnished with not fewer than one normally open and one normally closed spare auxiliary contact on the contactor, wired to the unit terminal blocks where terminal blocks are furnished.
−## Soft Starter Units {toc}
+## Feeder Units {toc}
−### The soft starter construction shall be as indicated in the datasheet.
+### Feeder units shall be furnished where indicated on [[drawing: the motor control center schedule]].
+### The feeder unit device type shall be as indicated in the datasheet.
+
```datasheet
−label: Soft Starter Type
+label: Feeder Unit Device Type
type: select
options:
− - "Solid-state (SCR-based) with electronic ramp"
− - "Solid-state with bypass contactor (energized at full speed)"
−default: "Solid-state with bypass contactor (energized at full speed)"
+ - "Thermal-magnetic circuit breaker"
+ - "Electronic-trip circuit breaker"
+ - "Fusible disconnect switch"
```
−### Solid-state soft starters with run bypass contactors are preferred for motors above 25 HP because the bypass contactor carries the running current after the motor reaches full speed, eliminating SCR heat dissipation at steady state and extending equipment life. {note}
+### A feeder unit serves a load that is not a motor controlled from the assembly, such as a panelboard, a transformer, or a packaged equipment item with its own controller, and its device is selected for that load rather than for a motor. {note}
−### Soft starters without bypass dissipate continuous heat through the SCRs and are limited to lower HP applications or duty cycles. {note}
+### Feeder unit devices shall be rated for the available fault current at the unit or shall be part of a series-rated combination where series rating is the assembly rating basis.
+## Variable Frequency Drive Units {toc}
+
+### Variable frequency drive units shall be furnished where indicated on [[drawing: the motor control center schedule]], and the drive performance, harmonic treatment, bypass arrangement, and configuration shall comply with [[sync/hvac-variable-frequency-drives]].
+
+### Each drive unit shall be listed to UL 61800-5-1 and installed by the manufacturer in a unit of its own construction, with the cooling the drive needs at full output current at the design ambient temperature of the assembly.
+
+### A drive whose heat dissipation exceeds what a plug-in compartment can ventilate shall be furnished in a frame-mounted unit with forced ventilation, and the manufacturer shall identify each such unit on the unit arrangement drawings.
+
+### Each drive unit shall have its own unit disconnect, interlocked with the unit door in the same manner as a starter unit.
+
## Metering Units {toc}
−### The extent of metering provided in the assembly shall be as indicated in the datasheet.
+### The metering furnished in the assembly shall be as indicated in the datasheet.
```datasheet
−label: Metering Configuration
+label: Metering Extent
type: select
options:
- "No metering"
- "Main incoming metering"
− - "Main and feeder metering"
− - "Main and per-motor metering"
−default: "Main incoming metering"
+ - "Main incoming and feeder unit metering"
+ - "Main incoming and per-motor metering"
```
−### The metered quantities and recording functions shall be as indicated in the datasheet.
+### Meters and their current transformers shall comply with [[sync/electrical-power-monitoring]], and shall be installed by the manufacturer in a unit or an instrument compartment of the manufacturer's construction.
−```datasheet
−label: Meter Functions
−type: checkbox
−options:
− - "Voltage (L-L, L-N all phases)"
− - "Current (per phase)"
− - "Power factor (per phase and total)"
− - "kW / kVA / kVAR (demand and instantaneous)"
− - "kWh / kVARh energy accumulation"
− - "Harmonics (THD per phase, individual to 31st)"
− - "Min/max recording with time stamp"
− - "Waveform capture (on event)"
−default:
− - "Voltage (L-L, L-N all phases)"
− - "Current (per phase)"
− - "Power factor (per phase and total)"
− - "kW / kVA / kVAR (demand and instantaneous)"
− - "kWh / kVARh energy accumulation"
− - "Min/max recording with time stamp"
−```
+### Per-motor metering makes each motor's power and energy visible for commissioning, fault diagnosis, and measurement and verification, at the cost of a meter and current transformers in every unit; where an electronic overload relay with a network interface is furnished, it already reports current and can report power on some models, which covers much of what per-motor metering is bought for. {note}
−### Where building energy code requires submetering of motor loads (ASHRAE 90.1 Section 8.4.3 or local amendments), kWh accumulation shall be a minimum required function and shall be accessible to the building automation system.
+### Where [[parameter: adopted-energy-code]] requires the motor loads served from the assembly to be submetered, the metering shall accumulate energy for those loads and shall report it to the building automation system.
−### Per-motor metering supports mechanical system commissioning, fault detection and diagnostics, and ongoing energy verification but adds material cost and is appropriate only for the largest motors and for facilities with measurement and verification programs in place. {note}
+# Communications {toc}
−# Common Control and Communications {toc}
+## Network Protocol {toc}
−## Common Control Bus {toc}
+### The communications protocol of the assembly network shall be as indicated in the datasheet.
−### Where Class I or Class II Type C wiring is specified, the assembly shall include a common control bus consisting of master terminal blocks at the top or bottom of each vertical section, with all unit-to-unit control conductors terminated at the master terminal blocks for field cross-connection.
−
−### Master terminal blocks shall be permanently identified with conductor designations matching the schematic diagrams.
−
−## Communications Network {toc}
−
−### Where a communications network is provided, the protocol shall be as indicated in the datasheet and shall be supported by the Owner's building automation or process control system.
−
```datasheet
label: Communications Protocol
type: select
options:
− - "No communications"
− - "Modbus RTU (RS-485 daisy-chain)"
− - "Modbus TCP/IP (Ethernet)"
+ - "No network"
+ - "Modbus RTU"
+ - "Modbus TCP"
- "EtherNet/IP"
- "PROFINET"
− - "PROFIBUS-DP"
+ - "PROFIBUS DP"
- "DeviceNet"
+ - "BACnet/IP"
+ - "BACnet MS/TP"
```
−### The protocol field is left blank on assemblies furnished without a communications network. {note}
+### The protocol has to match the system the assembly reports to; an assembly serving building mechanical equipment reports to the building automation system under [[sync/building-automation-system]], and one serving process equipment reports to the control system under [[sync/process-control-networks]]. {note}
−### The network topology shall be as indicated in the datasheet.
+### Where a network is furnished, the devices connected to it shall be as indicated in the datasheet.
```datasheet
−label: Communications Network Topology
−type: radio
+label: Networked Devices
+type: checkbox
options:
− - "Single network (all devices on one segment)"
− - "Segmented (drives/metering on separate segment from starters)"
− - "Redundant ring (managed switches with ring protocols)"
−default: "Single network (all devices on one segment)"
+ - "Electronic overload relays"
+ - "Soft starters"
+ - "Variable frequency drives"
+ - "Meters"
+ - "Main circuit breaker trip unit"
+ - "Feeder unit electronic trip units"
```
−### Where a communications network is specified, every electronic overload relay, soft starter, VFD unit, and metering device shall be furnished with a network interface compatible with the selected protocol.
+### Where a network is furnished, the network topology within the assembly shall be as indicated in the datasheet.
−### Network cabling, switches (for Ethernet protocols), and termination components shall be furnished within the MCC enclosure.
−
−### Network address assignments shall be documented on the submittal documents and updated on the as-built drawings.
−
−### For Ethernet-based protocols, redundant ring topologies using managed switches with rapid spanning tree or DLR (Device Level Ring) are appropriate for facilities where loss of motor status visibility would interrupt critical operations. {note}
−
−### For typical commercial HVAC service, a single network with unmanaged switches is sufficient. {note}
−
−### Coordinate the communications network design with [[sync/building-automation-system]] and with the building's overall converged network architecture.
−
−# Finish and Identification {toc}
−
−## The enclosure finish color shall be as indicated in the datasheet.
−
```datasheet
−label: Finish Color
−type: text
−default: "ANSI 61 gray"
+label: Network Topology
+type: radio
+options:
+ - "Single segment"
+ - "Segmented by device type"
+ - "Redundant ring"
```
−## Enclosure shall receive a minimum two-coat paint system: corrosion-resistant primer and manufacturer's standard polyester powder coat finish.
+### A single segment is the least equipment and the arrangement most assemblies are built with; segmenting keeps the high-traffic drives and meters off the segment the overload relays share; a redundant ring, using managed switches that support a ring protocol, keeps every device reachable after a single cable or switch failure, at the cost of managed switches and the configuration they need. {note}
−## Minimum total dry film thickness shall be 3 mils (75 microns).
+### Where a network is furnished, the network cable, the switches, the terminations, and the power supplies for the network shall be installed by the manufacturer within the assembly, and the network shall be brought to a terminal or a connector in a designated compartment for the field connection.
−## For installations classified C3 or higher, an enhanced paint system with a minimum 5 mils dry film thickness shall be applied.
+### Network cable inside the assembly shall be routed separately from the power conductors, and where it must cross a power conductor it shall cross at a right angle.
−## Labeling {toc}
+### Each networked device shall be assigned an address on the network address list submitted with the action submittals, and the address shall be marked inside the unit.
−### Manufacturer shall provide engraved nameplates for the MCC assembly, each vertical section, and each plug-in unit.
+# Identification {toc}
−### Nameplates shall identify:
+## Nameplates shall be furnished on the assembly, on each vertical section, and on each unit, and shall comply with [[sync/electrical-identification]] for material, lettering, and attachment.
−- MCC designation and one-line reference
−- Bus ratings (voltage, continuous current, short-circuit current rating)
−- Unit designation matching the one-line diagram and motor schedule
−- Connected motor designation, horsepower, full-load amps, and service
−- Branch device frame size and trip rating
−- Arc flash warning labels per NFPA 70E and IEEE 1584
+## The assembly nameplate shall state the assembly designation, the system voltage, the horizontal bus rating, the assembly short-circuit current rating, the series-rated combinations where series rating is the basis, and the source that feeds the assembly.
−### The nameplate material shall be as indicated in the datasheet.
+## Each unit nameplate shall state the unit designation, the load served, and for a starter unit the motor horsepower and full-load current, in the text listed on the nameplate schedule.
−```datasheet
−label: Nameplate Material
−type: radio
−options:
− - "Laminated phenolic (indoor)"
− - "Stainless steel (outdoor or corrosive)"
− - "Aluminum (anodized)"
−default: "Laminated phenolic (indoor)"
−```
+## The unit designation on the nameplate shall match the designation on the motor control center schedule, on the disconnect at the motor, and on the motor itself.
−### Unit designations and connected motor designations shall match the labels installed at each motor and at each disconnect switch downstream of the MCC, supporting trouble-shooting and lockout/tagout procedures.
+## A unit designation that differs between the assembly, the schedule, and the motor is the most common cause of a lockout applied to the wrong unit, which is why the three are required to agree. {note}
+## The available fault current and the date it was calculated shall be marked on the assembly in accordance with NFPA 70 110.24 where the assembly is service entrance equipment.
+
# Testing {toc}
## Factory Tests {toc}
−### The manufacturer shall perform the following production tests on the completed MCC assembly per UL 845 and NEMA ICS 18:
+### The manufacturer shall perform the production tests of UL 845 and NEMA ICS 18 on the completed assembly, including a dielectric withstand test of the bus, a continuity check of every control circuit against the schematic diagrams, a mechanical operation check of every unit and door interlock, and a functional check of every unit.
−- 60 Hz dielectric withstand test on horizontal and vertical bus
−- Insulation resistance measurement on each phase bus and the neutral bus
−- Mechanical operation of each plug-in unit (insertion, removal, door interlock)
−- Functional test of each combination starter (manual close/open, overload trip simulation)
−- Functional test of each VFD and soft-start unit per the device manufacturer's test specification
−- Current transformer ratio and polarity test (where CTs are installed)
−- Control wiring continuity verification against the as-built schematics
−- Communications network point-to-point continuity (where networks are installed)
−- Visual and dimensional inspection
−
### Factory acceptance test witnessing shall be as indicated in the datasheet.
```datasheet
−label: Factory Acceptance Test
+label: Factory Acceptance Test Witnessing
type: radio
options:
− - "Witnessed by Owner's representative"
− - "Unwitnessed with certified test report"
− - "Not required beyond standard production tests"
−default: "Unwitnessed with certified test report"
+ - "Witnessed by the Owner's representative"
+ - "Unwitnessed with a certified test report"
+default: "Unwitnessed with a certified test report"
```
−### Where witnessed factory testing is specified, the manufacturer shall provide a minimum of two weeks advance notice of test readiness.
+### Where witnessed testing is indicated, the manufacturer shall give the Owner not less than two weeks notice of test readiness, and the test procedure shall have been submitted and returned before the test date.
−### Test procedures shall be submitted for review prior to testing.
+### A witnessed test lets the Owner see every unit operate and every interlock work before the assembly ships, and it commits a representative to a trip to the factory; a certified report records the same tests without the trip, and leaves any discrepancy to be found at field acceptance testing instead. {note}
## Field Acceptance Tests {toc}
−### Where independent NETA testing is indicated in the datasheet, Contractor shall engage a qualified independent testing firm to perform acceptance testing per NETA ATS Section 7.16 (Motor Control Centers).
+### Field acceptance testing shall be performed after installation is complete and before the assembly is energized, in accordance with ANSI/NETA ATS Section 7.16 and with [[sync/electrical-acceptance-testing]].
−### Testing shall occur after installation is complete and before the equipment is energized.
+### Field acceptance tests shall include, at minimum:
−### The scope of field testing and startup services shall be as indicated in the datasheet.
+- visual and mechanical inspection of every section and unit, including bus splice bolt torque against the manufacturer's values
+- insulation resistance of the horizontal and vertical bus, phase-to-phase and phase-to-ground, with each unit withdrawn
+- contact resistance of every bolted bus joint
+- insertion and withdrawal of every plug-in unit, with the ground stab verified to engage first and release last
+- functional operation of every unit disconnect and door interlock
+- primary current injection of every overload relay at one point on its trip curve, or secondary injection where the relay accepts it
+- functional test of every starter, soft starter, and drive unit through its control circuit
+- verification of every networked device at its address
+- functional test of every interlock, alarm, and remote control point against the control diagrams
+### A unit or a joint that fails an acceptance test shall be corrected and retested, and the cost of the correction and the retest shall be borne by the Contractor.
+
+### Manufacturer start-up shall be provided where indicated in the datasheet.
+
```datasheet
−label: Field Testing Requirements
+label: Manufacturer Start-Up
type: radio
options:
− - "NETA acceptance testing and manufacturer startup"
− - "NETA acceptance testing without manufacturer startup"
− - "Manufacturer startup without independent NETA testing"
−default: "NETA acceptance testing and manufacturer startup"
+ - "Manufacturer's field service present at energization and start-up"
+ - "Not required"
```
−### Field acceptance tests shall include as a minimum:
+### Infrared thermographic inspection shall be as indicated in the datasheet.
−- Visual and mechanical inspection of all sections and units
−- Insulation resistance testing of horizontal and vertical bus (phase-to-phase and phase-to-ground)
−- Contact resistance measurement on all bolted bus connections
−- Plug-in unit insertion and withdrawal verification on every compartment
−- Overload relay primary current injection at one trip setpoint per relay
−- Branch device functional test (manual operation, trip indication)
−- VFD and soft-start unit commissioning per the device manufacturer's startup procedure
−- Communications network functional verification (every connected device responds at its address)
−- Ground continuity measurement from each unit compartment ground stab to the ground bus
−- Functional testing of all interlocks, alarms, and remote control points
−
−### The infrared thermographic inspection schedule shall be as indicated in the datasheet.
−
```datasheet
label: Infrared Thermographic Inspection
−type: radio
+type: select
options:
− - "Initial scan within 90 days of energization, follow-up at 11 months"
− - "Initial scan within 90 days of energization"
- "Not required"
−default: "Initial scan within 90 days of energization, follow-up at 11 months"
+ - "One inspection within 90 days of energization"
+ - "One inspection within 90 days of energization and a second at eleven months"
```
−### Where an infrared scan is indicated in the datasheet, it shall be performed under normal operating load conditions (minimum 40% of rated load on each scanned circuit).
+### Where infrared inspection is indicated, it shall be performed with the assembly carrying not less than 40% of its rated load on each scanned circuit, and every connection showing a rise of more than 10 °C above its neighbors shall be reported and corrected.
−### All connections exceeding 10°C rise above ambient shall be reported and corrected.
+### A second inspection near the end of the first year finds the joint that loosened through the first full cycle of seasonal load, which the first inspection cannot see; it costs a second visit under load and a warranty claim filed before the warranty ends. {note}
−### Follow-up scan at 11 months captures connections that may loosen during the initial thermal cycling period and is recommended for all MCCs serving critical loads. {note}
−
# Installation {toc}
−## Concrete Housekeeping Pad {toc}
+## Foundation and Anchorage {toc}
−### MCC location and arrangement shall be [[drawing: per the equipment room layout drawings]].
+### The assembly shall be set on a concrete housekeeping pad of the height indicated in the datasheet, extending not less than 3 in. beyond the assembly base on every side.
−### Anchor bolt pattern shall be [[drawing: per the manufacturer's certified anchorage drawings]].
+```datasheet
+label: Housekeeping Pad Height
+type: range
+unit: in.
+options:
+ min: 0
+ max: 6
+ setpoints: [0, 3, 4, 6]
+default: 4
+```
−### MCCs shall be mounted on a reinforced concrete housekeeping pad extending a minimum of 3 in. beyond the base of the assembly on all sides.
+### A pad keeps the base of the assembly above a wet floor and gives the anchors something to bite into that is not the slab's reinforcing; a pad height of zero is the direct-to-slab installation used where the floor is a raised platform or the anchors go into a slab designed for them. {note}
−### Pad shall be a minimum of 4 in. above finished floor for indoor installations and 6 in. above finished grade for outdoor installations.
+### The assembly shall be anchored to the pad as indicated on [[drawing: the seismic anchorage details]], using the anchor type, size, and embedment stated there.
−### Coordinate pad dimensions, conduit penetrations, and anchor bolt locations with equipment shop drawings prior to concrete placement.
+### Where seismic qualification is required, the anchorage shall be that on which the qualification depends, and a substitute anchor shall not be used without the manufacturer's written confirmation that the qualification remains valid.
−## Equipment Setting {toc}
+### Pad dimensions, conduit stub-up locations, and anchor locations shall be coordinated with the shop drawings before the pad is placed.
−### After assembly, and before energizing, the Contractor shall verify the following:
+## Setting and Assembly {toc}
−- All shipping restraints and temporary grounds removed
−- Horizontal and vertical bus joint torque verified per the manufacturer's specifications using a calibrated torque wrench
−- All plug-in units rack and operate freely with positive ground stab engagement
−- Conduit terminations sealed and cable terminations torqued to the manufacturer's specifications
−- Space heaters energized (outdoor or unconditioned installations)
−- Working clearances per NFPA 70 Article 110.26 are maintained
+### Shipping sections shall be set, aligned, and bolted together in accordance with the manufacturer's instructions, and the horizontal bus, the neutral bus, and the ground bus shall be spliced at every shipping split with the manufacturer's splice hardware torqued to the manufacturer's values with a calibrated tool.
−### Contractor shall comply with the manufacturer's installation instructions and applicable rigging requirements.
+### Every shipping brace, block, and desiccant shall be removed before the units are inserted.
−### Remove all temporary shipping braces, blocking, and desiccants prior to final assembly.
+### Each plug-in unit shall be inserted, latched, and withdrawn once before energization to confirm free operation and positive stab engagement.
−### Verify section alignment and bolt all sections together per the manufacturer's torque specifications.
+### The Contractor shall verify that every unit compartment is occupied by a unit, a blank cover, or a shutter before the assembly is energized.
−### Make horizontal bus splice connections at each shipping split per the manufacturer's procedure using calibrated torque tools.
+## Field Wiring {toc}
−## Wiring and Terminations {toc}
+### Power and control conductors shall comply with [[sync/conductors-and-cables]] and shall enter the assembly only through the wireway areas designated on the shop drawings.
−### Power and control conductors entering and leaving the MCC shall comply with [[sync/conductors-and-cables]].
+### Raceways shall comply with [[sync/raceways-and-conduit]].
−### Conduit entries to the MCC shall comply with [[sync/raceways-and-conduit]] and shall enter the assembly only through the wireway areas designated by the manufacturer; entries through bus compartments, unit compartments, or barrier walls are prohibited.
+### Every field termination shall be torqued to the device manufacturer's published value with a calibrated tool, and the torque values applied shall be recorded in the field test report.
−### Terminations at unit terminal blocks shall be torqued to the device manufacturer's published specifications using a calibrated torque tool, and torque application shall be documented for ground, line, and load terminations.
+### Field conductor labels at every unit shall match the conductor designations on the schematic diagrams and the unit designation on the nameplate.
−### Wire labels at each unit shall match the schematic conductor designations.
+## Working Space {toc}
−## Working Clearance {toc}
+### Working space in front of the assembly, and behind and beside it where it is accessible there, shall comply with NFPA 70 110.26 for the system voltage and the accessibility of the assembly.
−### Minimum working space shall be maintained per NFPA 70 Article 110.26 based on the nominal voltage and accessibility configuration:
+### The dedicated electrical space above the assembly required by NFPA 70 110.26(E) shall be kept clear of piping, ductwork, and equipment not associated with the assembly.
−| Voltage | Condition 1 (exposed on one side) | Condition 2 (exposed on both sides) |
−|---------|-----------------------------------|--------------------------------------|
−| 0-150V | 36 in. | 36 in. |
−| 151-600V | 36 in. | 48 in. |
+### Working space shall not be used for storage at any time.
−### Working space shall not be used for storage.
−
−### Dedicated electrical space above the assembly per NFPA 70 Article 110.26(E) shall be maintained free of foreign systems including piping, ductwork, and structure not associated with the MCC.
−
# Delivery, Storage, and Handling {toc}
−## MCCs shall be shipped in the largest factory-assembled sections that can be transported to and within the installation site.
+## The assembly shall be shipped in the largest sections that the route from the delivery point to the final location will pass, and the Contractor shall verify door, corridor, and hoistway dimensions along that route before the shipping splits are fixed on the shop drawings.
−## Verify all pathway dimensions (doors, hallways, elevator shafts) between the delivery point and the final installation location prior to ordering, and coordinate shipping splits on the shop drawings.
+## Each shipping section shall be lifted only at the lifting provisions the manufacturer furnishes, with the units installed and latched.
−## Equipment shall be stored indoors in a clean, dry, climate-controlled location.
+## The assembly shall be stored indoors, in a clean, dry location protected from construction dust and from water, and shall be kept covered until it is set.
−## Where indoor climate-controlled storage is not available, the manufacturer shall provide weatherproof packaging and condensation heaters shall be connected and energized during storage if the storage period exceeds 30 days or if the storage environment is not climate-controlled.
+## Where the assembly must be stored for more than 30 days or in a space that is not conditioned, the space heaters shall be connected to a temporary supply and energized for the duration of storage.
−## Plug-in units shall remain in their factory-installed compartments during shipment and storage and shall not be removed until field acceptance testing.
+## An assembly that has been wetted in transit or in storage shall be dried, inspected by the manufacturer's field service organization, and released in writing before it is energized.
# Warranty {toc}
−## The manufacturer shall warrant the MCC for the period indicated in the datasheet.
+## The manufacturer shall warrant the assembly, its bus, and every factory-installed unit and device against defects in materials and workmanship for the period indicated in the datasheet.
```datasheet
label: Warranty Period
+type: range
+unit: years
+options:
+ min: 1
+ max: 5
+ setpoints: [1, 2, 3, 5]
+default: 1
+```
+
+## The warranty period shall commence on the date indicated in the datasheet.
+
+```datasheet
+label: Warranty Commencement
type: select
options:
− - "1 year from substantial completion"
− - "2 years from substantial completion"
− - "3 years from substantial completion"
− - "5 years from substantial completion"
−default: "1 year from substantial completion"
+ - "Date of substantial completion"
+ - "Date of energization"
+ - "Date of shipment"
```
+## Warranty commencement at shipment is the manufacturer's usual term, and it consumes the warranty during storage and construction; commencement at energization or substantial completion moves the coverage to the period the Owner is operating the equipment, and the manufacturer prices the added months into the assembly. {note}
+
## The warranty coverage scope shall be as indicated in the datasheet.
…4 unchanged lines
- "Parts only"
- "Parts and labor"
−default: "Parts only"
```
−## Additional warranty services shall be provided as indicated in the datasheet.
+## A warranty repair shall include the replacement unit or device, its installation where labor is covered, and the retest of the affected unit, and shall not reduce the coverage of any other unit in the assembly.
+## A unit or device replaced under warranty shall be warranted for the remainder of the original period or for one year from the date of replacement, whichever ends later.
+
+## The manufacturer shall provide a replacement plug-in unit for a unit that fails under warranty within the response time stated in the qualification statement.
+
+# Spare Parts {toc}
+
+## Spare Units {toc}
+
+### The spare plug-in units furnished shall be as indicated in the datasheet, and shall be delivered before the assembly is accepted.
+
```datasheet
−label: Additional Warranty Services
+label: Spare Plug-In Units
type: checkbox
options:
− - "Emergency response (24/7 with 4-hour commitment)"
− - "Scheduled preventive maintenance (annual)"
+ - "One spare full-voltage non-reversing starter unit of each size installed"
+ - "One spare full-voltage reversing starter unit of each size installed"
+ - "One spare soft starter unit of the largest size installed"
+ - "One spare drive unit of the largest size installed"
+ - "One spare feeder unit of each frame installed"
```
−## Warranty shall cover defects in materials and workmanship under normal use and service conditions, including the MCC structure, bus, all factory-installed plug-in units, and integral control devices.
+### The spare unit space reserved in each vertical section shall be not less than the share indicated in the datasheet.
−## The manufacturer shall maintain a service organization capable of providing emergency replacement plug-in units and field service within 24 hours during the warranty period.
+```datasheet
+label: Spare Unit Space per Section
+type: range
+unit: '%'
+options:
+ min: 0
+ max: 50
+ setpoints: [0, 10, 20, 25, 33, 50]
+```
−# Spare Parts {toc}
+### Spare space is the compartment height left empty, with bus stab openings shuttered and doors installed, so that a unit can be added later without a new section; it costs floor length at the time of purchase and saves a section, a bus splice, and a shutdown at the time of the addition. {note}
−## Spare plug-in units shall be furnished as indicated in the datasheet.
+### Spare space shall be furnished with the vertical bus, the wireway, the doors, and the shutters or blanking covers in place, ready to receive a unit.
+## Spare Components {toc}
+
+### The spare components furnished shall be as indicated in the datasheet, and shall be delivered before the assembly is accepted.
+
```datasheet
−label: Spare Plug-In Units
+label: Spare Components
type: checkbox
options:
− - "One spare unit of each FVNR starter size installed"
− - "One spare unit of each FVR starter size installed"
− - "One spare VFD unit of largest size installed"
− - "One spare soft-start unit of largest size installed"
- "One spare overload relay of each rating installed"
− - "One spare control transformer of each rating installed"
− - "10% spare blank unit compartments (minimum one per section)"
+ - "One spare control power transformer of each rating installed"
+ - "One set of fuses of each type and rating installed"
+ - "One set of pilot lights and lenses of each type installed"
+ - "One set of pushbutton and selector switch operators of each type installed"
+ - "One unit withdrawal handle and one set of blanking covers"
default:
− - "One spare unit of each FVNR starter size installed"
- "One spare overload relay of each rating installed"
− - "One spare control transformer of each rating installed"
− - "10% spare blank unit compartments (minimum one per section)"
+ - "One set of fuses of each type and rating installed"
+ - "One set of pilot lights and lenses of each type installed"
```
−## Manufacturer shall provide the following additional spare parts:
+### Spare units and components shall be identical to and interchangeable with the installed items, shall be delivered in their original packaging, and shall be labeled with the unit designation or the device rating they serve.
−- One set of replacement fuses for each fuse type and rating installed in the assembly
−- One set of replacement indicating lights and lenses for each pilot device type installed
−- One set of replacement push-button operators and selector switches for each type installed
−- One set of unit-extraction handles, blanking shutters, and the manufacturer's standard tool kit for unit removal and reinstallation
−- One complete set of keys for all locks
−
−## Spare plug-in units shall be of the same type, rating, and configuration as the installed units and shall be fully interchangeable.
−
−## Spare units shall be stored in a manufacturer-provided storage cabinet or on shelving in the electrical room or motor control room, organized and labeled by unit designation.
+### The Contractor shall obtain a signed receipt from the Owner for the spare units and components delivered.