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SynC · SynC Standards

Low Voltage Switchboards

Rev7
IssuedAug 26, 2026
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1 Scope

NOTE This specification covers dead-front, free-standing distribution switchboards rated 600V and below, constructed and listed to UL 891 (Switchboards) and NEMA PB 2. (1.1)
NOTE Switchboards covered by this standard use group-mounted molded-case circuit breakers (MCCBs) or insulated-case circuit breakers (ICCBs) as the primary overcurrent protective devices. (1.2)
1.3 Devices may be fixed-mounted or individually drawout depending on project requirements.
NOTE For lighting and appliance branch-circuit panelboards or distribution panelboards, see PanelboardsPanelboardsResolves to the current adopted revision.sync/panelboards. (1.4)
NOTE For motor starter assemblies, see Motor Control CentersMotor Control CentersResolves to the current adopted revision.sync/motor-control-centers. (1.5)
1.6 Grounding and bonding shall be per Grounding And BondingGrounding and Bonding for Electrical SystemsResolves to the current adopted revision.sync/grounding-and-bonding.
1.7 Feeders and branch circuit conductors entering and leaving the switchboard shall comply with Conductors And CablesConductors and CablesResolves to the current adopted revision.sync/conductors-and-cables and Raceways And ConduitRaceways and ConduitResolves to the current adopted revision.sync/raceways-and-conduit.
NOTE Switchboards differ from low voltage switchgear in construction, testing standard, and breaker type. (1.8)
NOTE Switchgear (UL 1558, IEEE C37.20.1) uses individually compartmented drawout power circuit breakers and is typically front-and-rear accessible. (1.9)
NOTE Switchboards (UL 891) use group-mounted MCCB/ICCB devices in a more compact, often front-accessible enclosure and are tested as an assembly to UL 891 short-circuit current ratings. (1.10)
NOTE For power circuit breaker switchgear, see Low Voltage SwitchgearLow Voltage SwitchgearResolves to the current adopted revision.sync/low-voltage-switchgear. (1.11)

2 Referenced Standards

2.1 Equipment and installation shall comply with the latest edition of the following.
Standard Title
UL 891 Switchboards
UL 489 Molded-Case Circuit Breakers, Molded-Case Switches, and Circuit-Breaker Enclosures
UL 869A Reference Standard for Service Equipment
NEMA PB 2 Deadfront Distribution Switchboards
NEMA PB 2.1 General Instructions for Proper Handling, Installation, Operation, and Maintenance of Deadfront Distribution Switchboards Rated 600 Volts or Less
IEEE C37.13 Low-Voltage AC Power Circuit Breakers Used in Enclosures
IEEE C37.20.7 Guide for Testing Switchgear Rated Up to 52 kV for Internal Arcing Faults
IEEE C57.13 Requirements for Instrument Transformers
IEEE 1584 Guide for Performing Arc-Flash Hazard Calculations
IEEE 519 Recommended Practice and Requirements for Harmonic Control in Electric Power Systems
NFPA 70 National Electrical Code
NFPA 70E Standard for Electrical Safety in the Workplace
NEMA 250 Enclosures for Electrical Equipment (1000 Volts Maximum)
NETA ATS Acceptance Testing Specifications for Electrical Power Equipment and Systems
IBC International Building Code
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
ASHRAE 90.1 Energy Standard for Buildings (submetering requirements)
2.2 Where conflicts exist between referenced standards, the more stringent requirement shall govern unless otherwise directed by the Engineer of Record.

3 Submittals

3.1 Action Submittals

3.1.1 Contractor shall submit the following for review prior to fabrication:
  • Shop drawings showing front and side elevations with overall dimensions, section arrangement, and shipping splits
  • Single line diagram indicating bus rating, short-circuit current rating, breaker frame sizes, and trip ratings
  • Bill of materials listing all major components by type and rating
  • Time-current coordination curves for all protective devices including ground fault elements
  • Control schematic and wiring diagrams for any control, metering, and communication circuits
  • Bus bracing and short-circuit withstand calculations or UL 891 series test references
  • Heat loss data per section for ventilation and HVAC coordination
  • Seismic certification documentation, where required
  • Conduit entry diagrams showing top and bottom entry zones
Submittal Documentationcheckbox
☑ Shop drawings (front and side elevations, sections)
☑ Single line diagram with ratings
☑ Bill of materials
☑ Time-current coordination curves
☑ Control schematics and wiring diagrams
☑ Bus bracing and short-circuit calculations
☑ Heat loss data per section
☐ Seismic certification (IBC/ASCE 7)
☑ Conduit entry diagrams
☑ Catalog cut sheets for all protective devices and meters

3.2 Closeout Submittals

3.2.1 Contractor shall provide at substantial completion:
  • Operation and maintenance manuals, bound with table of contents and indexed by section
  • As-built shop drawings reflecting field modifications
  • Factory production test reports
  • Field acceptance test reports per NETA ATS
  • Arc flash incident energy analysis and labels
  • Warranty documentation
  • Spare parts inventory with reorder information
Required Closeout Submittalscheckbox
☑ Operation and maintenance manuals
☑ As-built shop drawings
☑ Factory production test reports
☑ Field acceptance test reports per NETA ATS
☑ Arc flash incident energy analysis and labels
☑ Warranty documentation
☑ Spare parts inventory with reorder information

4 Quality Assurance

4.1 Manufacturer Qualifications

4.1.1 Switchboard shall be manufactured by a single company responsible for the assembly, bus, integral protective devices, and metering as a coordinated package.
4.1.2 The manufacturer shall have a minimum of five years documented experience producing UL 891 listed switchboards.
4.1.3 The manufacturer shall maintain an ISO 9001 certified quality management system.
4.1.4 The manufacturer shall maintain a service organization with factory-trained field representatives available within 24 hours of notification.

4.2 Source Limitations

4.2.1 All switchboard sections, bus, circuit breakers, protective relays, instrument transformers, and metering equipment shall be produced or furnished by the switchboard manufacturer as an integrated assembly.
4.2.2 Third-party retrofit or field-assembled enclosures are not acceptable.
4.2.3 Devices and accessories shall be the manufacturer's standard catalog components for the listed assembly.

4.3 Listing

4.3.1 The complete switchboard, as assembled and shipped, shall bear the UL 891 listing label of a Nationally Recognized Testing Laboratory.
4.3.2 Service entrance assemblies shall additionally be listed as Suitable for Use as Service Equipment (SUSE) per UL 869A.

4.4 Testing Personnel Qualifications

4.4.1 Field acceptance testing shall be performed by a firm regularly engaged in testing electrical power equipment, employing technicians certified by NETA or equivalent.
4.4.2 Testing personnel shall have a minimum of three years experience testing low voltage distribution equipment.

5 Environmental and Service Conditions

5.1 Switchboard shall be suitable for continuous operation under the service conditions indicated in the datasheet.
5.2 The design maximum ambient temperature at the installation shall be as indicated in the datasheet.
Ambient Temperature (Maximum)range
°C
405055
NOTE The elevated selections apply to specific installations: 50°C to elevated-ambient spaces and 55°C to rooftop or unconditioned spaces. (5.3)
5.4 The installation altitude shall be as indicated in the datasheet.
Installation Altitudeselect
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
5.5 The corrosion severity classification of the installation environment shall be as indicated in the datasheet.
Corrosion Severityselect
C2 - Low (indoor, climate-controlled)
C3 - Medium (indoor, unconditioned)
C4 - High (coastal, chemical exposure)
C5 - Very High (industrial, marine)
NOTE 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. (5.6)
5.7 Where site conditions exceed these parameters, the Contractor shall notify the manufacturer and the equipment shall be derated accordingly.
5.8 Equipment rated for standard conditions (40°C ambient, below 6,600 ft) shall be derated per the manufacturer's published derating curves and NEMA PB 2 when installed outside these parameters.
5.9 The Engineer shall document derating calculations on the contract drawings.
5.10 For installations classified C4 or C5, bus bars shall be tin-plated or silver-plated copper, hardware shall be stainless steel, and the enclosure paint system shall provide enhanced corrosion protection.

5.11 Seismic Requirements

5.11.1 The seismic certification basis shall be as indicated in the datasheet.
Seismic Certificationselect
Not required
IBC/ASCE 7 - Importance Factor 1.0
IBC/ASCE 7 - Importance Factor 1.5 (essential facility)
OSHPD pre-approval required (California healthcare)
Per drawings — structural drawings (deferred by default)
NOTE The Seismic Design Category and Importance Factor are established by the project's structural design; the electrical scope adopts them rather than setting them. (5.11.2)
5.11.3 Where required by the applicable building code, switchboard shall be seismically certified by shake-table testing per ICC ES AC156 or by analysis per ASCE 7.
5.11.4 Seismic certification shall be by an independent third-party testing laboratory and shall cover the complete assembly as installed, including all circuit breakers, bus, and ancillary components.
5.11.5 Certification of individual components in isolation is not acceptable.
5.11.6 Anchorage details shall be coordinated with the structural engineer.

6 Electrical Requirements

6.1 System Ratings

6.1.1 Whether the switchboard serves as main service entrance equipment shall be as indicated in the datasheet.
Service Entrance Equipmentradio
○ Main service entrance equipment (UL 869A SUSE)
○ Downstream distribution equipment
Per drawings — one-line diagram (deferred by default)
6.1.2 The system voltage and configuration shall be as indicated in the datasheet.
System Voltageselect
120/208V 3Φ 4-wire
277/480V 3Φ 4-wire
480V 3Φ 3-wire
240V 3Φ 3-wire
240/120V 1Φ 3-wire
Per drawings — one-line diagram (deferred by default)
6.1.3 The system frequency shall be as indicated in the datasheet.
System Frequencyradio
● 60 Hz
○ 50 Hz
NOTE 60 Hz is the North American norm and is the datasheet default; 50 Hz equipment is a distinct product selection, available for systems that operate at that frequency. (6.1.4)
6.1.5 Where the switchboard serves as main service entrance equipment, it shall be listed as Suitable for Use as Service Equipment per UL 869A and shall comply with NFPA 70 Article 230 including provisions for service disconnect, utility metering, neutral-to-ground bonding, and available fault current labeling per NFPA 70 Article 110.24.
6.1.6 Coordinate metering current transformer compartment and termination requirements with the serving utility prior to submittal.

6.2 Bus Rating

6.2.1 Main bus continuous current rating shall be as indicated in the datasheet.
Main Bus Continuous Currentrange
A
4006008001200160020002500300040005000
Per drawings — one-line diagram (deferred by default)
6.2.2 The switchboard short-circuit current rating shall be as indicated in the datasheet.
Switchboard Short-Circuit Current Rating (SCCR)range
kAIC
2535426585100200
Per drawings — one-line diagram (deferred by default)
6.2.3 The short-circuit withstand duration shall be as indicated in the datasheet.
Short-Circuit Withstand Durationselect
3-cycle (0.05 seconds) - standard MCCB
30-cycle (0.5 seconds) - ICCB with short-time rating
6.2.4 Bus shall be braced for the available short-circuit current at the point of installation as determined by a short-circuit analysis.
6.2.5 The complete switchboard, including main and feeder devices, shall carry a UL 891 short-circuit current rating (SCCR) equal to or greater than the available fault current.
6.2.6 Switchboard short-circuit current rating shall equal or exceed the available fault current at the line-side terminals.
6.2.7 Verify available fault current with the utility provider and perform a short-circuit study per Short Circuit StudyShort-Circuit StudyResolves to the current adopted revision.sync/short-circuit-study prior to equipment procurement.
6.2.8 Series-rated combinations between main and feeder devices are permitted only when the combination is tested and listed by the manufacturer.
6.2.9 Series ratings shall not be used where downstream motor contribution invalidates the rating per NFPA 70 Article 240.86.
6.2.10 A 30-cycle short-time withstand rating is required where selective coordination with downstream breakers must be maintained without instantaneous trip on the upstream main.
NOTE A 30-cycle short-time withstand rating typically requires insulated-case circuit breakers (ICCBs) for the main device. (6.2.11)

6.3 Neutral and Ground Bus

6.3.1 The neutral bus rating shall be as indicated in the datasheet.
Neutral Bus Ratingselect
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)
NOTE A 3-wire system with no neutral records "Not applicable" rather than leaving the field ambiguous. (6.3.2)
6.3.3 Oversized neutral bus shall be specified where nonlinear loads exceed 30% of the total connected load to accommodate triplen harmonic currents.
6.3.4 The Engineer shall evaluate harmonic loading per IEEE 519 when selecting neutral bus sizing.
6.3.5 Whether a ground bus is furnished with the assembly shall be as indicated in the datasheet.
Ground Busradio
● Included — full length of the assembly
○ Not required
NOTE 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. (6.3.6)
6.3.7 Where a ground bus is furnished, it shall be bare copper, minimum 1/4 in. x 2 in. cross-section, extending the full length of the switchboard assembly.
6.3.8 Ground bus shall be accessible without removing any covers or barriers required for safe operation.
6.3.9 Bonding between the ground bus and the equipment enclosure shall be per Grounding And BondingGrounding and Bonding for Electrical SystemsResolves to the current adopted revision.sync/grounding-and-bonding.

7 Physical Construction

7.1 Enclosure

7.1.1 The enclosure NEMA rating shall be as indicated in the datasheet.
Enclosure Ratingselect
NEMA 1 - Indoor General Purpose
NEMA 1A - Indoor Gasketed (dust-resistant)
NEMA 3R - Outdoor Rainproof
NEMA 12 - Industrial (dust-tight)
7.1.2 The accessibility configuration shall be as indicated in the datasheet.
Accessibilityradio
● Front accessible (rear against wall)
○ Front and rear accessible
7.1.3 The number of vertical sections shall be as indicated in the datasheet.
Number of Vertical Sectionsrange
sections
112
Per drawings — one-line diagram (deferred by default)
7.1.4 The conduit entry direction shall be as indicated in the datasheet.
Conduit Entryselect
Top entry
Bottom entry
Top and bottom entry
Per drawings — electrical plans (deferred by default)
7.1.5 Enclosure shall be free-standing, dead-front, 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.
7.1.6 Sections shall be of uniform height and depth and shall align flush across the front.
7.1.7 All joints shall be continuously welded or bolted with gaskets as required for the specified NEMA rating.
7.1.8 For outdoor installations (NEMA 3R), enclosure shall include rain hoods over ventilation openings, drip shields above doors, and condensation heaters in each section.
7.1.9 Heater sizing shall be a minimum of 200W per vertical section.
7.1.10 Heaters shall be thermostat controlled and wired to remain energized whenever the switchboard is de-energized.
NOTE Front-accessible switchboards permit installation against a wall, which is the most common configuration. (7.1.11)
7.1.12 Rear-accessible configurations require minimum 36 in. working clearance at the rear per NFPA 70 Article 110.26 and shall have individual hinged rear doors or removable rear covers for access to bus connections and line/load lugs.
7.1.13 Switchboard location and arrangement shall be as indicated on the equipment room layout drawings.
7.1.14 Coordinate section count and overall length with shipping splits to ensure equipment can be transported to and through the installation pathway.
7.1.15 Conduit entry zones shall be coordinated with the section construction to maintain required bending space per NFPA 70 Article 312.6 and shall avoid interference with bus, devices, and barriers.

7.2 Bus Bars

7.2.1 The bus bar material and plating shall be as indicated in the datasheet.
Bus Bar Materialradio
○ Copper (unplated bar, plated joint contact surfaces)
○ Copper (tin-plated)
○ Copper (silver-plated)
○ Aluminum (tin-plated)
7.2.2 The bus insulation treatment shall be as indicated in the datasheet.
Bus Insulationradio
● Bare bus with isolation barriers
○ Fully insulated (flame-retardant sleeving or coating)
7.2.3 The bus current density basis shall be as indicated in the datasheet.
Bus Densityselect
1000 A/in² (standard, 65°C rise)
750 A/in² (conservative, 50°C rise)
7.2.4 Provisions for future bus extension shall be as indicated in the datasheet.
Bus Extension Provisionsradio
● No future extension
○ Provision for future extension at one end
7.2.5 Aluminum bus shall be specified only where explicitly accepted by the Owner and shall be tin-plated at all joint contact surfaces.
NOTE Copper is preferred for service entrance equipment and for installations in corrosive environments. (7.2.6)
7.2.7 Bus bar joints shall be bolted with Belleville washers to maintain contact pressure under thermal cycling.
7.2.8 All joint contact surfaces shall be plated.
7.2.9 Bus connections shall be accessible for re-torquing during maintenance.
7.2.10 Fully insulated bus shall be specified for outdoor (NEMA 3R) installations, for service entrance equipment over 1200A, and where required by Owner standards.
7.2.11 Bus insulation shall be flame-retardant and shall be continuous through barriers and bus transitions between sections.

7.3 Barriers and Compartmentalization

7.3.1 The degree of internal compartmentalization shall be as indicated in the datasheet.
Compartment Form (per NEMA PB 2 form designations)select
Form 1 - No internal segregation
Form 2 - Bus segregated from devices
Form 3 - Bus segregated from devices, devices segregated from each other
Form 4 - Bus, devices, and terminals all segregated
7.3.2 Switchboard shall provide insulating or metal barriers between the main bus compartment and the device/cable compartments.
7.3.3 Barriers shall reduce the likelihood of an arc fault propagating from one compartment to adjacent compartments.
7.3.4 Through-bus shall be barriered from feeder breaker line-side connections by isolating barriers.
NOTE Higher form designations reduce the risk of cascading faults during maintenance but increase cost and physical size. (7.3.5)
7.3.6 Form 3 or 4 should be specified for mission-critical facilities, healthcare, and data centers.

7.4 Arc Flash Mitigation

NOTE See Arc Flash StudyArc-Flash Hazard AnalysisResolves to the current adopted revision.sync/arc-flash-study for arc flash study requirements and labeling. (7.4.1)
7.4.2 Where arc energy reduction is required, the method shall be as indicated in the datasheet.
Arc Energy Reduction Method (1200A+ Devices)select
Zone-selective interlocking (ZSI)
Energy reducing maintenance switch (ERMS)
Differential relaying
Approved equivalent method
7.4.3 Where arc-resistant construction is specified for the project, the accessibility type shall be as indicated in the datasheet.
Arc-Resistant Constructionselect
Not required
Type 1 - front
Type 2 - front, rear, and sides
NOTE Arc-resistant construction is an added-cost option rather than a baseline requirement; projects that do not specify it record "Not required", and the field is left blank until the decision is made. (7.4.4)
7.4.5 Switchboard shall include arc flash hazard reduction features appropriate to the connected system.
7.4.6 Arc flash hazard analysis shall be performed per IEEE 1584.
7.4.7 NFPA 70 Article 240.87 requires that circuit breakers rated 1200A or more provide an arc energy reduction method.
NOTE ERMS is the most common solution for switchboard applications because it does not require coordination across multiple breakers and can be activated by a maintenance technician via a front-mounted switch with status indication. (7.4.8)
7.4.9 Where arc-resistant construction is specified, switchboard shall be tested per IEEE C37.20.7 at the specified short-circuit current rating and duration.
7.4.10 Arc-resistant construction does not eliminate the need for arc flash hazard analysis or arc flash labeling.

7.5 Infrared Scanning Provisions

7.5.1 Enclosure shall include removable infrared inspection windows or cover plates at the main device, bus joints between sections, and feeder breaker line-side connections.
7.5.2 Infrared inspection windows shall allow thermographic inspection of energized connections without removing covers or de-energizing the equipment.

8 Circuit Breakers

8.1 Main Device

8.1.1 The main device configuration shall be as indicated in the datasheet.
Main Device Configurationselect
Main circuit breaker
Main fusible switch
Main lugs only (no main device)
Through-bus (sub-feed, no main device)
Per drawings — one-line diagram (deferred by default)
8.1.2 The main breaker construction shall be as indicated in the datasheet.
Main Breaker Typeselect
Molded-case circuit breaker (MCCB), fixed-mounted
Insulated-case circuit breaker (ICCB), fixed-mounted
Insulated-case circuit breaker (ICCB), individually drawout
8.1.3 The main breaker trip unit shall be as indicated in the datasheet.
Main Breaker Trip Unitselect
Thermal-magnetic (available on smaller frames)
Electronic trip - LSI (Long-time, Short-time, Instantaneous)
Electronic trip - LSIG (Long-time, Short-time, Instantaneous, Ground Fault)
8.1.4 Main lugs only configurations are limited to NFPA 70 Article 408.36 requirements (maximum six service disconnects, where applicable).
8.1.5 Through-bus configurations require coordination with the upstream device for overcurrent protection of the switchboard bus.
NOTE Drawout ICCB mains are used where the main must be serviced or replaced without de-energizing the upstream source. (8.1.7)
8.1.8 Main breaker frame size and trip rating shall be as indicated on the one-line diagram.
8.1.10 Ground fault protection is required by NFPA 70 Article 230.95 for solidly grounded wye services over 150V to ground rated 1000A or more, and by Article 215.10 for feeders meeting the same criteria.
NOTE Even where not code-required, ground fault protection significantly reduces equipment damage from arcing faults. (8.1.11)

8.2 Feeder Devices

8.2.1 Feeder device quantities shall be as indicated on the one-line diagram.
8.2.2 Feeder device frame sizes and trip ratings shall be as indicated on the breaker schedule.
8.2.3 The feeder device type shall be as indicated in the datasheet.
Feeder Device Typeselect
Molded-case circuit breakers (MCCB), group-mounted
Molded-case circuit breakers (MCCB), individually mounted
Insulated-case circuit breakers (ICCB), group-mounted
Fusible switches (group-mounted)
8.2.4 The feeder breaker trip units shall be as indicated in the datasheet.
Feeder Breaker Trip Unitsselect
Thermal-magnetic (all feeders)
Electronic trip - LSI (all feeders)
Electronic trip - LSIG (all feeders)
Per drawings — breaker schedule (deferred by default)
NOTE Group-mounted feeder devices are the most common configuration and provide the highest device density. (8.2.5)
NOTE Individually mounted devices are used for larger frames (typically 800A and above) or where compartmentalization between feeders is required. (8.2.6)
8.2.7 Electronic trip units shall be specified for feeders 400A and larger to allow adjustable settings for selective coordination.
8.2.8 Thermal-magnetic breakers are acceptable for smaller feeders where coordination is not critical.

8.3 Selective Coordination

NOTE See Protective Coordination StudyProtective Device Coordination StudyResolves to the current adopted revision.sync/protective-coordination-study for coordination study requirements. (8.3.1)
8.3.2 The selective coordination requirement shall be as indicated in the datasheet.
Selective Coordination Requiredradio
○ Required - emergency or critical system per NFPA 70
○ Required - Owner standard
● Not required
8.3.3 Where required by NFPA 70 (for example, Articles 700.32, 701.27, and 708.54 for emergency, legally required standby, and critical operations power systems, respectively), feeder and main devices shall be selectively coordinated for the full range of available overcurrents and time durations.
8.3.4 Coordination shall be demonstrated by time-current curves overlaid on a common log-log plot.

8.4 Breaker Accessories

8.4.1 Breaker accessories shall be furnished as indicated in the datasheet.
Breaker Accessoriescheckbox
☑ Auxiliary contacts (1a + 1b minimum)
☐ Shunt trip
☐ Undervoltage release
☐ Bell alarm contact
☐ Mechanical interlock (paired breakers)
☐ Kirk key interlock
☐ Motor operator with remote close/trip
☐ Padlock provisions (open position)
8.4.2 Auxiliary contacts shall be provided on every device that participates in a control or status circuit.
8.4.3 All accessories on a given breaker shall be the manufacturer's standard catalog options for that frame.
8.4.4 Field-installed accessories that void the listing are not acceptable.

9 Protective Relaying

9.1 Where discrete protective relays are applied, the protection functions shall be as indicated in the datasheet.
Protective Relay Functionscheckbox
☐ Overcurrent (50/51)
☑ Ground fault (50G/51G)
☐ Under/overvoltage (27/59)
☐ Under/overfrequency (81)
☐ Reverse power (32)
☐ Phase reversal (47)
9.2 Relay settings shall be as indicated on the relay setting schedule.
NOTE Discrete protective relays in switchboards are typically limited to ground fault protection for the main device and any specialized functions for generator paralleling, utility intertie, or co-generation applications. (9.3)
9.4 Where applied, relays shall be microprocessor-based with digital displays, self-diagnostics, and event recording.
9.5 Where applied, relays shall be tested per IEEE C37.90.1 for surge withstand capability.

10 Metering and Instrumentation

10.1 Instrument Transformers

10.1.1 Current transformers shall comply with IEEE C57.13.
10.1.2 Accuracy class shall be appropriate for the connected metering function:
  • Revenue metering: Class 0.3 accuracy
  • Protective relaying: Class C200 or higher
  • General monitoring: Class 0.6 accuracy
10.1.3 Current transformers for metering and relaying shall be provided on separate cores.
10.1.4 CTs shall not be shared between metering and protection functions.
10.1.5 Where the switchboard serves as utility service equipment, the utility CT compartment shall be sized and located per the serving utility's standards and shall be sealable.

10.2 Power Monitoring

10.2.1 The metering provided at the switchboard shall be as indicated in the datasheet.
Metering Typeselect
No metering
Analog ammeter and voltmeter with phase selector switches
Digital multifunction meter at the main
Digital multifunction meter at the main and each feeder
Revenue-grade metering per utility requirements
10.2.2 The metered quantities and recording functions shall be as indicated in the datasheet.
Meter Functionscheckbox
☑ Voltage (L-L, L-N all phases)
☑ Current (per phase and neutral)
☑ 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
10.2.3 Where a meter is provided, its communication protocol shall be as indicated in the datasheet and shall be supported by the Owner's building management system.
Metering Communication Protocolselect
No communications
Modbus RTU (RS-485)
Modbus TCP/IP (Ethernet)
BACnet IP
DNP3
10.2.4 Where building energy code requires submetering (ASHRAE 90.1 Section 8.4 or local amendments), meter data shall be accessible via the selected communication protocol for integration with the building management system.
10.2.5 Coordinate communication wiring and protocols with Building Automation SystemBuilding Automation SystemResolves to the current adopted revision.sync/building-automation-system.

11 Surge Protection

11.1 Whether a surge protective device is provided at the switchboard shall be as indicated in the datasheet.
Surge Protective Device (SPD)radio
● Provided
○ Not provided
11.2 The SPD type shall be as indicated in the datasheet.
SPD Typeselect
Type 1 - permanently connected on the line side of the service disconnect
Type 2 - permanently connected on the load side of the service disconnect
Type 1+2 combination (line-side and load-side protection in one assembly)
11.3 The SPD nominal discharge current rating shall be as indicated in the datasheet.
SPD Nominal Discharge Current (In)range
kA
102040
NOTE For service entrance switchboards, NFPA 70 Article 230.67 requires a surge protective device for dwelling unit services and certain other occupancies. (11.4)
11.5 SPDs in switchboards shall be UL 1449 listed, integral to the assembly with a dedicated SPD disconnect, and located as close as practical to the bus connection point to minimize lead length.
11.6 Indicating lights and dry contacts shall be provided for remote status monitoring.

12 Finish and Identification

12.1 The enclosure finish color shall be as indicated in the datasheet.
Finish Colortext
ANSI 49 light gray
12.2 Enclosure shall receive a minimum two-coat paint system: corrosion-resistant primer and manufacturer's standard polyester powder coat finish.
12.3 Minimum total dry film thickness shall be 3 mils (75 microns).
12.4 For outdoor installations or environments classified C3 or higher, an enhanced paint system with a minimum of 5 mils dry film thickness shall be applied.

12.5 Labeling

12.5.1 Manufacturer shall provide engraved nameplates for the switchboard assembly and each individual device.
12.5.2 Nameplates shall identify:
  • Switchboard designation and one-line reference
  • Bus ratings (voltage, continuous current, short-circuit)
  • Individual breaker designation, frame size, and trip rating
  • Current transformer ratios and accuracy class
  • Arc flash warning labels per NFPA 70E and IEEE 1584
  • Available fault current and date of calculation per NFPA 70 Article 110.24 (service equipment)
12.5.3 The nameplate material shall be as indicated in the datasheet.
Nameplate Materialradio
● Laminated phenolic (indoor)
○ Stainless steel (outdoor or corrosive)
○ Aluminum (anodized)
12.5.4 Equipment labeling shall follow Equipment LabelingElectrical Equipment LabelingResolves to the current adopted revision.sync/equipment-labeling conventions.
12.5.5 Where the switchboard supplies emergency, legally required standby, or critical operations loads, additional identification per NFPA 70 Articles 700.10, 701.10, and 708.10 shall be provided.

13 Testing

13.1 Factory Production Tests

13.1.1 The manufacturer shall perform the following production tests on the completed switchboard assembly per UL 891 and NEMA PB 2:
  • 60 Hz dielectric withstand test on primary bus (phase-to-phase and phase-to-ground)
  • Insulation resistance measurement on each phase and neutral bus
  • Mechanical operation of each circuit breaker (minimum three open/close cycles)
  • Ground fault sensing system functional test (where applicable)
  • Control wiring continuity verification per the approved schematics
  • Current transformer ratio and polarity test
  • Visual and dimensional inspection against approved shop drawings
13.1.2 Factory acceptance test witnessing shall be as indicated in the datasheet.
Factory Acceptance Testradio
○ Witnessed by Owner's representative
● Unwitnessed with certified test report
○ Not required beyond standard production tests
13.1.3 Where witnessed factory testing is specified, the manufacturer shall provide a minimum of two weeks advance notice of test readiness.
13.1.4 Where witnessed factory testing is specified, test procedures shall be submitted for review prior to testing.

14 Field Quality Control

14.1 Field Acceptance Tests

14.1.1 Contractor shall engage a qualified independent testing firm to perform acceptance testing per NETA ATS Section 7.1 (switchboards) and Section 7.6 (low voltage circuit breakers).
14.1.2 Field acceptance tests shall include as a minimum:
  • Visual and mechanical inspection of all sections, bus joints, and devices
  • Bolted connection torque verification using a calibrated torque wrench, sampling per NETA ATS
  • Insulation resistance testing (phase-to-phase and phase-to-ground), minimum one minute, recorded at 30 seconds and 60 seconds
  • Contact resistance measurement on all main bus connections and feeder lug terminations
  • Circuit breaker operational testing (mechanical and electrical, all positions for drawout devices)
  • Primary current injection testing of all main and feeder trip functions (long-time, short-time, instantaneous, and ground fault pickup and time delay) at minimum one set point per function
  • Current transformer ratio and polarity verification
  • Metering accuracy verification against a calibrated reference
  • Ground impedance measurement of the equipment ground per IEEE 81
  • Functional testing of all control circuits, interlocks, and alarms
  • SPD verification of status indication and disconnect operation, where applicable
14.1.3 The scope of field testing and startup services shall be as indicated in the datasheet.
Field Testing Requirementsradio
● NETA acceptance testing and manufacturer startup
○ NETA acceptance testing without manufacturer startup
○ Manufacturer startup without independent NETA testing
14.1.4 Field acceptance testing shall occur after installation is complete and before the equipment is energized.

14.2 Infrared Thermographic Inspection

14.2.1 The infrared thermographic inspection schedule shall be as indicated in the datasheet.
Infrared Thermographic Inspectionradio
● Initial scan within 90 days of energization, follow-up at 11 months
○ Initial scan within 90 days of energization
○ Not required
14.2.2 Where an infrared scan is indicated in the datasheet, it shall be performed under normal operating load conditions (minimum 40% of rated load where practical).
14.2.3 All connections exceeding 10°C rise above ambient shall be reported and corrected.
NOTE The 11-month follow-up scan captures connections that may loosen during the initial thermal cycling period and falls within the standard one-year warranty window. (14.2.4)

15 Installation

15.1 Concrete Housekeeping Pad

NOTE See Concrete PadsConcrete Equipment PadsResolves to the current adopted revision.sync/concrete-pads for construction requirements. (15.1.1)
15.1.2 Switchboard shall be mounted on a reinforced concrete housekeeping pad extending a minimum of 3 in. beyond the base of the equipment on all sides.
15.1.3 Pad shall be a minimum of 4 in. above finished floor for indoor installations and 6 in. above finished grade for outdoor installations.
15.1.4 Coordinate pad dimensions, conduit penetrations, and anchor bolt locations with equipment shop drawings prior to concrete placement.

15.2 Equipment Setting

15.2.1 Contractor shall comply with the manufacturer's installation instructions, NEMA PB 2.1, and applicable rigging requirements.
15.2.2 After section assembly and before energizing, the Contractor shall verify the following:
  • All shipping restraints and temporary grounds removed
  • Bus splice joints torqued per the manufacturer's specifications using a calibrated torque wrench, with witness marks applied
  • Device line and load lugs torqued per the manufacturer's published values
  • Conduit terminations sealed and cable connections trained, supported, and torqued
  • Space heaters energized for outdoor or unconditioned installations
  • Working clearances per NFPA 70 Article 110.26 maintained
  • Equipment ground bus bonded to the building grounding electrode system per Grounding And BondingGrounding and Bonding for Electrical SystemsResolves to the current adopted revision.sync/grounding-and-bonding
15.2.3 Sections shall not be lifted by bus, doors, or device handles.
15.2.4 Remove all temporary shipping braces, blocking, and desiccants prior to final assembly.

15.3 Working Clearance

15.3.1 Minimum working space shall be maintained per NFPA 70 Article 110.26 based on the nominal voltage and accessibility configuration:
Voltage Condition 1 (exposed on one side) Condition 2 (exposed on both sides) Condition 3 (exposed on both sides + operator between)
0-150V 36 in. 36 in. 36 in.
151-600V 36 in. 42 in. 48 in.
15.3.2 Working space shall not be used for storage.
15.3.3 Dedicated electrical space above and below the equipment shall be maintained per NFPA 70 Article 110.26(E).
15.3.4 Where the switchboard is service entrance equipment over 1200A and over 6 ft wide, a second egress path from the working space is required per NFPA 70 Article 110.26(C)(2).

15.4 Identification of Source

15.4.1 Where the switchboard is fed from a remote source, a permanent label per NFPA 70 Article 408.4(B) shall identify the source location and circuit designation.
15.4.2 Where the switchboard supplies multiple sources (for example, normal and emergency), each source shall be clearly identified at the switchboard.

16 Delivery, Storage, and Handling

16.1 Switchboard shall be shipped in the largest factory-assembled sections that can be transported to and within the installation site.
16.2 Verify all pathway dimensions (doors, hallways, elevator shafts, turning radii) between the delivery point and the final installation location prior to ordering.
16.3 Coordinate shipping splits with the manufacturer on the approved shop drawings.
16.4 Equipment shall be stored indoors in a clean, dry location.
16.5 Where indoor storage is not available, the manufacturer shall provide weatherproof packaging.
16.6 Condensation heaters shall be connected and energized during storage if the equipment will be stored for more than 30 days or if the storage environment is not climate-controlled.

17 Warranty

17.1 The manufacturer shall warrant the switchboard for the period indicated in the datasheet.
Warranty Periodselect
1 year from substantial completion
2 years from substantial completion
3 years from substantial completion
5 years from substantial completion
17.2 The warranty coverage scope shall be as indicated in the datasheet.
Warranty Coverage Scoperadio
● Parts only
○ Parts and labor
17.3 Additional warranty services shall be provided as indicated in the datasheet.
Additional Warranty Servicescheckbox
☐ Emergency response (24/7 with 4-hour commitment)
☐ Scheduled preventive maintenance (annual)
17.4 Warranty shall cover defects in materials and workmanship under normal use and service conditions.
17.5 The manufacturer shall maintain a service organization capable of providing emergency replacement parts and field service within 24 hours during the warranty period.

18 Spare Parts

18.1 Spare breakers shall be furnished as indicated in the datasheet.
Spare Breakersradio
○ None
● One spare of each feeder frame size
○ 10% of each frame size (minimum one)
18.2 Manufacturer shall provide the following additional spare parts:
  • One set of replacement indicating lights for each type installed
  • One set of replacement control fuses for each type and rating installed
  • One complete set of keys for all locks and Kirk key interlocks
  • Touch-up paint matching the finish color (minimum one pint)
18.3 Spare breakers shall be of the same type, rating, and configuration as the installed breakers and shall be fully interchangeable.
18.4 Spare breakers shall be stored in a manufacturer-provided storage cabinet located in the electrical room.

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"Low Voltage Switchboards." SynC Standards. Licensed under CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/). Source: https://synergyinconstruction.com/wiki/sync/low-voltage-switchboards — reference material only; not professional engineering advice and provided without warranty. Verify against governing codes and have a licensed professional review before use.