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SynC · Editorial revision

Low Voltage Switchboards

Revision9
EditedOct 12, 2026
StatusCurrent
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Current revision. This is editorial revision 9, the current text of this standard. Read it on the standard's page.

SynC Standards Team — Specifier (Platform Standards) ✓ OfficialDiscloses employment SynC (SynC Platform Team)
Datasheet constraints: every range, checkbox and listbox field now states its direction

1 Scope

NOTE This standard governs the switchboard as a listed assembly: the structure and its sections, the bus and its supports, the main and feeder devices and their mounting, the compartments built into the structure for utility metering, surge protection, and power monitoring, and the field work that puts the switchboard into service. (1.1)
NOTE A switchboard is a large single panel, frame, or assembly of panels on which switches, overcurrent devices, buses, and instruments are mounted, accessible from the front or from the front and rear, and not intended to be installed in a cabinet; dead-front construction leaves no energized part exposed on the operating face. It is the equipment at the head of a low-voltage distribution system, taking the service or a transformer secondary and dividing it into the feeders that serve panelboards, motor control centers, and large loads. (1.2)
NOTE Four assembly standards divide low-voltage distribution equipment by construction and listing, and this one is the UL 891 dead-front switchboard. Low Voltage SwitchgearLow Voltage SwitchgearResolves to the current adopted revision.sync/low-voltage-switchgear is the assembly listed to UL 1558 and IEEE C37.20.1, built around IEEE C37.13 power devices on withdrawable rails in individual compartments; PanelboardsPanelboardsResolves to the current adopted revision.sync/panelboards is the UL 67 cabinet whose branch devices subdivide one feeder; Motor Control CentersMotor Control CentersResolves to the current adopted revision.sync/motor-control-centers is the UL 845 lineup of starter cells on a shared vertical bus; Medium Voltage SwitchgearMedium Voltage SwitchgearResolves to the current adopted revision.sync/medium-voltage-switchgear is anything above 1000 V. (1.3)
NOTE The switchboard is one listed product. Its short-circuit current rating, its seismic certification, and its arc-flash characteristics are properties of the whole assembly in the configuration shipped, and a device, a bus modification, or a compartment added outside that listing removes the switchboard from the condition under which it was rated. (1.4)
NOTE The following are governed elsewhere and are outside this standard: (1.5)
  • the service point, the service conductors, the meter socket, and the serving utility's metering requirements, under Electrical Service EntranceElectrical Service EntranceResolves to the current adopted revision.sync/electrical-service-entrance
  • the feeders that leave the switchboard and the conductors that enter it, and their terminations, under Conductors And CablesConductors and CablesResolves to the current adopted revision.sync/conductors-and-cables
  • the raceways entering the structure, under Raceways And ConduitRaceways and ConduitResolves to the current adopted revision.sync/raceways-and-conduit
  • the busway run, its supports, and its joints, under BuswayBuswayResolves to the current adopted revision.sync/busway
  • the wireway or auxiliary gutter trough that adjoins the structure, under Wireways And Auxiliary GuttersWireways and Auxiliary GuttersResolves to the current adopted revision.sync/wireways-and-auxiliary-gutters
  • the grounding electrode system, the equipment grounding conductors, and the bonding of a separately derived system, under Grounding And BondingGrounding and Bonding for Electrical SystemsResolves to the current adopted revision.sync/grounding-and-bonding
  • the surge protective device as a product, its ratings, its protection modes, and its lead length, under Surge Protective DevicesSurge Protective DevicesResolves to the current adopted revision.sync/surge-protective-devices
  • the meters, their accuracy class, their current transformers, and the monitoring system they report to, under Electrical Power MonitoringElectrical Power Monitoring and MeteringResolves to the current adopted revision.sync/electrical-power-monitoring
  • the transformer feeding the switchboard, under Medium Voltage TransformersMedium-Voltage Distribution TransformersResolves to the current adopted revision.sync/medium-voltage-transformers or Low Voltage Dry Type TransformersLow-Voltage Dry-Type TransformersResolves to the current adopted revision.sync/low-voltage-dry-type-transformers
  • the automatic transfer switch on either side of the switchboard, under Automatic Transfer SwitchesAutomatic Transfer SwitchesResolves to the current adopted revision.sync/automatic-transfer-switches
  • the short-circuit, coordination, and arc-flash studies, under Short Circuit StudyShort-Circuit StudyResolves to the current adopted revision.sync/short-circuit-study, Protective Coordination StudyProtective Device Coordination StudyResolves to the current adopted revision.sync/protective-coordination-study, and Arc Flash StudyArc-Flash StudyResolves to the current adopted revision.sync/arc-flash-study
  • the room the switchboard occupies, under Electrical RoomsElectrical RoomsResolves to the current adopted revision.sync/electrical-rooms
  • the housekeeping pad the switchboard stands on, under Concrete PadsConcrete Equipment PadsResolves to the current adopted revision.sync/concrete-pads
1.6 Switchboards shall comply with NEMA PB 2 and shall be listed and labeled to UL 891 by a Nationally Recognized Testing Laboratory.
1.7 The location and orientation of each switchboard shall be as indicated on the electrical plans.
1.8 Where a value stated on the one-line diagram for a particular switchboard differs from the datasheet selection under this standard, the one-line diagram shall govern for that switchboard.

2 Referenced Standards

2.1 Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
2.2 Where the contract documents, the serving utility's requirements, 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 891 Switchboards
UL 489 Molded-Case Circuit Breakers, Molded-Case Switches, and Circuit-Breaker Enclosures
UL 98 Enclosed and Dead-Front Switches
UL 977 Fused Power-Circuit Devices
UL 869A Reference Standard for Service Equipment
UL 1053 Ground-Fault Sensing and Relaying Equipment
UL 1449 Surge Protective Devices
UL 50 Enclosures for Electrical Equipment, Non-Environmental Considerations
UL 50E Enclosures for Electrical Equipment, Environmental Considerations
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
NEMA AB 1 Molded-Case Circuit Breakers, Molded-Case Switches, and Circuit-Breaker Enclosures
NEMA 250 Enclosures for Electrical Equipment (1000 Volts Maximum)
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
NFPA 70 National Electrical Code (Articles 110, 215, 230, 240, 250, 312, 408, 700, 701, and 708)
NFPA 70E Standard for Electrical Safety in the Workplace
ASTM B187 Copper, Bus Bar, Rod, and Shapes and General Purpose Rod, Bar, and Shapes
ASTM B317 Aluminum-Alloy Extruded Bar, Rod, Tube, Pipe, Structural Profiles, and Profiles for Electrical Purposes (Bus Conductor)
ANSI/NETA ATS Standard for Acceptance Testing Specifications for Electrical Power Equipment and Systems
ASCE 7 Minimum Design Loads and Associated Criteria for Buildings and Other Structures (Chapter 13)
ICC-ES AC156 Acceptance Criteria for Seismic Certification by Shake-Table Testing of Nonstructural Components

3 Submittals

3.1 Action Submittals

3.1.1 The Contractor shall submit the following for review before any switchboard is released for manufacture:
  • shop drawings for each switchboard giving the front and side elevations, the section widths, depths, and heights, the shipping splits, the weight and the lifting provisions of each shipping section, the conduit entry areas, and the anchorage pattern
  • an assembly one-line diagram showing the incoming connection, the main device, the bus with its continuous and short-circuit ratings, the neutral and ground bus, and every feeder device by its designation
  • a device schedule giving the frame size, the trip rating, the trip unit type, the interrupting rating, and the accessories of every device, and every spare and space position
  • the bus material, plating, and sizing basis, with the bus bracing rating
  • the assembly short-circuit current rating and the basis on which it is established, and where the basis is a series rating, the tested combination and the upstream device on which each rating depends
  • the heat release of each section at rated load, for coordination of the room ventilation
  • the seismic certification for the switchboard as furnished, where the datasheet requires one
  • product data for every device, for the metering and communications components, and for the surge protective device, where either is furnished within the assembly
  • schematic and wiring diagrams for the control, metering, ground-fault, and communications circuits
  • the nameplate schedule listing the text to appear on each assembly and device nameplate
Action Submittalscheckbox
☑ Shop drawings
☑ Assembly one-line diagram
☑ Device schedule
☑ Bus data and bracing rating
☑ Short-circuit current rating basis and series-rated combinations
☑ Heat release per section
☐ Seismic certification
☑ Device, metering, and surge protective device product data
☑ Schematic and wiring diagrams
☑ Nameplate schedule
3.1.2 A switchboard shall not be released for manufacture until the action submittals covering it have been reviewed and returned.
NOTE The short-circuit current rating is the submittal item that most often comes back wrong, because a catalog rating is the rating of the highest-rated device the structure accepts, and the rating that applies to the switchboard is the lowest rating among the bus bracing, the main device, and every feeder device actually installed, or the series-rated combination that covers them. (3.1.3)

3.2 Informational Submittals

3.2.1 The Contractor shall submit the following with or before the action submittals:
  • the manufacturer's qualification statement required under Quality Assurance
  • the qualifications of the firm and the technicians who will perform field acceptance testing
  • the factory test procedure, where the datasheet selects witnessed factory testing
  • the time-current characteristic curves and the setting ranges of every trip unit, relay, and fuse furnished, for use in the study performed under Protective Coordination StudyProtective Device Coordination StudyResolves to the current adopted revision.sync/protective-coordination-study
  • the manufacturer's published derating factors applied for ambient temperature and altitude, where either exceeds the rating basis of the listing
  • the serving utility's written acceptance of the metering compartment arrangement, where the switchboard is service equipment
Informational Submittalscheckbox
☑ Manufacturer's qualification statement
☑ Field testing firm and technician qualifications
☐ Factory test procedure
☑ Trip unit and fuse characteristic data for the coordination study
☐ Ambient and altitude derating factors
☐ Utility acceptance of the metering compartment

3.3 Closeout Submittals

3.3.1 The Contractor shall submit the following before any switchboard is accepted:
  • record drawings reflecting every field change to the device arrangement, the wiring, and the network addressing
  • the certified factory test report
  • the field acceptance test report for each switchboard, giving every measured value, the acceptance criterion applied, and the tester's determination
  • the ground-fault protection performance test record required by NFPA 70 230.95(C), where ground-fault protection of equipment is furnished
  • the arc energy reduction documentation and performance test record required by NFPA 70 240.87, where a device rated 1200 A or more is furnished
  • the final settings of every adjustable trip unit and relay, as commissioned
  • the network address list and the point list for every networked device, where a network is furnished
  • operation and maintenance data covering the structure, the bus, each device, and the inspection and re-torque intervals of NEMA PB 2.1
  • the warranty certificate identifying each switchboard by designation and the warranty commencement date
  • a signed receipt from the Owner for the spare parts and keys delivered
Closeout Submittalscheckbox
☑ Record drawings
☑ Certified factory test report
☑ Field acceptance test reports
☐ Ground-fault protection performance test record
☐ Arc energy reduction documentation and test record
☑ Final trip unit and relay settings
☐ Network address and point list
☑ Operation and maintenance data
☑ Warranty certificate
☑ Spare parts and keys receipt

4 Quality Assurance

4.1 Manufacturer Qualifications

4.1.1 The switchboard shall be produced by a manufacturer that has held a UL 891 listing for switchboards of the type furnished for not less than the period indicated in the datasheet.
Manufacturer Listing Historyrange
Not less than
years
351020
4.1.2 The manufacturer shall maintain a factory-trained field service organization able to reach the site, and shall state in the qualification statement the location of the nearest service center and the period, measured from the date of manufacture, for which replacement devices and bus components for the switchboard platform will remain available.

4.2 Source Limitations

4.2.1 The structure, the bus, the device mounting, the main and feeder devices, and the compartments built into the structure shall be furnished by the switchboard manufacturer under one UL 891 listing.
4.2.2 Every switchboard on the project shall be furnished by one manufacturer, so that spare devices interchange and the Owner maintains one device family.
4.2.3 A device from another maker shall be installed in a switchboard only where the switchboard manufacturer has listed the device for the assembly under UL 891, and the assembly short-circuit current rating with that device installed shall be stated in the action submittals.
NOTE A meter, a relay, or a surge protective device from another maker remains covered by the assembly listing only where the switchboard manufacturer installed it in a compartment of its own construction and evaluated it as part of the assembly; a device added to the structure in the field without that evaluation removes the switchboard from the condition under which its rating was established. (4.2.4)

4.3 Field Testing Firm

4.3.1 Field acceptance testing shall be performed by the firm indicated in the datasheet.
Field Acceptance Testing Firmradio
○ Independent testing firm accredited to ANSI/NETA ATS
○ Manufacturer's field service organization
○ Installing contractor's own technicians
4.3.2 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 switchboards of the type furnished.
NOTE An independent firm has no stake in whether the switchboard passes and reports against a published acceptance standard; the manufacturer's organization knows the product best and is already on site where start-up services are furnished; 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. (4.3.3)

5 Environmental and Service Conditions

5.1 Ambient Temperature

5.1.1 The switchboard shall carry its nameplate ratings continuously at the design ambient temperature of the space it is installed in.
5.1.2 The design ambient temperature for a switchboard installed indoors shall be as indicated in the datasheet.
Indoor Design Ambient Temperaturerange
Not less than
°C
2530405055
NOTE UL 891 establishes the assembly ratings at a 40 °C ambient, and the circuit breakers inside are calibrated at 40 °C under UL 489, so a 40 °C design ambient is the condition at which every rating applies without correction; a higher value covers an electrical room whose ventilation cannot hold 40 °C at design load, at the cost of a larger bus or a larger device for the same load. (5.1.3)
5.1.4 A switchboard installed outdoors or in a space that follows the outdoor temperature shall be rated for Site Ambient Temperature MaximumSite Ambient Temperature MaximumParameterEach project supplies its own value.site-ambient-temperature-maximum where that temperature exceeds 40 °C, and the manufacturer shall state the derating applied in the action submittals.

5.2 Altitude

5.2.1 The switchboard and its devices shall be derated for AltitudeAltitudeParameterEach project supplies its own value.altitude in accordance with the manufacturer's published correction factors where the altitude exceeds the 2000 m rating basis of the listing.
NOTE Air thins with altitude, which reduces both the convective cooling that sets the continuous current rating of the bus and the devices and the dielectric strength of the clearances inside the structure, so a switchboard rated at sea level carries less current and less insulation margin at elevation than its nameplate states. (5.2.2)
5.2.3 Ambient temperature derating and altitude derating shall be applied cumulatively where both conditions apply.

5.3 Condensation Control

5.3.1 Where the switchboard is installed outdoors or in a space that is not conditioned, a thermostatically controlled space heater shall be furnished in each vertical section.
5.3.2 Where space heaters are furnished, they shall be sized to hold the interior of each section above the dew point at Site Ambient Temperature MinimumSite Ambient Temperature MinimumParameterEach project supplies its own value.site-ambient-temperature-minimum, and shall be supplied from a circuit that stays energized while the switchboard main device is open.
NOTE A switchboard that stands in an unconditioned space cycles through the dew point with every cold night, and the condensation that forms on the bus, the device terminals, and the insulating supports is the mechanism behind most tracking failures on outdoor and unheated switchboards. (5.3.3)

5.4 Seismic Qualification

5.4.1 The seismic certification required for the switchboard shall be as indicated in the datasheet.
Seismic Certification Requirementselect
Not required
Anchorage design only per ASCE 7 Chapter 13
Special seismic certification by shake-table test per ICC-ES AC156 or by analysis accepted by the Authority Having Jurisdiction
Derived — Seismic Design CategorySeismic Design CategoryParameterEach project supplies its own value.seismic-design-category and the component importance factor assigned to the switchboard under ASCE 7 Chapter 13 (by default)
NOTE Anchorage keeps the switchboard on its pad; special certification demonstrates that the devices in it still function after the design earthquake, which ASCE 7 requires of a component whose importance factor is above 1.0, such as a switchboard serving egress lighting, a fire pump, smoke control, or another load a Risk Category IV facility depends on. (5.4.2)
5.4.3 Where seismic certification is required, it shall be performed in accordance with the seismic provisions of Adopted Building CodeAdopted Building CodeParameterEach project supplies its own value.adopted-building-code and ASCE 7 Chapter 13, and the certificate shall cover the switchboard as furnished, including the structure, the bus, and every device installed, in the heaviest section arrangement furnished.
5.4.4 A certificate covering a single section, an empty structure, or a component tested apart from the assembly shall not be accepted as certification of the switchboard.
5.4.5 A field change to the devices installed or to the anchorage that departs from the certified configuration shall be re-evaluated by the manufacturer against the certification before the switchboard is energized.

6 Electrical Ratings

6.1 Service Configuration

6.1.1 Whether the switchboard is service equipment shall be as indicated in the datasheet.
Service Configurationradio
○ Service equipment
○ Downstream distribution equipment
Per drawings — the one-line diagram (deferred by default)
6.1.2 Where the switchboard is service equipment, it shall be listed and marked as suitable for use as service equipment under UL 891 and UL 869A and shall comply with NFPA 70 Article 230, including the service disconnecting means, the available fault current marking, the main bonding jumper, and the grounding electrode conductor termination furnished under Electrical Service EntranceElectrical Service EntranceResolves to the current adopted revision.sync/electrical-service-entrance and Grounding And BondingGrounding and Bonding for Electrical SystemsResolves to the current adopted revision.sync/grounding-and-bonding.
6.1.3 Where the switchboard is service equipment, the number of service disconnects shall not exceed the number NFPA 70 230.71 permits for the service, each shall be marked as a service disconnect, and where more than one is furnished they shall be grouped in a section or sections separated from the remainder of the switchboard by a barrier as NFPA 70 230.71(B) requires.
6.1.4 Where the switchboard is service equipment, the serving utility's metering requirements shall be confirmed in writing before the switchboard is released for manufacture, and the arrangement accepted shall be shown on the shop drawings.

6.2 Main Arrangement

6.2.1 The main arrangement of the switchboard shall be as indicated in the datasheet.
Main Arrangementselect
Single main
Double-ended, main-tie-main
Multiple mains on a common bus
Per drawings — the one-line diagram (deferred by default)
NOTE A single main is the arrangement most switchboards are built with; a double-ended switchboard takes two sources onto two bus halves joined by a tie device, so that either source can carry the whole bus with the other out of service; multiple mains on a common bus is the service arrangement in which up to the number of disconnects NFPA 70 230.71 permits each protect a portion of the bus without a single main. (6.2.2)
6.2.3 Where a main-tie-main arrangement is furnished, the two mains and the tie shall be interlocked so that not more than two of the three devices can be closed at one time unless the one-line diagram indicates a closed-transition scheme, and the interlock method shall be as indicated in the datasheet.
Main-Tie-Main Interlock Methodradio
○ Key interlock
○ Electrical interlock through the device auxiliary contacts
○ Key and electrical interlock
NOTE A key interlock enforces the two-of-three rule mechanically and works with the control power lost, but it depends on the operator carrying the key between devices; an electrical interlock acts through the device trip and close circuits and lends itself to an automatic transfer scheme, but it is only as good as the control power that feeds it; furnishing both covers each one's failure mode at the cost of both. (6.2.4)
6.2.5 Where the one-line diagram indicates an automatic transfer scheme at a main-tie-main switchboard, the transfer controller, its sensing, and its time delays shall be furnished by the switchboard manufacturer under the assembly listing, and the devices it operates shall be electrically operated.

6.3 System Voltage and Frequency

6.3.1 The system voltage and configuration shall be as indicated in the datasheet.
System Voltageselect
120/240 V 1Φ 3-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
Per drawings — the one-line diagram (deferred by default)
NOTE The number of phases and the number of wires follow from the system voltage selected, and the number of poles on the devices and the presence of a neutral bus follow from them in turn. (6.3.2)
6.3.3 The switchboard voltage rating shall equal or exceed the system voltage, and where the switchboard is fed from a transformer secondary the Contractor shall confirm the rating against the secondary configuration of the transformer before the switchboard is released for manufacture.
6.3.4 Where the system is a high-leg delta, the high leg shall be connected to the B phase of the bus and shall be identified in accordance with NFPA 70 110.15 and 408.3(F).
6.3.5 Where the system is a 3-wire delta or another system with no grounded conductor at the switchboard, the switchboard shall be furnished without a neutral bus and the devices shall be rated for the line-to-line voltage.
6.3.6 The system frequency shall be as indicated in the datasheet.
System Frequencyradio
● 60 Hz
○ 50 Hz

6.4 Main Bus Continuous Current

6.4.1 The main bus continuous current rating shall be as indicated in the datasheet.
Main Bus Continuous Currentrange
A
4006008001000120016002000250030003200400050006000
Per drawings — the one-line diagram (deferred by default)
6.4.2 The main bus rating shall be not less than the rating of the main device where one is furnished, not less than the rating of the feeder overcurrent device ahead of the switchboard where it has main lugs only, and not less than the sum of the ratings of the service disconnects where multiple mains are furnished without a single main.
NOTE The bus rating is fixed by the calculated load of NFPA 70 Article 220, the transformer or service ahead of the switchboard, and the spare capacity the project wants to leave, and it is stated on the one-line diagram with the main device that protects it; a bus cannot be uprated after manufacture without replacing the sections that carry it, which is why the rating is chosen against the ultimate source rating rather than the first-day load. (6.4.3)
6.4.4 The through-bus rating basis for the distribution sections shall be as indicated in the datasheet.
Through-Bus Rating Basisradio
○ Full main bus rating through every section
○ Tapered, each section rated for the load it and the sections beyond it carry
NOTE A full-rated through-bus carries the main bus rating to the far end of the lineup, so that a feeder of any rating can be added in any section and a section can be added at the end without re-rating the bus; a tapered through-bus is sized in each section for the devices actually downstream of it, which saves bus material on a long lineup and fixes the lineup to the device arrangement it was built for. (6.4.5)
6.4.6 Where a tapered through-bus is selected, the rating of the bus in each section shall be shown on the shop drawings, and no feeder device shall be installed in a section whose through-bus rating is less than the sum of the feeder ratings it carries.

6.5 Short-Circuit Current Rating

6.5.1 The available fault current at the line terminals of each switchboard shall be as indicated on the one-line diagram.
6.5.2 The assembly short-circuit current rating marked on the nameplate of each switchboard shall equal or exceed the available fault current at its line terminals as established under Short Circuit StudyShort-Circuit StudyResolves to the current adopted revision.sync/short-circuit-study, and shall be as indicated in the datasheet.
Assembly Short-Circuit Current Ratingrange
Not less than
kA
22253542506585100150200
Per drawings — the one-line diagram (deferred by default)
NOTE The marked assembly rating is the lowest of the bus bracing, the interrupting rating of the main device, and the interrupting rating of every feeder device, or the rating of the series-rated combination that covers them, so a single device of a lower rating installed in the field lowers the rating of the whole switchboard. (6.5.3)
6.5.4 The bus short-circuit bracing shall be as indicated in the datasheet.
Bus Short-Circuit Bracingrange
Not less than
kA
22253542506585100150200
Derived — the assembly short-circuit current rating; the bus is braced to not less than the rating marked on the switchboard (by default)
6.5.5 The short-time withstand rating of the assembly shall be as indicated in the datasheet.
Short-Time Withstand Ratingradio
● 3-cycle short-circuit rating only
○ 30-cycle short-time withstand rating
NOTE A UL 891 switchboard is tested to carry its short-circuit current for 3 cycles, which is the time a molded-case device takes to clear, and that is the construction most switchboards are built with; a 30-cycle short-time rating braces the bus and the structure to carry the fault for a half second, which is what a main device needs if its instantaneous element is to be set above the arcing current or defeated so that a downstream device clears first. The 30-cycle rating is bought with heavier bus supports and a main whose frame carries a short-time rating, and it is the construction a selectively coordinated system often requires at the main. (6.5.6)
6.5.7 Where a 30-cycle short-time withstand rating is selected, the main device shall carry a short-time rating not less than the assembly rating for 30 cycles, and the bus bracing shall be established for that duration.

6.6 Interrupting Rating Basis

6.6.1 The basis on which the interrupting ratings of the devices in the switchboard are established shall be as indicated in the datasheet.
Interrupting Rating Basisradio
● Fully rated
○ Series rated
NOTE In a fully rated switchboard every device carries an interrupting rating that stands on its own at the available fault current; in a series-rated switchboard the feeder devices carry a lower individual rating and reach the marked rating only in combination with the specific upstream device they were tested with, which NFPA 70 240.86 permits where the combination is listed. Series rating lowers the cost of the feeder devices where the available fault current is high, and it makes the rating depend on an upstream device that must stay in place for the life of the installation. The switchboard stands at the head of the system, where the fault current is highest and where the device it would depend on is a utility fuse or sits in another assembly, which is why a fully rated switchboard is the norm here while the series combinations a project uses are more often applied in the panelboards it feeds. (6.6.2)
6.6.3 The interrupting rating of the feeder devices shall be as indicated in the datasheet.
Feeder Device Interrupting Ratingrange
Not less than
kA
22253542506585100150200
Derived — the assembly short-circuit current rating and the interrupting rating basis; under a fully rated basis every device equals or exceeds the assembly rating, and under a series rated basis the listed combination fixes the feeder device rating (by default)
6.6.4 Where series rating is the basis, the combination shall be one the manufacturer has tested and listed under UL 891 and UL 489 in accordance with NFPA 70 240.86(B), and the upstream device on which each rating depends shall be identified in the action submittals.
6.6.5 Where series rating is the basis, the switchboard shall be field-marked in accordance with NFPA 70 110.22(C) to identify the series combination and the replacement devices it depends on.
6.6.6 Where series rating is the basis, the Contractor shall confirm that the sum of the motor full-load currents connected between the upstream device and the feeder device does not exceed the limit NFPA 70 240.86(C) sets for the feeder device rating, and shall report a combination that exceeds it to the Engineer of Record before the switchboard is released for manufacture.
6.6.7 Where the switchboard serves a system that NFPA 70 Article 700, 701, or 708 requires to be selectively coordinated, a series-rated combination shall not be relied on within the coordinated path, because the upstream device of a series combination opens with the feeder device on a high-magnitude fault.
6.6.8 Where a device in a series-rated switchboard is replaced, the replacement shall be of the same manufacturer, type, and rating named in the listed combination.

6.7 Neutral Bus

6.7.1 The neutral bus shall be as indicated in the datasheet.
Neutral Busselect
No neutral bus
Neutral bus rated 50% of the phase bus
Neutral bus rated 100% of the phase bus
Neutral bus rated 200% of the phase bus
Derived — the system voltage configuration and the share of nonlinear load served from the switchboard (by default)
NOTE A three-wire system has no neutral to carry; a four-wire system whose load is largely three-phase or balanced line-to-neutral carries a neutral that NFPA 70 220.61 lets be reduced below the phase bus; a four-wire system with ordinary single-phase load carries one rated with the phase bus; and a four-wire system whose load is predominantly single-phase nonlinear equipment, such as switch-mode power supplies, LED drivers, and single-phase drives, 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. (6.7.2)
6.7.3 Where a neutral bus is furnished, it shall be insulated from the structure, shall extend the full length of the switchboard, and where the switchboard is service equipment the main bonding jumper shall be furnished by the manufacturer and installed in accordance with Grounding And BondingGrounding and Bonding for Electrical SystemsResolves to the current adopted revision.sync/grounding-and-bonding.
6.7.4 Where a neutral bus is furnished, a neutral terminal shall be furnished for every feeder device position, including spare and space positions, sized for the neutral conductor of the feeder it serves.

6.8 Ground Bus

6.8.1 The ground bus shall be as indicated in the datasheet.
Ground Busradio
● Full-length ground bus
○ No ground bus
NOTE A switchboard 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 switchboard carries one. (6.8.2)
6.8.3 Where a ground bus is furnished, it shall be copper of not less than 1/4 in. by 2 in. cross-section, shall be bonded to each section of the structure, shall extend the full length of the switchboard, and shall carry a terminal for the equipment grounding conductor of every feeder device position.
6.8.4 The ground bus shall be accessible from the front of each section without removing a bus barrier or a device cover.
6.8.5 Grounding and bonding of the switchboard shall comply with Grounding And BondingGrounding and Bonding for Electrical SystemsResolves to the current adopted revision.sync/grounding-and-bonding.

7 Main Device

7.1 Main Device Type

7.1.1 The main device of the switchboard shall be as indicated in the datasheet.
Main Device Typeselect
Main lugs only
Main circuit breaker
Main fusible switch
Main bolted-pressure switch with fuses
Per drawings — the one-line diagram (deferred by default)
7.1.2 The main device frame size and trip rating, or the switch rating and the fuse class and rating, shall be as indicated on the one-line diagram.
NOTE A main circuit breaker gives the switchboard a disconnecting means and an overcurrent device at the assembly, and its trip unit is the place the coordination study sets the main's characteristic; main lugs only leaves both functions to the device upstream and saves the cost and the section of the main, which is the construction a switchboard fed from a transformer secondary device or from another assembly's feeder is built with; a main fusible switch is the construction used where the fault current calls for a current-limiting fuse or where the Owner's device family is fused; a bolted-pressure switch is the fused main built for the large service, with contacts clamped under bolt pressure after closing so that the switch carries the full bus current without heating at the blades. (7.1.3)
7.1.4 Where the switchboard has main lugs only, it shall be protected by an overcurrent device on the supply side whose rating does not exceed the bus rating, in accordance with NFPA 70 408.36, and that device shall be accessible as the disconnecting means for the switchboard.
7.1.5 Where the switchboard is service equipment and has a single main, the main device shall be the service disconnecting means and shall be rated in accordance with NFPA 70 Article 230.
7.1.6 Where a main fusible switch or a bolted-pressure switch is furnished, it shall be listed to UL 98 or UL 977 for the rating furnished, shall carry an interrupting rating with the fuse class installed not less than the assembly rating, and shall be furnished with rejection-type fuse clips for the fuse class indicated on the one-line diagram.
7.1.7 Where a bolted-pressure switch is furnished, it shall be electrically operated with a stored-energy mechanism and shall be furnished with blown-fuse indication and an open-fuse trip that opens the switch when any one fuse opens.
7.1.8 The main device operating handle shall accept a padlock in the open position.

7.2 Main Circuit Breaker Construction

7.2.1 Where a main circuit breaker is furnished, its construction shall be as indicated in the datasheet.
Main Circuit Breaker Constructionselect
Molded-case circuit breaker, fixed-mounted
Insulated-case circuit breaker, fixed-mounted
Insulated-case circuit breaker, drawout-mounted
Low-voltage power circuit breaker, drawout-mounted
NOTE A molded-case breaker is the smallest and least expensive main, is built with a thermal-magnetic or an electronic trip unit, and clears every fault instantaneously in the larger frames, which limits how a downstream device can be coordinated with it; an insulated-case breaker is a molded-case breaker built on a stored-energy, two-step mechanism with a short-time rating, which lets its instantaneous element be set high or defeated so that a feeder device clears first, and it is the construction the 30-cycle short-time withstand rating is built on; mounting the insulated-case breaker drawout lets it be racked out for inspection or exchange with the bus energized, at the cost of the drawout cradle and the section depth it needs; a low-voltage power circuit breaker listed to IEEE C37.13 can be furnished in a UL 891 switchboard where a project wants its 30-cycle rating and its maintainable contacts, and the assembly remains a switchboard listed to UL 891 rather than switchgear. (7.2.2)
7.2.3 Where a drawout-mounted main is furnished, the cradle shall carry connected, test, and disconnected positions, shall have a position indicator visible with the door closed, and shall interlock so that the breaker cannot be racked between the connected and disconnected positions while closed.
7.2.4 Where a drawout-mounted main is furnished, automatic shutters shall cover the primary disconnects when the breaker is withdrawn.
7.2.5 Where a main circuit breaker is furnished, it shall be electrically operated where the one-line diagram indicates a transfer scheme, a remote operator, or a ground-fault or arc-flash scheme that closes or opens the main from a remote contact.

7.3 Main Circuit Breaker Trip Unit

7.3.1 Where a main circuit breaker is furnished, its trip unit shall be as indicated in the datasheet.
Main Circuit Breaker Trip Unitselect
Thermal-magnetic
Electronic with long-time and instantaneous functions
Electronic with long-time, short-time, and instantaneous functions
Electronic with long-time, short-time, instantaneous, and ground-fault functions
Per drawings — the one-line diagram (deferred by default)
NOTE A thermal-magnetic trip unit has a fixed time-current characteristic, an instantaneous setting that is adjustable on the larger frames only, and no communications, and it is the construction the smaller frames are built with; an electronic trip unit has adjustable long-time, short-time, and instantaneous settings, which is what selective coordination with the feeder devices is set with, and it is the construction the larger frames are built with; the ground-fault function on an electronic trip unit is one of the two ways ground-fault protection of equipment is furnished where code requires it. (7.3.2)
7.3.3 Where a main circuit breaker with an electronic trip unit is furnished, its settings shall be as established under Protective Coordination StudyProtective Device Coordination StudyResolves to the current adopted revision.sync/protective-coordination-study, and the settings as commissioned shall be recorded in the closeout submittals.
7.3.4 Where an electronic trip unit is furnished, it shall display the settings applied and the cause of the last trip at the device, and shall carry a test port for secondary injection testing.

7.4 Ground-Fault Protection of Equipment

7.4.1 Ground-fault protection of equipment on the main device shall be as indicated in the datasheet.
Ground-Fault Protection of Equipment on the Main Deviceselect
Not provided
Integral to the main circuit breaker electronic trip unit
Separate ground-fault relay and sensor listed to UL 1053
Derived — NFPA 70 230.95 and 215.10 applied to the system voltage, the main device rating, and whether the switchboard is service equipment (by default)
NOTE 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 can add ground-fault protection where code does not require it, and where it is required the means of providing it is the project selection, with the separate relay being the means used on a fused main, which has no trip unit to carry the function. (7.4.2)
7.4.3 Where ground-fault protection of equipment is furnished, it shall open all ungrounded conductors of the switchboard at a ground-fault pickup not exceeding 1200 A and within one second for a ground-fault current of 3000 A or more, in accordance with NFPA 70 230.95(A).
7.4.4 Where ground-fault protection of equipment is furnished on a switchboard that is not service equipment, its pickup and delay shall be set to coordinate with the ground-fault protection upstream as established under Protective Coordination StudyProtective Device Coordination StudyResolves to the current adopted revision.sync/protective-coordination-study.
7.4.5 Where ground-fault protection of equipment is furnished on the main and the feeders carry ground-fault functions of their own, the main's ground-fault delay shall be set so that a feeder clears its own ground fault before the main opens, and where the switchboard serves a health care facility the two levels shall be coordinated as NFPA 70 517.17 requires.
7.4.6 Where ground-fault protection of equipment is furnished, the Contractor shall have it performance-tested by primary current injection after installation in accordance with NFPA 70 230.95(C), and the written record shall be delivered with the closeout submittals.
NOTE Ground-fault protection of equipment protects the bus and the conductors from the arcing damage of a low-magnitude ground fault that the main device would not clear promptly; it does not protect a person, and it is not a substitute for the ground-fault circuit-interrupter protection NFPA 70 210.8 requires on branch circuits. (7.4.7)

7.5 Arc Energy Reduction

7.5.1 Where a circuit breaker in the switchboard 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.
Arc Energy Reduction Methodselect
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
Derived — NFPA 70 240.87 applied to the rating of the main device and of each feeder device shown on the one-line diagram (by default)
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. (7.5.2)
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 by light and current and clears it faster than any trip unit, at the highest cost; an instantaneous setting below the arcing current works only where the arcing current at the switchboard is well above the load current, and it is the method a fused main cannot use. (7.5.3)
7.5.4 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.
7.5.5 Where a fused main rated 1200 A or more is furnished, arc energy reduction shall be provided in accordance with NFPA 70 240.67 by a method the fuse and switch combination supports, and the method shall be identified in the action submittals.
7.5.6 Where arc energy reduction is furnished, the Contractor shall perform the performance test NFPA 70 240.87(C) requires and shall deliver the documentation NFPA 70 240.87(A) requires with the closeout submittals.

8 Feeder Devices

8.1 Feeder Device Type

8.1.1 The feeder devices of the switchboard shall be as indicated in the datasheet.
Feeder Device Typeselect
Molded-case circuit breakers, group-mounted
Molded-case and insulated-case circuit breakers, individually mounted
Fusible switches, group-mounted
Fusible switches, individually mounted
8.1.2 Where the one-line diagram indicates a device type for a particular feeder that differs from the datasheet selection, the one-line diagram shall govern for that feeder.
NOTE Group-mounted molded-case breakers bolt side by side onto a common panel-mounted bus in a distribution section, which gives the highest device density per section and the lowest cost, and it is the construction most switchboards are built with; individual mounting gives each device its own compartment and its own bus connection, which is how the larger frames are mounted and how a project separates feeders so that work on one does not expose the line side of its neighbors; fusible switches are the construction used where the Owner's device family is fused or where the current-limiting fuse is what holds the downstream rating. (8.1.3)
8.1.4 The frame size, the pole count, the trip rating, and the fuse class and rating of every feeder device shall be as indicated on the one-line diagram.
8.1.5 Every feeder device shall be rated for the system voltage, and a feeder circuit breaker shall be listed to UL 489 and built to NEMA AB 1.
8.1.6 Multi-pole feeder breakers shall be common-trip, so that every pole opens when any pole trips.
8.1.7 Every feeder device shall have a trip-free mechanism, a handle that indicates the on, off, and tripped positions, and a handle that accepts a padlock in the open position.
8.1.8 Where fusible feeder switches are furnished, each shall be listed to UL 98, shall be furnished with rejection-type fuse clips for the fuse class indicated on the one-line diagram, and shall be interlocked so that its cover cannot be opened with the switch closed.

8.2 Feeder Trip Units

8.2.1 The trip unit of the feeder circuit breakers shall be as indicated in the datasheet.
Feeder Circuit Breaker Trip Unitselect
Thermal-magnetic
Electronic with long-time and instantaneous functions
Electronic with long-time, short-time, and instantaneous functions
Electronic with long-time, short-time, instantaneous, and ground-fault functions
Per drawings — the one-line diagram (deferred by default)
8.2.2 Where the one-line diagram indicates a trip unit type for a particular feeder that differs from the datasheet selection, the one-line diagram shall govern for that feeder.
NOTE A thermal-magnetic feeder breaker is the construction the frames below about 400 A are built with and costs least; an electronic trip unit on a feeder is what lets that feeder be coordinated with the main above it and the panelboard main below it, and its ground-fault function is one of the two ways NFPA 70 215.10 is satisfied on a feeder that requires ground-fault protection of equipment. (8.2.3)
8.2.4 Where a feeder circuit breaker with an electronic trip unit is furnished, its settings shall be as established under Protective Coordination StudyProtective Device Coordination StudyResolves to the current adopted revision.sync/protective-coordination-study, and the settings as commissioned shall be recorded in the closeout submittals.
8.2.5 Where NFPA 70 215.10 requires ground-fault protection of equipment on a feeder, it shall be furnished at that feeder device unless the one-line diagram indicates that the ground-fault protection on the main satisfies the requirement for that feeder.

8.3 Device Accessories

8.3.1 Shunt trips, undervoltage releases, auxiliary contacts, bell alarm contacts, motor operators, key interlocks, and mechanical interlocks shall be furnished on the devices designated on the one-line diagram.
NOTE A shunt trip lets a device be opened from a remote contact, as at a kitchen hood suppression system, an emergency power off station, or a fire alarm interface; an undervoltage release opens the device when its control voltage is lost, which is the behavior wanted on a device that must not stay closed through a loss of control power and the behavior to avoid on one that must; an auxiliary contact reports the device position to a control or monitoring system; a bell alarm contact reports a trip as distinct from a manual opening; a motor operator lets the device be closed and opened from a remote point or by a transfer controller. (8.3.2)
8.3.3 Where a shunt trip or an undervoltage release is furnished, its control voltage and the source of its signal shall be as indicated on the one-line diagram, and the circuit shall be tested through its initiating device before the switchboard is accepted.
8.3.4 Every accessory shall be the device manufacturer's accessory listed for the frame it is installed on, and shall be installed by the switchboard manufacturer under the assembly listing.

8.4 Spare Devices and Spaces

8.4.1 The share of feeder device positions in each switchboard left for future feeders shall be not less than the share indicated in the datasheet, in addition to the spare and space positions the one-line diagram designates.
Spare Feeder Positionsrange
Not less than
%
1015202530
8.4.2 The form in which spare positions are furnished shall be as indicated in the datasheet.
Spare Position Provisionradio
○ Bussed spaces with mounting hardware and covers
○ Spare devices installed
NOTE A bussed space is a position with its bus connection, its mounting hardware, and a blank cover in place, ready to receive a device of any listed frame that fits it without drilling live bus; a spare device installed is a device bought now, marked spare, and left open, which lets a feeder be added without a purchase but commits the frame and the trip rating in advance. (8.4.3)
8.4.4 Where spare devices are installed, the frame size and trip rating of the spares shall be as indicated on the one-line diagram, and each spare shall be left in the open position and identified as a spare.
8.4.5 Every space position shall be bussed and provided with the mounting hardware needed to receive a device without modifying the bus or the structure, and shall be covered by a blank cover when the switchboard is delivered.

9 Bus

9.1 Phase Bus Material

9.1.1 The phase bus material shall be as indicated in the datasheet.
Phase Bus Materialradio
○ Copper
○ Aluminum
NOTE Copper bus carries more current per unit cross-section, has the lower contact resistance at a bolted joint, and costs more; aluminum bus is lighter and less expensive for the same rating, and its joints depend on the plating and on the joint hardware to hold their resistance through thermal cycling, which is why aluminum is chosen where the cost difference on a large bus matters and copper is chosen where the joint count is high, where the bus is to be field-extended, or where the environment attacks aluminum. (9.1.2)
9.1.3 Where copper bus is selected, it shall be copper bus bar conforming to ASTM B187 with a conductivity of not less than 98% IACS.
9.1.4 Where aluminum bus is selected, it shall be an aluminum alloy bus conductor conforming to ASTM B317 with a conductivity of not less than 55% IACS, and shall be plated over its full length.
9.1.5 A joint between an aluminum bus and a copper conductor, terminal, or bus shall be made with a connector or a plated joint listed for the combination.

9.2 Bus Plating

9.2.1 The bus plating shall be as indicated in the datasheet.
Bus Platingradio
○ Unplated, with plated joint contact surfaces
○ Tin-plated over the full length
○ Silver-plated over the full length
Manufacturer's standard (by default)
9.2.2 The manufacturer shall state the plating in the product data.
NOTE Bare copper bus with plating at the joints holds its contact resistance in a clean, dry interior and is the construction most copper switchboards are built with; tin plating over the full length resists the sulfur compounds that blacken silver and raise its contact resistance, and is the plating that holds its resistance where the atmosphere carries hydrogen sulfide, as in a wastewater facility; silver plating has the lowest contact resistance in a clean atmosphere. Aluminum bus is plated in every construction because its oxide forms within minutes of exposure and is an insulator. (9.2.3)
9.2.4 Plating shall be continuous over every bolted joint contact surface, every device line and load connection, and every splice at a shipping split.

9.3 Bus Sizing Basis

9.3.1 The basis on which the bus cross-section is sized shall be as indicated in the datasheet.
Bus Sizing Basisselect
Temperature rise per UL 891
Current density not exceeding 1000 A per square inch of copper
Current density not exceeding 750 A per square inch of copper
NOTE UL 891 sizes the bus so that its temperature rise under rated current does not exceed 65 °C over a 40 °C ambient, and that is the basis every listed switchboard is built to and the basis the manufacturer applies unless told otherwise; a density limit of 1000 A per square inch of copper gives a bus near the UL 891 rise in most sections and a larger bus in the compact ones; a limit of 750 A per square inch gives a cooler bus with more margin for an elevated room ambient, a future load increase, or harmonic heating, at the cost of more copper and sometimes a deeper section. (9.3.2)
9.3.3 Where a current density basis is selected for a copper bus, the equivalent density for an aluminum bus shall be the selected value multiplied by the ratio of the aluminum conductivity to the copper conductivity, and the manufacturer shall show the resulting bus cross-section on the shop drawings.

9.4 Bus Insulation

9.4.1 The bus insulation shall be as indicated in the datasheet.
Bus Insulationradio
● Bare bus with isolating barriers
○ Insulated bus with flame-retardant sleeving or coating
NOTE Bare bus behind barriers is the construction most switchboards are built with; insulated bus covers every bus surface a dropped tool or a misplaced hand could reach with a cover off, and reduces the chance that an arcing fault started at one point propagates along the bus, at the cost of the insulation and of the heat it holds in, which can call for a larger bus for the same rating. (9.4.2)
9.4.3 Where insulated bus is selected, the insulation shall be flame-retardant, shall be rated for the system voltage, and shall be continuous through the barriers and the bus transitions between sections, with the joints covered by removable insulating boots.

9.5 Bus Arrangement, Joints, and Bracing

9.5.1 The phase bus shall be arranged so that the phase sequence is A, B, C from front to back, top to bottom, or left to right as viewed from the front, in accordance with NFPA 70 408.3(E).
9.5.2 The bus shall be supported on insulating supports that withstand the bus short-circuit bracing indicated in the datasheet without damage, and the bus and its supports shall be rated for the system voltage.
9.5.3 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 listing.
9.5.4 The bus shall be spliced at every shipping split by a bolted splice plate furnished by the manufacturer, and the splice shall carry the full rating of the bus it joins.
9.5.5 Bus joints shall be accessible for inspection and re-torquing from the front of the switchboard, or from the rear where the switchboard is rear-accessible, without removing a device.

9.6 Bus Extension Provisions

9.6.1 The provisions for future extension of the switchboard shall be as indicated in the datasheet.
Bus Extension Provisionsselect
No extension provisions
Extension provisions at one end
Extension provisions at both ends
NOTE Extension provisions consist of a removable end closure, phase bus ends drilled for a splice, and neutral and ground bus ends drilled to match, so that a section can be added without drilling live bus; most switchboards are built against a wall or an end of the room with no section to come, which is why none is the default, and a lineup that is expected to grow carries the provisions at the end that will remain open. (9.6.2)
9.6.3 Where extension provisions are furnished, the end at which they are furnished shall be as indicated on the electrical plans, and the through-bus to that end shall carry the rating the extension is to be made at.

10 Structure and Enclosure

10.1 Enclosure Type

10.1.1 The enclosure type shall be as indicated in the datasheet.
Enclosure Type per NEMA 250select
Type 1
Type 1 gasketed
Type 2
Type 3R
Type 4
Type 4X
Type 12
NOTE A dry, conditioned electrical room is the installed location on most projects, which is why Type 1 is the default; every other location named in the clauses of this article calls for the type those clauses require. (10.1.2)
10.1.3 The enclosure shall comply with UL 50 and, for a type other than Type 1, with UL 50E and NEMA 250 for the type selected, and the type shall be marked on the structure.
10.1.4 A switchboard installed outdoors shall have an enclosure of Type 3R, Type 4, or Type 4X, with rain hoods over ventilation openings and a drip shield over each door.
10.1.5 A switchboard installed where it is subject to hose-directed water or wash-down shall have an enclosure of Type 4 or Type 4X.
10.1.6 A switchboard installed where the atmosphere carries salt, chemical vapor, or another corrosive agent, including a coastal site, a wastewater facility, and a food-processing area, shall have a Type 4X enclosure.
10.1.7 A switchboard installed indoors where airborne dust, lint, or fibers accumulate shall have an enclosure of Type 12, Type 1 gasketed, Type 4, or Type 4X.
10.1.8 A switchboard installed indoors where dripping or light splashing of a non-corrosive liquid occurs shall have an enclosure of Type 2, Type 12, Type 4, or Type 4X.
10.1.9 Where a rating higher than the datasheet selection is required by the clauses of this article for the installed location, the higher rating shall be furnished and the conflict reported to the Engineer of Record before the switchboard is released for manufacture.
NOTE A field opening cut in a Type 3R, Type 4, Type 4X, or Type 12 structure other than at a location and by a method the listing permits removes the environmental rating, and the rework is charged to the party that made the cut. (10.1.10)
10.1.11 Where the switchboard is installed outdoors, the outdoor housing arrangement shall be as indicated in the datasheet.
Outdoor Housing Arrangementradio
● Non-walk-in
○ Walk-in aisle
NOTE A non-walk-in housing is the smaller and lighter structure and the one most outdoor switchboards are built as, and its working space is the outdoor pad in front of it; a walk-in housing puts the working space inside a weatherproof room so that a device can be serviced in any weather, at the cost of a larger and heavier structure. (10.1.12)
10.1.13 Where a walk-in housing is furnished, the aisle shall provide the working space required by NFPA 70 110.26 in front of every device, and the housing shall have lighting, a convenience receptacle, and a door openable from inside without a key.

10.2 Enclosure Material and Finish

10.2.1 The enclosure material shall be as indicated in the datasheet.
Enclosure Materialselect
Painted steel
Type 304 stainless steel
Type 316 stainless steel
NOTE Painted steel is the construction the switchboard is built with and serves every enclosure type in a non-corrosive exposure; stainless steel is what a Type 4X rating is built in, with Type 316 holding up where chlorides are present. (10.2.2)
10.2.3 Where the datasheet selects a Type 4X enclosure, the enclosure material shall be one for which the Type 4X rating is listed.
10.2.4 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 or cover does not deflect when opened or removed with its devices installed.
10.2.5 A painted steel enclosure shall carry a baked powder coat or enamel finish over a phosphate pretreatment, and the manufacturer shall state the finish system and its dry film thickness in the product data.
10.2.6 The finish color shall be as indicated in the datasheet.
Finish Colorselect
ANSI 61 light gray
ANSI 49 medium gray
ANSI 70 sky gray
Custom color matched to a sample furnished by the Owner
NOTE ANSI 61 is the color the equipment is finished in unless told otherwise and the one the other electrical equipment on a project most often matches; the other grays and a custom color are chosen to match existing equipment in the room or an Owner's standard. (10.2.7)

10.3 Section Arrangement and Accessibility

10.3.1 The accessibility of the switchboard shall be as indicated in the datasheet.
Section Accessibilityselect
Front-accessible, front-connected
Rear-accessible, rear-connected
Front- and rear-accessible
NOTE A front-accessible switchboard makes every bus joint and every device connection from the front, stands against a wall, and needs working space on one face only, which is the construction the smaller bus ratings are built as; a rear-accessible switchboard lands the main and feeder conductors on the back of the devices, which gives the large conductor bundles of a high-rated service the bending space they need and keeps the cable away from the operating face, at the cost of a rear working space the room has to provide; a front- and rear-accessible switchboard is the rear-connected construction with the device fronts also serviceable, which is what a switchboard that sits in the open with aisles on both faces is built as. The choice follows the bus rating, the conductor count at the main, and the room, so the field asserts no default. (10.3.2)
10.3.3 Where a rear-accessible or a front- and rear-accessible switchboard is furnished, the rear shall be closed by hinged doors or bolted covers over every section, and the working space behind the switchboard shall be as NFPA 70 110.26 requires for the condition.
10.3.4 Sections shall be of uniform height and depth across the switchboard, shall align flush at the front, and shall be bolted together to form a rigid continuous assembly.
10.3.5 The number of vertical sections shall be the number needed to house the devices on the one-line diagram with the spare and space provisions this standard requires, and shall be shown on the shop drawings.
10.3.6 Section height and depth shall be the manufacturer's standard for the largest device installed and the accessibility selected, and shall be shown on the shop drawings.
10.3.7 The device covers shall be as indicated in the datasheet.
Device Coversradio
○ Hinged covers over bolted dead-front
○ Bolted removable covers
NOTE A hinged cover swings open on its own hinges so that the device line and load connections behind it can be inspected or re-torqued by one person without a cover to set down, and it is closed with a tool so that the dead-front stays in place during operation; a bolted removable cover costs less and is the construction the smaller switchboards are built with, and each inspection means a cover lifted off and set aside with the bus behind it exposed. (10.3.8)
10.3.9 Every device handle shall be operable with the device cover closed, and no energized part shall be exposed with the covers in place and the doors closed.

10.4 Internal Barriers

10.4.1 The internal barriers furnished within the structure shall be as indicated in the datasheet.
Internal Barrierscheckbox
☑ Barrier between the main bus compartment and the device compartments
☐ Barrier isolating the main section from the distribution sections
☐ Barriers between the line-side connections of adjacent individually mounted devices
☐ Barrier isolating the utility metering compartment
☐ Barrier isolating the surge protective device compartment
NOTE A barrier between the bus and the devices is what keeps a worker at a device cover away from the through-bus and is the one every switchboard is built with; a barrier at the main section keeps a fault in the distribution sections from the main and its line-side connections; barriers between individually mounted devices let one be worked on with its neighbors energized; the metering and surge protective device barriers keep those compartments, which are opened by different people for different reasons, away from the bus and the device connections. Each barrier adds cost and section depth, and each reduces what a worker can reach with a cover off. (10.4.2)
10.4.3 Barriers shall be grounded metal or an insulating material rated for the system voltage, and a barrier required by the listing or by NFPA 70 230.71(B) shall be furnished whatever the datasheet selects.

10.5 Conduit Entry and Wiring Space

10.5.1 Conduit entry to the switchboard shall be as indicated in the datasheet.
Conduit Entryradio
○ Top entry
○ Bottom entry
○ Top and bottom entry
Per drawings — the electrical plans (deferred by default)
10.5.2 Conduit shall enter only through the areas designated on the shop drawings, and the bus compartments, the device compartments, and the barriers between them shall not be penetrated by a raceway.
10.5.3 The wiring space at every device shall satisfy the bending space NFPA 70 312.6 requires for the conductors indicated on the one-line diagram, and where the standard section does not provide it the manufacturer shall furnish a deeper or wider section, or a pull section, and shall show the wiring space on the shop drawings.
10.5.4 Where a busway terminates at the switchboard, the busway flange, the bus connection, and the barrier at the entry shall be furnished by the switchboard manufacturer under the assembly listing, located as indicated on the electrical plans, and matched to the busway furnished under BuswayBuswayResolves to the current adopted revision.sync/busway.
10.5.5 Where a wireway or an auxiliary gutter adjoins the switchboard, the connection shall be made through the wiring space the manufacturer designates on the shop drawings with a coupling listed for the connection, and the trough shall comply with Wireways And Auxiliary GuttersWireways and Auxiliary GuttersResolves to the current adopted revision.sync/wireways-and-auxiliary-gutters.
10.5.6 A structure in a Type 3R, Type 4, or Type 4X enclosure shall be entered only with hubs or fittings listed for the enclosure type, and every unused opening shall be closed with a fitting listed for the type.

11 Arc-Flash Mitigation and Maintenance Safety

11.1 Arc-Resistant Construction

11.1.1 Arc-resistant construction shall be as indicated in the datasheet.
Arc-Resistant Constructionselect
Not required
Type 1 accessibility per IEEE C37.20.7
Type 2 accessibility per IEEE C37.20.7
NOTE Arc-resistant construction directs the products of an internal arcing fault away from the front of the switchboard, and Type 2 extends that protection to the sides and rear. It protects a worker standing at the switchboard 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, which is why most switchboards are built without it and a project whose arc-flash study or whose operating practice calls for workers at the energized switchboard buys it. (11.1.2)
11.1.3 Where arc-resistant construction is selected, the switchboard shall have been tested to IEEE C37.20.7 in the configuration furnished at the assembly short-circuit current rating and the short-time withstand duration selected, and the exhaust plenum and its discharge location shall be shown on the shop drawings.
NOTE Arc-resistant construction does not lower the incident energy at a device whose cover is open, and does not substitute for the arc energy reduction required by NFPA 70 240.87. (11.1.4)

11.2 Maintenance Safety Provisions

11.2.1 The maintenance safety provisions furnished shall be as indicated in the datasheet.
Maintenance Safety Provisionscheckbox
☐ Infrared inspection windows at the main connections and the bus splices
☐ Voltage presence indicator at each section
☐ Absence-of-voltage tester at the main device
☐ Remote operator for the main device
☐ Remote racking device for a drawout-mounted main
NOTE Each provision lets a task be performed with less exposure than the alternative: an infrared window lets a connection be scanned under load with the cover on, a voltage indicator confirms the state of a section before its cover is removed, 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 remote racking device lets a drawout main be racked with the operator outside the boundary. (11.2.2)
11.2.3 Arc-flash warning 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 Arc Flash StudyArc-Flash StudyResolves to the current adopted revision.sync/arc-flash-study, placed so that each is read before a cover is removed or a door opened.

12 Service Entrance, Surge Protection, and Metering Provisions

12.1 Utility Metering Compartment

12.1.1 The utility metering compartment shall be as indicated in the datasheet.
Utility Metering Compartmentselect
Not furnished
Utility current transformer compartment ahead of the main, cold sequence
Utility current transformer compartment after the main, hot sequence
Derived — the service configuration and the serving utility's metering requirements as confirmed in writing (by default)
NOTE Whether a utility compartment is furnished follows from whether the switchboard is service equipment, and whether the utility's transformers sit ahead of the main or after it follows from the serving utility's metering rules, so the field records the consequence of those inputs; a cold-sequence compartment is de-energized by the service disconnect so that the utility can work in it without a utility-side disconnect, and a hot-sequence compartment is energized ahead of any customer device so that the main cannot be used to interrupt the metering. (12.1.2)
12.1.3 Where a utility metering compartment is furnished, it shall be sized, arranged, barriered, and provided with sealing provisions in accordance with the serving utility's published requirements, and the utility's current transformers and meter shall be mounted on provisions the switchboard manufacturer furnishes.
12.1.4 Where a utility metering compartment is furnished, it shall be separated from every other compartment by a barrier and shall be accessible only through its own cover or door.

12.2 Surge Protective Device Provisions

12.2.1 A surge protective device shall be furnished at the switchboards indicated on the one-line diagram, and the device, its type, its ratings, its protection modes, and its lead length shall comply with Surge Protective DevicesSurge Protective DevicesResolves to the current adopted revision.sync/surge-protective-devices.
12.2.2 Where a surge protective device is furnished at a switchboard, its mounting arrangement shall be as indicated in the datasheet.
Surge Protective Device Mounting Arrangementradio
○ Integral, factory-installed in a compartment of the switchboard
○ External, mounted adjacent to the switchboard and connected through a dedicated feeder device
NOTE An integral device is connected to the bus by the manufacturer with the shortest lead the structure allows, is covered by the assembly listing, and is replaced from within the switchboard; an external device is connected through a feeder device with a lead of whatever length the installation produces, is replaced without opening the switchboard, and is the arrangement used where the switchboard is existing or where the Owner standardizes on one device family across equipment of several makers. (12.2.3)
12.2.4 Where an integral surge protective device is furnished, it shall be listed to UL 1449, shall be installed by the switchboard manufacturer under the UL 891 listing, shall be connected to the bus through a dedicated disconnect so that it can be isolated for replacement without de-energizing the switchboard, and shall have its status indication visible with the cover closed.
12.2.5 Where the switchboard is service equipment, the surge protective device at it is the service-equipment surge protection that Lightning ProtectionLightning Protection SystemsResolves to the current adopted revision.sync/lightning-protection coordinates with, and its connection to the grounding electrode system shall be as Grounding And BondingGrounding and Bonding for Electrical SystemsResolves to the current adopted revision.sync/grounding-and-bonding requires.

12.3 Metering Provisions

12.3.1 The metering furnished within the switchboard shall be as indicated in the datasheet.
Metering Provisionsselect
No metering
Current transformer and meter mounting provisions only
Main metering
Main and feeder metering
NOTE Main metering records the switchboard as one load, which is what a service or a tenant main needs for demand and energy; feeder metering makes each feeder visible for commissioning, submetering, and measurement and verification, at the cost of current transformers on every feeder and a meter able to read them; mounting provisions leave the compartment and the current transformer space in place for a meter bought later. Whether a switchboard carries any meter depends on what the monitoring system under Electrical Power MonitoringElectrical Power Monitoring and MeteringResolves to the current adopted revision.sync/electrical-power-monitoring wants from it, so the field asserts no default. (12.3.2)
12.3.3 Meters, their accuracy class, their current transformers, and their communications shall comply with Electrical Power MonitoringElectrical Power Monitoring and MeteringResolves to the current adopted revision.sync/electrical-power-monitoring, and where metering is furnished within the switchboard it shall be installed by the manufacturer under the UL 891 listing in an instrument compartment separate from the wiring space and the bus.
12.3.4 Current transformers furnished within the switchboard shall comply with IEEE C57.13, and current transformers serving a protective relay shall be on cores separate from those serving a meter.
12.3.5 Where Adopted Energy CodeAdopted Energy CodeParameterEach project supplies its own value.adopted-energy-code requires the loads served from the switchboard to be submetered, the metering shall accumulate energy for those loads and shall report it to the building energy monitoring system under Electrical Power MonitoringElectrical Power Monitoring and MeteringResolves to the current adopted revision.sync/electrical-power-monitoring.

12.4 Protective Relays

12.4.1 Where the one-line diagram indicates a protective relay at the switchboard other than the ground-fault relay furnished under Ground-Fault Protection of Equipment, the relay, its current and voltage transformers, and its control wiring shall be furnished and installed by the switchboard manufacturer under the assembly listing, and the relay settings shall be as established under Protective Coordination StudyProtective Device Coordination StudyResolves to the current adopted revision.sync/protective-coordination-study.
NOTE A discrete relay at a switchboard is the exception rather than the rule, and it appears where the switchboard takes a generator or a second source and needs the under- and overvoltage, frequency, reverse-power, or phase-sequence functions a trip unit does not carry. (12.4.2)

13 Communications

13.1 Network Protocol

13.1.1 The communications protocol of the switchboard network shall be as indicated in the datasheet.
Communications Protocolselect
No network
Modbus RTU
Modbus TCP
BACnet/IP
BACnet MS/TP
EtherNet/IP
DNP3
NOTE The protocol has to match the system the switchboard reports to: a switchboard whose meters and trip units report to the building automation system speaks the protocol that system reads, which is settled under Building Automation SystemBuilding Automation SystemResolves to the current adopted revision.sync/building-automation-system, and one reporting to a power monitoring system speaks what that system reads under Electrical Power MonitoringElectrical Power Monitoring and MeteringResolves to the current adopted revision.sync/electrical-power-monitoring; the serial protocols run on a two-wire bus and cost least, the Ethernet protocols carry more data and allow the trip units to be read and the maintenance switch status to be seen remotely, and DNP3 is the protocol a utility or a generation control system reads. (13.1.2)
13.1.3 Where a network is furnished, the devices connected to it shall be as indicated in the datasheet.
Networked Devicescheckbox
☐ Meters
☐ Main circuit breaker trip unit
☐ Feeder circuit breaker trip units
☐ Ground-fault relay
☐ Surge protective device status contacts
☐ Energy-reducing maintenance switch status
13.1.4 Where a network is furnished, the network cable, the gateways, the terminations, and the power supplies for the network shall be installed by the manufacturer within the switchboard, and the network shall be brought to a terminal or a connector in a designated compartment for the field connection.
13.1.5 Network cable inside the switchboard shall be routed separately from the power conductors and the bus, and where it must cross a power conductor it shall cross at a right angle.
13.1.6 Each networked device shall be assigned an address on the network address list submitted with the action submittals, and the address shall be marked at the device.

14 Identification

14.1 Nameplates, arc-flash warning labels, available fault current markings, and source identification shall comply with Equipment LabelingElectrical Equipment LabelsResolves to the current adopted revision.sync/equipment-labeling for material, lettering, attachment, and content, and the text shall be that listed on the nameplate schedule.
14.2 Each switchboard shall carry an assembly nameplate stating the switchboard designation, the system voltage with the number of phases and wires, the main bus rating, the main device rating where one is furnished, the assembly short-circuit current rating, the short-time withstand rating where one is furnished, and the source that feeds it.
14.3 Each device shall carry a nameplate stating the device designation, the frame size and trip rating or the switch and fuse rating, and the load served, and the designation shall match the designation on the one-line diagram.
14.4 The manufacturer shall mark on the structure the UL 891 listing, the series-rated combinations where series rating is the basis, and the devices listed for installation in each position.
14.5 Where the switchboard is fed from a source that is not within sight, the location of that source and its circuit designation shall be marked on the switchboard in accordance with NFPA 70 408.4(B), and where more than one source feeds the switchboard each shall be identified at the switchboard.
14.6 The available fault current at the line terminals and the date it was calculated shall be field-marked on each switchboard that is service equipment, in accordance with NFPA 70 110.24.
14.7 Where the switchboard serves an emergency, legally required standby, or critical operations power system, it shall be marked as a component of that system in accordance with the article of NFPA 70 that governs the system.
14.8 Whether a mimic bus is furnished shall be as indicated in the datasheet.
Mimic Busradio
● Not furnished
○ Furnished
NOTE A mimic bus is a colored line drawn on the front of the switchboard that traces the bus and the devices as the one-line diagram does, so that an operator can see which device feeds what without reading the nameplates; it earns its cost on a main-tie-main or a multi-source switchboard whose operation depends on the operator understanding the arrangement, and most single-main switchboards are built without one. (14.9)

15 Testing

15.1 Factory Tests

15.1.1 The manufacturer shall perform the production tests of UL 891 and NEMA PB 2 on every switchboard before shipment, including a dielectric withstand test of the bus, a continuity check of every control, metering, and ground-fault circuit against the schematic diagrams, a mechanical operation check of every device and interlock, an inspection of every bus joint against the listed torque, and an inspection of the assembly against the reviewed shop drawings.
15.1.2 Factory test witnessing shall be as indicated in the datasheet.
Factory Test Witnessingradio
○ Witnessed by the Owner's representative
● Certified test report without witnessing
15.1.3 Where witnessing is selected, the manufacturer shall give not less than two weeks' notice of test readiness, shall submit the test procedure for review before the test, and shall not ship a switchboard until the witness has accepted the results or has waived attendance in writing.
NOTE A witnessed test lets the Owner see every device operate and every interlock work before the switchboard ships, and it commits a representative to a trip to the factory for each shipment; a certified report records the same tests without the trip, and leaves any discrepancy to be found at field acceptance testing. (15.1.4)

15.2 Field Acceptance Tests

15.2.1 Field acceptance tests shall be performed on every switchboard after installation is complete and before it is energized, in accordance with ANSI/NETA ATS and Electrical Acceptance TestingElectrical Acceptance TestingResolves to the current adopted revision.sync/electrical-acceptance-testing, and shall include the tests indicated in the datasheet.
Field Acceptance Testscheckbox
☑ Visual and mechanical inspection including anchorage, nameplates, clearances, barriers, and covers
☑ Bolted connection torque verification against the manufacturer's values, with the applied values recorded
☑ Insulation resistance of each phase bus and the neutral bus, phase-to-phase and phase-to-ground
☑ Contact resistance of the bus splices and the main and feeder terminations
☑ Operation of every device through one open and close cycle, and of every drawout device through every position
☐ Primary current injection of every electronic trip unit at one point per function
☐ Ground-fault protection of equipment performance test by primary current injection
☑ Trip unit and relay settings verification against the coordination study
☐ Shunt trip, undervoltage release, and interlock operation from the initiating device
☐ Current transformer ratio and polarity verification
☐ Meter and network function verification against the point list
☑ Neutral-to-ground separation verification on every switchboard that is not service equipment
15.2.2 Insulation resistance shall be measured for one minute at 1000 V DC on a system rated above 250 V and at 500 V DC on a system rated 250 V and below, and a reading below the minimum ANSI/NETA ATS states for the voltage class shall be investigated before the switchboard is energized.
15.2.3 A switchboard that fails a field acceptance test shall not be energized, the Contractor shall report the failure to the Engineer of Record within one working day with the measured values, and the cost of the correction and of every repeated test shall be borne by the Contractor.
15.2.4 Manufacturer start-up services shall be as indicated in the datasheet.
Manufacturer Start-Up Servicesradio
○ Not required
○ Manufacturer's field service engineer present for energization and trip unit commissioning
NOTE A manufacturer's engineer at energization sets and verifies the trip units, the ground-fault scheme, the interlocks, and the network with the maker's tools and documentation, and the visit is what the manufacturer's warranty terms often require on a switchboard with electronic trip units or a transfer scheme; a switchboard with thermal-magnetic devices and no network has little for that engineer to do. (15.2.5)
15.2.6 Infrared thermographic inspection shall be as indicated in the datasheet.
Infrared Thermographic Inspectionselect
Not required
One inspection within 90 days of energization
One inspection within 90 days of energization and a second at eleven months
15.2.7 Where infrared inspection is indicated, it shall be performed with the switchboard carrying not less than 40% of its rated load on each scanned connection, and every connection showing a rise of more than 10 °C above its neighbors shall be reported and corrected.
NOTE A second inspection near the end of the first year finds the termination 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. (15.2.8)

16 Installation

16.1 Location and Working Space

16.1.1 The room in which the switchboard is installed shall satisfy Electrical RoomsElectrical RoomsResolves to the current adopted revision.sync/electrical-rooms where that room is an electrical room.
16.1.2 Working space in front of the switchboard, and behind it where it is rear-accessible, shall comply with NFPA 70 110.26 for the system voltage and the condition of the space, and no door swing shall reduce that space.
16.1.3 Where the switchboard is rated 800 A or more and is over 6 ft wide, the working space shall have an entrance at each end in accordance with NFPA 70 110.26(C)(2), unless the arrangement satisfies one of the exceptions that section permits, and the doors of a room containing the switchboard shall open in the direction of egress and be equipped with listed panic hardware where that section requires it.
16.1.4 The dedicated electrical space above the switchboard required by NFPA 70 110.26(E) shall be kept clear of piping, ductwork, and equipment not associated with the electrical installation.
16.1.5 Working space shall not be used for storage at any time.
16.1.6 The switchboard shall be set on a concrete housekeeping pad constructed under Concrete PadsConcrete Equipment PadsResolves to the current adopted revision.sync/concrete-pads, extending not less than 3 in. beyond the structure on every side and not less than 4 in. above the finished floor indoors or 6 in. above finished grade outdoors, with the conduit stub-ups and the anchor locations coordinated with the reviewed shop drawings before the pad is placed.
16.1.7 The switchboard shall be anchored to the pad as indicated on the seismic anchorage details, and where seismic certification is required the anchorage shall be that on which the certification depends, with no substitute anchor used without the manufacturer's written confirmation that the certification remains valid.

16.2 Setting and Assembly

16.2.1 The Contractor shall handle, set, and assemble the switchboard in accordance with NEMA PB 2.1 and the manufacturer's instructions, lifting each shipping section by the lifting provisions furnished and never by the bus, the doors, or the device handles.
16.2.2 Shipping sections shall be set plumb and level, aligned flush at the front, bolted together, and the bus spliced at every shipping split with the splice plates furnished, torqued to the manufacturer's values with a calibrated torque tool and witness-marked.
16.2.3 Every shipping brace, blocking, desiccant, and temporary ground shall be removed before the switchboard is energized, and the manufacturer's shipping checklist shall be completed and included in the field test report.
16.2.4 Where the switchboard is installed in an unconditioned space or outdoors, its space heaters shall be energized from a temporary source from the day the switchboard is set until its permanent heater circuit is in service.

16.3 Conductor Terminations

16.3.1 The main and feeder lugs shall be of the type indicated in the datasheet.
Main and Feeder Lug Typeradio
○ Mechanical set-screw lugs
○ Compression lugs
Manufacturer's standard (by default)
16.3.2 The manufacturer shall state the lug type furnished in the product data.
NOTE Mechanical lugs accept a range of conductor sizes and are the lugs the switchboard ships with; compression lugs are crimped to one conductor size with a tool matched to the lug, hold their pressure without re-torquing, and are used where the Owner's practice or the conductor material calls for them. (16.3.3)
16.3.4 Every lug shall be listed for the conductor material and size terminated in it, shall be rated for 75 °C conductors, shall accept the number of conductors per phase indicated on the one-line diagram, and where aluminum conductors are terminated shall be listed for aluminum and the conductor prepared as the lug listing requires.
16.3.5 Every conductor termination shall be torqued to the device manufacturer's published value with a calibrated torque tool, and the values applied shall be recorded in the field test report.
16.3.6 Conductors within the switchboard shall be trained and supported so that each feeder can be identified and reached without disturbing its neighbors, shall not bear on the bus or on a device, and shall be arranged so that the conductors of each phase are grouped as the phase sequence of the bus requires.
16.3.7 Conductor selection and installation shall comply with Conductors And CablesConductors and CablesResolves to the current adopted revision.sync/conductors-and-cables, and raceways shall comply with Raceways And ConduitRaceways and ConduitResolves to the current adopted revision.sync/raceways-and-conduit.

17 Delivery, Storage, and Handling

17.1 Each switchboard shall be shipped in the largest factory-assembled sections the delivery route and the installation pathway admit, and the Contractor shall verify the door, corridor, elevator, and turning dimensions between the delivery point and the installed location against the shipping section dimensions before the switchboard is released for manufacture.
17.2 Each shipping section shall be delivered in the manufacturer's packaging with the listing marks and the nameplates intact, and shall be inspected for shipping damage at receipt.
17.3 Switchboards shall be stored indoors in a clean, dry space where the temperature is held above the dew point, and where indoor storage is not available they shall be stored under cover on pallets, off the ground, and protected from condensation, precipitation, dust, and physical damage.
17.4 Where a switchboard will stand more than 30 days in an unconditioned space before energization, its space heaters, where furnished, shall be energized from a temporary source, or the structure shall otherwise be protected from condensation.
17.5 The structure shall remain in its packaging or covered until the conductors are pulled, so that construction dust does not settle on the bus and the device terminals.
17.6 A switchboard damaged or wetted in transit, in storage, or in handling shall be repaired or replaced as the manufacturer directs and as the Engineer of Record accepts in writing.

18 Warranty

18.1 The manufacturer shall warrant each switchboard, its bus, and every factory-installed device against defects in materials and workmanship for the period indicated in the datasheet.
Manufacturer's Warranty Periodrange
Not less than
years
1235
18.2 Where a warranty period is not selected in the datasheet, the manufacturer's standard warranty shall apply, and its term shall be stated in the product data.
18.3 The warranty period shall commence on the date indicated in the datasheet.
Warranty Commencementselect
Date of substantial completion
Date of energization
Date of shipment
NOTE 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 switchboard. (18.4)
18.5 The warranty coverage scope shall be as indicated in the datasheet.
Warranty Coverage Scoperadio
○ Parts only
○ Parts and labor
18.6 The Contractor shall warrant the installation, including every termination, the bus splices, the anchorage, and the field-installed accessories, for the project warranty period.
18.7 A device or bus component 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, and the replacement shall not reduce the coverage of any other component in the switchboard.

19 Spare Parts

19.1 The Contractor shall deliver the spare parts indicated in the datasheet to the Owner before the switchboards are accepted, and shall obtain a signed receipt for them.
Spare Parts to Be Furnishedcheckbox
☐ One spare feeder circuit breaker of each frame size and trip unit type installed
☐ One set of fuses of each class and rating installed, plus one set of control fuses
☑ One set of blank covers for every space position on the project
☐ One set of indicating lamps of each type installed
☑ Two sets of keys for every lock and key interlock
☐ One pint of touch-up paint matching the finish
19.2 Spare devices shall be identical to and interchangeable with the installed devices, shall be delivered in their original packaging, and shall be labeled with the switchboard designation and the device rating they serve.
19.3 Spare devices and fuses shall be stored in a labeled cabinet in the electrical room furnished by the Contractor, and shall not be stored inside an operating switchboard.

Written and maintained by SynC. Licensed under CC BY 4.0.