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Busway Plug-In Units and Rack Power Distribution Units

Written and maintained by SynC.

Rev5
IssuedOct 19, 2026
LicenseCC BY 4.0
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1 Scope

NOTE This standard governs two families of product that take power from a distribution run and hand it to a load at the point of use: the plug-in unit that mounts on an opening of a plug-in busway run, and the rack power distribution unit that mounts in an equipment rack or cabinet and feeds the cord-connected equipment in it. (1.1)
NOTE A busway plug-in unit is a listed enclosure with stabs that engage the bus bars of a plug-in busway run through an opening in its housing, carrying a fusible switch, a circuit breaker, a non-fused disconnect, or a set of receptacles from which a load is served; it is the point at which a run becomes a branch, and it is listed under UL 857 with the busway series it mounts on rather than on its own. (1.2)
NOTE A rack power distribution unit is a cord-connected or hardwired strip of outlets, listed to UL 62368-1 or UL 60950-1, that mounts in a rack or cabinet and distributes one branch circuit to the equipment in the rack, with or without circuit breakers, metering, network reporting, and outlet switching; a relocatable power tap is the simpler cord-connected strip listed to UL 1363, and a special-purpose relocatable power tap is the version listed to UL 1363A for use with medical equipment in a patient care vicinity. (1.3)
NOTE The two families share a procurement pattern: each is the last device before the load, each is bought by the dozen or the hundred from a schedule, each carries the overcurrent device or the metering the project expects at the load end, and each is the product that is wrong on the submittal when the load-end requirements were left to the catalog. The requirements they share, identification, testing, warranty, and spares, are written once; the requirements that differ are written under the articles for each family. (1.4)
NOTE The term "PDU" names two unrelated products. In this standard it means the rack-mount unit. The floor-standing data center power distribution unit, a transformer and panelboards assembled in one listed cabinet that feeds the rack units, is a different product with a different listing and is not covered by this standard. (1.5)
NOTE The following are governed elsewhere and are outside this standard: (1.6)
  • the busway run, its fittings, hangers, joints, plug-in openings and their covers, and the joint spares, under BuswayBuswayResolves to the current adopted revision.sync/busway
  • the panelboard that feeds a plug-in run or a rack, and its branch breakers, under PanelboardsPanelboardsResolves to the current adopted revision.sync/panelboards
  • fixed receptacles, their plates, and the branch-circuit outlet a rack unit plugs into, under Wiring DevicesWiring DevicesResolves to the current adopted revision.sync/wiring-devices
  • floor boxes and poke-through devices and their covers, under Electrical Floor Boxes And Poke ThroughsFloor Boxes and Poke-Through DevicesResolves to the current adopted revision.sync/electrical-floor-boxes-and-poke-throughs
  • the uninterruptible power supply ahead of the distribution, under Uninterruptible Power Supply SystemsUninterruptible Power Supply SystemsResolves to the current adopted revision.sync/uninterruptible-power-supply-systems
  • permanently connected surge protective devices and the coordination between them, under Surge Protective DevicesSurge Protective DevicesResolves to the current adopted revision.sync/surge-protective-devices
  • the conductors in conduit landed on a plug-in unit, the flexible cord of a cord drop, and their terminations, under Conductors And CablesConductors and CablesResolves to the current adopted revision.sync/conductors-and-cables
  • the raceways, boxes, and rough-in, under Raceways And ConduitRaceways and ConduitResolves to the current adopted revision.sync/raceways-and-conduit
  • the equipment grounding conductors and the bonding of the system the units are part of, under Grounding And BondingGrounding and Bonding for Electrical SystemsResolves to the current adopted revision.sync/grounding-and-bonding
  • the telecommunications cabling in the racks and the layout of the room they stand in, under Structured CablingStructured Cabling SystemsResolves to the current adopted revision.sync/structured-cabling
  • nameplate and label material, lettering, and attachment, under Equipment LabelingElectrical Equipment LabelsResolves to the current adopted revision.sync/equipment-labeling
  • the monitoring system the metered units report to, under Electrical Power MonitoringElectrical Power Monitoring and MeteringResolves to the current adopted revision.sync/electrical-power-monitoring
  • 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
  • field acceptance testing method, instruments, and the compiled test report, under Electrical Acceptance TestingElectrical Acceptance TestingResolves to the current adopted revision.sync/electrical-acceptance-testing
NOTE The plug-in units of lighting busway and trolley busway, plug-in units for metal-enclosed bus above 600 V, the floor-standing data center power distribution unit, and power taps in hazardous classified locations are not covered by any standard in this library. The equipment rack or cabinet a rack unit mounts in is furnished under the documents that govern the rack, and this standard governs only the unit and its attachment to the rack. (1.7)
1.8 Busway plug-in units shall be listed and labeled to UL 857 by a Nationally Recognized Testing Laboratory as plug-in units for the busway series they mount on.
1.9 Rack power distribution units, relocatable power taps, and special-purpose relocatable power taps shall be listed and labeled by a Nationally Recognized Testing Laboratory to the standard this standard requires for each product.
1.10 The run, the opening position, the type, and the load served of each busway plug-in unit shall be as indicated on the busway plug-in unit schedule.
1.11 The rack served, the feed designation, and the circuit serving each rack power distribution unit shall be as indicated on the rack power schedule.
1.12 Where a value stated on a schedule for a particular unit differs from the datasheet selection under this standard, the schedule shall govern for that unit.

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 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 857 Busways
NEMA BU 1 Busways
NEMA BU 1.1 General Instructions for Handling, Installation, Operation, and Maintenance of Busway Rated 600 Volts or Less
UL 98 Enclosed and Dead-Front Switches
UL 489 Molded-Case Circuit Breakers, Molded-Case Switches, and Circuit-Breaker Enclosures
UL 248-1 Low-Voltage Fuses, Part 1: General Requirements
UL 62368-1 Audio/Video, Information and Communication Technology Equipment, Part 1: Safety Requirements
UL 60950-1 Information Technology Equipment, Safety, Part 1: General Requirements
UL 1363 Relocatable Power Taps
UL 1363A Outline of Investigation for Special Purpose Relocatable Power Taps
UL 498 Attachment Plugs and Receptacles
UL 1682 Plugs, Receptacles, and Cable Connectors, of the Pin and Sleeve Type
UL 817 Cord Sets and Power-Supply Cords
UL 1449 Surge Protective Devices
NEMA WD 6 Wiring Devices, Dimensional Specifications
IEC 60320-1 Appliance Couplers for Household and Similar General Purposes, Part 1: General Requirements
IEC 60309-1 Plugs, Fixed or Portable Socket-Outlets and Appliance Inlets for Industrial Purposes, Part 1: General Requirements
NEMA 250 Enclosures for Electrical Equipment (1000 Volts Maximum)
NFPA 70 National Electrical Code (Articles 110, 210, 240, 368, 400, and 645)
NFPA 70E Standard for Electrical Safety in the Workplace
NFPA 99 Health Care Facilities Code
NFPA 75 Standard for the Fire Protection of Information Technology Equipment
ANSI/NETA ATS Standard for Acceptance Testing Specifications for Electrical Power Equipment and Systems

3 Submittals

3.1 Action Submittals

3.1.1 The Contractor shall submit the following for review before any unit is released for manufacture or procured:
  • product data for each busway plug-in unit type, giving the busway series and manufacturer it is listed with, the unit type, the ampere rating, the overcurrent device and its interrupting rating, the fuse class or the trip unit, the enclosure type, the interlocks and padlock provisions, the operating provision, and the load-side terminations
  • the busway plug-in unit schedule as the manufacturer will furnish it, reconciled against the schedule on the drawings, with the opening position of each unit marked on the busway shop drawings submitted under BuswayBuswayResolves to the current adopted revision.sync/busway
  • the series rating documentation for the device pair, where the datasheet selects a series rating basis
  • product data for each rack power distribution unit type, giving the listing standard, the class, the input voltage, phase configuration, and current rating, the plug configuration, the cord length, the outlet types and count, the outlet bank breakers, the metering and its accuracy, the network interface, the sensors, and the mounting form
  • the rack power distribution unit schedule by rack and feed, reconciled against the rack power schedule on the drawings
  • for monitored and switched units, the protocols supported, the management software the units report to, and the firmware revision to be shipped
  • product data for each relocatable power tap and special-purpose relocatable power tap, giving the listing, the rating, the cord length, and the outlet configuration
Action Submittalscheckbox
☑ Busway plug-in unit product data
☑ Busway plug-in unit schedule reconciled to the busway shop drawings
☐ Series rating documentation
☑ Rack PDU product data
☑ Rack PDU schedule by rack and feed
☑ Network interface, software, and firmware data
☐ Relocatable power tap product data
3.1.2 No unit shall be released for manufacture or procured until the action submittals covering it have been reviewed and returned.
NOTE A plug-in unit is ordered against the busway series, the opening spacing, and the side of the run, and a rack unit is ordered against the plug, the cord, and the outlet mix of one rack; the reconciled schedules are the submittal that finds the unit ordered for the wrong opening or the wrong receptacle before it ships, because neither can be altered in the field. (3.1.3)

3.2 Informational Submittals

3.2.1 The Contractor shall submit the following with or before the action submittals:
  • the listing certificate of each product: the UL 857 listing of each plug-in unit type with the busway series, the UL 62368-1 or UL 60950-1 listing of each rack unit type, and the UL 1363 or UL 1363A listing of each power tap
  • the manufacturer's published derating of the plug-in units for ambient temperature and altitude, where either departs from the rating basis of the listing
  • the manufacturer's statement of the period for which firmware security updates will be issued for the monitored and switched units furnished
  • the qualifications of the firm and the technicians who will perform the field tests
Informational Submittalscheckbox
☑ Listing certificates
☐ Ambient and altitude derating factors
☑ Firmware security update period statement
☑ Field testing firm and technician qualifications

3.3 Closeout Submittals

3.3.1 The Contractor shall submit the following before any unit is accepted:
  • operation and maintenance data for each unit type, including the fuse and breaker replacement procedure, the insertion and withdrawal procedure for the plug-in units, and the firmware update and configuration backup procedure for the monitored and switched units
  • the record busway plug-in unit schedule, giving the as-installed opening position, the fuse rating or trip setting, and the load served of every unit
  • the record rack power distribution unit schedule by rack and feed, giving the equipment assigned to each unit and the continuous load on each unit, bank, and phase
  • the network configuration record for each monitored and switched unit: the address, the host name, the SNMP and web settings, the user accounts created, the alarm thresholds, and the firmware revision as left
  • the field test reports
  • the warranty certificate identifying each unit type and the warranty commencement date
  • a signed receipt from the Owner for the spare parts delivered
Closeout Submittalscheckbox
☑ Operation and maintenance data
☑ Record busway plug-in unit schedule
☑ Record rack PDU schedule with load assignment
☑ Network configuration record
☑ Field test reports
☑ Warranty certificate
☑ Spare parts receipt

4 Quality Assurance

4.1 Listing and Labeling

4.1.1 Each busway plug-in unit shall be listed to UL 857 as a plug-in unit for the busway series on which it is installed, its fusible switch shall be listed to UL 98, its fuses to UL 248-1, and its circuit breaker to UL 489, as components of that listing.
4.1.2 Each rack power distribution unit shall be listed to a standard the datasheet accepts.
Rack PDU Listing Standards Acceptedcheckbox
Any of:
☑ UL 62368-1
☐ UL 60950-1
NOTE UL 62368-1 is the hazard-based safety standard that replaced UL 60950-1 for information and communication technology equipment, and every rack unit certified since the 2020 transition carries it, which is why it is the accepted standard by default; a UL 60950-1 listing remains on products certified before the transition and still in production, and a project accepts it where it wants those products to remain eligible. (4.1.3)
4.1.4 A relocatable power tap shall be listed to UL 1363, and a power tap used with medical equipment in a patient care vicinity shall be a special-purpose relocatable power tap listed to UL 1363A, applied as NFPA 99 permits.
4.1.5 Where a rack unit carries an integral surge protective device, the device shall be listed to UL 1449 as a component of the unit's listing.
4.1.6 Receptacle outlets on any unit shall be of a NEMA WD 6 configuration listed to UL 498, and IEC 60320 outlets shall be of the C13, C19, or combination form rated for the current the unit's listing assigns to them.

4.2 Source Limitations

4.2.1 Every busway plug-in unit shall be furnished by the manufacturer of the busway series on which it mounts, as BuswayBuswayResolves to the current adopted revision.sync/busway requires, and shall be listed with that series.
4.2.2 Every rack power distribution unit on the project shall be of one manufacturer and shall report to one management platform, unless the Engineer of Record accepts another arrangement in writing.
NOTE A rack unit from a second manufacturer reports to its own software, with its own addressing, its own alert format, and its own firmware schedule, so a mixed population doubles the management work from the day of commissioning; the single source is the condition under which the monitoring the project paid for is actually used. (4.2.3)

4.3 Regulatory Requirements

4.3.1 The installation shall comply with Adopted Electrical CodeAdopted Electrical CodeParameterEach project supplies its own value.adopted-electrical-code and with the amendments of the Authority Having Jurisdiction, and shall be made available for the inspections that authority requires.

5 Environmental and Service Conditions

5.1 Busway Plug-In Unit Service Conditions

5.1.1 Each busway plug-in unit shall carry its ampere rating at the design ambient temperature selected for the run under BuswayBuswayResolves to the current adopted revision.sync/busway, and its overcurrent device shall be rated or derated by the manufacturer for that ambient.
5.1.2 A plug-in unit installed on an outdoor portion of a run 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 informational submittals.
5.1.3 The interrupting rating of the overcurrent device in a plug-in unit shall be derated for AltitudeAltitudeParameterEach project supplies its own value.altitude in accordance with the manufacturer's published correction factors where the altitude exceeds 2000 m.
5.1.4 The weight of every plug-in unit, with its load-side conductors and any cord drop, shall be included in the hanger and restraint loads of the run under BuswayBuswayResolves to the current adopted revision.sync/busway.

5.2 Rack PDU Operating Ambient

5.2.1 Each rack power distribution unit shall be rated for continuous operation at its full input current at an ambient temperature not less than the value indicated in the datasheet, measured at the unit's mounting position in the rack.
Rack PDU Operating Ambient Temperaturerange
Not less than
°C
404550556065
NOTE A unit mounted vertically at the rear of a cabinet sits in the exhaust air of the equipment, which runs 20 °C or more above the cold-aisle supply, so a unit rated at the 40 °C basis of its listing is operating beyond its rating in a cabinet whose supply is above 20 °C; the manufacturers that sell into data centers rate their units at 60 °C for that reason, and a unit in a network closet or an open two-post rack sits in room air. The rating a project needs follows from where the unit sits and what the cabinet exhausts, so the field carries no default. (5.2.2)
5.2.3 Rack units shall be rated for operation at 5% to 95% relative humidity, non-condensing, and the manufacturer shall state the operating and storage temperature range in the product data.

6 Busway Plug-In Unit Ratings

6.1 Overcurrent Device Type

6.1.1 The overcurrent device furnished in the busway plug-in units that carry one shall be as indicated in the datasheet.
Busway Plug-In Unit Overcurrent Device Typeradio
○ Fusible switch
○ Molded-case circuit breaker
NOTE A fusible unit holds its interrupting rating in the fuse, which is 200 kA for a current-limiting class, limits the let-through current the load-side conductors see, and after a fault is restored by a person with the right spare fuses in hand; a circuit breaker unit is reset at the handle with nothing to stock, carries an interrupting rating that is a property of the frame and is lower than a current-limiting fuse at the same ampere rating, and offers an adjustable trip where the coordination study needs one. The fusible unit is bought where the available fault current is high, where selective coordination with upstream fuses is wanted, or where the plant already stocks fuses; the breaker unit is bought where the units will be operated and reset by people without fuse stock, where remote operation or an electronic trip is wanted, and where the frame rating covers the fault current. Neither is distinctly the norm, so the field carries no default. (6.1.2)
6.1.3 Every unit that taps a feeder or a branch circuit from a run used as a feeder shall contain the overcurrent device NFPA 70 368.17(C) requires, and a non-fused disconnect unit or a receptacle unit without an overcurrent device shall be installed only on a run protected as a branch circuit under NFPA 70 368.17(D) or where an exception to 368.17(C) applies.

6.2 Ampere Rating

6.2.1 The ampere rating of each busway plug-in unit, which is the rating of its fusible switch or the frame rating of its circuit breaker, shall be as indicated in the datasheet.
Busway Plug-In Unit Ampere Ratingrange
A
20306010020022540060080010001200
Per drawings — the busway plug-in unit schedule (deferred by default)
NOTE The rating differs from one unit to the next on the same run and is fixed by the load each serves, so it is a schedule value rather than a project policy; the fuse or the trip inside the unit is selected at or below the unit rating to protect the load-side conductors, and a unit is ordered one rating above the trip where the load is expected to grow, because the switch or the frame is the part that cannot be changed in the field. (6.2.2)
6.2.3 The fuse rating or the breaker trip rating installed in each unit shall protect the load-side conductors in accordance with NFPA 70 240.4 and shall be as indicated on the busway plug-in unit schedule.

6.3 Short-Circuit Current Rating

6.3.1 The short-circuit current rating of each busway plug-in unit, and the interrupting rating of the overcurrent device in it, shall equal or exceed the available fault current at the opening where the unit is installed as established under Short Circuit StudyShort-Circuit StudyResolves to the current adopted revision.sync/short-circuit-study, and shall be not less than the value indicated in the datasheet.
Busway Plug-In Unit Short-Circuit Current Ratingrange
Not less than
kA
10141822253542506585100150200
Per drawings — the one-line diagram (deferred by default)
NOTE A plug-in unit sees the fault current the run carries at its opening, which is close to the source-end value on a short run and lower at the far end of a long one, and the unit's rating is the lower of the enclosure's withstand and the device's interrupting rating; a fuse of a current-limiting class carries 200 kA and makes the rating a question of the enclosure alone, and a breaker frame carries a rating that rises with the frame and with the price. (6.3.2)

6.4 Interrupting Rating Basis

6.4.1 The basis on which the interrupting rating of the circuit-breaker plug-in units is established shall be as indicated in the datasheet.
Circuit Breaker Interrupting Rating Basisradio
● Fully rated
○ Series rated with the device ahead of the run
NOTE A fully rated unit carries a breaker whose own interrupting rating covers the available fault current, which is how most plug-in units are bought and is why it is the default; a series rating uses a tested combination of the device ahead of the run and the breaker in the unit, listed together, so that a lower-rated and cheaper breaker is acceptable in the unit, at the cost that the combination holds only for the exact device pair, that NFPA 70 240.86 requires the combination to be marked on the equipment and re-verified when either device is replaced, and that a motor load contributing fault current between the two devices can void it. (6.4.2)
6.4.3 Where a series rating is selected, the combination shall be listed by the plug-in unit manufacturer for the specific device ahead of the run, shall satisfy NFPA 70 240.86, and shall be identified on the submittal and on a label at the unit and at the upstream device.

7 Busway Plug-In Unit Construction

7.1 Fuse Class

7.1.1 Where fusible units are selected, the fuse classes the fuse holders accept shall be as indicated in the datasheet.
Plug-In Unit Fuse Classes Acceptedcheckbox
Any of:
☐ Class J
☐ Class T
☐ Class RK1
☐ Class RK5
☐ Class L
NOTE Class J and Class T fuses are current-limiting with rejection dimensions that accept no other class, so a holder built for them cannot take a non-current-limiting replacement; Class RK1 is current-limiting in the dimensions of the older Class H fuse and fits a holder that also takes an RK5 or an H fuse unless rejection clips are fitted; Class RK5 has the time delay a motor load needs and the lowest cost, and the least current limitation; and Class L is the bolt-in class every unit above 600 A is built for. A plant that stocks one class buys units for that class, and a project that wants the let-through of a current-limiting fuse to protect the load-side conductors accepts J, T, or RK1 and fits rejection clips where RK1 is chosen; no set of classes is the norm across projects, so the field carries no default. (7.1.2)
7.1.3 Where Class RK1 or Class RK5 is accepted, each fuse holder shall be fitted with rejection clips that reject Class H fuses.
7.1.4 Fuses shall be furnished installed in each fusible unit at the rating indicated for the unit, and the fuses of one class and rating shall be of one manufacturer across the project.

7.2 Circuit Breaker Trip Unit

7.2.1 Where circuit-breaker units are selected, the trip unit of each breaker shall be as indicated in the datasheet.
Plug-In Unit Circuit Breaker Trip Unitselect
Thermal-magnetic, fixed
Thermal-magnetic with adjustable instantaneous
Electronic with adjustable long-time, short-time, and instantaneous
Electronic with adjustable long-time, short-time, instantaneous, and ground-fault
Derived — the frame rating of the unit and the settings required for it under [[sync/protective-coordination-study]] (by default)
NOTE A thermal-magnetic trip is the trip of the frames to 250 A and costs least; an adjustable instantaneous lets the trip clear the inrush of a motor load; an electronic trip is built into the larger frames and offers the long-time and short-time adjustments a coordinated system sets, and the ground-fault element where NFPA 70 215.10 requires one on the feeder the unit taps. The trip unit follows from the frame and from the settings the coordination study assigns, which is why the field is derived. (7.2.2)
7.2.3 The settings the coordination study assigns to each breaker shall be set and recorded before the unit is energized.

7.3 Stabs and Ground Connection

7.3.1 Each unit shall engage the phase bars, and the neutral bar where the load requires a neutral, with spring-loaded or bolted stabs plated as the bus bars are plated, and shall make its ground connection in the manner the ground path furnished under BuswayBuswayResolves to the current adopted revision.sync/busway requires: a ground clamp or ground stab to the housing where the housing is the equipment grounding conductor, a ground stab to the internal ground bar where one is furnished, and an isolated ground stab in addition where an isolated ground bar is furnished.
7.3.2 The ground connection of each unit shall make before and break after the phase stabs on insertion and withdrawal.
7.3.3 Each unit shall be mountable from either side of a run that carries openings on both sides, shall connect its poles to the same phases from either side, and shall be marked with the phase sequence of its stabs.
7.3.4 No stab, clamp, or ground connection shall be modified in the field to fit an opening, and a unit shall not be installed on a run of a series other than the one it is listed for.

7.4 Interlocks and Padlocking

7.4.1 Each unit with a switch or a circuit breaker shall carry the interlock and padlock provisions indicated in the datasheet.
Plug-In Unit Interlock and Padlock Provisionscheckbox
☑ Interlock preventing insertion or withdrawal with the switch or breaker on
☑ Cover interlock preventing the cover from opening with the switch or breaker on
☑ Padlock provision for the handle in the off position
☐ Padlock provision for the handle in the on position
☐ Defeatable cover interlock for inspection under load by a qualified person
☐ Key interlock to the load-side equipment
NOTE The insertion interlock keeps a unit from being stabbed onto or pulled off a live run with its contacts closed, which is the condition under which the stabs arc; the cover interlock keeps the fuses and terminals covered while the unit is on; and the off-position padlock is what a lockout under NFPA 70E and the lockable disconnect of NFPA 70 110.25 need. Those three are built into most units and are the default; an on-position padlock holds a unit on for a load that is not to be switched off casually, a defeatable cover interlock lets a qualified person open the cover under load for a measurement, and a key interlock ties the unit to a transfer scheme or to a machine disconnect downstream. (7.4.2)
7.4.3 The handle of each unit shall indicate the on and off position legibly from the floor, and the padlock provision shall accept a padlock with a shackle not less than 6 mm in diameter.

7.5 Enclosure Type

7.5.1 The enclosure type of the busway plug-in units shall be as indicated in the datasheet.
Plug-In Unit Enclosure Typeselect
Type 1
Type 12
Type 3R
NOTE A plug-in run sits indoors on most projects, in a plant bay, a riser, or a ceiling space, and the Type 1 unit is what the series is built with, which is why it is the default; a Type 12 unit is gasketed against the dust and the oil mist of a machine shop or a mill and is bought where the run crosses that air; and a Type 3R unit sheds rain and drains, and is bought for the outdoor portion of a run where the busway manufacturer lists the opening and the unit for it. (7.5.2)
7.5.3 A unit installed on an outdoor portion of a run, or where it is exposed to rain or to water from washing, shall be of Type 3R and shall be listed by the busway manufacturer for the outdoor opening it mounts on.
7.5.4 A unit installed where the atmosphere carries conductive dust, oil mist, or lint shall be of Type 12.
7.5.5 A unit installed where the atmosphere carries salt, chemical vapor, or another corrosive agent shall have an enclosure and hardware the manufacturer states in writing are suitable for that atmosphere.
7.5.6 The enclosure type shall be designated in accordance with NEMA 250 and marked on the unit.

7.6 Out-of-Reach Operation

7.6.1 Each unit whose handle is more than 2.0 m (6 ft 7 in.) above the floor or working platform shall be furnished with the operating provision indicated in the datasheet, so that its disconnect is operable from the floor as NFPA 70 368.17(C) and 240.24(A) require.
Out-of-Reach Plug-In Unit Operating Provisionradio
○ Hook-stick operable handle
○ Cable or chain operator to a handle within reach of the floor
NOTE A hook-stick handle is a loop on the unit's handle that a stored insulated stick reaches, costs nothing beyond the stick, and leaves the person operating it standing under the unit while it opens; a cable or chain operator brings a handle down to reach height on a wall or a column, where it can be padlocked and operated from the side, and costs a run of cable and a bracket per unit. A plant with a few units and a stick at each bay operates them by stick, and a run whose units are switched or locked out often is given cable operators; neither is distinctly the norm, so the field carries no default. (7.6.2)
7.6.3 Where hook-stick handles are furnished, the Contractor shall furnish one insulated hook stick rated for the system voltage, stored on a bracket within sight of each run.
7.6.4 Where cable or chain operators are furnished, the handle within reach shall carry the padlock provision the unit carries, and the operator shall be marked with the designation of the unit it operates.

7.7 Load-Side Terminations and Cord Drops

7.7.1 The load-side terminals of each unit shall be lugs listed for the conductor material and size indicated for the unit, rated for 75 °C conductors, with the conduit hub or knockout arrangement the enclosure type requires, and the conductors landed on them shall comply with Conductors And CablesConductors and CablesResolves to the current adopted revision.sync/conductors-and-cables.
7.7.2 Where the busway plug-in unit schedule indicates a cord drop from a unit, the unit shall be furnished with a strain-relief cord connector listed for the cord, the cord shall be a flexible cord that NFPA 70 Article 400 permits for the use and shall comply with Conductors And CablesConductors and CablesResolves to the current adopted revision.sync/conductors-and-cables, and the cord shall be suspended so that no tension reaches the unit's terminals.
NOTE A cord drop hangs from the unit at a height where it is pulled by the equipment it serves and by what passes beneath it; the strain relief at the unit is what keeps that pull off the terminals, and a drop that reaches the floor is a trip hazard while a drop that stops short puts tension on the plug. (7.7.3)

7.8 Receptacle Tap-Off Units

7.8.1 Where the busway plug-in unit schedule indicates a receptacle unit, the unit shall carry the receptacle configurations and the outlet count indicated for it, with each outlet circuit protected by a circuit breaker in the unit at the receptacle rating, and shall carry the metering indicated in the datasheet.
Receptacle Tap-Off Unit Meteringselect
No metering
Local display of current per outlet circuit
Network-reported metering of current, voltage, and energy per outlet circuit
NOTE A receptacle tap-off unit on an overhead run in a data center or a laboratory feeds the rack units or the bench equipment below it, and the metering in it is where the branch-circuit load is measured when the project measures it there rather than in the rack unit; an unmetered unit is what most plug-in runs carry, which is why it is the default, a local display is read at the unit from a lift, and a network-reported unit reports to the monitoring system under Electrical Power MonitoringElectrical Power Monitoring and MeteringResolves to the current adopted revision.sync/electrical-power-monitoring over the interface this standard requires of a monitored rack unit. (7.8.2)
7.8.3 A network-reported receptacle tap-off unit shall meet the network interface, security, and configuration requirements this standard sets for a monitored rack unit.

8 Rack PDU Class and Input

8.1 Monitoring and Control Class

8.1.1 The monitoring and control class of the rack power distribution units shall be as indicated in the datasheet.
Rack PDU Monitoring and Control Classradio
○ Basic, no metering
○ Metered, local display
○ Monitored, network-reported metering
○ Switched, network-reported metering and per-outlet control
NOTE A basic unit distributes one circuit to its outlets and costs least, and the rack load is known only from the breaker ahead of it; a metered unit shows the load on a display at the rack, which is what a technician loading a rack reads to stay under the 80% ceiling; a monitored unit reports its metering over the network, so that capacity is managed from a desk and an overload alarms before a breaker trips; and a switched unit adds a relay at each outlet, so that a hung server is power-cycled from a desk and an idle outlet is locked off, at the cost of the relays and of the attention the outlet state then requires. The class a project wants follows from whether anyone will read the data and from whether the equipment is managed remotely, so the field carries no default. (8.1.2)
8.1.3 Units shall not be substituted downward in class from the class selected for a rack.

8.2 Input Feeds

8.2.1 The number of input feeds of each rack power distribution unit shall be as indicated in the datasheet.
Rack PDU Input Feedsradio
● Single input
○ Dual input with integral automatic transfer
NOTE A single-input unit is fed from one circuit, and a rack with dual-corded equipment carries two of them, an A unit and a B unit on separate feeds, so that the loss of either feed leaves every load powered; this is the arrangement of most racks and the default. A dual-input unit carries an automatic transfer switch that feeds its outlets from one of two feeds and transfers when the live feed fails, which is what single-corded equipment in a dual-feed room needs, at the cost of the transfer switch, of a unit whose full load sits on one feed after a transfer, and of a rack whose redundancy ends at that switch. (8.2.2)
8.2.3 A dual-input unit shall transfer between its feeds within the hold-up time of the equipment it serves and in not more than 16 ms, shall return to its preferred feed automatically after that feed is restored and stable, and shall report the active feed and each transfer on its network interface where it is a monitored or switched unit.

8.3 Input Voltage and Current Rating

8.3.1 The input voltage and phase configuration of each rack unit shall be as indicated in the datasheet.
Rack PDU Input Voltageselect
120 V 1Φ
120/240 V 1Φ 3-wire
208 V 1Φ
240 V 1Φ
277 V 1Φ
120/208 V 3Φ 4-wire
208 V 3Φ 3-wire
240/415 V 3Φ 4-wire
480 V 3Φ 3-wire
Per drawings — the rack power schedule (deferred by default)
8.3.2 The input current rating of each rack unit shall be as indicated in the datasheet.
Rack PDU Input Current Ratingrange
A
1520305060100
Per drawings — the rack power schedule (deferred by default)
NOTE The voltage follows the facility's distribution and the power supplies of the equipment: a 120 V unit serves a closet of small equipment, a 208 V single-phase unit at 30 A is the unit of most cabinets, a three-phase 120/208 V unit carries both voltages on one cord at a higher rack density, a 240/415 V unit serves a room distributed at that voltage so that every power supply runs at 240 V, and the 277 V and 480 V units serve industrial racks whose equipment accepts them. The current follows the rack's design load. A rack unit is loaded continuously, so the 80% limit of NFPA 70 is the usable rating: a 30 A unit carries 24 A and a 60 A unit carries 48 A, and the schedule that assigns racks to units is written against those figures and not the nameplate. Both values are schedule values. (8.3.3)
8.3.4 The continuous load assigned to each rack unit, counted as the sum of the demand of the equipment plugged into it, shall not exceed 80% of its input current rating on any phase, in accordance with NFPA 70 210.19 and 210.20.

8.4 Input Connection

8.4.1 The input connection of the rack units shall be as indicated in the datasheet.
Rack PDU Input Connectionradio
● Cord with attachment plug
○ Hardwired
NOTE A cord-and-plug unit is replaced by unplugging it and is what nearly every rack unit is, which is why it is the default; a hardwired unit is bought at a rating above 60 A, where no plug configuration exists for the current, or where the Owner's practice is to land the circuit in a junction box at the rack rather than furnish a receptacle, and its circuit is disconnected at the panelboard or at a disconnect at the rack rather than by unplugging. (8.4.2)
8.4.3 A hardwired rack unit shall be connected through a junction box or a disconnect at the rack with a listed flexible conduit or cord connector, and a disconnecting means for the unit shall be within sight of the rack or the breaker serving it shall be lockable in the open position.
8.4.4 The attachment plug configuration of each cord-connected rack unit shall be as indicated in the datasheet.
Rack PDU Attachment Plug Configurationselect
NEMA 5-15P
NEMA 5-20P
NEMA L5-20P
NEMA L5-30P
NEMA 6-20P
NEMA L6-20P
NEMA L6-30P
NEMA L14-30P
NEMA L15-30P
NEMA L21-20P
NEMA L21-30P
NEMA L22-30P
IEC 60309 2P+E 30 A
IEC 60309 2P+E 60 A
IEC 60309 3P+E 30 A
IEC 60309 3P+E 60 A
IEC 60309 3P+N+E 30 A
IEC 60309 3P+N+E 60 A
Derived — the input voltage, the phase configuration, and the input current rating of the unit on the rack power schedule (by default)
NOTE The plug is fixed by the voltage, the phase configuration, and the current: NEMA WD 6 assigns a straight-blade and a locking configuration to each pairing up to 30 A, a locking configuration is what a rack unit is nearly always ordered with so that the plug cannot be pulled out by the cord, and the IEC 60309 pin-and-sleeve configurations are what a 60 A unit and most three-phase units carry because no NEMA locking configuration is listed above 30 A for them; the plug is therefore derived rather than chosen. The receptacle that mates with it is furnished under Wiring DevicesWiring DevicesResolves to the current adopted revision.sync/wiring-devices. (8.4.5)
8.4.6 The cord set of each cord-connected unit shall be listed to UL 817 as a power-supply cord, shall carry a plug of a NEMA WD 6 configuration listed to UL 498 or a pin-and-sleeve plug listed to UL 1682, and shall be furnished factory-attached to the unit.

8.5 Input Cord Length

8.5.1 The input cord of each cord-connected rack unit shall reach the receptacle serving it without an extension cord, and shall be not less than the length indicated in the datasheet.
Rack PDU Input Cord Lengthrange
Not less than
ft
3610121520
8.5.2 Where a cord length is not selected in the datasheet, the manufacturer's standard length shall be furnished and stated in the product data.
NOTE A cord reaches from the unit's inlet, at the top or the bottom of a vertical unit, to a receptacle in the cabinet, on an overhead tap-off unit, or under the raised floor, and a 10 ft cord is what most units ship with and reaches most of those arrangements; a shorter cord leaves less to coil in the cabinet, and a longer cord is ordered where the receptacle is at the far end of a cabinet row or across a raised-floor tile, subject to the length limit in an NFPA 70 Article 645 room under this standard. No length is the norm across the arrangements, so the field carries no default. (8.5.3)

9 Rack PDU Outlets and Protection

9.1 Outlet Types

9.1.1 The outlet types furnished on the rack units shall be as indicated in the datasheet, and the count of each type on each unit shall be as indicated on the rack power schedule.
Rack PDU Outlet Typeslistbox
IEC 60320 C13
IEC 60320 C19
IEC 60320 combination outlet accepting C14 and C20 plugs
NEMA 5-15R
NEMA 5-20R
NEMA L5-20R
NEMA L5-30R
NEMA 6-20R
NEMA L6-20R
NEMA L6-30R
NOTE A C13 outlet carries 10 A at 250 V under IEC 60320 and is the inlet of most servers, switches, and storage, and a C19 outlet carries 16 A and is the inlet of a blade chassis, a large storage array, or a GPU server; a combination outlet accepts either plug, so that the C13-to-C19 ratio is not fixed when the unit is ordered, at a higher cost per outlet. A NEMA 5-15R or 5-20R is the outlet of 120 V equipment and of the monitor, the console, and the cart in a network closet, and the locking NEMA configurations are the outlets of equipment with a matching locking cord. A 208 V unit carries IEC outlets on most projects, which is why the default is C13 and C19. (9.1.2)
9.1.3 Each outlet shall be rated for the current the unit's listing assigns to it, and the equipment assigned to an outlet shall not load a C13 outlet above 10 A, a C19 outlet above 16 A, or a NEMA outlet above its configuration rating.
9.1.4 Outlets on a three-phase unit shall be grouped by the phase pair that feeds them, and each group shall be marked with its phases, so that the rack load can be balanced among the phases by outlet assignment.

9.2 Outlet Retention

9.2.1 The outlet retention of the rack units shall be as indicated in the datasheet.
Rack PDU Outlet Retentionradio
○ None, friction-fit outlets
○ Locking IEC outlets that grip a standard plug
○ Outlet retention clips or sleeves fitted over the plug
○ Locking cord sets mated to standard outlets
NOTE A friction-fit IEC outlet holds a plug by the spring of its contacts and lets a cord fall out when a cabinet is worked on behind the equipment; a locking outlet built into the unit grips a standard IEC plug with a latch released at the outlet and needs no special cord; a retention clip or sleeve is fitted to each outlet after the cord is plugged in and is lost or left off in service; and a locking cord set carries the latch on the plug and mates with a standard outlet, so that the retention is bought cord by cord and the unit is ordinary. A rack that is rarely touched is served by friction fit, and a rack in a high-traffic room or a seismic area is given one of the three retaining forms, which one depending on whether the Owner wants the retention in the unit, in an accessory, or in the cord. No form is distinctly the norm, so the field carries no default. (9.2.2)

9.3 Outlet Bank Overcurrent Protection

9.3.1 The overcurrent protection of the outlet banks of the rack units shall be as indicated in the datasheet.
Rack PDU Outlet Bank Overcurrent Protectionradio
○ None, outlets protected by the branch-circuit overcurrent device
○ Circuit breakers listed to UL 489, one per outlet bank
Derived — the input current rating of the unit and the rating of the outlets furnished on it (by default)
NOTE A unit whose input rating does not exceed the rating of its outlets, such as a 20 A unit with 20 A outlets, is protected by the breaker in the panelboard; a unit fed at 30 A or more with 16 A and 10 A outlets carries a breaker at each bank of outlets so that no outlet is on a circuit above its rating, as the unit's listing and NFPA 70 210.21 require, and that is what every unit above 20 A is built with. The protection therefore follows from the ratings and the field is derived. (9.3.2)
9.3.3 Outlet bank circuit breakers shall be listed to UL 489, shall be of the hydraulic-magnetic or thermal-magnetic type, shall be accessible on the face of the unit without removing it from the rack, shall indicate their tripped state, and shall be positioned or guarded so that a cord or a hand cannot trip them unintentionally.

9.4 Integral Surge Protection

9.4.1 Whether the rack units carry an integral surge protective device shall be as indicated in the datasheet.
Rack PDU Integral Surge Protectionradio
● No integral surge protection
○ Integral surge protective device listed to UL 1449
NOTE A rack in a room fed through an uninterruptible power supply and a panelboard with its own surge device sees no transient a unit-level device would add protection against, and a surge device in the unit is a wear part that reaches end of life without the Owner's notice, so most rack units are bought without one and that is the default; a unit in an equipment closet fed from a general panelboard with no surge device ahead of it, or at a site with a lightning exposure, is the case where the integral device is bought, applied as the point-of-use stage of the coordinated arrangement Surge Protective DevicesSurge Protective DevicesResolves to the current adopted revision.sync/surge-protective-devices describes. (9.4.2)
9.4.3 Where an integral surge protective device is furnished, it shall indicate on the face of the unit whether its protection remains functional, shall continue to pass power at end of life while so indicating, and shall be coordinated with the upstream surge devices as Surge Protective DevicesSurge Protective DevicesResolves to the current adopted revision.sync/surge-protective-devices requires.

10 Rack PDU Metering and Network Interface

10.1 Metering Granularity

10.1.1 Where a metered, monitored, or switched class is selected, the metering granularity of the rack units shall be as indicated in the datasheet.
Rack PDU Metering Granularityradio
○ Inlet metering, per phase
○ Inlet and outlet bank metering
○ Inlet, outlet bank, and per-outlet metering
NOTE Inlet metering gives the load of the rack per phase, which is what capacity planning and the 80% ceiling need; bank metering adds the load on each breaker, so that an overloaded bank is seen before its breaker trips; and per-outlet metering gives the power of each piece of equipment, which is what a colocation operator bills on, what a search for stranded capacity needs, and what costs a metering circuit per outlet. The granularity a project wants follows from what will be done with the data, so the field carries no default. (10.1.2)
10.1.3 Each metered point shall report current, voltage, active power, apparent power, power factor, and accumulated energy, and a monitored or switched unit shall alarm on its network interface at a current threshold settable by the Owner for the inlet, for each bank, and for each outlet where it is metered.

10.2 Metering Accuracy

10.2.1 The accuracy of the metering of the rack units, stated as a percentage of reading over the range from 10% to 100% of the rated current, shall be as indicated in the datasheet.
Rack PDU Metering Accuracyrange
Not more than
% of reading
0.5123
NOTE An accuracy of ±1% of reading is what the units sold for capacity management and tenant billing carry and what most projects accept, which is why it is the default; a tighter 0.5% is bought where the metering is the basis of a billing dispute, and a looser 2% or 3% is the accuracy of a display-only metered unit and is accepted where the reading guides loading and nothing else. (10.2.2)
10.2.3 The manufacturer shall state the accuracy and the current range over which it holds in the product data.

10.3 Network Interface

10.3.1 Monitored and switched units shall provide the network interface and protocols indicated in the datasheet.
Rack PDU Network Interface and Protocolscheckbox
☑ 10/100/1000BASE-T Ethernet port
☑ SNMP v3
☑ HTTPS web interface
☐ RESTful or Redfish API
☐ Modbus TCP
☐ BACnet/IP
☐ Cascading of several units on one network connection
☐ Serial console port
NOTE Ethernet with SNMP v3 and a web interface is what every monitored unit carries and what the monitoring platforms read, which is why those three are the default; a RESTful or Redfish API serves a data center infrastructure management system that polls by API rather than SNMP; Modbus TCP and BACnet/IP serve a building management system that reads the rack load as a point; cascading lets a row of units share one switch port and one address through a daisy chain, at the cost that the first unit's failure takes the chain offline; and a serial console is the recovery path when the network configuration is lost. (10.3.2)
10.3.3 Monitored and switched units shall support SNMP v3 with authentication and privacy, shall support HTTPS with the Owner's certificate installed, shall allow SNMP v1, SNMP v2c, HTTP, and Telnet to be disabled, and shall require the default credentials to be changed at first login.
10.3.4 Monitored and switched units shall accept firmware updates over the network interface with a signed image, and shall allow their configuration to be exported and restored.
10.3.5 Switched units shall provide per-outlet on, off, and cycle control, outlet grouping, a settable power-on delay per outlet for staged start-up after an outage, and a settable state for each outlet on recovery of power.
10.3.6 The Contractor shall request the management network addresses, the host naming convention, the time source, the SNMP and certificate settings, the user accounts, and the alarm thresholds from the Owner in writing not later than 30 days before the first rack is scheduled for service, and a unit for which the settings have not been furnished by that date shall be configured with a temporary address and reported to the Engineer of Record.
10.3.7 The Contractor shall configure each monitored and switched unit with the settings the Owner furnishes before the rack it serves is placed in service, and shall record the configuration in the closeout submittals.
NOTE A monitored unit left at its factory address and credentials is an unmonitored unit with an open management port, which is the condition in which most intelligent units are found a year after installation; the configuration before service, with the Owner's settings, is what turns the hardware into monitoring. (10.3.8)

10.4 Environmental Sensors

10.4.1 The environmental sensors furnished with the monitored and switched units in each rack shall be as indicated in the datasheet.
Rack PDU Environmental Sensors per Rackcheckbox
☐ Inlet air temperature sensor at the front of the rack
☐ Exhaust air temperature sensor at the rear of the rack
☐ Humidity sensor
☐ Door contact sensor
☐ Water leak sensor
☐ Airflow or differential pressure sensor
NOTE The sensor port on a monitored unit is the least expensive way to put a temperature reading in every rack, and the inlet temperature at the front of the rack is the value the cooling is managed against; an exhaust sensor shows a rack whose airflow is blocked, a humidity sensor is placed in a few racks rather than all, a door contact records cabinet access, a leak sensor serves a rack near a cooling unit or under a pipe, and an airflow sensor serves a containment system. The set a project wants follows from what the room monitors elsewhere, so the field carries no default. (10.4.2)
10.4.3 Sensors shall connect to the unit through its sensor port with plug-in cables, shall be reported on the unit's network interface with settable alarm thresholds, and a temperature sensor shall be accurate to ±1 °C.

11 Rack PDU Mounting

11.1 Mounting Form

11.1.1 The mounting form of the rack units shall be as indicated in the datasheet.
Rack PDU Mounting Formradio
○ Vertical, zero-U, in the rear channel of the cabinet
○ Horizontal, 1U, in the equipment rails
○ Horizontal, 2U, in the equipment rails
NOTE A vertical unit mounts in the rear of a cabinet beside the equipment, consumes no rack units, puts an outlet near every piece of equipment so that the cords are short, and needs a cabinet with the depth and the mounting points for it; a horizontal unit mounts in the rails of any rack, including a two-post open rack and a wall cabinet, consumes one or two rack units, and puts its outlets on a row the cords reach down to. A full-height cabinet is served by a vertical unit and an open rack or a shallow cabinet by a horizontal one, so the form follows the rack and the field carries no default. (11.1.2)
11.1.3 Vertical units shall mount with the manufacturer's toolless buttons or brackets at the cabinet's mounting points, shall not obstruct the cable routing or the airflow at the rear of the equipment, and shall have their inlet cord at the end nearest the receptacle that serves them.
11.1.4 Horizontal units shall mount with the manufacturer's rack-mount brackets in the equipment rails, with the outlets facing the rear of the rack unless the rack elevations indicate otherwise.
11.1.5 The chassis of each unit shall be of formed steel or extruded aluminum with no sharp edge at an outlet or a cable path, and the A-feed and B-feed units in one rack shall be distinguished by chassis color, by outlet color, or by a label at each outlet group.

12 Relocatable Power Taps

NOTE A relocatable power tap is a cord-connected strip of NEMA outlets with a switch and an overcurrent device, listed to UL 1363 for 15 A or 20 A at 125 V or 250 V and intended for equipment that is moved; it is a different product from a rack power distribution unit, and this standard calls for it only where a schedule indicates one. (12.1)
12.2 Where a relocatable power tap is indicated for a rack, a bench, or a workstation, it shall be listed to UL 1363, shall have an attachment plug and an overcurrent device at the rating of the tap, and shall have a cord not longer than 25 ft.
12.3 A relocatable power tap shall be plugged directly into a permanently installed receptacle, shall not be connected to another relocatable power tap or to an extension cord, shall not be routed through a wall, a floor, a ceiling, or a doorway, shall not be fastened to the building structure, and shall be attached to a rack or a bench only by the mounting means the manufacturer furnishes.
12.4 The equipment plugged into a relocatable power tap shall not load it above its rating and shall be counted against the branch circuit that serves the receptacle it plugs into.
12.5 A special-purpose relocatable power tap in a patient care vicinity shall be listed to UL 1363A, shall be permanently attached to the medical equipment assembly it serves, shall be loaded to not more than 75% of its rating by the equipment connected to it, and shall be applied under the conditions NFPA 99 sets for its use in that location.
NOTE The special-purpose tap is the device NFPA 99 permits in a patient care vicinity because a general relocatable power tap is not, and it is bought by the clinical engineering group with the equipment cart more often than by the construction project, which is why the requirement here is a listing and an application rather than a schedule. (12.6)

13 Identification

13.1 Nameplates, warning labels, and field-applied markings shall comply with Equipment LabelingElectrical Equipment LabelsResolves to the current adopted revision.sync/equipment-labeling for material, lettering, and attachment.
13.2 Each busway plug-in unit shall carry a nameplate stating the unit designation, the run it mounts on, the ampere rating, the fuse rating or the trip setting, and the load served, and the designation shall match the busway plug-in unit schedule.
13.3 Each busway plug-in unit shall carry the manufacturer's marking of the voltage rating, the ampere rating, the short-circuit current rating, the series rating where one is applied, and the busway series it is listed for, visible with the unit installed.
13.4 Each busway plug-in unit that carries an overcurrent device shall carry an arc-flash warning label 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.
13.5 Each rack unit shall carry a label at its inlet end stating the rack it serves, its feed designation, and the panelboard and circuit that serve it, and the designation shall match the rack power schedule.
13.6 Each outlet or outlet group on a rack unit shall be marked with its number and, on a unit with outlet bank breakers or a three-phase input, with the breaker and the phases that feed it, and a switched unit shall report each outlet on its network interface by the same number.
13.7 Each hardwired rack unit shall carry a label identifying the location of its disconnecting means.

14 Testing

14.1 Factory Tests

14.1.1 The manufacturer shall perform the production tests of UL 857 on every busway plug-in unit, including a dielectric withstand test and a verification of the interlocks, and shall furnish a certified production test report with the closeout submittals.
14.1.2 The manufacturer shall perform the production tests of the listing standard on every rack unit, including dielectric withstand, grounding continuity, and a functional test of every outlet, breaker, relay, and metering channel, and shall furnish a certified production test report with the closeout submittals.
14.1.3 The leakage current of each rack unit and power tap shall not exceed the limit its listing standard sets for its class of equipment.

14.2 Busway Plug-In Unit Field Tests

14.2.1 Field tests on busway plug-in units shall be performed after every unit is installed and before the run 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.
Busway Plug-In Unit Field Testscheckbox
☑ Visual and mechanical inspection of seating, latching, cover closure, and padlock provisions at every unit
☑ Verification of the fuse class and rating or the breaker trip setting at every unit against the schedule
☑ Operation of every interlock, including an attempted withdrawal with the device on
☑ Insulation resistance of each unit, phase-to-phase and phase-to-ground, with the device open
☑ Ground connection continuity from the load-side ground terminal of every unit to the ground path of the run
☑ Phase sequence at the load terminals of every unit
☐ Operation of the hook stick or the cable operator at every out-of-reach unit
14.2.2 The insulation resistance test shall be performed for one minute at 1000 V DC on a unit rated above 250 V and at 500 V DC on a unit rated 250 V and below, with the run de-energized and isolated, and a reading below the ANSI/NETA ATS minimum for the voltage class shall be investigated before the run is energized.
NOTE The infrared inspection of the installed plug-in units under load is performed with the inspection of the run under BuswayBuswayResolves to the current adopted revision.sync/busway, which scans every installed unit; this standard adds no second scan. (14.2.3)
14.2.4 A plug-in unit that fails a field 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.

14.3 Rack PDU Field Tests

14.3.1 Field tests on rack units shall be performed after installation and configuration and before the rack is placed in service, and shall include the tests indicated in the datasheet.
Rack PDU Field Testscheckbox
☑ Test of the receptacle serving each unit for polarity, grounding, and voltage before the unit is plugged in
☑ Voltage and phase rotation at the outlets of every unit
☑ Grounding continuity from the chassis and from the ground contact of an outlet on every unit to the grounding pin of its plug
☑ Operation of every outlet bank breaker
☑ Network reachability, SNMP response, and web login of every monitored and switched unit
☐ Metering verification of every monitored unit against a reference meter at a known load
☑ Outlet switching and power-on delay of every switched unit
☑ Transfer and retransfer of every dual-input unit on loss of each feed
☑ Reading and alarm of every environmental sensor
14.3.2 The metering verification shall be performed at a load of not less than 25% of the unit's rating, with a reference meter of an accuracy better than the unit's, and a unit whose reading differs from the reference by more than the accuracy indicated in the datasheet shall be corrected or replaced.
14.3.3 A rack unit that fails a field test shall be corrected or replaced and retested at the Contractor's cost, and the test reports shall be included in the closeout submittals.

15 Installation

15.1 Busway Plug-In Unit Installation

15.1.1 Busway plug-in units shall be installed in accordance with NFPA 70 Article 368, NEMA BU 1.1, and the busway manufacturer's instructions, on the openings indicated on the busway plug-in unit schedule, with every unit fully seated and latched and every unused opening closed by its cover before the run is energized.
15.1.2 A unit shall be installed on or removed from a run only with the run de-energized, unless the unit and the run are listed for insertion and withdrawal with the run energized, and in that case only with the unit's device open and by a qualified person working under NFPA 70E.
15.1.3 The handle of every unit shall be within 2.0 m (6 ft 7 in.) of the floor or working platform, or the unit shall be furnished with the operating provision this standard requires for an out-of-reach unit, in accordance with NFPA 70 240.24(A) and 368.17(C).
15.1.4 The working space in front of every unit and at every cable operator handle shall comply with NFPA 70 110.26, and no unit shall be installed where its cover cannot be opened or its fuses replaced from a stable footing.
15.1.5 A unit shall be supported by the run alone only where the manufacturer's instructions permit it for the unit's weight, and a unit heavier than the limit stated in those instructions, or one carrying a cord drop or a transformer, shall be supported by a hanger of its own to the structure.
15.1.6 A cord drop from a unit shall be suspended by a strain-relief grip at the unit and by a support at the equipment end, shall hang clear of walkways and vehicle paths, and shall terminate in a connector or a plug held at a height where it is not pulled by passing traffic.

15.2 Rack PDU Installation

15.2.1 Rack units shall be installed in the rack indicated on the rack power schedule, mounted with the manufacturer's hardware as the Mounting Form article requires, with the inlet cord routed to its receptacle without strain on the plug and dressed clear of the equipment cable paths.
15.2.2 The receptacle serving each cord-connected unit shall be furnished under Wiring DevicesWiring DevicesResolves to the current adopted revision.sync/wiring-devices at the location indicated on the electrical plans, within the reach of the cord length selected, in the cabinet, on an overhead receptacle tap-off unit, or under a raised floor where NFPA 70 645.5 permits.
15.2.3 The input cord of a rack unit shall not pass through a wall, a floor, a ceiling, or a doorway, shall not be concealed behind the building structure, and shall not be used as a substitute for the fixed wiring of the building, in accordance with NFPA 70 400.12.
15.2.4 Where a rack stands in an information technology equipment room to which NFPA 70 Article 645 applies, the Contractor shall confirm that the room satisfies every condition of NFPA 70 645.4 before the wiring methods of that article are used, and the input cord of each unit shall not exceed 4.5 m (15 ft) in length, shall be of a type NFPA 70 645.5 permits, and where run under a raised floor shall be listed for that use.
15.2.5 In a room to which Article 645 does not apply, the input cord of a rack unit shall be installed as a cord-and-plug connection under NFPA 70 400.10, exposed and accessible for its full length, and shall not run under a raised floor.
NOTE Article 645 is an elective article: a room that meets its conditions for a disconnecting means, a fire-rated boundary, a dedicated cooling system, and a listed equipment population is wired with its cord and under-floor allowances, and a room that does not meet them is wired under the general articles, where a cord under a raised floor is not permitted. Deciding that a room is an Article 645 room because it holds servers, without the conditions, is the common error. (15.2.6)
15.2.7 The equipment plugged into each rack unit shall be assigned so that the continuous load on the unit, on each outlet bank, and on each phase does not exceed 80% of the respective rating, and the assignment shall be recorded on the record rack power distribution unit schedule.
15.2.8 Each monitored and switched unit shall be connected to the management network and configured as the Network Interface article requires before the rack it serves is placed in service.

16 Delivery, Storage, and Handling

16.1 Units shall be delivered in the manufacturer's packaging with the listing marks and the catalog designation intact, shall be inspected at receipt for damage and for conformance with the reviewed submittal, and a damaged unit shall be replaced at no cost to the Owner.
16.2 Units shall be stored indoors in a clean, dry space within the manufacturer's published storage temperature range, off the floor, with the stabs of busway plug-in units and the plugs and outlets of rack units protected from dust, moisture, and impact until installation.
16.3 Busway plug-in units shall be handled by the enclosure and never by the stabs, the handle, or the cover, and a unit whose stabs are bent or whose plating is damaged shall not be installed.

17 Warranty

17.1 The manufacturer shall warrant each busway plug-in unit and each rack unit, including its overcurrent devices, relays, metering, and network interface, against defects in materials and workmanship for the period indicated in the datasheet.
Manufacturer's Warranty Periodrange
Not less than
years
1235
17.2 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.
NOTE Busway plug-in units carry the warranty of the busway series, which runs one to two years on most series, and rack units carry warranties that run from one year to five across the market and longer on units sold as a monitored product with its software, so no period is the norm and the field carries no default; the longer periods are bought for the electronics of monitored and switched units, which fail before the outlets do. (17.3)
17.4 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 Commencement at shipment is the manufacturer's usual term and consumes the warranty while the units sit in storage; commencement at energization or at substantial completion moves the coverage to the period the Owner operates the units, and the manufacturer prices the added months into the units. (17.5)
17.6 The Contractor shall warrant the installation, including every termination, every cord drop, every configuration, and the results of the field tests, for the project warranty period, and shall correct a unit that fails, trips without cause, loses its configuration, or does not perform its test during that period at no cost to the Owner.
17.7 A unit, device, or component replaced under warranty shall be warranted for a full new term equal to the original period from the date of replacement, or for the remainder of the original period, whichever ends later.

18 Spare Parts

18.1 The Contractor shall deliver the spare parts indicated in the datasheet to the Owner before the units are accepted, and shall obtain a signed receipt for them.
Spare Parts to Be Furnishedcheckbox
☑ Fuses, three of each class and rating installed, and not fewer than one full set per fusible unit rating
☐ One busway plug-in unit of each type and rating installed
☐ One input cord set of each plug configuration and length installed
☐ Two of each environmental sensor type installed
☐ Outlet retention clips or locking cord sets for 10% of the installed outlet count
☐ One rack unit of each class, input rating, and outlet configuration installed
NOTE A fusible plug-in unit that has cleared a fault is restored only with the right fuse in hand, so the spare fuses are the one spare nearly every project carries, which is why they are the default; a spare plug-in unit lets a load be added or a failed unit swapped without waiting on the busway manufacturer's lead time, and a spare rack unit does the same for a rack whose unit fails, which in a monitored population is usually the network card rather than the outlets. (18.2)
18.3 Spare parts shall be identical to and interchangeable with the installed parts, shall be delivered in their original packaging, and shall be labeled with the unit type, the rating, and the busway series or the rack population they serve.

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"Busway Plug-In Units and Rack Power Distribution Units," SynC Standards, revision 5. Licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://synergyinconstruction.com/standards/general/feeder-busway-plug-in-units. Reference material only; not professional engineering advice and provided without warranty. Verify against governing codes and have a licensed professional review before use.