UPS Panelboards / Circuit Breakers Design Notes and Material Selection
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UPS Panelboards / Circuit Breakers Design Notes
UPS Panelboards / Circuit Breakers Material Checking
QC Before Installation- Panelboards / CB’s shall conform to all applicable requirements, standards, and specifications prior to release to be used as part of work.
Incoming Panelboards / CB’s shall be visually inspected for damage / defects occurred during transportation and conformance to all applicable requirements.
Panelboards / CB’s shall be new and unused.
Panelboards / CB’s shall be in accordance with the approved project-specific design drawings, diagrams, schedules, lists, databases, and associated design documents.
Check that the Contractor or approved third party inspector performed the quality activities at the supplier and sub-supplier locations as required by the inspection level assigned for the materials and equipment identified in Inspection Requirements.
UPS Panelboards / Circuit Breakers Design Notes
UPS loads shall be distributed through panelboards. Protection for the outgoing circuits shall be accomplished through fast acting circuit breakers rated for continuous operation with capability to quikly open and clear short-circuit or overload condition and have current limit feature.
Commentary Note: Panelboards specification does not allow the fuses to be within the panelboard enclosure. However, fast acting fuses type KTK, if required to protect specific loads, would have to be installed in a separate enclosure.
The maximum current rating of the largest branch circuit breaker in the distribution panel shall be no greater than one-half the rated current output of the inverter. In the case of fuses, the largest load-side fuse shall be no greater than one-fourth the rated current output of the inverter. This is to ensure proper selectivity between the tripping of the load circuit protective devices and the inverter’s internal protective devices.
The requirements of paragraph 8.5.6 shall not apply when the UPS is equipped with a static bypass switch for transferring to the bypass (alternate) line. In that case, the protective devices for the outgoing loads shall be selected to achieve selective coordination with the primary breaker on the line side of the bypass transformer.
Branch circuit fuses shall be coordinated with the load crest factor (in-rush current) as applicable.
Panelboards shall fully comply with NEMA PB 1 and UL 67.
For Panelboards which provide branch circuits operating at phase-to-neutral voltage levels, a neutral bus shall be provided within the panelboard.
Panelboard rating shall be Continuous, have a minimum rated current of 100A, and a Short Circuit Rating of 10kA rms.
All conductors shall be copper, silver or alloys of these materials. Plating of the copper, silver or copper/silver alloy base conductor material is acceptable.
The main circuit bus system shall be of rigid material (i.e., cable or flexible conductors shall not be used).
A ground bus shall be provided within the panelboard.
If the breaker size is not specified within the purchasing documents, breakers shall have a minimum trip rating of 20 A.
When main circuit disconnectors are used, they shall be sized to allow the main bus to be operated at its full current rating
White Nameplates with black lettering shall be provided to identify the panelboard with the tag number indicated within Data Schedule 1.
Panelboards shall be durably marked by the manufacturer with the voltage and the current rating and the number of phases for which they are designed and with the manufacturer’s name or trademark in such a manner so as to be visible after installation, without disturbing the interior parts or wiring. NEC 408-13 and NEMA PB-1 Sec. 4
The minimum wire-bending space at terminals and minimum gutter space provided in Panelboards shall be as required in 312.6. NEC 408-3 (F)
All circuits and circuit modifications shall be legibly identified as to purpose or use on a circuit directory located on the face or inside of the panel door in the panelboard. NEC 408-4
The Panelboard shall be supplied with a safety label in accordance with ANSI Z535. NEMA PB1 Sec. 2.11.1
Voltage, Current and Frequency ratings shall be in accordance with Section 3. NEMA PB1 Sec. 3
UPS Panelboards / Circuit Breakers International Codes and Standards