This article is about DC Panelboard / Circuit Breaker Material Selection Criteria & Design Requirements of Electrical Power System as per International Codes and standards for Commercial Buildings, Plants and Refinery Projects.
DC Panelboard / Circuit Breaker Material Selection Criteria & Design
DC Panelboard Material Receiving-General
Electrical materials shall be new and unused.
“Electrical materials shall be in accordance with the Saudi
Aramco-approved project-specific design drawings, diagrams,
schedules, lists, databases, and associated documents.”
Electrical materials shall be free of damage.
Electrical materials shall conform to all applicable requirements, standards, and specifications prior to release to be used as part of the work.
Electrical materials shall be identified by using tags, stamps, color coding, stencils or labels. The location and method of identification shall not affect the function or quality of the materials.
Electrical materials shall be traceable from the manufacturer and supplier through delivery, storage, fabrication, erection, installation, repair, modification and use.
DC Panelboard
“The panelboard shall be from the manufacturers list below: SAES-P-101, 29 Feb. 2004 SAES-P-101, 09 Jun. 2007
Panelboards shall fully comply with NEMA PB 1 and UL67.
If installed in an electrically classified area, the panelboard branch circuit shall be factory sealed in separate compartments.
Panels shall be completely filled with breakers.
White nameplates with black lettering shall be provided to identify the panelboard with the tag number indicated within Data Schedule 1.
No equipment other than circuit breakers shall be allowed in panelboards.
“Panelboards shall:
a) be rated for continuous duty
b) have rated current- minimum of 100A
c) have short circuit interrupting rating minimum of 10 kA rms”
“Panelboards shall be durably marked by the manufacturer with the:
a) voltage
b) current rating
c) number of poles for which they are designed
d) manufacturer’s name or trademark in such a manner so as to be visible after installation, without disturbing the interior parts or wiring. (NFPA 70, NEC 408.58, Panelboard Marking)”
Enclosures rated Type 3, 4 or 4X per NEMA 250 shall be equipped with Type 300 Series stainless steel hardware.
All conductors shall be copper, silver or alloys.
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.
Breakers shall have a minimum trip rating of 20 A.
Breakers operating at greater than 240 Volts shall be equipped with padlockable lock-off devices.
Tandem, twin, or half-size breakers shall not be used.
When main circuit disconnectors are used, they shall be sized to allow the main bus to be operated at its full current rating.
Panelboards rated for installation in an electrically classified environment shall be installed completely filled with breakers.
All other panelboards shall be equipped with a minimum of 10% spare breakers and a minimum of 10% spare pole spaces.
If not indicated in the engineering documents, the sizes of the spare breakers shall be representative of the connected breakers within the panelboards.
“Conductors and busbars shall be located so as to be free from physical damage and shall be held firmly in place.
(NFPA 70, NEC 408.3 (A) (1))”
Load terminals for field wiring, including grounded circuit conductor load terminals and connections to the ground bus for load equipment grounding conductors, shall be located so that it is not necessary to reach across or beyond an uninsulated ungrounded line bus in order to make connections. (NFPA 70, NEC 408.3 (D))
“The minimum wire-bending space at terminals and minimum space provided in panelboards and switchboards shall be as required
in Table 312.6 (A) and (B). (NFPA 70, NEC 408.55)”
Circuit directory or circuit identification – Every circuit and circuit modification shall be legibly identified as to its clear, evident and specific purpose or use. (NFPA 70, NEC 408.4)
Not more than 42 overcurrent devices (other than those provided for in the mains) of a lighting and appliance branch-circuit panelboard shall be installed in any one cabinet or cutout box. (NFPA 70, NEC 408.36, Exception No.2)
Panelboard cabinets and panelboard frames, if of metal, shall be in physical contact with each other and shall be connected to an equipment grounding conductor. (NFPA 70, NEC 408.40, Table 250.122, NEC)
Table 250.122 – NFPA 70, NEC
The distance between bare metal parts, busbars, and so forth shall not be less than specified in NFPA 70, NEC Table 408.56.
International Standard and Codes for DC Panelboard / Circuit Breaker
- Non-Hazardous Indoor Enclosures, Installation and Pre-Commissioning
- Boxes, Enclosures, and Accessories Materials Selection & Requirements
- SAES-J-902 — Electrical Systems for Instrumentation.
- SAES-J-601 — Emergency Shutdown and Isolation Systems.
- NEMA 250 Enclosures for Electrical Equipment (1000 Volts Maximum), 2003 Edition.
- SAES-P-100 Basic Power System Design Criteria, 25 June 2007.
- SAES-P-101 Regulated Vendors list for Electrical Equipment, 09 June 2007.
- NEMA PB1 Panelboards, 2006 Edition.
- UL 67 Panelboards, 2006 Edition.
- NFPA 70 National Electrical Code (NEC), 2008 Edition.
- 16-SAMSS-518 Low Voltage Panelboards.