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What is the maximum number of two pole branch breakers which can be added to an 84 circuit NF panelboard?

Issue:
Selection

Product Line:
Panelboards

Environment:
UL 67, UL 50, CSA C22.2 No.'s 20-M1989 & 94-M91, NEMA PB1, NFPA 70 Art. 408, Federal Specification W-P-115C Type 1 Class 1 , 2003 IBC, NFPA

Cause:
With the introduction of 84 circuit panelboards following a change to the NEC it is desirable to understand the maximum number of two pole breakers which can be accommodated.


Resolution:
Because of their method of construction, it is not possible to install more than 40 two pole breakers in an 84 circuit NF panelboard.  To illustrate, using a conventional circuit numbering of 1 - 84 with odd-numbered circuits on the left, and even-number circuits on the right, it is not physically possible to install a two pole breaker in an 84 circuit NF panelboard on circuits 41-43; nor is it possible for circuits 42-44.  A break in the interior prevents this.   Also, it is not possible to install a two pole breaker on circuits 83 and 84, as they are across from one another in the interior.  With the above in mind, the maximum number of two pole breakers which may be installed in an 84 circuit NF panelboard is 40.
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