2008 NEC Change-Panelboard circuit limitations relaxed

[Paul W. Abernathy]

408.36- Panelboard Limitations Relaxed
By Paul W. Abernathy- 7/13/2009

The National Electrical Code went through some major changes regarding panelboards in the 2008 code cycle. In doing these changes the code making panel took on the task of eliminating the limitations regarding lighting and appliance panelboards. The previous limitations of 42 circuits have finally been removed for the most part. The NEC no longer provides the terms lighting and appliance panelboard or power panelboard. These sections pertaining to them have been totally removed from the code. Let's examine what the NEC is saying and break it down with the exceptions.

NEC 2008- 408.36 [Code Change]

A. The classification and definitions defining “lighting and appliance panelboards” and “power panelboards” has been stricken from the NEC.

B. All panelboards are to be sized “not smaller” than the feeder. This is what the previous 2005 NEC was trying to allude to but left much to be desired. It has now been corrected and clarified in the 2008 NEC.

C. All panelboards are to be protected “at not greater than” their rating by a single overcurrent protective device within or ahead of the panelboard. The distinction here is the term "single“ is what sets this apart from the exceptions like #2 below. Now let’s look at the exceptions to this rule.

Exceptions
The following three exceptions remove the single overcurrent protective device mandate in 408.36.

Exception No. 1:
Individual protection shall not be required for a panelboard used as service equipment with multiple disconnecting means in accordance with 230.71. In panelboards protected by three or more main circuit Breakers or sets of fuses, the circuit breakers or sets of fuses shall not supply a second bus structure within the same panelboard assembly; a split buss setup would be the key example.

Exception No. 2:
Individual protection is not required for a panelboard protected on its Supply side by two main circuit breakers or two sets of fuses having a combined rating “not greater than” that of the panelboard. A panelboard constructed or wired under this construction should not contain more than 42 overcurrent protective devices. For the purposes of this section, a 2-pole circuit breaker or fusible switch shall be considered two overcurrent devices; a 3-pole circuit breaker or fusible switch shall be considered three overcurrent devices.

Exception No. 3:
For existing panelboards, individual protection shall not be required for a Panelboard used as service equipment for an individual residential occupancy.

D. NEC 408.54 requires panelboards to be provided with physical means to prevent the installation of more overcurrent protective devices than the number for which the panelboard was designed, rated, and listed so if the manufacturer creates a 60 circuit panelboard, it can allow 60 circuit breakers but only 60 as that is the listing.

So the best example I can give to the impact of this change is that I can have a panelboard now with more than 42 circuits except when I am protecting the panelboard with a 2 main circuit breakers or fuses (not a single pole main breaker) upstream of my panelboard where the old rules of 42 circuits would still apply.

Copyright 2009-Paul W. Abernathy
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