42 Circuit Rule

[steve66]

It looks like under the 2008 code, I can use a 54 circuit panelboard to supply some receptacles in a data center as long as I protect the panelboard at its ampacity, and the box meets the requirements for wire bending space.

Does anyone disagree?

And after a second look at the 2005 code, it looks like I still could of used a 54 space panel since almost all the receptacles will be 2 pole, 208V, NEMA L6-30R.

Or am I not reading this part right?

Steve

 

[charlie b]

I don?t have the 2008 yet; no need yet. But under the 2005, if you want to use a 54 circuit panel, and if no more than 5 of the slots (i.e., under 10%) are single pole, then you can use it for your data center.

 

[Pierre C Belarge]

I don?t have the 2008 yet; no need yet. But under the 2005, if you want to use a 54 circuit panel, and if no more than 5 of the slots (i.e., under 10%) are single pole, then you can use it for your data center.

As Charlie has mentioned, you may have a panel that is not considered a lighting and appliance branch circuit panelboard. There is the 10% rule of 408.34(A) that you need to review and then check to your panel.
The 42 circuit limitation is for lighting and appliance branch circuit panelboards as per 408.35.

 

[tallguy]

The 42 circuit limitation is for lighting and appliance branch circuit panelboards as per 408.35.

408.35 has been removed entirely for 2008 though. I know it won't matter to Pierre for about 10 more years :wink:, but the OP did ask about 2008.

 

[M. D.]

Here is an analysis of the change for 2008

http://www.iaei.org/subscriber/magazine/06_e/johnston.html

Revision: 408.36 Overcurrent Protection
Sections 408.36(A) and (B) and the associated exceptions have been restructured into one section with three exceptions. Under this revision, the differentiation between power panelboards and lighting and appliance branch-circuit panelboards has been removed. Existing subdivisions (C), (D), (E), and (F) of this section have been re-identified as subdivisions (A), (B), (C), and (D), respectively. Sections 408.34 and 408.35 which included definitions of power panelboard and lighting and appliance branch-circuit panelboard have both been deleted as a result of these revisions to Section 408.36. The revisions to this section essentially remove the 42 overcurrent device limitations for panelboards and also result in requirements that now address power panelboards and lighting and appliance panelboards in the same fashion. The newly created Exception No. 1 is based on the 2005 exception to 408.36(B) which is intended to recognize a long-standing practice of allowing a small panel to be used as service equipment, with large line-to-line loads leaving at this point and a smaller feeder entering the building to supply what formerly was called a lighting and appliance branch-circuit panelboard. The limitations now contained in this exception prevent the extension of this limited practice to what could otherwise become a split-bus panelboard with an unlimited number of overcurrent devices in the future. The six-circuit limit mirrors the customary service limitation contained in 230.71. Exception No. 2 corresponds to the 2005 language at 408.36(A) [see figure 10].

 

[steve66]

Wow, thanks. There's a lot in that analysis.

I guess it was easy to get used to the idea that 42 spaces were the limit. I ran in few (if any) cases where the limit didn't apply.

Steve