ECN Forum Forums General Topics of the Trade General Discussion Area The archaic 42-circuit limit

It was definitely a lighting panelboard. It was made by Square D, Power-link I think, and had low-voltage contol busses on the sides, for remote switching of the lighting circuits.

resqcapt19 ---

If I read your code section right:

1) I can build a 431 circuit panel,

2) Install 43 lighting circuits, and

3) fill the remaining spaces with breakers with ratings over 30 amps.

I think that complies with the letter of that section (but not the spirit).

The 42 circuit limit is foolish, but due to voltage drop over distance in most cases a better solution is to provide subpanels remote from the main panel.

Hmmm... even though I'm planning on only a 200 amp service upgrade (up from 100 amp in a 2200 sq. foot house built in 1978), the twin subpanel idea sounds like a good one. I could put the 240-volt circuits in one panel and the 120's in the other, with a 200 amp main disconnect ahead of them. This would give me plenty of expansion opportunity. It might raise the AHJ's eyebrows, though as it might be considered overkill for such a house. I still am a big fan of planning for the future as best as can be done.

Square D makes 54 pole NQOD panelboards for sale in the US. I presume that, if you use one as a "lighting and appliance branch-circuit panelboard" you are not permitted to install more than 42 poles of breakers.

As someone already mentioned on the thread, for export to Canada they make NQOD panelboards with as many as 84 spaces.

It looks like an old topic resurrected...one thing that was noted in some Handbook somewhere is that a panel used to supply only circuits of >30A is _not_ a 'lighting and appliance panelboard', even if _all_ of those >30A circuits are used to feed lights.

-Jon

I've heard stories of people smuggling toilet cisterns in from Canada to get round the federal water-saving limit (what is it now, 1.2 gallons maximum per flush?).

WIth cisterns and panelboards, I wonder what will be next!

The 42 circuit limit did indeed result from a fire in the Waldorf-Astoria Hotel in New York in 1928. This was a lighting panel wired with type R wire. This story was confirmed by the late Anthony Montouri, Chief Inspector, New York Board of Fire Underwriters. It was judged at the time that there was too much insulation and braid in one enclosure, and the 1933 NEC in Section 1303g. established the 42 circuit limit. It may have been over-reacting. To change this would require extensive testing and I doubt there is any interest willing to put up the money for such an investigatrion.
Creighton

Thought they were going to open up the 84 circuit panels for the US after they force us all to have AFCI everything. Isn't that the current rumor?

It might be more hazardous to fall in a panel that big.

Sometimes have trouble trying to get 24 circuits into the top, and bottom through framing. Every panel would need a cable tray to get it all over to the panel without turning the building into swiss cheese.

How many are using the 30 space 100A Loadcenter?

Les