2008 Nec 42 circuit max

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yzman720

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I was doing some reading into the lift of the 42 circuit max of the nec on an inspectors website which he states his understanding is -

"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."


My ?'s -A 200 amp panel technically has a double pole service disconnect main breaker so with this I cannot run a 200 amp panel with 60 spaces that is rated for 60 circuits on that panel? or am I misunderstanding him? If I am misunderstanding when would you have 2 main breakers if they are not referring to the 2 pole main breaker as the exemption? Please clarify for me

Here is the link to the panel I am wanting to use: http://www.homedepot.com/p/Square-D-by-Schneider-Electric-QO-200-Amp-60-Space-60-Circuit-Indoor-Main-Breaker-Plug-on-Neutral-Load-Center-with-Cover-QO160M200PC/204246798

Is this panel ok with the main breaker style under the new 2008 nec guidlines of having more than 42 circuits?
 
If a main panel has the 42 circuit limitation, that does not in any way impose any restriction on how many circuits you can have in a panel whose feeder comes from the 42 circuit panel.
The 42 circuit limitation is motivated by the design and wiring of the panel, and the number of circuits that can be installed in circuits downstream of that are just not, IMHO, relevant.
The fact that the 42 circuit limitation was at one time enshrined in the NEC does not give any force extending to downstream panels, nor does it apply once the jurisdiction has moved on past the 42 circuit limitation.
If the panel manufacturer documents a 42 circuit limitation on their UL listed device that would survive the change in the NEC, but that also has no effect downstream.

Would the inspector also argue that if my main panel has only 24 slots, including a feeder to another 24 circuit panel which is filled up, that that would be a violation of the 24 circuit limit in the upstream panel? I doubt it.

One more angle: If the inspector is arguing that any equipment installed under a more restrictive version of the NEC has those limitations "grandfathered" in even when the NEC gets less restrictive, he needs a lesson in logic. That would potentially force us to use knob and tube wiring for a house which was originally built when conduit and NM did not yet exist.
 
I agree with goldigger. The main thing is your load calculation.


You know as well as I do a lot of times extra panels are added just because of the circuit requirements needed. They the (NEC ) started this rule when they started requiring afcis. Then you could easily need more then 42 circuit and still fall way below your 200 amp rating.
 
Maybe I am just over thinking it. I do not want to do a sub panel so I was just going to put in the 60 space 200 amp panel that I posted a link for but the wording of the breaker style exception in the nec had me kind of confused to conforming to the nec requirement. I am not missing anything am I? The panel I posted a link to with the main breaker it has conforms to nec fine doesn't it?
 
yzman720 said:
I was doing some reading into the lift of the 42 circuit max of the nec on an inspectors website which he states his understanding is -

"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."


My ?'s -A 200 amp panel technically has a double pole service disconnect main breaker so with this I cannot run a 200 amp panel with 60 spaces that is rated for 60 circuits on that panel? or am I misunderstanding him? If I am misunderstanding when would you have 2 main breakers if they are not referring to the 2 pole main breaker as the exemption? Please clarify for me
Click to expand...

Yes, you are misunderstanding him. The inspector was referring to applications using a split-bus MLO panel protected upstream by two separate OCPD's. Those type of panels are still limited to 42 circuits max.
 
What was removed in the 2008 NEC was the "Lighting and appliance" panelboard and it's definition. These were limited to no more then 42 overcurrent devices.

You still have to use a panelboard within it's listing requirements, so if it says maximum of 20, 30, or 42 overcurrent devices you are still limited to those values, but since that change you can now find panelboards that are listed to accept more then 42.
 
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