42 space panel with subfeed breaker (Sec 408.35)

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blainebenson

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Does a 42 space panel with a subfeed breaker violate the 42 overcurrent protective devce rule of 408.35?

I am thinking the panel I want to add could be classified as lighting and appliance branch circuit board, but I need to add a subfeed breaker.

My choices are a 30 space panel or a 42 space panel . I would like to use the 42 space panel to give me more flexibility for future circuits.
 
Not quite sure what your question is, but you are allowed a maximum of 42 overcurrent devices through which power can feed out of the panel. If you are needing more circuits and your load calculation will allow it, then it is customary to set another panel and move enough circuits from the original (full) panel to the new sub-panel to allow for space to install a large branch breaker in the original panel that will feed the new sub panel.
Some panelboards have "feed-thru" lugs that allow for you to feed the second panel from the first without taking up breaker space. However, this requires the sub-panel to be rated same as the original.
 
Let me rephrase my question as I may not have been clear.

I want to add a 400A panel. It needs to feed an existing 200A panel.
I can not get a 200A branch breaker for the 400A panel, so I have to use a subfeed breaker. (I do not want to replace the existing 200A main lugs only panel).

Can I use a 42 space panel board with a 200A subfeed breaker, or would this violate the 42 space rule?

If I can't use a 42 space pale with a 200A subfeed breaker without breaking the rule, the next size is a 30 space panel with a subfeed breaker.
 
you can have as many panel boards as you want, as long as none of them individually has more than 42 over current devices in it (forgetting for the moment any load calculations).

I am not quite sure what you are referring to when you say "sub-feed" breaker.

A feeder coming off a branch CB to the existing MLO panel counts just like any other breaker. If it is a 2 pole breaker it counts as two of the 42 devices allowed, if a three pole breaker, it counts as three.
 
I don't know about the other manufacturers, but with Siemens, you can get a 200 amp breaker mounted in a panelboard. It's not a "subfeed" breaker, but just a branch breaker like any other. It's just mounted at the bottom of the panel.

The short answer is, this breaker would count against your 42 circuit total, IMO.
 
A subfeed breaker is the type of breaker you are describing by Siemens where instead of being on the sides of the panels like the branch breakers, it is at the bottom of the panel at the bottom of the bus bars.

In fact the Siemens product data refers to it as a subfeed breaker.
 
I would check to see what the manufacturers offer. If a sub-feed breaker is available and does not infringe on the 42 circuit capacity according to the manufacturers documentation then its probably okay. Rarely does a manufacturer build and sell something that does not comply with NEC.

Now, having said that, I would bed that Siemens subfeed breaker is included in the 42 breaker count! :D [/b]
 
ramdiesel3500 said:
If a sub-feed breaker is available and does not infringe on the 42 circuit capacity according to the manufacturers documentation then its probably okay.
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Although the NEC does not govern the manufacturer, it does govern the person who builds the power system. The rule is 42, and the manufacture cannot overrule that rule.

ramdiesel3500 said:
I would bet that Siemens subfeed breaker is included in the 42 breaker count!
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I would not take that bet.
 
Charlie

"Although the NEC does not govern the manufacturer"

Are you sure about this? What about the Part IIIs of some of the Chap 3 wiring methods?

I thought that NMB was developed for the requirements put in the NEC. I know that UL and others develop the standards, but I always thought some of it went hand in hand.
 
Posted by petersonra:

I am not quite sure what you are referring to when you say "sub-feed" breaker.
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It is a breaker mounted at the opposite end of the panel (opposite from teh main breaker or lugs). It is often used to feed another panelboard, it can usually be a larger ampacity than the branch breakers. It also adds more height to the panel cabinet.

I specifically asked one of the Sq D engineers the same question about the 42 OCP rule. He said it they get by with it as long as the subfeed breaker is larger than the branch breakers.

I don't see a real issue with an extra breaker because it is separate from the others, it makes the cabinet larger, and the added wiring doesn't share the same gutter space.

I think maybe somehow it might be considered a separate cabinet or cutout box. Or maybe it is considered as being for the "mains".

Steve
 
Square D does not include the subfeed breaker in the count of total spaces available. This means it is possible to build a panelboard that has more than 42 circuits. But an NEC violation only occurs if the installer uses it as a lighting and appliance panelboard and uses all of the available space.

Square D includes the warning phrase "Refer to 42 circuit rule?NEC Article 408-14 and 408-15" in their catalog.
 
Square D includes the warning phrase "Refer to 42 circuit rule?NEC Article 408-14 and 408-15" in their catalog
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The only place I see that warning is for the 54 space panels.
 
Many times when a sub feed breaker is installed the panel shop installs one way screws in three consecutive branch positions making the panel only capable of holding 39 branch breakers.

At least that is what I run into.

It is usually a rude surprise when it looks like three available spaces only to find once the panel is opened up they are unusable.
 
iwire said:
It is usually a rude surprise when it looks like three available spaces only to find once the panel is opened up they are unusable.
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Hopefully, they apply those "do not remove these twist-outs" stickers.
 
benaround said:
I agree with Jim on this,42 circuit limitation is only on lighting & appliance panelboard .
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I agree as well. But it's really hard to find a residential panel that is not a L&A panel. Does it have 5 or more circuits (i.e., 10% or more) that are rated 30 amps or lower and that use the neutral? Then it's an L&A.
 
Charlie, it is also hard to find a residential 42 circuit panelboard that has a seperately mounted sub-feed breaker.

What it really comes down to is: Manufacturers can make panels with as many circuits as they want. It is up to the "electrician and inspector" to make sure the installation does not violate the NEC.
 
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