Panelboards 408.36

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goldstar

goldstar

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While cruising through HD yesterday I noticed that they now are selling 20/40 (20 space, 40 circuit), 30/60 and 40/80 breaker panels. The 2014 NEC, section 408.36 Ex-2 states that a panel-board shall not contain more 42 over-current devices. Is there another section of the NEC that overrides this ? Do the manufacturers know something that we don't ? Just curious.:?
 
goldstar said:
While cruising through HD yesterday I noticed that they now are selling 20/40 (20 space, 40 circuit), 30/60 and 40/80 breaker panels. The 2014 NEC, section 408.36 Ex-2 states that a panel-board shall not contain more 42 over-current devices. Is there another section of the NEC that overrides this ? Do the manufacturers know something that we don't ? Just curious.:?
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The Ex. No. 2 states that a panelboard using the exception for the single overcurrent protection device providing protection to the panelboard shall not have more than 42 overcurrent devices.

If you are not using the exception to the main panelboard overcurrent protection, then you do no need to meet the 42 device limit.
 
Thanks. I've read over this section several times and I'm still not understanding your point. I'm sure something changed in the NEC over the years but I still don't see where the NEC allows mfrs. to fabricate panel-boards capable of 80 circuits.
 
"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."

Cut and pasted from other sources...
 
goldstar said:
Thanks. I've read over this section several times and I'm still not understanding your point. I'm sure something changed in the NEC over the years but I still don't see where the NEC allows mfrs. to fabricate panel-boards capable of 80 circuits.
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Where do you see that the NEC prevents manufacturers from fabricating panelboards capable of 80 circuits?

You are correct that NEC has changed. It used to designate panels as "lighting and appliance" panelboards, and they were limited to 42 devices. That designation went away in the 2008 Code (I think.)
 
david luchini said:
Where do you see that the NEC prevents manufacturers from fabricating panelboards capable of 80 circuits?

You are correct that NEC has changed. It used to designate panels as "lighting and appliance" panelboards, and they were limited to 42 devices. That designation went away in the 2008 Code (I think.)
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I'm sure you're correct. I started seeing 60 circuit panel-boards made by CH several years ago but they actually had 60 spaces with no possibility for tandem breakers. However, in the case of say a 40/80 MB breaker panel the inference is that you could choose to use 80 tandem breakers and fill the panel to its maximum. In reality I can't see that ever happening but the possibility exists.
 
goldstar said:
I'm sure you're correct. I started seeing 60 circuit panel-boards made by CH several years ago but they actually had 60 spaces with no possibility for tandem breakers. However, in the case of say a 40/80 MB breaker panel the inference is that you could choose to use 80 tandem breakers and fill the panel to its maximum. In reality I can't see that ever happening but the possibility exists.
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Here you go...this may assist you.

http://static.schneider-electric.us...nce Branch-Circuit Panelboards/1600DB0701.pdf
 
goldstar said:
. . . but I still don't see where the NEC allows mfrs. to fabricate panel-boards capable of 80 circuits.
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I only understand part of this rule. I get the part where 408.36 tells us (for example) that you must protect a 100 amp panel with a SINGLE overcurrent device rated not higher than 100 amps. One, single device. I always use either an MCB panel (for which the one single device is internal to the panel) or an MLO panel (for which the one single device is the feeder breaker on the upstream panel).

Then we encounter Exception 2. It says we don't need to provide that one single OCPD ifwe instead provide two upstream breakers (or fuses) to protect the panel. Then, and only then, does the 42 circuit limit comes into play. Thus, if you have an MCB panel or an MLO panel protected by its upstream feeder breaker, then there is no 42 circuit limit.

What I don't get is how you can protect one panel with two breakers. Can anyone explain that, or provide a sketch? Are we talking about that rare instance in which breakers are allowed to be connected in parallel?
 
charlie b said:
I only understand part of this rule. I get the part where 408.36 tells us (for example) that you must protect a 100 amp panel with a SINGLE overcurrent device rated not higher than 100 amps. One, single device. I always use either an MCB panel (for which the one single device is internal to the panel) or an MLO panel (for which the one single device is the feeder breaker on the upstream panel).

Then we encounter Exception 2. It says we don't need to provide that one single OCPD ifwe instead provide two upstream breakers (or fuses) to protect the panel. Then, and only then, does the 42 circuit limit comes into play. Thus, if you have an MCB panel or an MLO panel protected by its upstream feeder breaker, then there is no 42 circuit limit.

What I don't get is how you can protect one panel with two breakers. Can anyone explain that, or provide a sketch? Are we talking about that rare instance in which breakers are allowed to be connected in parallel?
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I'm not 100% sure, but I think the exception is for something like a split bus panel. One breaker for part of the bus, and another breaker for the other part of the bus.
 
I think GE (good enough) or some other brand made a MCB panel where they installed (1) 2 Pole 100A breaker per leg as the main and called it a 200A panel (single phase panel). So that there were (2)100A double pole breakers tied together as the main. Cheesy design but UL. The panel was single bus though not split bus.

Maybe this is what they are talking about?
 
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goldstar said:
I'm sure you're correct. I started seeing 60 circuit panel-boards made by CH several years ago but they actually had 60 spaces with no possibility for tandem breakers. However, in the case of say a 40/80 MB breaker panel the inference is that you could choose to use 80 tandem breaker and fill the panel to its maximum. In reality I can't see that ever happening but the possibility exists.
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Sorry, I need to correct this. It should have read 40 tandem breakers (or 80 circuits). But I'm sure you all know what I meant anyway.:p
 
charlie b said:
I only understand part of this rule. I get the part where 408.36 tells us (for example) that you must protect a 100 amp panel with a SINGLE overcurrent device rated not higher than 100 amps. One, single device. I always use either an MCB panel (for which the one single device is internal to the panel) or an MLO panel (for which the one single device is the feeder breaker on the upstream panel).

Then we encounter Exception 2. It says we don't need to provide that one single OCPD ifwe instead provide two upstream breakers (or fuses) to protect the panel. Then, and only then, does the 42 circuit limit comes into play. Thus, if you have an MCB panel or an MLO panel protected by its upstream feeder breaker, then there is no 42 circuit limit.

What I don't get is how you can protect one panel with two breakers. Can anyone explain that, or provide a sketch? Are we talking about that rare instance in which breakers are allowed to be connected in parallel?
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Here you go Charlie...this is the intent of 408.36 Ex. 2

A panelboard with two mains as shown in the image is permitted with the limitation of 42 circuits. The overall combined main breaker ratings must not exceed the actual panel ratings, in the example we will assume the panel rating is 200A.
 

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MasterTheNEC said:
That is not the intent of 408.36 Exception 2
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It looks like it fits the rule to me.

I can't really read the example you posted, but the only difference I see is the second breaker in your post supplies a feeder, instead of another bus. I don't see anything in 408.36 Exception 2 that differentiates between the two types of panels shown in this thread.

It also seems like one could normally avoid the 42 OCP rule just by adding an upstream breaker with a rating that isn't any greater than the panel rating. It does make one wonder - can we assume the rating of a split bus panel with (2) 100A busses would be 200 amps?
 
boptrop said:
It would be great if it were a better picture so one could read what it says...or maybe I need glasses!
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Why not download the image and zoom in....I just snapped a picture of it out of the mcgraw-hill handbook...because I knew it had a picture for Don.
 
steve66 said:
It looks like it fits the rule to me.

I can't really read the example you posted, but the only difference I see is the second breaker in your post supplies a feeder, instead of another bus. I don't see anything in 408.36 Exception 2 that differentiates between the two types of panels shown in this thread.

It also seems like one could normally avoid the 42 OCP rule just by adding an upstream breaker with a rating that isn't any greater than the panel rating. It does make one wonder - can we assume the rating of a split bus panel with (2) 100A busses would be 200 amps?
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Does not overly fit it...Ex 3 is for existing applications....technically speaking the use of a split bus loadcenter with more than two mains is permitted in residential service equipment in existing applications so not technically the same.....but in argumentative respects the same.
 
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