Sub-Panel Feeders

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In-spector

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I was told by an electrician in the field that the largest size breaker that can be used to feed a sub-panel or other large load in a 1 phase, 200 amp, 240 vac service panel board is a 2 pole 70 amp breaker. I'm having trouble locating this in the code book. Please help me find this in the NEC.

Also, why is the word "sub panel" not found in the code book??
 
In-spector said:
I was told by an electrician in the field that the largest size breaker that can be used to feed a sub-panel or other large load in a 1 phase, 200 amp, 240 vac service panel board is a 2 pole 70 amp breaker. I'm having trouble locating this in the code book. Please help me find this in the NEC.
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It is likely that the electrician is referencing the labeling on the panel itself. Many panels have limits to how large of a breaker can be installed. It is not directly an NEC violation, you will not find an NEC section that directly address it. But because it is listed and labelled equipment NEC 110.3(B) applies and requires us to follow the instructions that are part of the listing and labeling of the panel.


Also, why is the word "sub panel" not found in the code book??
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No real reason it needs to be, the rules covering feeders and grounding are the same for supplying equipment or a panel.
 
In-spector said:
I was told by an electrician in the field that the largest size breaker that can be used to feed a sub-panel or other large load in a 1 phase, 200 amp, 240 vac service panel board is a 2 pole 70 amp breaker. I'm having trouble locating this in the code book. Please help me find this in the NEC.
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Probably as Iwire indicated, a restriction of the breaker panel. You'll have to do some research to find out what the limitation is. I believe the largest "plug-in" CB you'll find is a 100 amp breaker. However, if you use SER cable to feed the "sub-panel" you'll have to "de-rate" and use a 90 amp breaker. If is adjacent to the MB panel and you nipple into it use # 3 THHN copper and you can then use the 100 amp breaker.

Also, why is the word "sub panel" not found in the code book??
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You won't find it in the NEC. While the vast majority of us use that term (and we all know what we're talking about) I believe the accepted term is something to the nature of "auxiliary" or "supplemental" breaker panel, but yet another term you won't find in the NEC.

BTW, I still use terms like "de-rate", "sub-panel" and "MCM". People still know what I'm talking about. When the counter help in the supply houses get young enough to not know what I'm talking about - it's time to hang up the tools.:happyyes:
 
goldstar said:
Probably as Iwire indicated, a restriction of the breaker panel. You'll have to do some research to find out what the limitation is. I believe the largest "plug-in" CB you'll find is a 100 amp breaker. However, if you use SER cable to feed the "sub-panel" you'll have to "de-rate" and use a 90 amp breaker. If is adjacent to the MB panel and you nipple into it use # 3 THHN copper and you can then use the 100 amp breaker.

You won't find it in the NEC. While the vast majority of us use that term (and we all know what we're talking about) I believe the accepted term is something to the nature of "auxiliary" or "supplemental" breaker panel, but yet another term you won't find in the NEC.

BTW, I still use terms like "de-rate", "sub-panel" and "MCM". People still know what I'm talking about. When the counter help in the supply houses get young enough to not know what I'm talking about - it's time to hang up the tools.:happyyes:
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There are larger then 100 amp plug on breakers. Square D QO goes to 125 in the basic 2 pole version, for some reason 100 amp is max in the basic three pole versions though. There are 150 to 225 amp breakers that take two slots per pole out there as well, you just don't run into them too often.
 
In-spector said:
I was told by an electrician in the field that the largest size breaker that can be used to feed a sub-panel or other large load in a 1 phase, 200 amp, 240 vac service panel board is a 2 pole 70 amp breaker. I'm having trouble locating this in the code book. Please help me find this in the NEC.
Also, why is the word "sub panel" not found in the code book??
Click to expand...



.Rule of thumb when I was learning 50% -- The OCPD attached to a panel is basically a tap. the OCPD protecting the panel is exactly that "protects the panel from overload" you can have, for example 40 - 20A breakers all fully loaded in a 200A MB panel but when the load exceed 200A panel is protected. I've seen ITE 125A plug ins. The true answer has already been given as it relates to max OCPD your are allowed to plug in per manufactures specs. Take a look at a lug type plug in tap kit the instructions are specific and panel boards have restrictons for them..


A panelboard is a panelboard - a switchboard is a switchboard whether you call it auxzillary, sub, main, or supplemental the same code sections regulate the installation. I prefer & still use sub-panel as a reference to a load fed panel from a OCPD.
 
kwired said:
There are larger then 100 amp plug on breakers. Square D QO goes to 125 in the basic 2 pole version, for some reason 100 amp is max in the basic three pole versions though. There are 150 to 225 amp breakers that take two slots per pole out there as well, you just don't run into them too often.
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Thanks for that info. I would bet they are special order. I've never seen one. The other thing about using a sub-panel with such a large breaker is that you have to come up with creative (but legit) ways to land the neutral in the MB panel.
 
mwm1752 said:
.Rule of thumb when I was learning 50% -- The OCPD attached to a panel is basically a tap. the OCPD protecting the panel is exactly that "protects the panel from overload" you can have, for example 40 - 20A breakers all fully loaded in a 200A MB panel but when the load exceed 200A panel is protected. I've seen ITE 125A plug ins. The true answer has already been given as it relates to max OCPD your are allowed to plug in per manufactures specs. Take a look at a lug type plug in tap kit the instructions are specific and panel boards have restrictons for them..


A panelboard is a panelboard - a switchboard is a switchboard whether you call it auxzillary, sub, main, or supplemental the same code sections regulate the installation. I prefer & still use sub-panel as a reference to a load fed panel from a OCPD.
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I used to use that rule of thumb as well until I found out that it was not necessary. I remember working (years ago) at a high rise condo complex under construction. There was a 200A, MB panel loaded with 100 amp breakers to each unit. To my recollection there were no excessive loads (like AC units, dryers, etc) only electric ranges & ovens.

Just curious, why did you post in green ? Trying to get noticed ?:cool:
 
goldstar said:
Thanks for that info. I would bet they are special order. I've never seen one. The other thing about using a sub-panel with such a large breaker is that you have to come up with creative (but legit) ways to land the neutral in the MB panel.
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Special order for one supplier/distributor is not the same as it maybe is for another. Ever seen a 10 amp breaker single, double or three pole? They are in the QO line - I have seen single and double pole units. Or how about a single pole 70 amp breaker, a three pole GFCI breaker, shunt trip or switched neutral options? They are all standard items - just not always standard stocked items for some suppliers. The 3 pole GFCI is not available in all "standard sizes" but is a catalog item in 15, 20, 30, 40, 50 amp sizes - I imagine if you really wanted a 25, 35 or 45 amp version you could have a true special order at a special cost.
 
The panels also have instructions that limit the amount of load on the same tabs. I take this to mean load not the breaker size although I agree some panels also limit the breaker size.

I have seen some panels that limit a stab to 110 amps ( I believe ). Again does this mean 2 Dp 60 breakers across from each other isn't compliant or do they mean load. I think it is the load they are concerned about
 
mwm1752 said:
so my answer is not mistaken for the quote -- I like green -- are yo bustin on me "GOLD STAR":lol:
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FWIW, the light green is almost impossible to read on my phone, while the dark green is not great either. If your goal is to be read, you are making a tactical mistake. :(
P.S. Tapatalk distorts the colors to less readable shades (and not of Gray) :)
 
I have a CH2150 breaker feeding my garage. Yes, it is a 4 pole space breaker, but it wasn't a problem buying it from the supply house. I also found the appropriate lug for attaching the neutral (4/0 copper due to line length!) to the neutral bar.

I would have had a separate meter set for it, but the power company quoted $18K to 20K to run the power there. Ouch!

I use QO110 breakers at work. QO110B even in most situations. R&D projects. Two and three pole not as common, but we have them.

Frank DuVal
 
goldstar said:
Thanks for that info. I would bet they are special order. I've never seen one. The other thing about using a sub-panel with such a large breaker is that you have to come up with creative (but legit) ways to land the neutral in the MB panel.
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Use one of these Add-a-Lug....GE, SQ D, Siemens, Cutler Hammer all offer a version of add-a-lug
 

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GoldDigger said:
FWIW, the light green is almost impossible to read on my phone, while the dark green is not great either. If your goal is to be read, you are making a tactical mistake. :(
P.S. Tapatalk distorts the colors to less readable shades (and not of Gray) :)
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Will keep that in mind digger, I've never used the forum from other than my laptop -- Thanks for the headsup :thumbsup:
 
John120/240 said:
Avoid Yellow text at all cost. It is near impossible to read IMHO.
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Depends on the background color -


Just don't use same color as background or you will not read it at all unless you try to highlight like you would for editing purposes then you can see it;)
 
jimknowle said:
sub panel = remote panel
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To most of us Sub panel is anything that does not contain the service disconnecting means or the first overcurrent protection of a separately derived system. It may be remote from an upstream panel or right next to it.

It is not a term used by the NEC. Most accurate name one may call it with NEC terminology is a panel supplied by a feeder.
 
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