Question on total branch circuit breakers adding to more than the main breaker

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Dogtrooper

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Troy, NY, USA
Hello. I have a question regarding the total of amp form adding up all branch circuit breakers in a panel compared to the main circuit breaker. I have ask tons of fellow electricians and several engineers and electrical inspectors. No one can pin point a code section(s) or something in writing that explains why.
Here is a senerio.
You have a 200amp service 120/240 volt service.
Main breaker is 200 amp.
There are 2 150amp 2 pole branch circuit breakers in the panel.

I'm being told by a power company that this is illegal.
Myself and every other electrical professional I know or talk to says that this is legal.

If you look in any panel in just about any building the branch circuit breakers ratings most always add to more than the main breaker rating.

I know this is figured using load calculations And as long as the total load is under the rating of the main breaker ( using proper calculations and percentages from the nec of course) that it is ok.

I'm looking for something that explains this to the average person that does not know about electric.

The owner is questioning me about why and other than because this is how it is done. I cant explain it to him.

So I have a power company guy telling me this is wrong. And the owner now not trusting me that it was done right.
Is there any help you could give in helping me explain this to the power company and the owner of the building that this legal.
Thank
 
Perfectly legal, as long as the load calculations do not exceed the capacity of the main.

One thing to keep in mind is that utilities aren't involved in, or governed, by the NEC 99.99% of the time. Towards that end, very few of them even know what's in it.
 
One thing that might be a problem is the two 150A breakers. The stab/bus rating might not allow 150A, especially if the breakers are side by side, which makes both on the same stab. Other than that, it's dependent on the load calculation.
 
What about this -- exception 2

408.36 Overcurrent Protection. In addition to the requirement
of 408.30, a panelboard shall be protected by an overcurrent
protective device having a rating not greater than that of
the panelboard. This overcurrent protective device shall be
located within or at any point on the supply side of the panelboard.
Exception No. 1: Individual protection shall not be required for a
panelboard used as service equipment with multiple disconnecting
means in accordance with 230.71. In panelboards protected by three or
more main circuit breakers or sets of fuses, the circuit breakers or sets of
fuses shall not supply a second bus structure within the same panelboard
assembly.
Exception No. 2: Individual protection shall not be required for a
panelboard protected on its supply side by two main circuit breakers or
two sets of fuses having a combined rating not greater than that of the
panelboard. A panelboard constructed or wired under this exception
shall not contain more than 42 overcurrent devices. For the purposes of
determining the maximum of 42 overcurrent devices, a 2-pole or a
3-pole circuit breaker shall be considered as two or three overcurrent
devices, respectively.
Exception No. 3: For existing panelboards, individual protection shall
not be required for a panelboard used as service equipment for an individual
residential occupancy.
Click to expand...
 
Here is my stab at an explanation:

Breaker and circuit sizing depends upon the connected load. You don't want to overload the circuit conductors, you don't want to overload the breaker, that is the reason for the rules.

A breaker or a circuit is not itself a load. A circuit carries current to loads, and the breaker protects the circuit. While a circuit creates a place where a load can be connected, it is not a load and doesn't itself add load to the upstream breaker.

So each circuit in a panel is individually sized for its connected loads.

Then the entire panel and main breaker are sized for the total of all connected loads to the panel.

Two separate calculations each giving the size of their respective breakers and circuit conductors.

The sum of the handle ties in the panel does not enter into either calculation.

-Jon
 
Does that exception not say you cannot have 2- breakers protecting the panel if the rating of the breakers was higher than the panel. Isn't the op's situation 2- 150 amp breakers in a 200 amp panel. Maybe I am reading it wrong but today has been hectic-- in and out and I gtg again
 
Dennis Alwon said:
Does that exception not say you cannot have 2- breakers protecting the panel if the rating of the breakers was higher than the panel. Isn't the op's situation 2- 150 amp breakers in a 200 amp panel. Maybe I am reading it wrong but today has been hectic-- in and out and I gtg again
Click to expand...

That's exactly what it says, but, the OP's panel does have a single main in it. :)


JAP>
 
Dennis Alwon said:
Does that exception not say you cannot have 2- breakers protecting the panel if the rating of the breakers was higher than the panel. Isn't the op's situation 2- 150 amp breakers in a 200 amp panel. Maybe I am reading it wrong but today has been hectic-- in and out and I gtg again
Click to expand...

The Exception is referring to two breakers ahead of the panel, not two breakers in it feeding two loads.
 
Dogtrooper said:
Hello. I have a question regarding the total of amp form adding up all branch circuit breakers in a panel compared to the main circuit breaker. I have ask tons of fellow electricians and several engineers and electrical inspectors. No one can pin point a code section(s) or something in writing that explains why.
Here is a senerio.
You have a 200amp service 120/240 volt service.
Main breaker is 200 amp.
There are 2 150amp 2 pole branch circuit breakers in the panel.

I'm being told by a power company that this is illegal.
Myself and every other electrical professional I know or talk to says that this is legal.

If you look in any panel in just about any building the branch circuit breakers ratings most always add to more than the main breaker rating.

I know this is figured using load calculations And as long as the total load is under the rating of the main breaker ( using proper calculations and percentages from the nec of course) that it is ok.

I'm looking for something that explains this to the average person that does not know about electric.

The owner is questioning me about why and other than because this is how it is done. I cant explain it to him.

So I have a power company guy telling me this is wrong. And the owner now not trusting me that it was done right.
Is there any help you could give in helping me explain this to the power company and the owner of the building that this legal.
Thank
Click to expand...

The power company is mistaken.
 
You could have say 100-20 amp circuit breakers one for every receptacle and light in the house and it would not change the only thing that really matters which is the load calculation. Counting CB values is a waste of time. If you want to know that the panel is of adequate size you need to do a load calculation, the size and number of CB's is irrelevant.
 
Little Bill said:
One thing that might be a problem is the two 150A breakers. The stab/bus rating might not allow 150A, especially if the breakers are side by side, which makes both on the same stab. Other than that, it's dependent on the load calculation.
Click to expand...

+1
 
electrofelon said:
Dennis, I am not following how that relates to the OP?
Click to expand...

Dennis Alwon said:
Does that exception not say you cannot have 2- breakers protecting the panel if the rating of the breakers was higher than the panel. Isn't the op's situation 2- 150 amp breakers in a 200 amp panel. Maybe I am reading it wrong but today has been hectic-- in and out and I gtg again
Click to expand...

480sparky said:
The Exception is referring to two breakers ahead of the panel, not two breakers in it feeding two loads.
Click to expand...
Correct, section quoted is about overcurrent protection of the panelboard, which in OP is already taken care of by the 200 amp main (presuming it is protecting a panelboard rated at least 200 amps).
 
Dogtrooper said:
Hello. I have a question regarding the total of amp form adding up all branch circuit breakers in a panel compared to the main circuit breaker. I have ask tons of fellow electricians and several engineers and electrical inspectors. No one can pin point a code section(s) or something in writing that explains why.
Here is a senerio.
You have a 200amp service 120/240 volt service.
Main breaker is 200 amp.
There are 2 150amp 2 pole branch circuit breakers in the panel.

I'm being told by a power company that this is illegal.
Myself and every other electrical professional I know or talk to says that this is legal.

If you look in any panel in just about any building the branch circuit breakers ratings most always add to more than the main breaker rating.

I know this is figured using load calculations And as long as the total load is under the rating of the main breaker ( using proper calculations and percentages from the nec of course) that it is ok.

I'm looking for something that explains this to the average person that does not know about electric.

The owner is questioning me about why and other than because this is how it is done. I cant explain it to him.

So I have a power company guy telling me this is wrong. And the owner now not trusting me that it was done right.
Is there any help you could give in helping me explain this to the power company and the owner of the building that this legal.
Thank
Click to expand...
Some have touched on some of what I have to say already, but just because you have enough branches in the panel to allow for more than 200 amps, the 200 amp main is still going to limit what you can run and will trip if you go with too much. Doesn't matter if there are two 150 amp breakers in there or 40 20 amp breakers. Reality is in many cases not all those circuits draw maximum rating and even those that do don't all draw it at once. Some commercial/industrial situations that can be more likely - there the 200 amp main isn't enough, but proper load calculations in those cases will give more than 200 amp result being necessary for the main supply.

If this a dwelling in the op, and you have that 200 amp service chances are POCO is only supplying it with 15 or 25 KVA transformer, both well under 200 amps capability - but they are doing so because actual demand never is that high, or is not for very long if it does get that high. If you have all electric heat and water heat, you may actually get a 37.5 kVA transformer, but even that is only rated for about 156 amps - they are still betting it isn't loaded too high or for very long when it is loaded.
 
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