Is this panel overloaded?

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qcroanoke

Sometimes I don't know if I'm the boxer or the bag
Location
Roanoke, VA.
Occupation
Engineering
200 amp main breaker with a calculated load of 179 amps.
Is this overloaded?
Thanks!
 

david luchini

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Location
Connecticut
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Engineer
I'd say its impossible to know if the panel is overloaded without knowing how much of the load is continuous and how much is non-continuous.

If the load is calculated per 220.40, by the sum of the loads on the branch circuits supplied as determined by Part II of article 220, then the load is 100% of the continuous plus 100% of the non-continuous. You need to know how much is continuous/non-continuous to ensure compliance with 215.3.
 
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david luchini

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Location
Connecticut
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Engineer
That wouldn't be the calculated load then, would it?
The calculated load could be all continuous, or all non-continuous, or some combination thereof. If the calculated load is 100kVA;

That could be 50kVA continuous and 50kVA non-continuous, or...
That could be 10kVA continuous and 90kVA non-continuous, or...
That could be 87.5kVA continuous and 12.5kVA non-continuous...

I think there is a misconception that if you have a load that is 50kVA continuous and 50kVA non-continuous, then the "calculated load" is 112.5kVA. I don't think you'll find anything in 220.40 that says the calculated load is 100% of the non-continuous plus 125% of the continuous load. The 125% of continuous load is found in Article 215 relating to the sizing of the feeder conductors and OCP for the feeder.

Take a look at example D3 in the appendix. It show a non-continuous load of 12.2kVA, a continuous load of 16.2kVA, and a total load of 28.4kVA (not a total load of 32.75kVA.)
 

Smart $

Esteemed Member
Location
Ohio
The calculated load could be all continuous, or all non-continuous, or some combination thereof. If the calculated load is 100kVA;

That could be 50kVA continuous and 50kVA non-continuous, or...
That could be 10kVA continuous and 90kVA non-continuous, or...
That could be 87.5kVA continuous and 12.5kVA non-continuous...

I think there is a misconception that if you have a load that is 50kVA continuous and 50kVA non-continuous, then the "calculated load" is 112.5kVA. I don't think you'll find anything in 220.40 that says the calculated load is 100% of the non-continuous plus 125% of the continuous load. The 125% of continuous load is found in Article 215 relating to the sizing of the feeder conductors and OCP for the feeder.

Take a look at example D3 in the appendix. It show a non-continuous load of 12.2kVA, a continuous load of 16.2kVA, and a total load of 28.4kVA (not a total load of 32.75kVA.)
True....

...but then there is this regarding panelboards:

408.30 General. All panelboards shall have a rating not
less than the minimum feeder capacity required for the load
calculated in accordance with Parts II, III, IV, or V of Article
220 as applicable.
So panels must also be rated not less than 125% of the continuous plus 100% of the non-continuous loads that it supplies.
 

Smart $

Esteemed Member
Location
Ohio
It could be overloaded if it were carrying 161A and all the loads were continuous...
That wouldn't be the calculated load then, would it?
No. I intentionally made certain I did not say it was, and only that it "could be" overloaded.
So here's the real question...

If a 200A panel is supplying over 200A of current for more than 3 hours (without tripping the main), per the NEC, is it overloaded for certain, not overloaded for certain, or perhaps overloaded but not necessarily?
 

david luchini

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Location
Connecticut
Occupation
Engineer
So panels must also be rated not less than 125% of the continuous plus 100% of the non-continuous loads that it supplies.
Yes...that's why it is impossible to know if the panel is overloaded given the information in the OP. You must know how much of the load is continuous and how much is non-continuous.
 

infinity

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Location
New Jersey
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Journeyman Electrician
Yes...that's why it is impossible to know if the panel is overloaded given the information in the OP. You must know how much of the load is continuous and how much is non-continuous.
The OP did say "200 amp main breaker with a calculated load of 179 amps". Why assume that there's a problem with the calculation? Don't the words calculated load imply that both continuos and non-continuos loads have been considered or are we working from a new definition in this thread?
 
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