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# how much of a load can a sub panel handle?

#1
10-03-06, 11:44 PM
Member
Join Date: Sep 2006
Posts: 288
how much of a load can a sub panel handle?

i know how to add up everything on a planned new circut to see if i am going overload it and need to add another circuit.

but if you are going to add a sub panel, how do you know if your main panel can handle it ?

i can only use 16A on a 20A circuit, correct ?

and i can only use 160A on a 200A panel, correct?

so if i have a 200A main panel using 150A, can i only have a 10A sub panel(10A being whats left of the 160A), or can i have a 200A sub panel?

what is the limit of a sub panel?

or, another way to look at it is, if i have a 200A main panel with a 100A breaker and 5 20A breakers ,with all circuits drawing 80% of max, what amp size sub panel can i add ?

#2
10-04-06, 03:31 AM
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Join Date: Nov 2003
Posts: 2,455
A demand load calculation is the only way to tell if the main service is capable.

BTW- "ALL" circuits will never be at 80% at the same time.

#3
10-04-06, 07:28 AM
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Join Date: Feb 2005
Location: Near Lansing, Michigan
Posts: 10,335
> so if i have a 200A main panel using 150A, can i only
> have a 10A sub panel(10A being whats left of the 160A),
> or can i have a 200A sub panel?

You can have a 200A subpanel. The subpanel can be up to the rating of the feeding panel. Technically, you could do a 200A panel to a 200A panel to a 200A panel, etc., so long as the actual load does not exceed the 200A service capability.

http://www.selfhelpandmore.com/homewiringusa/2002/definitions/demandcalc/

#4
10-04-06, 08:04 AM
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Join Date: Sep 2006
Posts: 288
thanks for the help. and thanks for the link.

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