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#62515 - 02/16/06 07:56 PM Circuit breakers and load calculations
Clydesdale Offline
Member

Registered: 11/25/04
Posts: 139
Ok...in a residential 200A service, if you add up the breakers you can have well over 200A. I realize that not all the loads are on at the same time which is why the main doesn't trip...but how does one really KNOW if the service can handle all the ciriuts..and is this information found in the NEC??

Also...as far as subpanels go....what's stopping me from putting a 100A sub at the end of the house opposite the main panel? and then adding another 100A sub in the garage for a welder and other shop machines?

Are these found in the code too?

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#62516 - 02/16/06 08:02 PM Re: Circuit breakers and load calculations
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6805
Loc: Brick, NJ USA
Clyde:
Math 40 circuit panel....20 amp, 1 pole cb's
800 amps; divide by 2 hot legs (resi)= 400 amp max connected load. BUT, the 200 amp main would trip.

Load calcs are in the NEC

Theory is you can have an unlimited quantity of "sub-panels", the limitations are the OCP of the main, and the OCP of the feeders.

John
_________________________
John

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#62517 - 02/16/06 08:14 PM Re: Circuit breakers and load calculations
Active 1 Offline
Member

Registered: 02/22/03
Posts: 684
Loc: Grayslake IL, USA
Overcurrent protection is not the load. Also figure in the demand factor. I tend to be suprised how little draw I find on a panel for a big place on a normal day.

Besides reading the NEC you might try books explaining the NEC. I like Illistrated ones because a picture is worth a lot of big words for me.

Tom

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#62518 - 02/16/06 08:28 PM Re: Circuit breakers and load calculations
ShockMe77 Offline
Member

Registered: 06/11/05
Posts: 823
Loc: Rahway, New Jersey
Article 220 would seem helpful in this situtation.

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#62519 - 02/22/06 08:20 PM Re: Circuit breakers and load calculations
Clydesdale Offline
Member

Registered: 11/25/04
Posts: 139
thanks...will definately check out 220

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