quick question

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ronaldsax

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if the load calculation for the house is 151 amps should I use a 150 amp breaker or a 200 amps breaker?

I have a main disconect (200 amps), from there I need to feed a panel(house circuits) in the garage , the wires used are 2/o , from the meter to the main disconect and from the main disconect to the garage panel. there is currently a 150 amp breaker for the garage panel , but the load calculation is 151.3 I believe , can I just replace the 150 amp breaker for a 200 amp breaker? .Then from the main disconect there is another feeder for a sub panel a 100 amp breaker , this is confusing to me. if the main disconect is 200 amps then how can I have a 150 amp breaker and a 100 amp breaker in it?
thank you very much for any help.
 
First, are the wires feeding the garage panel CU or AL. 2/0 Cu can be used for 200Amps and you can up the breaker size for the garage, however if the conductors are AL you will need 4/0 for 200 Amps. Second you don't add breaker Amp ratings to get to the main breaker size. There is a concept called Demand Factor that you may want to look up, it will clear up the confusion.
 
Assuming the load calculations are correct (including any demand factors), using a 150 Amp service to feed a premises with a calculated load of 151.3 Amps is a violation. You would have to use a higher Amp service for such a load.

Replacing a 150 Amp breaker with a 200 Amp one can be fine in some instances, and problematic in others. The question to be answered here is:

Is the bus assembly rated for 200 Amps? If so, no problem. It not, you may have to replace more than just the main breaker.
 
thank you for answering, yes , the conductors are Cu and the bus asembly are rated for 200 amps, so I guess it's just a matter of replacing the 150 amp breaker for a 200 amp breaker.
 
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