Question on sizing service

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KWH

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When sizing a service when you combine continuous and non-continuous loads and come up with 170amps , you can breaker this at 200amps or is there a derating on the breaker also.
 
KWH said:
When sizing a service when you combine continuous and non-continuous loads and come up with 170amps , you can breaker this at 200amps or is there a derating on the breaker also.
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No, that is your calculated load. Breaker can be loaded up to 200A if you want. You really don't have to figure the continious loads in for the service, that's for the branch circuit. You would include the largest motor used if there is any.
 
Little Bill said:
Perhaps I shouldn't have said just branch circuits, but I was referring to calculating the load for services in 220. No where in the standard or optional method do I see where you count continuous loads, just largest motor.
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Article 220 provides the requirements for calculating loads for Branch-Circuits, Feeders, and Services. There is nothing in the standard or optional methods for feeders and services about continuous and noncontinuous loads. Nor is there anything in Part II "Branch-Circuit Load Calculations" about continuous and noncontinuous loads.

You will have to look in Art 210, Art 215 and Art 230 for Branch-Circuits, Feeders and Services respectively, to find out how to apply continuous and noncontinuous loads when sizing conductors and OCP.
 
david luchini said:
Article 220 provides the requirements for calculating loads for Branch-Circuits, Feeders, and Services. There is nothing in the standard or optional methods for feeders and services about continuous and noncontinuous loads. Nor is there anything in Part II "Branch-Circuit Load Calculations" about continuous and noncontinuous loads.

You will have to look in Art 210, Art 215 and Art 230 for Branch-Circuits, Feeders and Services respectively, to find out how to apply continuous and noncontinuous loads when sizing conductors and OCP.
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Good post. Basically- ya gotta deal with it when sizing the conductors at some point.

220 calculates the loads, but the other articles make you apply the correction factors for continuous loads.
 
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