# Branch Circuit Selection Current



## RePhase277 (Feb 5, 2008)

waco said:


> Does anybody know how "Branch Circuit Selection Current" is derived for central AC systems and, is this supposed to be on the data plates?


It is supposed to be marked on systems that are intended to be used with motor-compressors, not sure about the derivation.


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## Magnettica (Jan 23, 2007)

I got this info from a prominent electrician who posts here. :thumbsup:

If the name tag rating is missing or unreadable check for the HP rating on the compressor and check the motor amperage tables in 430. It's usually within 3-4 amps of the name tag rating.


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## raider1 (Jan 22, 2007)

I have yet to see a nameplate on an A/C unit that didn't include the branch circuit selection current. Sometimes this value is refered to as "minimum circuit ampacity".

Here is the NEC definition for branch circuit selection current.



> Branch-Circuit Selection Current. The value in amperes to be used instead of the rated-load current in determining the ratings of motor branch-circuit conductors, disconnecting means, controllers, and branch-circuit short-circuit and ground-fault protective devices wherever the running overload protective device permits a sustained current greater than the specified percentage of the rated-load current. The value of branch-circuit selection current will always be equal to or greater than the marked rated-load current.


Chris


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## waco (Dec 10, 2007)

Thanks. I have one with the "Min. circuit ampacity," but not the "Branch Circuit Selection Current." I was not aware they were one and the same.

Anyway, thanks again.


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