3 phase load calculation

[Smart $]

That is correct. MCA and branch-circuit selection current are not the same thing. Per 440.32 the MCA = 1.25 * BSSC.

If MCA = BSSC, as you suggest, then BSSC = 1.25 * BSSC?!?!?! That doesn't make sense.



Not sure what you are asking here. The MCA marked on the nameplate indicates the minimum required ampacity of the conductors that supply the unit. The conductors must have an ampacity equal to or greater than the marked MCA to comply with the NEC.

Apologies. I am feeling much under the weather and not thinking clearly. You are correct that MCA is not BCSC.

 

[Smart $]

Apologies. I am feeling much under the weather and not thinking clearly. You are correct that MCA is not BCSC.

While I'm not thinking clearly, can someone tell me if they have ever seen BCSC marked on the same nameplate as MCA???

 

[kwired]

440.2 Definitions.

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.

Minimum circuit ampacity is nothing more than same calculations done in 430.24 they are just done for you and marked on nameplate as MCA. I believe that BCSC takes a service factor that is allowed by the overload into consideration and you can have a higher value than you would otherwise have using 430.24.

I have not ever seen a hermatic compressor draw what its RLA states, although I can't claim to ever measure current when unit is working at its hardest. The more heat they are moving the more they will draw.