Motor calculations 430.53 single branch circuit

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Mustwin351 said:
My thought is it should be sized as a feeder for GFSC since the circuit feeds two separate motor starters as opposed to sizing it for the smallest motor. But I don’t believe you then need to run individual branch circuits.
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If you have a branch circuit, then the GFSC protection must be sized as required for branch circuits. Which means, per the section you previously mentioned, sized for the smallest motor.
 
david luchini said:
If you have a branch circuit, then the GFSC protection must be sized as required for branch circuits. Which means, per the section you previously mentioned, sized for the smallest motor.
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That’s what I initially thought but was confused as it also says two or more motors.
Why include two or more motors?

I would think it would just say sized per the smallest motor and leave it at that.
 
Mustwin351 said:
No each motor is fed from its own motor starter.
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With motor overload protection but not a SCGF device of any kind right?

And if so are they jumpered together on supply side and only set up to accept a single set of supply conductors?

If it were a control panel built to listing standards it probably should have had SCGF protection somehow incorporated for each motor on motors this large, bet it is not listed. Run into this all the time on agricultural equipment.
 
Mustwin351 said:
That’s what I initially thought but was confused as it also says two or more motors.
Why include two or more motors?

I would think it would just say sized per the smallest motor and leave it at that.
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Does it allow both motors to run at same time? It may or may not hold starting current of second motor if they both can run at same time. If they alternate but never run at same time, it should be fine, it essentially is a single motor application to the SCGF device.
 
So far my replies been off top of my head. After looking at NEC and scanning through this thread, I don't think 430.7(D) has come up yet.

Still sort of comes down to if the thing has listed control panel or not, but still guessing if it is listed would have individual scgf protection on each motor. If strictly connecting these according to NEC I think you need two branch circuits unless possibly they will never run at same time. If they were small enough motors they both can run on max allowed SCGF that would probably be fine. This situation is high enough starting current it is marginal at best that they will work on properly sized common SCGF device.
 
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