Nameplate or Ohms Law

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Cletis

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When sizing feeders, circuits, overloads etc... do you size by the equiptment nameplate or actual amperage and factors for wire size, breaker size and so on.

Ex. You have a 120/208V panel your coming off of feeding a motor thats 230V. Obviously, it's going to run on 208V which will change everything potentially from wire size to OCPD. Which one do you go by if it's an inspected job and what can inspector hold you to if they are following the NEC latest ??
 
Cletis said:
When sizing feeders, circuits, overloads etc... do you size by the equiptment nameplate or actual amperage and factors for wire size, breaker size and so on.

Ex. You have a 120/208V panel your coming off of feeding a motor thats 230V. Obviously, it's going to run on 208V which will change everything potentially from wire size to OCPD. Which one do you go by if it's an inspected job and what can inspector hold you to if they are following the NEC latest ??
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What about article 430? Look at 430.6. The only thing the nameplate is used for is to size the overloads. 430.32
 
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In most cases where a calculation is based on unit equipment, you'd use the nameplate value. However, in the case of a non-refrigeration motor, you have to use a Table value.
 
Smart $ said:
In most cases where a calculation is based on unit equipment, you'd use the nameplate value. However, in the case of a non-refrigeration motor, you have to use a Table value.
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And for unit equipment the overload will be inside the unit, so no need to calculate that. The external branch OCPD only needs to cover short circuit and ground fault.
If the only motor in the equipment is impedance protected, then there may not be any overload. But that is generally only found in smaller fan motors.
 
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