Sizing an Equipment Grounding Conductor (EGC) for electric motors
- Thread starter davedan
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kwired
Electron manager
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- NE Nebraska
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- EC
equipment ground is sized according to overcurrent protection device not the equipment
davedan,
Welcome to the forum.
Is this a test question ?
In any event, kwired gave you the answer, so you would need to determine the ampacity of the short circuit protective device.
In the most common situation, the SCGF device would be between 100 and 175 amps and the EGC for that scenario would be a #8 cu, but a smaller SCGF device could be used.
Welcome to the forum.
Is this a test question ?
In any event, kwired gave you the answer, so you would need to determine the ampacity of the short circuit protective device.
In the most common situation, the SCGF device would be between 100 and 175 amps and the EGC for that scenario would be a #8 cu, but a smaller SCGF device could be used.
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Dear Gentlemen
Thank you for your replies. The posted question is for me to know the correct way to select EGC for motors.
I read Article 250.122(D) where in other words (if my understanding is correct) says that if I used instantaneous protection like the HMCP that CH uses in their MCCs then the EGC can be sized based on the rating of the motor OL protective device.
It means that when using different kind of OC protection like Inverse Time CB I need to select EGC according to the rating of that OC protective device, don't I?.
I will appreciate your answers.
Davedan
Thank you for your replies. The posted question is for me to know the correct way to select EGC for motors.
I read Article 250.122(D) where in other words (if my understanding is correct) says that if I used instantaneous protection like the HMCP that CH uses in their MCCs then the EGC can be sized based on the rating of the motor OL protective device.
It means that when using different kind of OC protection like Inverse Time CB I need to select EGC according to the rating of that OC protective device, don't I?.
I will appreciate your answers.
Davedan
- Location
- Illinois
- Occupation
- retired electrician
You are correct that the type of branch circuit short circuit and ground fault protective device has an impact on the sizing of the EGC for a motor circuit. There has been a change for the 2008 code for the cases where the motor starter uses a instantaneous device. Under the 2008 code the EGC is no longer sized by the overload rating, but is based on the maximum size dual element fuse that is permitted for the motor. Note that 250.122(A) does apply and the EGC is never required to be larger than the motor circuit conductors.
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