Dsg319
Senior Member
- Location
- West Virginia
- Occupation
- Wv Master “lectrician”
Have been pondering on this for a minute.
In the event of sizing conductors for motors, I know how, but have never had to personally size conductors for a larger moter and was curious as to how to size the EGC.
I know conductors are sized 125% of rated FLC. And EGC is based off of OCPD, but if you have a OCPD sized 250% larger than conductors, obviously your EGC need not be larger than phase conductors.
Example say I have a 75hp, 3phase 480v motor.
FLC-96amperes x 125%= 120amp conductors needed. Okay so I get some #1AWG copper rated at 130amperes.
OCPD- 96 x 250%=240amp.
Have to choose a stand size so 225amp OCPD.
Obviously I do not need an EGC that large. So how do I properly size it?
Idea#1— Do I size it to original size of FLC x125%? So in this case it would be 125ampere OCPD I would size the EGC to without the addintional 250%?
In the event of sizing conductors for motors, I know how, but have never had to personally size conductors for a larger moter and was curious as to how to size the EGC.
I know conductors are sized 125% of rated FLC. And EGC is based off of OCPD, but if you have a OCPD sized 250% larger than conductors, obviously your EGC need not be larger than phase conductors.
Example say I have a 75hp, 3phase 480v motor.
FLC-96amperes x 125%= 120amp conductors needed. Okay so I get some #1AWG copper rated at 130amperes.
OCPD- 96 x 250%=240amp.
Have to choose a stand size so 225amp OCPD.
Obviously I do not need an EGC that large. So how do I properly size it?
Idea#1— Do I size it to original size of FLC x125%? So in this case it would be 125ampere OCPD I would size the EGC to without the addintional 250%?