250.102 verse 250.122 Grounding Table Question

[Cgriggs]

Hello, when sizing your ground conductors running with your phase conductors, when do you use the 250.102 table instead of the 250.122 table? Is it solely a SDS that does not have a disconnecting means in the same enclosure? Any other scenarios?

Also, I just wanted to confirm that a GEC and EGC is required for SDS over 1000VA?

Thank you!

 

[ActionDave]

250.122 is for equipment grounding conductors and is based on the size of the overcurrent device. 250.102 is new, in the old days we would use 250.66, either way it is based on the size of the phase conductors.

I can't tell from your question what the application is. The basic rule is everything before the service disconnect is sized off table 250.66/250.102, everything after the service use 250.122.

 

[infinity]

Hello, when sizing your ground conductors running with your phase conductors, when do you use the 250.102 table instead of the 250.122 table? Is it solely a SDS that does not have a disconnecting means in the same enclosure? Any other scenarios?

Also, I just wanted to confirm that a GEC and EGC is required for SDS over 1000VA?

Thank you!

Can you clarify, what do you mean by "ground conductors"?

 

[don_resqcapt19]

250.122 is for equipment grounding conductors and is based on the size of the overcurrent device. 250.102 is new, in the old days we would use 250.66, either way it is based on the size of the phase conductors.

I can't tell from your question what the application is. The basic rule is everything before the service disconnect is sized off table 250.66/250.102, everything after the service use 250.122.

The supply side bonding jumper between a transformer and the the OCPD is sized from 250.102.

 

[Cgriggs]

Can you clarify, what do you mean by "ground conductors"?

Thank you for the responses. The ground conductors i am referencing is the equipment ground ran with the phase conductors. So i noticed from secondary side of transformer to OCPD, the supply side bonding jumper table (102) would be used to correctly size it. However, say for a Generator to ATS where the generator is a SDS. You would use the 250.122 to correctly size the EGC that is ran with the phase conductors. I was hoping to see if there was a basic rule of thumb as to when you use the 250.102/66 table to size the EGC/Ground Conductor that is ran with the phase conductors instead of 250.122. I also just wanted to confirm that a GEC is required for SDS over 1000VA as well. Thank you for all the help!