Secondary on Step-Dn to Disconnect

[Aistobasbistoc9]

Hi,

I have a situation where there is a disconnect before the panel on the secondary of a 480-208 3PH step down transformer (panel located about 50' away and disconnect within 25' of the transformer). The GEC on the transformer is a #6 (30kVA unit), and the secondary feeder is a to a 100A disconnect and also has a #6 gnd. wire. Does the feeder after the disconnect to the panel also require a #6 gnd. wire? Or can this be a typical #8 gnd. that would be minimum for a 100A feeder?

Thank you

 

[infinity]

The conductor between the transformer and the OCPD would be a SSBJ or supply size bonding jumper. It is sized according to the ungrounded conductor size between the XFMR and the OCPD. Look at Table 250.102(C)(1).

After the OCPD you would use Table 250.122 since it's an EGC.

 

[ptonsparky]

Where is the

The conductor between the transformer and the OCPD would be a SSBJ or supply size bonding jumper. It is sized according to the ungrounded conductor size between the XFMR and the OCPD. Look at Table 250.102(C)(1).

After the OCPD you would use Table 250.122 since it's an EGC.

Dang, your moment ago was too fast.

 

[Aistobasbistoc9]

The conductor between the transformer and the OCPD would be a SSBJ or supply size bonding jumper. It is sized according to the ungrounded conductor size between the XFMR and the OCPD. Look at Table 250.102(C)(1).

After the OCPD you would use Table 250.122 since it's an EGC.

Thank you for the clarification!

 

[infinity]

Just for reference the SBJ would also be sized according to 250.102(C)(1) based on the secondary conductor size.