Xfmr Secondary Tap Grounding

[belkymd]

I have 112.5 KVA transformer that feeds (4) tapped lighting and appliance panelboards from the secondary. Which NEC table should be utilized for sizing the panelboard equipment grounds? (250.66 or 250.122)

 

[raider1]

Are you asking about the equipment bonding jumper between the transformer and the panelboards?

If you are take a look at 250.30(A)(2).

Chris

 

[charlie b]

Presuming you are creating a new Separately Derived System with this transformer, there will have to be a connection between neutral and ground somewhere nearby. The wire that goes from that point to planet Earth is sized by 250.66. Equipment grounding conductors are sized by 250.122.

 

[belkymd]

Thanks

Thanks

Thanks guys! We were on the same page, however a consulting engineer had a different opinion.

 

[infinity]

One the primary side you would use 250.122 to size the EGC in the feeder. On the secondary side you would use 250.66 to size the GEC, the equipment bonding jumper and the system bonding jumper.