Transformer grounding and or bonding.

[smorse]

We installed and customer supplied transformer for a piece of equipment. We fed it from an existing panel. Panel is 208V 3 Ph transformer is 400V 3 Ph. The transformer was grounded to a new ground rod and bonded to the panel ground. Now we are being told by the city they want the new ground rod bonded by a separate wire all the way back to the service entrance ground & the Building water pipes and Building steel. We are looking for something to convince the customer & the city inspector that we should not be required to do that.

 

[raider1]

Take a look at 250.30 for the requirements for grounding and bonding a separately derived system. Specifically look at 250.30(A)(7) for the grounding electrode requirements.

Chris

 

[benaround]

I don't see why you can't come from the nearest building steel and run to

any point on the derived system from the source to the 1st disc. means.

IMO the main water pipe and the service ground are not required. After all

this is an ungrounded system and the GE will only serve as a referance to

ground.

 

[sandsnow]

Now we are being told by the city they want the new ground rod bonded by a separate wire all the way back to the service entrance ground & the Building water pipes and Building steel.

An informal interpretation from NFPA agrees with your City.

Here is the link to the thread with the interpretation:
http://forums.mikeholt.com/showthread.php?t=81654