transformer and panel ques?

[wireman1]

a 100 kva transformer 480 volt 3 phase step down transformer is going to fed a service panel with 208 /120 volt 3 phase .if you ground and bond at x0 terminal in the transformer is the panel now considered a sub panel and you isolate the grounds and neutrals . but if bond and ground in the panel and land the grounds and neutrals on the same bar is it considered a service . what do you do with the x0 terminal in the transformer just bond it to the frame of the transformer. because you cant bond and ground in both the transformer and the panel which of the above is mostly widely used? also which articles would apply and is this considered a separately derived system.

 

[jumper]

This link may help. I refer to it a lot.

http://ecmweb.com/contractor/transformer-installation-made-easysort

 

[ActionDave]

I make the bond in the panel mostly because that is the way I was taught. Besides, panels are out in open and have to meet work space requirements; transformers end up down on the floor, up in the ceiling, in poorly lit rooms.....all kinds of places I'd rather not have to do any extra work in.

Along with Jumper's link any copy of the NEC Handbook has some good illustrations why either location is acceptable.

 

[iwire]

Given the choice I bond at the transformer.

 

[infinity]

a 100 kva transformer 480 volt 3 phase step down transformer is going to fed a service panel with 208 /120 volt 3 phase .if you ground and bond at x0 terminal in the transformer is the panel now considered a sub panel and you isolate the grounds and neutrals . but if bond and ground in the panel and land the grounds and neutrals on the same bar is it considered a service . what do you do with the x0 terminal in the transformer just bond it to the frame of the transformer. because you cant bond and ground in both the transformer and the panel which of the above is mostly widely used? also which articles would apply and is this considered a separately derived system.

Can you explain the bold part, how does this bond make it a service?

 

[Smart $]

Before jumping the gun on proper grounding, the first clarification needed is whether this is a service transformer, or non-separately-derived or separately-derived system...??? Given the primary voltage is 480V, I'm guessing not a service transformer... but need confirmation. What determines this is the service disconnecting means will be on the primary side of the transformer. If on the secondary side, it is... otherwise leaves the other two possibilities (and odds favor the latter).

 

[augie47]

May help