Transformers

[HDHeritage]

Hi,
My names Carl
Just found this site on the web and I think it's very cool.
I've been wiring for a while now and have had this question in the back of my mind. Wiring a 3phase transformer from an existing panel say 480 volts to 208/120, is considered a Separately Derived System.

In Ca. I install a ground rod and run a ground wire to the water line where it enters the building and usually bond the neutral in the trans.
OK, here's the question. If I install a transformer that's dedicated to one machine only, say 208 3 phase to 480 3phase.
Transformer may not be installed by the machine. Is it still considered a Separately Derived System and needing a water line ground and ground rod
or just a ground wire run in conduit with phase conductors as water line grounds run across buildings can get expensive.
Some machines from other countries have transformers as part of the machine .
We just run power to the safety switch like 3 phase with ground and were done

 

[chris kennedy]

If I install a transformer that's dedicated to one machine only, say 208 3 phase to 480 3phase.

Hi Carl, welcome to the Forum.

Does it fit this defination?

Separately Derived System. A premises wiring system whose power is derived from a source of electric energy or equipment other than a service. Such systems have no direct electrical connection, including a solidly connected grounded circuit conductor, to supply conductors originating in another system.

Some machines from other countries have transformers as part of the machine .
We just run power to the safety switch like 3 phase with ground and were done

And many that are still built in this country have transformers intergral also. You are not installing these transformers.

 

[gk351]

I still wonder about this all the time. It seems like no one can give me a straight answer. Just today we had a contractor come and install a 480/120-240 Single Phase Dry XFMR. They only ran 2 ungrounded + 1 grounding wire from our 480 V MDP. They were supplying a 120/240 100 Amp CH Lighting Panel.They ran the grounding wires to a lug tapped to the XFMR case. They didn't bond in either the dry xfmr, nor the 100 Amp panel. From what I have learned/been taught, is that you bond either/or, but not both. Any clarification?

Not to mention....We have fully capable military electricians, yet we had to pay a contractor to put this in? I was angered, especially when I have been twiddling thumbs lately!

Oh yeah....also....I would say where I work is an industrial environment....everything is either 277/480 volt, or stepped down to 120/208....yet my upper management decided for this upgrade....to install 120/240 single phase. I was pretty mad when I heard this...because most likely in 6 months, they will find something to buy, and the only available power now is 120/240 Single phase. IMO, nothing like shooting ourselves in the foot!