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Joined: Aug 2004
Posts: 15
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I have 277/480 Y at work and I need to hook up an exit sign that uses 25V. So, I am planning to use a transformer, I assume 277/25V transformer.
I looked up the code book which said, I need to ground a system if it is less than 50V, and if it is fed by a supply system of more than 150V.
But, how do I system ground the secondary side, which is the exit sign? Run a grounding wire to concrete? Even if I did that, what do I connect it to? All the electrodes, the building metal structure, and water pipes are being used as electrodes for the building.

Am I wrong about the code?

Jon


What is the "objectionable current" at the code

Joined: Aug 2001
Posts: 7,520
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I'm not up on the finer code requiements on this sort of situation, but you could ground the 25V side by just linking one side of the secondary to the equipment grounding conductor (which would also be grounding the transformer frame).

Joined: Aug 2004
Posts: 15
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what about the neutral of the secondary side? Do I need to bond that to the same side's equipment grounding bus and after that, make connection to the primary side eqiupment grounding conductor?

thanks

Joined: Aug 2001
Posts: 7,520
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Yes, you would need to bond the neutral on the secondary to ground. Some of our code experts might throw in details of any specific code-requirements here.


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