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#202127 - 07/19/11 02:20 PM 2 machines 1 transformer?
bot540 Offline

Registered: 09/14/04
Posts: 177
Loc: Vernon Hills, IL
Looking for a little help maybe sooner then my AHJ calls me back. I have a machine shop where I'm looking to use one 30kva transformer to step down the voltage to 120/208. If I fuse both machines at the disconnects for 20 amps is this acceptable versus buying and installing 2 15 kva transformers?
Jesus may have been a capenter,but God was an electrician.Genesis1:3

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#202129 - 07/19/11 06:04 PM Re: 2 machines 1 transformer? [Re: bot540]
HotLine1 Offline


Registered: 04/03/02
Posts: 6791
Loc: Brick, NJ USA
With primary and secondary OCP, you are allowed 6 disconnects max. Watch your conductor sizes on the secondary.

Read the exceptions under 450.(3)(b) table.

Exc. 2:
"2. Where secondary overcurrent protection is required, the secondary overcurrent device shall be permitted to consist of not more than six circuit breakers or six sets of fuses grouped in one location. Where multiple overcurrent devices are utilized, the total of all the device ratings shall not
exceed the allowed value of a single overcurrent device."

Edited by HotLine1 (07/19/11 06:05 PM)
Edit Reason: restructure paste


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