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Old 06-14-2007, 06:00 PM
Peter C Peter C is offline
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Default How to hook up 480V 3 phase on the power panel side?

Hi guys I been searching for diagrams on how to hook up 480V and can't find any.

So here is the problem:
I have a box W.A. Benjamin (old one) that is rated at 480Y/277.
I tested the three leads against the ground and got 208V each. How to get get 3 wires of 480V from this box? Do I do the following?

Connect the 3 live wires the following way.
A-B = for the first 480V wire going into the circuit breaker input 1
B-C = for the second 480V wire going into the circuit breaker input 2
A-C = for the third 480V wire going into the circuit breaker input 3

then run it to my motor. The motor is already hooked up just waiting for the (3) 480V wires.

Just wanted to get a confirmation before I make the hookup. I don't want anything to blow because of the high voltage.

Thanks in advance.
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Old 06-15-2007, 05:13 AM
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thingmaker3 thingmaker3 is offline
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Your description makes no sense. (No offense intended.) 208Vac is a measurement from a 120/208 system. A 277/480 system would measure 277Vac.

Do NOT connect phase-to-phase! People get killed that way!

Please have an experienced electrician hook up your panel.
"I want to establish in your mind very clearly that you must not think I deny all that I do not admit. On the contrary, I think there are many things which may be true, and which I shall receive as such hereafter, though I do not as yet receive them; but that is not because there is any proof to the contrary, but that the proof in the affirmative is not yet sufficient for me"
- Michael Faraday
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Old 06-17-2007, 05:10 AM
tincat2 tincat2 is offline
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don't know for sure from your post, but it sounds like you've got 208 VAC coming out of the wall(or transformer, possibly a computer room ups setup). what you call a box sounds like a three pole breaker-you should find out what you're dealing with before you proceed, e.g., is your motor a 480v three phase, etc.? listen to thingmaker3 and get someone in there who can check things out.

Last edited by tincat2; 06-17-2007 at 06:38 AM.
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Old 06-26-2007, 03:37 PM
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recca02 recca02 is offline
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Originally Posted by Peter C View Post
I have a box W.A. Benjamin (old one) that is rated at 480Y/277.
is this a three phase transformer?

if thats the case you can get 480 V between phases not line and ground since generally line values are specified.
also do you have 277 V phase to phase at the primary?
there are lots of questions.
this is the reason god made creatures called electricians.

Originally Posted by thingmaker3 View Post
Please have an experienced electrician hook up your panel.
mr thingmaker is himself a good electrician btw

Last edited by recca02; 06-26-2007 at 03:40 PM.
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