# How to hook up 480V 3 phase on the power panel side?

#### Peter C

Joined Jun 14, 2007
1
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.

Peter

#### thingmaker3

Joined May 16, 2005
5,083
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!

#### tincat2

Joined Jun 7, 2007
9
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.

#### recca02

Joined Apr 2, 2007
1,212
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.