480 v. 277 V clarification?
480 v. 277 V clarification?
(OP)
Hello,
I'm a relative newbie in the industry. I often look at panel schedules and wonder what the actual voltage of certain equipment is.
Say I'm looking at a panel schedule and I see equipment being called out as 3 phase, is this automatically 480V? Would 2 phase be 277V? I would think that I'd need to know whether it was a Delta of Wye configuration to know this.
What about single v. double pole? Is this an indication?
I'm most often confused when it comes to lighting...
Anyone know of a good resource to clarify any of this?
I'm a relative newbie in the industry. I often look at panel schedules and wonder what the actual voltage of certain equipment is.
Say I'm looking at a panel schedule and I see equipment being called out as 3 phase, is this automatically 480V? Would 2 phase be 277V? I would think that I'd need to know whether it was a Delta of Wye configuration to know this.
What about single v. double pole? Is this an indication?
I'm most often confused when it comes to lighting...
Anyone know of a good resource to clarify any of this?






RE: 480 v. 277 V clarification?
Any basic electricity book should give you some help with this.
Hope this helps,
Mike
RE: 480 v. 277 V clarification?
If your looking at a lighting panel (like what is in your house), it is usually single phase 120/240 V.
Some ways to detect 3 phase - the higher voltage will be the lower voltage times SQRT 3 and 3 phase is usually on a motor control center or switch.
The pole on a breaker is the contact for the circuit - a single phase circuit will be one pole, 2 pole is still single phase and 3 poles for a 3 phase circuit breaker.
wbd
RE: 480 v. 277 V clarification?
WBD, you hit the hail right on the head. I have a few 3 phase loads, but what I've read tells me it can be either 277 or 480.
I guess I'm looking to verify the voltage with no vendor info, looking only at the panel schedule.
I contend that it's not really possible since delta/wye is not specified.
I guess I'll have to break down and find the exact requirements from each vendor!
Thanks again for both your responses!
CM
RE: 480 v. 277 V clarification?
The only way you would get 277V three phase would be a 277Y/160V system or a 277V delta, neither of which is very likely.