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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => AC Power and Grounding => Topic started by: Her Xiong on September 08, 2015, 01:23:56 pm

Title: Standard Outlet Question
Post by: Her Xiong on September 08, 2015, 01:23:56 pm
How can you tell if two outlet are on the same circuit (breaker) or on two different circuit (breaker)?

Title: Re: Standard Outlet Question
Post by: TJ (Tom) Cornish on September 08, 2015, 01:25:24 pm
How can you tell if two outlet are on the same circuit (breaker) or on two different circuit (breaker)?
I wrote an article that covers this to some degree. http://tjcornish.com/articles/power-distribution-part-1--.html
Title: Re: Standard Outlet Question
Post by: Jonathan Johnson on September 08, 2015, 01:41:52 pm
The only way to be sure is to cycle the suspected branch circuit breaker for the receptacles in question.

When disconnecting the power to a receptacle or other electrical device, I use this procedure:

The purpose of this method is to guard against an inadvertent false reading, or simultaneous failure or misunderstanding between you and a helper. The lock out/tag out step is necessary to ensure that the circuit is not energized by someone else while you are working on it. Of course, lock out/tag out is not needed when you are just identifying circuits.
Title: Re: Standard Outlet Question
Post by: TJ (Tom) Cornish on September 08, 2015, 02:24:54 pm
The only way to be sure is to cycle the suspected branch circuit breaker for the receptacles in question.
That's the only way to be absolutely sure which specific breaker feeds a particular outlet, however you can be sure that two receptacles aren't on the same circuit via other means of varying degrees of confidence, and in at least one case with 100% confidence. 

The reason I wrote articles on power is so I don't have to continually re-type my answers in the forum, so I'm going to stop now so as to not defeat my own purpose.
Title: Re: Standard Outlet Question
Post by: Frank DeWitt on September 08, 2015, 02:54:39 pm
I believe Mike has a method where he uses a cycle relay to apply a large load (about 1000 watts) to a outlet for a short time (about .1 sec if I remember right)  This load will lower the voltage on that outlet and any outlet on that circuit breaker.  It will lower the voltage on other outlets as well, but not near as much.

Do I have that anywhere near right Mike?
Title: Re: Standard Outlet Question
Post by: Mike Sokol on September 08, 2015, 04:17:11 pm
I believe Mike has a method where he uses a cycle relay to apply a large load (about 1000 watts) to a outlet for a short time (about .1 sec if I remember right)  This load will lower the voltage on that outlet and any outlet on that circuit breaker.  It will lower the voltage on other outlets as well, but not near as much.

Do I have that anywhere near right Mike?

Sort of but not exactly.... I use that test to identify swapped neutral and ground wires. And the pulse is more like 1 second on and one second off. That so there's enough time for a digital meter to respond to the change. I also use to identify double Ground-Neutral bonds in sub-panels. 
Title: Re: Standard Outlet Question
Post by: Brook Hovland on September 08, 2015, 04:32:00 pm
"The reason I wrote articles on power is so I don't have to continually re-type my answers in the forum, so I'm going to stop now so as to not defeat my own purpose."

If there is a best best quote of the day award, that gets it in my book!
Title: Re: Standard Outlet Question
Post by: Frank DeWitt on September 08, 2015, 05:35:17 pm
Sort of but not exactly.... I use that test to identify swapped neutral and ground wires. And the pulse is more like 1 second on and one second off. That so there's enough time for a digital meter to respond to the change. I also use to identify double Ground-Neutral bonds in sub-panels.

OK Thanks Mike,  It seems as if a 1 sec long load would be readable with a analog meter. so my misuse could be done?
Title: Re: Standard Outlet Question
Post by: Mike Sokol on September 08, 2015, 09:11:48 pm
OK Thanks Mike,  It seems as if a 1 sec long load would be readable with a analog meter. so my misuse could be done?
Yes, you would certainly see an analog meter needle swinging back and forth at 1/2 Hz. In fact, that's easier to see than a digital display updating at some unknown rate.
Title: Re: Standard Outlet Question
Post by: frank kayser on September 09, 2015, 11:06:33 pm
"The reason I wrote articles on power is so I don't have to continually re-type my answers in the forum, so I'm going to stop now so as to not defeat my own purpose."

If there is a best best quote of the day award, that gets it in my book!

Yeah. That's about as good as it gets. Brought a smile to my face.