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Old 07-27-2019, 07:38 AM   #1
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Trying to identify wires...


Three #8's pulled for a garage sub panel, but none are marked. Two of the wires are landed on a 2 pole breaker, the other is a neutral. If I turn on the breaker, I can easily identify the two hots. However, I do not know which is A and which is B. My question: can I disconnect one of the wires from the 2 pole breaker, turn the breaker back on, and then test to see which one is hot? That way isolating A from B? Help!
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Old 07-27-2019, 07:43 AM   #2
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Re: Trying to identify wires...


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Originally Posted by Mercyful_Mike View Post
Three #8's pulled for a garage sub panel, but none are marked. Two of the wires are landed on a 2 pole breaker, the other is a neutral. If I turn on the breaker, I can easily identify the two hots. However, I do not know which is A and which is B. My question: can I disconnect one of the wires from the 2 pole breaker, turn the breaker back on, and then test to see which one is hot? That way isolating A from B? Help!
It doesn't matter which is which.
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Old 07-27-2019, 07:49 AM   #3
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Re: Trying to identify wires...


Yes you can do that with a voltage tester, tick tracer.
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Old 07-27-2019, 07:51 AM   #4
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Re: Trying to identify wires...


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It doesn't matter which is which.
Even if the sub panel is a main lug panel?
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Old 07-27-2019, 07:57 AM   #5
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Re: Trying to identify wires...


IT doesn't matter. Both are carrying 120 volts and can be interchanged. You know which one is neutral, so you are good.
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Old 07-27-2019, 08:00 AM   #6
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Sure. Them you can mark 1 with colored tape such as red, but not white, gray, or green. Orange and Brown are usually for high voltage/3 phase.
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Old 07-27-2019, 08:44 AM   #7
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Re: Trying to identify wires...


Quote:
Originally Posted by Mercyful_Mike View Post
Three #8's pulled for a garage sub panel, but none are marked. Two of the wires are landed on a 2 pole breaker, the other is a neutral. If I turn on the breaker, I can easily identify the two hots. However, I do not know which is A and which is B. My question: can I disconnect one of the wires from the 2 pole breaker, turn the breaker back on, and then test to see which one is hot? That way isolating A from B? Help!

Your method would work but it causes unnecessary risks. And as mentioned below it doesn't matter which is A or B. If you move the double-pole feeder breaker up or down a space you've just changed it.



Phase identification matters in 3 phase installations because motor rotation is affected by phase rotation. Single phase installations use induction motors or ECM, not synchronous motors, thus phase rotation isn't a concern.



A safer method to test wiring (if you didn't know what was phase or neutral) would be to pull the wires off the main panel/breaker and simply put a 9V battery between them (alligator clips are handy here), noting polarity. Then when you measure VDC on the other end you'll be able to figure out which is which.



For your installation, just leave it as-is and don't take the risk for no gain.
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