Wiring Outlet - Testing for Line vs Load


Old 03-06-05, 10:47 AM
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Wiring Outlet - Testing for Line vs Load

Hi -

Can someone explain how to do the following:

I have an outlet box with 4 wires - two black hotwires and two white neutral wires and a ground wire. My problem - how can I figure out which pair of black/white are the load and which pair are the line?

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Old 03-06-05, 11:16 AM
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You will need a multimeter or voltage tester. Turn off breaker and separate the two pairs. Turn on breaker and test each set for power by reading voltage from hot to neutral. The set with voltage is your source (line), the other is load (no voltage, feeds downstream outlets).

Old 03-06-05, 03:00 PM
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I might assume that since you are trying to figure out line vs. load, you might be installing a GFCI receptacle. For most other purposes, you don't need to know.

So pick one black/white pair at random. Connect it to the "line" side of your GFCI. Leave the other black/white pair unconnected (but isolated). Turn the breaker back on. If the receptacle works, then the pair you chose is line. If it doesn't work, then the pair you chose is load (and thus you need to move that pair to the load connections).
Old 03-06-05, 04:33 PM
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I only have the 'light' type of voltmeter detector (e.g. it lights up when it detects, but doesn't give me an actual 'reading' like a proper voltmeter.)

However, when I put my tester probes on a hotwire AND a neutral on either pair. I get nothing. But when I put it on either of the hotwires OR either of the neutrals and the ground, it lights up.

Also, I have one of those plug sensors that tells you what it thinks is wrong with your wiring.

When I do that it says that I have a hotwire and a ground reversed.
The result of which is that nothing on that run is working now.
The problem is - wouldn't a reverseal of hotwire and ground require that I have a bare copper (ground) wire in where a hotwire should be and a black hotwire where the ground should be? That - I obviously don't have.....

So as you might imagine - I'm a bit confused.
Old 03-06-05, 05:49 PM
Join Date: Sep 2000
Location: United States
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You do not have a hot/ground reverse (despite what your tester says). You have an open neutral. There's no magic way to find it. Just look in every box on the circuit. If you want, search the last few months of this forum for "open neutral". It's a very common problem. It's usually a weak backstab connection that fails when you use a vacuum cleaner.

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