Electrical Outlet weird wiring


Old 04-23-19, 05:47 PM
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Electrical Outlet weird wiring

Hi there, in my garage I have 5 outlets. One of the outlets is to service the central vacuum system. I have been replacing all my outlets in my house and decided to do the garage ones as I had leftovers.

All outlets were normal with 1-3 black, 1-3 white coming in and out, as well as a ground. The one for the central vacuum was wired in a strange way.

This outlet has 2 black wires pigtailed at the back of the box, two neutrals, one of which was inserted into hot push in connector, and one red connected to the other hot! This was done by the builder as we are original owners. The outlet has always worked...

So I put the other neutral white in a neutral push in. It works perfectly.

What is the red wire since I have two hots at the back of the box? This outlet is not connected to any switch, so its not that? Why was one white inserted into a hot line?

What could it be? This is the only one in my house wired like this!

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Old 04-23-19, 06:08 PM
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Welcome to the forums.

With the appearance of the red wire on a receptacle that usually indicates a multi wire branch circuit. (MWBC) That would mean two circuits sharing the same neutral. Is it possible the receptacles are on one circuit breaker and the vacuum is on another ?
Old 04-24-19, 04:54 AM
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Hi, I wouldn’t be using the back stab connections on the receptacles but instead use the screw terminals.
Old 04-24-19, 07:22 AM
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It sounds to me like a switched outlet. Does this picture represent the situation?

You did good by connecting the orphaned neutral to the existing neutral. The builder was supposed to wirenut those neutrals together and use a pigtail to connect to your outlet. Technically speaking, a switch does not require a neutral, but new NEC code requires that a neutral must go to every box anyway. They had a neutral, but I guess were too lazy to connect it. In any case, whether you connected it or not should not affect the operation of anything, but it should be connected.

Do you see how the power flows from the black wire, into the 1st box, then continues to the 2nd box. Here the black wire goes into the switch. When the switch is turned on, power flows from the black wire into the red wire and goes back to the 1st box.

Since you said the red wire was reading as hot, that means you have a switch somewhere that is in the on position.

Old 04-24-19, 08:28 AM
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Thanks for your replies! There is no switch present, that is what is confusing me!

The breaker is a double one that is connected (i.e. 29-30 are two attached switches).

What gets me is that there was only one hot (the red wire) inserted into the outlet, so it couldn't be a split outlet since the other outlet wouldn't have worked (both black wires are pigtailed at the back of the box).

Old 04-24-19, 08:35 AM
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The original installer must have had a change of heart after the rough-in installation was complete. They planned for a 20A MWBC, but only used one leg of it for whatever reason. Probably just forgot.
Old 04-24-19, 09:04 AM
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No switch, huh? Strange. In your original post, you never specified what the 2nd neutral was connected to. Was it just capped with a wirenut? Did it look like this drawing (before you connected it to the receptacle)?

A real photograph might be helpful.

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