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Light switch has 2 hot wires

Posted by duo001 (My Page) on
Wed, May 29, 13 at 21:00

I recently purchased a condo and am going through replacing switches and such. I have had this one switch that has always powered nothing, not a light nor a plug.
So I pulled it out to test and see if the switch itself were bad. I have a voltage tester and checked the wiring in the wall to find that I have 2 hot wires going to the switch.
There are a total of 4 wires that went to the switch, 3 black, 1 red.
I know that normally the red means "traveler" which should be used in a 3 way switch setup. I found no other switch in the house that this could turn on/off. I checked all switches on that circuit and found nothing.
In the picture the two wires to the left are the hot wires, and the two black wires to the right lead elsewhere.
One of the black wires on the right has to be hooked up for the rest of the first floor to function, and the other I did not finish with yet, but has to power something.

So I guess my question is why would there be 2 hot wires going to a light switch?


Follow-Up Postings:

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RE: Light switch has 2 hot wires

An ordinary switch only has 2 screws. Did you original switch have more than 2 screws.

Can you describe how the wires were attached to the switch? Maybe post a picture of the switch itself?


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RE: Light switch has 2 hot wires

Wires 1, 3, and 4 were attached to the bottom screw on the switch and the red was attached to the top screw on the switch.


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RE: Light switch has 2 hot wires

Where is this switch located in your condo?


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RE: Light switch has 2 hot wires

Three wires under one screw makes me think that along the line somebody, probably without a lot of electrical experience, changed something. Question is what.

When you say wires a hot, how did you test them?

Are wires 1 and 2 part of the same cable (the cable is a bundle of wires wrapped a plastic sheath). Or is the red with one of the other of the blacks?

Is there another switch in the room that, logically, could have been part of a three-way circuit?


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RE: Light switch has 2 hot wires

If this is an early 1970s or older condo unit, with this light switch near the door entrance and the breaker/fuse panel:

The first switch installed when the place was built was probably a "twin switch" essentially two half thickness switches in a regular size single switch box with a special cover plate. The problem was that the cover was always cheap and super ugly. One switch was for the hallway ceiling light and the other controlled half of one living room receptacle where a floor lamp was usually plugged in.

The special dual switch and cover fell out of favor soon after, leaving people who wanted something more current in appearance to go back to a single switch as best as they could while trying to figure out what was involved. The builders at the time often just went forward with a regular box holding two regular sized switches with the usual cover plate.

This post was edited by laat2 on Thu, May 30, 13 at 17:46


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RE: Light switch has 2 hot wires

I tested to see if the lines were hot with a Klein Tools voltage tester.
Oddly enough both of the lines that are hot come from the same romex.
The location of this switch is in the living room, right around the corner of the wall from the door, where you would expect the ceiling fan light to be.


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RE: Light switch has 2 hot wires

I tested to see if the lines were hot with a Klein Tools voltage tester.
Oddly enough both of the lines that are hot come from the same romex.
The location of this switch is in the living room, right around the corner of the wall from the door, where you would expect the ceiling fan light to be.


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RE: Light switch has 2 hot wires

What kind of Klein voltage tester? Both non-contact and digital multimeters can give false positives under certain circumstances. Any chance you have a solenoid type tester or an analog voltmeter?

You might want to take a few more receptacles/switches apart to see if you can find that red wire. Any indication that there might have been a ceiling fan or light in that room. Usually there will be a difference in texture to the drywall. Sometimes shining a flashlight at an angle along the ceiling can help locate it.


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RE: Light switch has 2 hot wires

There is a ceiling fan w/light in at room...but there is a switch in the room for it.
As for the voltage tester, it is a ncvt-1.
I do not have an analog volt meter.


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RE: Light switch has 2 hot wires

Is it possible that this used to control one half of a duplex outlet, so you could have a lamp plugged in that would be controlled by the switch, and the other half of the outlet was always on?
Then, somebody replaced the duplex but didn't break the tabs on the side, so the 'always on' half of the outlet is now feeding the 'switched hot' wire?


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RE: Light switch has 2 hot wires

Okay I now have an analog multimeter. I have no idea how to use it however...what probe goes to what wire from the wall?


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RE: Light switch has 2 hot wires

I started to write up some steps, but if you do not even know how to operate the meter find someone who does.

"I know that normally the red means "traveler" "

Or switched hot.

120 V is not all that dangerous if you have dry hands and shoes on, but you WILL know if you touch it by accident.

If you do not have any understanding of wiring, get someone who does.

Ether hire an electrician to figure out what to do, or an experienced friend willing to lend a hand.

The most likely thing is that one of the blacks is 'always on' and feeds the others, or when there where two switches was the 'other' switched hot.

The red was most likely on the other screw of the switch and is a 'switched hot' feeding a light or receptacle.

The problem is that you have to figure out a lot of what is what with the power on.

Simple for an experienced person, not so simple if you do not understand wiring.

This post was edited by brickeyee on Thu, May 30, 13 at 16:37


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RE: Light switch has 2 hot wires

I did as greg suggested and removed the closest outlet to the switch. I found the red wire that goes to the switch.
It looks like the previous owner put in a new switch to control the light/fan in the living room and rigged the old switch up incorrectly.
I removed the red wire from the outlet, also unhooked it from the light switch.
I tied all the black wires at the switch back together and covered with a blank wall plate, since the switch did nothing anyways.
Everything is funtioning as it should be.

thank you everone for the ideas and suggestions.


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RE: Light switch has 2 hot wires

Thank you for telling us how it turned out.


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RE: Light switch has 2 hot wires

It sounds like somebody replaced the outlet but didn't break the jumper between the switched and unswitched sides.


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RE: Light switch has 2 hot wires

I found out a little more information.
The condo used to have vaulted ceilings in the living and dining rooms, it looks like they dropped those ceilings, possibly for energy conservation, and when they did that had to relocate the wiring from the original light location, to the new ceiling 3 feet lower. Rather than doing that with the living room, they just wired up a new switch but somehow wired the old switch incorrectly and left it there.


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