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Switch doesn't switch correctly.
July 30, 2012 9:00 AM   Subscribe

Please help me understand this bizarre home electrical-wiring problem, and how to fix it. I've got a mid-50s house. I wanted to put an outlet into the second bathroom, which has none, and it looked like the easiest way to do that would be to replace a wall switch with a combination switch/outlet (specifically, this one).

This is not a GFCI outlet, but there is a GFCI outlet on the same circuit, which is sufficient (right?).

The instructions for the combo device show a few ways to wire it up, depending on the wiring going to it. The only way that made sense for me to wire it up was to make the outlet switched with the light. This required me to create a jumper (which I did, out of a conductor scavenged from some romex) between two connectors on the unit, and break off a built-in jumper. I triple-checked that I had everything hooked up correctly according to the instructions.

Like most older houses, this one has some weird electrical stuff going on. Most of the wiring in the house was updated a few years ago, but apparently not the leg to the light switch. And for some reason, there are two neutral wires and one hot wire connecting to the light (but only one each at the switch).

Since the wiring for the light switch does not include a ground wire, I grounded the switch to the adjacent fan switch, which is grounded (it has a ground wire, at any rate).

Anyhow, here's what happened when I got everything hooked up: Turning on the light did not result in the light turning on. When I plugged in my work light to the outlet and turned that on with the light switch on, the work light did not come on, but the ceiling light did. Weird. I felt like I was in a Marx Brothers sketch for a moment.
posted by adamrice to Home & Garden (10 answers total)
 
This is not a GFCI outlet, but there is a GFCI outlet on the same circuit, which is sufficient (right?).

No, not necessarily. Depends how it was wired.

When I plugged in my work light to the outlet and turned that on with the light switch on, the work light did not come on, but the ceiling light did. Weird. I felt like I was in a Marx Brothers sketch for a moment.

A guess: Is the wattage of the work light considerably higher than the wattage of the ceiling light? Because it sounds like you've got the outlet wired in series with the switch.
posted by jon1270 at 9:09 AM on July 30, 2012


The GFCI socket only works for the rest of the circuit if it's the first outlet on the circuit, and the rest of the circuit is wired correctly from that socket (ie: There aren't pigtails to the socket, but the rest of the circuit comes off the appropriate screws on the socket).

Also, it's generally bad practice to put lights on the same circuit as sockets: If you trip a socket circuit, you don't want your lights to go out. Even if you think "I know how this is wired, I won't be confused if the lights go out". Trust me on this.

It sounds like the "two neutrals" situation is confusing. I'm also going to bet that your work light is a halogen or incandescent, and your ceiling light is a compact fluorescent, or a bulb of considerably lower wattage than your work light. Here's what I think happened:

You wired your switch, the socket, and the ceiling light in series. Your work light being on allows current to flow, but because of good ol' Ohm's Law, it wasn't able to draw enough current to light up. It was, however, able to pass enough current to light the ceiling light.

I think you definitely need to figure out what that "second neutral" is really about: Something left over from a 3-way switch? The circuit not really flowing from where you think it is?
posted by straw at 9:20 AM on July 30, 2012 [1 favorite]


What jon1270 said.

So, the electrical box that light switch was in - does it have just one romex cable coming into it, and the black and white are connected to the switch?
posted by rmd1023 at 9:30 AM on July 30, 2012


The "series connection" explanation makes sense, although I'm not clear why that is happening with this combo device. It doesn't seem like it's meant to work that way.

rmd1023—Yes, the switch has one old (cloth-wrapped) romex cable running to it, connected to black and white. There's also a fan switch in the same box, but it's got new romex.

it's generally bad practice to put lights on the same circuit as sockets I won't dispute that, but unless I add new circuits at the panel (I won't), it's not going to get fixed.
posted by adamrice at 10:07 AM on July 30, 2012


It doesn't seem like it's meant to work that way.

It's not meant to work that way, but we can't see what you did with the jumpers. You might've unintentionally made it work that way.

Yes, the switch has one old (cloth-wrapped) romex cable running to it, connected to black and white

Sounds like the black is the hot wire and the white is meant to be the switched hot going back to the light, not a neutral wire at all.
posted by jon1270 at 10:17 AM on July 30, 2012


That single cable coming to the switch isn't a hot leg and a neutral leg. The white wire (should) be the hot leg, and the black wire (should) be the one that goes back up to the light. That way, that black wire can connect directly to the light and provide the switched power. Using a 2 wire switch leg (where a single cable goes from the light fixture box down to the switch) is the only circumstance where you are allowed (in fact, required) to have high voltage on a white wire.

The two neutrals on the light fixture are (presumably) because further back in the box are two black hot wires connected up with the white wire that goes down to the switch.
posted by rmd1023 at 11:27 AM on July 30, 2012


Here are photos of the outlet installation instructions and the outlet itself with the jumper I've added, and the "break off tab" broken off—it had been between the two black screws.
posted by adamrice at 11:43 AM on July 30, 2012


Okay, here's the thing: the instructions presume that you have a neutral wire to connect to the silver screw, which isn't seen in the photo because it's on the other side of the device. But if you have only one two-conductor cable coming into the box then there is no neutral, and you can't wire this device (or any other device with an outlet) without running a new wire with a neutral conductor to it. All you've currently (heh) got is a switched hot and an unswitched hot.

If you connected the white wire (which you assumed was neutral) to the silver screw, and the black wire to the middle black screw as shown in the direction, then you'd see exactly the behavior you described. Current passes from the silver screw to once side of the outlet, through your work light to the other side of the outlet, out through the black screw that's furthest from the switch, through your jumper, through the switch, out the middle black screw and thence to the light.
posted by jon1270 at 12:10 PM on July 30, 2012 [1 favorite]


Another potentially helpful clarification: the directions you linked to describe how to have the switch control ONLY the outlet, not the outlet and a light fixture. That's why the illustration doesn't show a third conductor.
posted by jon1270 at 1:44 PM on July 30, 2012


Okay, here's the thing: the instructions presume that you have a neutral wire to connect to the silver screw, which isn't seen in the photo because it's on the other side of the device. But if you have only one two-conductor cable coming into the box then there is no neutral, and you can't wire this device (or any other device with an outlet) without running a new wire with a neutral conductor to it.

Seconded, and I feel bound to add, with no disrespect implied, that people to whom this is not immediately obvious are people who should not be attempting to modify house electric wiring.
posted by flabdablet at 10:14 PM on July 30, 2012


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