Electricians: need some help with a home wiring problem

Factual Questions
1

I was trying to install this device to replace a simple SPST switch in the kitchen that controls our exterior lights, so I could remotely control them from the car. But when I followed the directions (connect the switch’s white wire to neutral, red wire to load, black wire to line), it didn’t work. I tried reversing the black and red leads. Same thing.

Tech support asked me to check the circuit with a tester. The results: 124 volts across the load and line, but 0 volts across either load or line and neutral and 0 volts across either load or line and ground.

This stumped him, and he suggested I call an electrician. Before doing that, I thought I’d get the advice of my favorite batch of experts here at the Dope.

What’s going on here? Is there any way to get this thing to work?

FYI, the house was built in 1922, and I suspect the original wiring was knob and tube. It was upgraded sometime before my wife moved in about 15 years ago. I think this room’s wiring is somewhat more modern (not all of the outlets in the house have a neutral wire) it’s a still a little funky.

Thanks.

2

That’s bizarre. Was the neutral cut like that in the original installation? Did the switch work? Are there any outlets on the same circuit? Do they all work? Check the reading between the two “neutrals” – I wonder if your wiring has something backwards between this box and the next, and one of them is actually hot. For a normal switch installation this wouldn’t be possible, but who knows?

3

Test for continuity between the ground and the neutral.

Lets make sure that I understand what you have before I begin to guess. You have a hot wire, one load wire both of these wires colored. neutral wires coming into and out of the box. Ground wire coming into and out of box? That would be a total of 6 wires.

4

What!!!
This is a serious code violation, seriously unsafe, and I just don’t see how it could work! How is the circuit completed? Through the ground? Through another hot, from the other leg of the 240-v feed? Both of those would work, sorta, but are NOT safe.

Are you sure you don’t mean that some outlets are missing the ground wire? That’s not uncommon in older houses.

5

There are a lot of ways to hook up a light switch. That device assumes that the power feed is coming in from the top of the box and the wire to the light goes out through the bottom. If you don’t have that general arrangement then the device you have chosen won’t work.

It’s fairly common to run a wire from the light down to the switch, in which case you’d have the unswitched hot wire and the switched hot wire and nothing else (you wouldn’t have a second set of wires coming into the box). The electrician is supposed to wrap black electrical tape around the white wire to show that it’s not being used as a neutral in that case, but I’ve seen a lot of examples where the wires weren’t marked to code.

Another possibility is that there is a second switch somewhere that controls the light, in which case you wouldn’t have a simple SPST switch, but you’d have a SPDT switch instead. Again, the wires are supposed to be taped to mark that you don’t have a hot and a neutral.

Neither one of these seems to match up with the description in the OP though. But if you have either one of these then the device you bought won’t work.

You’ve got two hots (black wires) two neutrals (white wires) and two grounds (bare copper), with one set of hot, neutral, and ground coming through the top of the box and the other set coming through the bottom of the box. Is that correct?

When you measured “load” to neutral, were the neutrals tied together at that point or were you only measuring to one neutral? If so, which one?

Did you try measuring the neutral to ground voltage? If you get 120 volts there then they simply have the hot and neutral reversed somewhere on the circuit (not all that uncommon of a mistake). Check the voltage BEFORE you try to do a continuity check per Snnipe 70E’s suggestion. If there’s voltage present when you try to do a continuity check you can fry your meter.

If you have missing neutrals in your outlets you have a major problem. If you have missing grounds it’s still a problem, though not quite as bad, and either way it’s not to code.

If your location is correct, I’m somewhat in your area (I live in PA but I work in Owings Mills). I’d like to come out and take a look at your house some night after work, but I can’t do it any time in the next week or so. If you are interested, send me an e-mail (my address is in my profile). From your description, it sounds like you have a lot more going on than just a weird switch.

6

Wait…124 volts between load and line? You shouldn’t have a voltage reading there, since they are at the same potential. You’re basically putting the meter in line instead of across the line. Or am I misreading something? I’d agree that you may have something miss-wired upstream, either at the panel or at a splice somewhere. And it sounds to me like your red load wire may be connected to your neutral/ground bar, and that your supposed neutral and ground wires are not connected to anything at all.

7

I took that to mean the reading was done without the switch in the circuit (ETA: or if the switch was in the circuit it was turned off). Since the meter is a high impedance, you’ll have very little current flowing through it. The “hot” side of the light bulb will be at close to 0 volts, and the line voltage will be up somewhere around 120 volts.

What you have is this:

120 volt source (breaker box)-----wiring—(a)-meter-(b)–light bulb----neutral side wiring—0 volts

with the meter measuring the voltage between points a and b.

8

If your old switch was SPST then it has only one cable entering and one exiting. It is only switching the hot cable, while the neutral is permanently connected.

Can you post a photo of the cabling on the wall?

9

Sorry if I wasn’t clear enough, or if I misstated anything. I probably have just enough knowledge in this area to be dangerous.

The box in question has two switches, the one I was working on, which controls our external lights, and another, which doesn’t appear to do anything. (This may be relevant, or not.) There are other outlets on this circuit, and they work fine.

I removed the SPST switch, which I assumed was connecting the load and the line (both black wires) and saw 120 volts when I put the meter between those two wires. Also in the box, connected to each other but to nothing else, are two white wires, which I assumed were neutral. I did not separate them and measure across them. But as I said, between them and either of the black wires was 0 volts. Likewise between either of the black wires and the box itself, which has a ground wire, was 0 volts.

The black wires are all coming in from the top of the box. I believe the white wires are coming in from the bottom, as is the ground.

I didn’t try testing anything with the other, non-working, switch or the leads going to it. I believe it is another SPST, with two separate black wires, but I won’t swear to that until I check again.

I’m a little busy with work the next day or two, so I may not be able to get back to playing with this right away, but I’ll try some of the suggestions posted here when I can, and get back with the results. In the meantime, any other ideas or suggestions are welcome.

10

Based on this, I would suggest you not make any assumptions about what any of the wires are.

If there is 120 between the two black wires, but you get zero between each of them and the “ground” on the box, the box can’t be attached to ground. It has to be floating.

I think the first thing you need to do is determine which wire is which, with no starting assumptions. I’d detach the two white wires from each other, then label the two white wires W1 and W2, and label the two black wires B1 and B2. Then measure the voltage between each pair of wires. Hopefully you get 120 volts between one pair of wires, and 0 volts between every other pairs. Then the two that give you a voltage are your hot and neutral (but you don’t know which is which yet), and the other two are (hopefully) the two wires to the light. If you get something else, it’s probably too much to handle yourself.

11

The black wires both are comming in the top of the box. And the white wires are comming out of the bottom? I am assuming that the wiring is not romex?

12

Instead of using a multimeter, get a tester screwdriver like this from your local hardware store.

Then you will be able to find exactly which one is the hot cable.

13

What happened? Did you fix it?

14

Not yet. Too much life going on. Maybe next weekend.

Thanks for all the advice.

15

Okay, back to work, finally. Here is a picture of the switch box. The switch on the left is the one I’m working on. The one on the right has no apparent function.

The inventory is as follows:

2 black wires (old, fabric coated) coming in from the top left, both connected to the working switch.

1 white, 1 black (nomex), 1 ground coming in from top right.

Same coming in from the bottom. The black wire of each pair is connected to one side of the non-working switch, and the whites are tied to each other. The grounds are tied to the box

Following the advice posted by several of you, I have done the following tests.

Checking for voltage with my multimeter, I get 120 between the two wires connected to the working switch, and between **no other pairs. **

There is no continuity between ground and either white wire.

Using a screwdriver-type tester, I get tone at one of the black wires on the working switch, one of the white wires, and one of the black wires on the non-working switch.

So what does all this tell us?

16

I think what you have there is 2 separate power feeds into that box.

The left side old cloth covered wires is a switch loop for the light. The power feed from the breaker panel comes up to the light in the ceiling, and then 2 wires run down to the switch, to control that light.

On the right side, you have newer cables (Romex™, brand name for type NM plastic cable), with one of them bringing in power from the house breaker panel, the other running on from the switch to whatever it controls (probably half of a receptacle for a floor lamp somewhere in the room).

So when working with this, these 2 switched & the wires to each should be treated as completely separate circuits – like they were in separate boxes. There isn’t any connection between them, and testing between them (the old cloth wires and the newer NM wires) will just confuse everyone.

Oh, to answer your original question – that device won’t work on a switch loop wiring, which is what you have at that box on the left side). It assumes the presence at the switch location of a power feed from the house breaker box, which you don’t have.

17

I was afraid of this. Do our other electrical experts agree with t-bonham@scc.net?

I bought a number of these cool Insteon devices in the hope of being able to remotely control lights and other things around the house. But this and other attempts to hook them up seem to indicate that this house’s ancient wiring won’t support them. And it’s taken me more than 30 days to figure this out, so I can’t return them anymore.

Damn.

18

There are ways to deal with switch loops and Insteon. Some legal and safe. Some illegal and relatively safe. Some illegal and highly dangerous. The legal and safe ways are either running a new cable from the light to the switch, or installing an InlineLinc in the junction box at the fixture, if the box is big enough (and if it isn’t installing a bigger box may be easier than running a new cable).

19

the device you want to use needs a neutral wire (to provide power to the new device), which doesn’t exist in a switching loop. you can connect to a neutral wire (not directly involved in this switching) in the box to get that.

20

I’ll look into this.

Could you be more specific?