Electricians: need some help with a home wiring problem

[johnpost]

@johnpost

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.

@commasense

Could you be more specific?

in the diagrams (at the website) for the device it has a white neutral wire connected to it because the new device needs power to function.

the diagrams at the website don’t show a switch loop. in a switch loop the line and load wires are in the same cable (they would come into the box through the same opening).

with the old wires (if a switch loop) you have one black wire having the power from the fuse box (line) and another black wire going out to the light (load); these are in a single cable going to the light fixture. in the box you also have neutral wires (white) used in the lights going to other rooms. you can connect a short piece of white wire from these wires to the new device to supply power to the new device.

[commasense]

@johnpost

in the diagrams (at the website) for the device it has a white neutral wire connected to it because the new device needs power to function.

the diagrams at the website don’t show a switch loop. in a switch loop the line and load wires are in the same cable (they would come into the box through the same opening).

with the old wires (if a switch loop) you have one black wire having the power from the fuse box (line) and another black wire going out to the light (load); these are in a single cable going to the light fixture. in the box you also have neutral wires (white) used in the lights going to other rooms. you can connect a short piece of white wire from these wires to the new device to supply power to the new device.

I think I’ve already tried that: one black line to device’s line wire, one black line to device’s load wire, and white wires to device’s neutral wire. It didn’t work.

[johnpost]

@commasense

I think I’ve already tried that: one black line to device’s line wire, one black line to device’s load wire, and white wires to device’s neutral wire. It didn’t work.

you may have had the black wires connected wrong. the line black wire should have voltage on it compared to the white wire. the load black wire should not have voltage on it compared to the white wire.

[Mdcastle]

If the neutral is on the same circuit, it’s fine and legal.
If the neutral is not on the same circuit, it will work but it not legal, but realistically speaking you’re not going to overload the neutral of another circuit with the less than 10 watts consumed by the switch. The real hazard is if the other circuit breaker is turned off and the neutral connection is broken you would have a shock hazard on the neutral.

[commasense]

@johnpost

you may have had the black wires connected wrong. the line black wire should have voltage on it compared to the white wire. the load black wire should not have voltage on it compared to the white wire.

As I said, the only wires that have voltage between them are the two black lines that are connected to the switch.

[johnpost]

@commasense

As I said, the only wires that have voltage between them are the two black lines that are connected to the switch.

you need to measure voltage between a black wire and a white (neutral wire).

[commasense]

Post #15: “Checking for voltage with my multimeter, I get 120 between the two wires connected to the working switch, and between no other pairs.”

I checked for voltage between every possible pair of wires, and only got voltage between the two black ones.

[johnpost]

if the two older black wires were in a switch loop then you would find a voltage between them if an incandescent bulb was in the fixture. if you removed the bulb then you would find no voltage.

if you don’t find voltage between black wires (some of them) and the white wires (when joined together as a group) then you have a problem (either you have no electricity or a blown/disconnected fuse or a wiring failure or switches turned off further towards the source).

[commasense]

@Mdcastleman

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).

According to the wiring diagram, InlineLinc needs a working neutral, too. If there’s no neutral at the switch, would there be one at the junction box?

[ZenBeam]

@commasense

Post #15: “Checking for voltage with my multimeter, I get 120 between the two wires connected to the working switch, and between no other pairs.”

I checked for voltage between every possible pair of wires, and only got voltage between the two black ones.

It’s possible those other wires simply aren’t hooked up to anything anymore.

As johnpost said, it could be affected by other switches, though. It might be worth checking voltages with other nearby switches in different positions.

[Mdcastle]

Given that the other switch doesn’t appear to do anything, I’m guessing that when whatever it did was changed the neutral was cut somewhere between the switch and the load center, or else disconnected at the load center. This would explain why there is no voltage between either black and the neutrals, and why the switch does not work when connected between the blacks and the neutrals.

If wired correctly there has to be a neutral at the fixture box because the fixture requires a neutral to operate.