Screwed up wiring?

[Scouter]

I could use some help trying to figure this out. This started because I wanted to install a self-monitoring humidity switch in the bathroom to replace the manual exhaust fan, when I opened up the switch box I got confused as all hell.

There are two switches in the box. The first switch controls the lights in the bathroom, the second controls the fan. Easy, huh?

Pulling out both switches this is what I see:

Switch 1: hot wire comes into the switch; neutral wire goes out of the switch.
Switch 2: hot wire comes into the switch.
Now, here is where it gets confusing: there is a neutral wire that runs from the neutral on switch 1 and goes to the neutral on switch 2.

I'm not sure if there is any way I can install this humidity switch since it has hot, neutral, and one to the fan.

For that matter, I can't understand how the two switches even work as they do.

The house, and the wiring, are 65 years old. Since this was a model home for the plan, so they put everything together fast and cut a lot of corners to show it off. This included, but not limited to, joining two wires together when they ran out of wire to extend the run. The wires were twisted together, lineally, then wrapped with electric tap, no wire nuts, no junction boxes. Then covered with rockwool insulation. Found this out when I was putting new lighting in the kitchen. I replaced all of that, and every other issue I've run across.

[meackerman]

are you sure they just didn't use whatever color wire they wanted instead of using the correct colored wire?

[Scouter]

are you sure they just didn't use whatever color wire they wanted instead of using the correct colored wire?

I metered the black wires, both were hot when checked against the one neutral wire in switch #1.

[TDKPE]

I metered the black wires, both were hot when checked against the one neutral wire in switch #1.

Did you check voltage on the white wire(s) to ground, with the switches off?  They may just be switch legs, with the power in the fan box.  They'll show 120V to the other wire if there's a load connected, which there is.  Your meter is completing the circuit, albeit with a very high impedance link; much too high to actually make any real current pass through.


If so, the white carries the voltage to the switch, and the black wire goes back to the fixture, or fan in this case.  And the white was supposed to be marked with some color other than green to indicate its status as an ungrounded (hot) conductor.  Not needed at the fixture, as it would be clearly connected to the black hot conductor (per older NEC editions - don't know what it says now; please don't make me go looking for it
), but always a good idea.

If that's the case, there is no neutral in the switch box, so you'd need to bring a power cable in.

[barryvabeach]

Scouter,  check out the diagrams here -  https://blog.smartthings.com/how-to/how-...ht-switch/  power into light - power into switch.  If yours is wired power into light,  I agree with TDKPE you may not be able to use the humidity switch.

[daddo]

It can't be wired the way you're explaining it and function. You need to look again and be sure where the wires are actually going. Those white wires are not neutral wires. You are reading resistive voltage through the appliance (light- fan).

Provide a pic.

[srv52761]

Did you check voltage on the white wire(s) to ground, with the switches off?  They may just be switch legs, with the power in the fan box.  They'll show 120V to the other wire if there's a load connected, which there is.  Your meter is completing the circuit, albeit with a very high impedance link; much too high to actually make any real current pass through.


If so, the white carries the voltage to the switch, and the black wire goes back to the fixture, or fan in this case.  And the white was supposed to be marked with some color other than green to indicate its status as an ungrounded (hot) conductor.  Not needed at the fixture, as it would be clearly connected to the black hot conductor (per older NEC editions - don't know what it says now; please don't make me go looking for it
), but always a good idea.

If that's the case, there is no neutral in the switch box, so you'd need to bring a power cable in.

This seems to be it.  Except for not coding the white, this is the way I was taught; if using a two wire assembly for the switch loop the final wire to the fixture was supposed to be black.

Edit: so you have three conductors in the box; two black, one white?  Plus a white jumper from one switch to the other?  
If so, you may have two runs of romex, A and B.  They used the white from A to supply power to the switches, jumping from one to the other.  They cut off the last 6” of the white from B and used it for the jumper, may not even be in the box.  They used the black from each to run power to the fixtures. The neutrals are still in the light fan box.  Bet the white from B is cut off in the fan box also. 

If you look in the box and see even 3/4” of the truncated white, you may be able to pigtail it with a Wago connector, they only need less than 1/2” stripped.    If that is true at the fan, you will have your neutral wire.
You may have to pull the switch box to work on the wire, then use an old work box as a replacement, but it may be easier than running a new circuit.

[Scouter]

Did you check voltage on the white wire(s) to ground, with the switches off?  They may just be switch legs, with the power in the fan box.  They'll show 120V to the other wire if there's a load connected, which there is.  Your meter is completing the circuit, albeit with a very high impedance link; much too high to actually make any real current pass through.


If so, the white carries the voltage to the switch, and the black wire goes back to the fixture, or fan in this case.  And the white was supposed to be marked with some color other than green to indicate its status as an ungrounded (hot) conductor.  Not needed at the fixture, as it would be clearly connected to the black hot conductor (per older NEC editions - don't know what it says now; please don't make me go looking for it
), but always a good idea.

If that's the case, there is no neutral in the switch box, so you'd need to bring a power cable in.

When I checked the voltage all wires were disconnected from the switches. No, I didn't check the white to ground I can do that if you still think it's pertinent.

[Scouter]

It can't be wired the way you're explaining it and function. You need to look again and be sure where the wires are actually going. Those white wires are not neutral wires.  You are reading resistive voltage through the appliance (light- fan).

Provide a pic.

Sadly, I can't check the wires to the fan without busting open the plaster ceiling, there is no other access. They created a drop-box from the ceiling in the tub area, no access to the actual wiring.

[TDKPE]

This seems to be it.  Except for not coding the white, this is the way I was taught; if using a two wire assembly for the switch loop the final wire to the fixture was supposed to be black.

I knew someone would poke me into looking it up. 


NEC 1990

200-7. Use of White or Natural Gray Color.  A continuous white or natural gray covering on a conductor or a termination marking of white or natural gray color shall be used only for the grounded conductor.* 

Exception No. 1: An insulated conductor with a white or natural gray finish shall be permitted as an ungrounded conductor where permanently reidentified to indicate its use, by painting or other effective means at its termination, and at each location where the conductor is visible and accessible.

Exception No. 2: A cable containing an insulated conductor with a white or natural gray outer finish shall be permitted for single-pole, 3-way, or 4--way switch loops where the white or natural gray conductor is used for the supply to the switch, but not as a return conductor from the switch to the switched outlet.**  In these applications, reidentification of the white or natural gray conductor shall not be required.  [emphasis added]

So it wasn't necessarily a code violation to not mark the white conductor if it was done some decades ago, assuming it is a switch leg, and further assuming the white is the ungrounded conductor from the outlet.  Lotta iffy stuff in the older code books ha ha.  

By the 1999 code cycle, that permission was removed.  I don't have any book in between, so I don't know when exactly it was removed, but there's an edit bar next to that paragraph in the '99, so that may have been when it was revised out.  The 1996 NEC was unchanged, so starting in 1999 it was disallowed.  It now specifically calls for reidentifying the white or gray conductor on switch legs in similar fashion to Exception 1, and switch locations are required to have both power and neutral for timers, dimmers, and other such controls.

*In NEC-speak, for anyone unfamiliar, "grounded conductor" means "neutral" conductor, and is not limited to the common residential split-phase systems.  Not to be confused with the "equipment grounding conductor", aka "safety ground", or just "ground".
**In NEC-speak, an "outlet", again for anyone unfamiliar, can be a receptacle outlet, or a lighting or appliance outlet, such as a permanent light fixture.  Or a bathroom fan.  Any point on the wiring system at which current is taken to supply utilization equipment.

Edit:  Found my '96 NEC, so edited above to reflect that.