How did it work?

[nizak]

I was recently called to a job for a bath remodel. I found K+T spliced to 2 wire romex in the wall that led to a single pole switch, hot and neutral were landed on respective screws. This switch was in an adjacent room and controlled a recep above the ceiling that a florescent shop light was plugged into. There was only the one romex in the switch box, the power coming from the wall splice. At the recep in the ceiling was K+T with the hot and neutral landed on respective screws. I only know that when I got there the fixture was working and I could turn it on and off with the switch. I put a meter on the 2 wire romex that was leading to the switch(traveled thru finished wall about 6 ft)and confirmed it was the line going to the switch.I made the proper repairs to the bathroom and deleted the K+T that was in there, but can't figure out how the switch ever worked. Seems that when the switch would be turned on it would ground out immediatetly to the neutral conductor. Any Thoughts?

 

[LarryFine]

Not every white wire is a grounded conductor; sometimes it's just a white wire.

Picture a wall switch next to the door to a room, wired to control a light. The supply and load cables both enter the box. Whites tied together, two blacks on the switch. Got it so far? Okay.

Now, let's say that, for whatever reason, the homeowner wants to relocate the door to the other side of the room, and wants the convenience of the switch being next to the new door.

You now have to extend the two black wires attached to the existing switch. The easiest way is to run a new 2-conductor cable from the existing switch box to the new one, a black and a white.

Obviously, one of the two wires in the new cable will be white, but it won't be a grounded conductor, will it? No, because you're going to connect it to the old incoming black wire, the hot.

Then, you'll connect the new black wire to the outgoing old black wire that feeds the load. So, the switch still effectively connects the two old blacks together, just through an extension.

This is what we usually refer to as a switch loop. The white is the hot and the black is the load so the load won't be supplied by two white wires, if the load happens to be in that box.

So, it's just two wires, one white and one black. Whether it's hot, grounded, or switched depends on what we connect it to.

 

[Charlie Bob]

back in the day of K&T they used to switch the neutral.Ran into this several times.
I don't know if that is your case.Sorry if i misunderstood your post.

 

[al hildenbrand]

Yeah, Charlie Bob, I agree.

Nizak, you've experienced a K&T switched neutral.

With the light fixture connected, and the switch off, the "switched leg" between the light and the switch rises of line voltage.

The other side of the switch IS the neutral.

When the switch is on, the switched leg extends the neutral to the light, all the voltage drop happens, then, on the load, the light itself, and the light goes on.

 

[LarryFine]

I didn't get the impression that the question was about whether the hot or grounded conductor was the one being switched, only that he wondered how a single cable could be used on a switch, and why connecting the white and black through the switch didn't cause a short.

I could be wrong. Hey, it could happen.

 

[nizak]

Yes, how can you open the switch with a known hot and grounded conductor connected to it and not create a fault? Even if the CB doesn't open, there has to be some point where this would at the very least heat up the wire to the point of breakdown.

 

[Power Tech]

Yes, how can you open the switch with a known hot and grounded conductor connected to it and not create a fault? Even if the CB doesn't open, there has to be some point where this would at the very least heat up the wire to the point of breakdown.

Are you sure it is a neutral?

Could it be you are reading (lamp load) it as a neutral through the filament.

If you remove the lamp do you still get a neutral reading.

I know an open neutral will read the same also.

It doesn't sound like what has been coined as the farmers 3 way. 3 way with only 2 wires by switching the neutral.

 

[LarryFine]

Yes, how can you open the switch with a known hot and grounded conductor connected to it and not create a fault?

Read my first response again. The answer is that, while it may be a white wire, it's not a grounded conductor.

Closing the switch is not creating a short circuit, it's merely closing a circuit.