No power to wire?

Question

I'm removing an old bathroom fan/light/heater combo unit and replacing it with a new one. There are two sets of wiring coming in the box, one from each side. It's the same setup as the old one.

Here's the problem. The wiring worked fine on the old box. Now when I hook up the new box, the side that controls the heater is fine, but I'm not getting juice on the side that controls the fan and light. I confirmed the fan and light both work. One catch - I have the white hooked to white, and black to black, but there is a blue wire "left over" coming from one of the plugs in the box. It says attach it to a red wire, but there is no red wire in the romex set.

I don't know if the blue wire is the key, but it seems like I'm not getting juice in that romex set of wires. This is odd, because nothing has changed. The circuit breakers are fine.

Help!!

(the brand is Broan)

RBM · Accepted Answer

For a fan-light-heat unit to work you'll need three hot wires from the switch and one neutral. It appears that you don't have a four conductor cable which would have white red black and blue wires, but instead you have two two wire cables, so you've got two whites and two blacks. One of those whites is the neutral and the other is the hot from the switch that goes to the blue wire in the unit.

Joseph Meehan · Answer

Another example of why you should mark both ends of the wires when you do this kind of wiring.

mm · Answer

Did your previous setup allow you to turn on each of those three things separately? Or did two of them work together? The latter, right? If the former see **.

I think the instructions for the new one are meant to allow all 3 to work separately.

**I"m sleepy. If the former, post again. :)

buffalobill · Answer

just buy an inexpensive multimeter. measure AC wire to wire with thevarious timers or switches on and off.

Airkings · Answer

I have 5 total wires coming in:From the one side: white, black, ground.Other side: white, blackThe catch is that the unit worked before (it's the same style of unit) with 3 switches - one for each function!Why can't I replicate what worked fine before??Dave

Doug Miller · Answer

Because, as RBM said, one of those white wires is the neutral, and the other one is a [switched] hot leg for one of the three functions. You'll need a voltmeter or circuit tester to tell which is which.

With all wires disconnected from everything, and carefully separated so they are not touching each other or anything else, turn the circuit breaker on. Test for current between black and white on each of the two cables. When you find it, you've got the hot and neutral. (Start by testing the side that has the ground wire -- that's probably the right one.)

Mark Lloyd · Answer

ALL the 120V & 240V wiring in my house is like that (12/2 romex). The wire between 2 3-way switches uses black & white. So does the 240V wiring. None of it is labeled. I guess the builder (I don't know, I didn't buy the house new) used what was cheaper.

Joseph Meehan · Answer

What you appear to be describing is different than what I assumed to be the case above. If I understand your comments correctly, it is acceptable, however three-ways using a neutral again should be marked. Tape or paint.

Anyone who has worked on old work very long has a healthy respect for the fact that not everyone does what they should.

jimmiedee · Answer

Replaced my old trutones recntly with Broan ran into basically the same problem. Unit was controlled by 3 switches on the wall. Light , fan, heat. Everthing was black and white coming out of the wall there were thre cables. All the whites turned out to be neutrals with each black wire hot. In your case with 2 cables I would guess that one white is neutral and the other is a hot wire. USe a meter and carfully turn on one switch at a time measuring to ground to see whats what. Neutral should be white wire with no voltage to ground on it no mater which switch is on.

No power to wire?

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