Welcome all. I have a question about a 1960 vintage heat/vent light combo unit. I describe the switch as hot/black-- in neutral/white into switch box. 3 switches and a pilot lite here. 2 whites leave switch box 1 with black reidentifing it a current carrying conductor, 2 black wires leave switch box as current carrying conductors. all 4 of these wires go to 2 receptacles in the fan compartment. 1 black and one white on each receptacle. lite switch turns on lite, fan switch make fan blow out, heat switch make fan blow in and heat come and pilot lite come on. I can see this working on a newer style unit with 2 fans with 1 neutral and 3 hots and 3 receptacles . Thats easy to do. But the theory behind having 1 neutral and 3 hots cause the single fan motor to reverse have me wondering. I replaced this unit at house today And haven't seen this wiring set up before. A friend said maybe a shaded pole motor might be reversed to make this work. I have done new house wiring and much industrial wiring for over 20 years but this is the first time I've seen this setup. thanks Gary
This is about the only way I think they could have done it as you described with 3 hots and a neutral. Do you know if there is a capacitor in the fan unit? I have never seen a setup wired this way but it could probably be done. Joe
Is there a relay in the fan compartment? Seems like a pretty trivial job for a 3P2T relay. "Fan Out" on NC / "fan in" NO with the heat switch powering the coil; with the neutral on the third pole as double-throw.
Joe: in your diagram, the fan switch does nothing, and the fan comes on with the light?
I have an old fan light like that. There are two SPDT center off switches controlling it. One is the fan/heat, the other is light/nightlight. It seems to be wired like Joe's picture if you put SPDT switches in there. The cable is 4 hots and a neutral. The 4th going to the candelabra base nightlight.
OK, I will try attaching it one more time with a wider line width before conversion.
Steve, The fan switch would do nothing if you have selected heat. If not, it flips the windings that get the direct and phase shifted voltage, switching direction. Obviously, the motor windings, capacitor selection and effects of the parallel heating element would all be design considerations. Again, I've never seen it but think it can be done. You might get some heat out of a scheme like this when on fan but minimal compared to directly driving the heating element. Depending on the pilot light, it might illuminate this way. Better to make the "HEAT" switch DPDT and drive the pilot lamp from the 2nd pole. Joe
Greg, Your unit makes much more sense than the OP's with 3 switches. The 4th hot on yours accounts for the night light. Yours has to go through off to switch direction while his would jam the motor switching HEAT on & off with FAN on. Does the pilot on yours light dimly on FAN? I think yours would be more cost effective with 2, SPDT- Center off switches than my drawing with 3, SPDTs or 1 SPDT & 2 SPSTs. I just drew it to match the way he described it. Joe