Background: I have a 12/3 wire coming up from the circuit panel in the basement to the attic that was wired when the house was built (~1971). The two live wires are connected to separate 20 amp circuit breakers in the panel box. Each of the live wires are connected to separate load (1 is connected to an attic fan and 1 is connected to an AC air handler) - I think the attic fan draws about 6-7 amps and the air handler draws about 14 amps, and both are connected to the white wire in the 12/3 BX.Q: Is this ok? Specifically, if the sum of electricity from the 2 load wires is greater than 20 amps, is it ok for the white wire going back to the circuit panel, e.g. will that get dangerously hot/is it against code? (This is in NY State)
The AC air handler is supposed to be on a dedicated circuit. Same thing with the compressor. It sounds as if someone wired in this fan afterwards not knowing what they were doing. I would disconnect the fan from the AC circuit, and bring up another 14/2 15 amp line for the fan.
The nuetral -white-is not a load carrier.It's presence is to keep the 60 hz cycle present. The black and red supliers are mere conductors to the load, wich consumes all of the amperage. Yes- the neutral will take on a load level, if the prescribed load directly shorts. The extra bare ground connections are designed to sweep this dangerious excess ,away quickly. If you study your breaker-box, you will see that the grounds and the neutrals are connected at the exact same place. The both terminate to the ground,pipe,s connections. As does the 3'rd , bare wire connection, into your weatherhead mast.
If what you say is true, then things are wired wrong. It sounds like some one took a 220V circuit which would consist of three wires (one to neutral, one to one leg of the 220 and the other to the other leg). Using a tiny bit of knowledge, they made two 110 volt circuits that share a neutral. The neutral is carrying BOTH loads and is not really protected from over-current. c says, oddly enough, on AC loads that share a neutral the amperage cancels each other out, so if there is 10A on one hot leg and 14A on the other and they share the neutral than the neutral will be carrying 4A, not 24A. Not if both breakers are on the same leg. In this case the amperage would be additive. In other words, if each appliance was drawing 16 amps, neither breaker would trip, but there would be 32 amps carried by the 12 ga. neutral which would cause it to overheat and possibly start a fire. Catastrophic problems usually require several links in a chain to occur. Wiring you described could conceivably over-load the circuit or catch an electrician off-guard and harm him. I'm inclined to get stuff like that corrected. In all likelyhood, they ARE on opposite sides since it was probably a converted 220 v circuit. You'll have to visually trace the wiring and buss bars in the breaker box to determine this. Once you've found a bit of 'creativiy' with respect to the wiring though, you can't assume too much about the rest.
