Most of the heat-fan-light combos I have installed also have a nite lite so they are 4 function. They are mostlyNutone brand and come with switches that are back stab only-no screw terminals. I never use the supplied switches. As for wiring them, using 12-2 and 12-3 NM cables can get real crowded and you end up with an extra conductor or two. If it's new construction I like to use 4 steel boxes ganged together for the switch box. I feed 2 circuits to the switch box, one for the heater and one for the fan and lights. I then like to come out of the switch box and go up with 1/2" EMT to a 4x4x2-1/8" j-box on top of the plate. I then go the rest of the way(usually less than 3') with 1/2" flex to the fan/heater/light. I pull 2 #12 neutrals, one for the heater circuit and one for the fan & lights, one #12 ungrounded conductor for each function and a #12 green all THHN. This may seem like a lot of trouble but it makes for a more managable situation in the small wiring space the fan/heat/light provides and avoids extra conductors or re-identifying conductors like when using a combination of NM cables.
Redsy, Our local inspector insists you can't use it in lengths exceeding 6'. I've argued this with him and it's just easier to do the EMT thing and keep the flex short. You can read him 350-10(a) until you're hoarse and he just doesn't get it.
Yeah, Inefficient and expensive... about $80 for the cheapest ones...
I use 14-3-G NMB Cable for vent and light and use a 12-2-G NMB Cable on a dedicated circuit for the heater. I recommend a timer/switch for the heater to reduce the chance of an outrageous electric bill.
-Virgil Residential/Commercial Inspector 5 Star Inspections Member IAEI
The importnat thing, in my opinion, is to ignore any manufacturers instructions that have you running the grounded conductor for any load in a different cable from the the ungrounded conductor.
In interior windowless bath rooms I offer the owner a three way switch wired to turn on the night light or the main light depending on it's position. Iknow that a constantly lit night light does use some electricity but some home owners want that feature. -- Tom
"This alternating current stuff is just a fad. It is much too dangerous for general use" Thomas Alva Edison
That's the subject I was waiting to come up. I've seen these things wired a number of ways and most are not correct. I just saw an installation yesterday that pulled a neutral from some other location just to make it work. (3 wire and a 1 wire cable)
I was waiting to hear how you'd get so many #12s in there, because I've heard you say that's all you use. (you surprised me with the 14/3)