Wiring new bathroom vent/light/heat combo

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mappley811

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I'm installing a light/vent/heater combo in a new bathroom, and I'm looking for some guidance on the proper (code-compliant) way to wire it so that each of the three functions is on its own switch. I'm going to install it on a dedicated 20A circuit per the manufacturers instructions, and will be running 12/2 from the panel to the switch box. The way I see it, from there I have basically three options:

1. Run 12/4 from the switch box to the unit, using each of the three hots (red, black, and blue) for each function of the unit. This makes the most sense to me, but I see a lot of talk that /4 wire is intended for 3-phase applications, so I'm not positive if this would be code-compliant.
2. Same as 1, but use 12/2/2. I don't think this is the way to go, because while it's the same wire as 12/4, it's color-coded with a white/red instead of a blue, which I think means it's intended to be used as a second neutral. I think it would not be kosher to use the white/red as a hot.
3. Run 12/3 to the light and vent, and then a separate 12/2 for the heater. I would wire nut the neutrals together in the vent unit's junction box, connect them to the unit's neutral with a pigtail, and connect both neutral to the neutral from the 12/2 in the switch box. Is it legal to have the unit's neutral to be using 2 neutral wires between the unit and switch box?

Thanks for any guidance!

Edit: I don't think it will matter, but I'm in Connecticut and doing the electrical myself under a homeowner's electrical permit.
 

Stuff

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12/4 is the cleanest solution. Yes, it can be used for 3-phase but is used frequently for your situation.
12/2/2 is ok but have to re-identify the white/red as will be hot. Electrical tape or black marker.
12/3 and 12/2 is OK but do not connect the neutrals in the unit, only at the switch. If you look the unit should have separate neutral for heater than fan/switch. Otherwise neutrals are in parallel which isn't allowed.

Side issues: If over a tub/shower then it normally needs GFCI. Also it was once argued that light needs to be on a separate circuit but is inspector's call.
 

WorthFlorida

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As Stuff stated 12/4 is the best way to go. If you already have a light-fan switch combination you can use that for the new fan/light and a new circuit for just the heater. The heater alone may draw 13-15 amps where as the fan and LED light will be less than 1 amp.
 

mappley811

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Thanks guys! I couldn't buy 12/4 at the big box store, so I opted to go the 12/2 and 12/3 route. Stuff you were right, each function has its own neutral. So I'll connect the two hots from the 12/3 to the fan and light respectively, and tie both fan and light neutrals to the 12/3 neutral in the junction box. Then I'll connect the 12/2 to the heater hot and neutral. In the switch box I'll connect both the 12/3 and 12/2 neutrals to the neutral coming from the panel.
 
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