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I have 3 cables coming in from the ceiling, with one being the supply. At the switch box I have 2 cables with neither being hot. In the switch box I have a black/white and another set being black/white/color.
How do I wire in the connection at the fixture in order to have my 3 switches work for each individual function? Which one do I need to wire to be my common? My switch has a common and 3 terminals on the other side.
If you were using separate switches:
Use the two wire cable to switch device #1. Use the white as the hot and mark it with black tape or marker. Use the black as the switched feed back to the ceiling box.
Use the three wire cable to power the other two devices. Use the white as the hot and mark it with black tape or marker. Use the black as the return switched hot for device #2 and the red as the return for device #3.
At the ceiling box, attach the incoming hot to the two white wires going to the switch box. Mark both of those whites with black tape or marker. Attach black and red wires from the switches to their respective devices.
Also in the ceiling box, attach the white (neutral) from the feed cable to the white on each device.
Attach all ground wires (green or bare) to all other grounds in each box.
If you re using one switch with a common hot:
Mark both white wires in the switch box with black tape or marker. Attach them together with a pigtail (a short length of wire). Attach the pigtail to the common terminal on the switch. Use the black wire from the two wire cable to one of the three other terminals. This will switch device #1.
Use the black from three wire cable as the return switched hot for device #2 and the red as the return for device #3.
At the ceiling box, attach the incoming hot to the two white wires going to the switch box. Mark both of those whites with black tape or marker. Attach black and red wires from the switches to their respective devices.
Also in the ceiling box, attach the white (neutral) from the feed cable to the white on each device.
Attach all ground wires (green or bare) to all other grounds in each box.
[Note: This may seem a bit strange since you are running parallel hot wires and attaching them to each other at both ends of the run. This is done to comply with the rule that a circuit must be complete within each cable, to avoid possible induction heating.]
When you say "black/white/color" you probably mean a 14/3 cable with black/white/red. The "common" you are referring to, will be a hot wire (supply wire) from the fan junction box to the switch.
Use the black/white cable for power (black) and neutral (white) from the power supply to the switch location. The neutral you can cap off and leave in the box for future use. (Or use it if your switch requires a neutral.)
Use the 3 conductor cable for return power back to your fan/heater/light combo. You choose which color to connect to which function. However, you should re-identify the white as blue in this case. It is a switched wire and is not a neutral and therefore should not be left white.
Connect the fan neutral (white) to the supply neutral at the fan box.
Good luck!
