ground and and neutral bonding for parallel 14/3 romex runs
I have a bathroom fan with multiple loads built in (nightlight, fan, 60w light, and humidistat). It's configured to use a single 14/2 feeder that utilized state changes at the switch to power the fan/humidistat on and off right now. The nightlight is currently unpowered.
Alternately, the ability exists to have each light and the fan/humidistat controlled separately, but it would require more conductors (basically a pair of 14/3s or a 14/2 and a 14/3). The schematic in the instructions covers the switched conductors, but it shows all the neutral and ground conductors simply "running into each other" as a junction. I know that electrically, the whole system should have all the neutrals and grounds bonded, but I don't know if it's proper to do it at the fixture, the switch box, both, or simply only use one conductor for ground and one for neutral in the pair of wires. The parallel romex runs to and from the same place would allow for any combination.