Rewiring a Vent/Heat/Light unit in bathroom

I'm in the process of replacing an existing Vent/Heat/Light unit in my bathroom. The old wiring setup on this system seems odd to me.
The previous installer is running three Romex wires to the unit. There is a two gang switch controlling (with one double switch).     One wire holds the Neutral and ground (other wire is clipped), coming from source junction box.     Another wire is holding two feeds from the switch (the ground is clipped).     The last wire is holding one feed from the switch (the other wires are clipped).
Here is my question:     Due to new location of the new unit, and existing cable size, I need to extend the two feed Romex cables coming from the switch. Hence, I need a junction box to extend the lines. The issue is, if I use a metal box then shouldnt those wires be grounded to the box? Normally, I would say yes ground the wires to the box. However, the previous installer cut the grounds on those cables so what value would there be in grounding them? Another solution is to use a plastic junction box (which is legal in my town), to avoid the grounding issue.
Any thoughts?
Thanks, Raj
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On Apr 22, 1:12pm, snipped-for-privacy@gmail.com wrote:

re: "The old wiring setup on this system seems odd to me."
Is it possible to eliminate the existing (and bizarre) wiring and do it correctly?
I would seem to me that this is the perfect time to correct a bad wiring installation instead of simply extending it.
WWALED? (What would a licensed electrician do?)
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wrote:

re: "The old wiring setup on this system seems odd to me."
Is it possible to eliminate the existing (and bizarre) wiring and do it correctly?
I would seem to me that this is the perfect time to correct a bad wiring installation instead of simply extending it.
WWALED? (What would a licensed electrician do?)
This electrician would run a 12/4 Romex, and if the unit had four functions, light-heat-fan- night light, I would run 1/2 inch greenfield with a ground, neutral, and four hots
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Sorry for the ignorance... here are some questions: 1) "1/2 inch greenfield" is a type of conduit? 2) This unit does have four functions, for the "ground and neutral", would you use a 12/2 and clip the other wire? Would this also mean the 12/4 would have its ground clipped?
Raj
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snipped-for-privacy@gmail.com wrote:

yes. think BX without the wires in it. You pull individual conductors of THHN through it.

No it doesn't, he's talking about how many hots you need. you have three functions, plus you need a neutral and ground.

No. read my earlier post - you need to get rid of all that's existing and pull new cable. I guess RBM has actually seen 12/4, I haven't but I haven't looked nor had a need for it. The whole point is, you need your currents to sum to zero within every single cable assembly, and that's not currently happening with what you have. The reason for this is to minimize inductive heating of the wires.
Like I said before, if you have one of the functions where you can isolate the neutral you can pull one 12/2 and one 12/3 and make it work. If you can't, you need to either pull a 12/4 if such is available or else go with greenfield, EMT or something like that - which will likely involve painting and patching at some point.
good luck
nate
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Thanks Nate, RBM, and DerbyDad.
The fog is finally lifting. After sitting down and drawing the solution with pen and paper I understand everyones suggestions. (BTW Nate, the new unit does have four functions: Vent/Heat/Light and Night- Light).
What I also understand now is what the original installer did and why he did it. Basically, he wanted to keep the actual wire count down in the switch box. Hence, instead of taking a Neutral from one of 12/2 wires going from the switch to the unit, he ran a separate Neutral wire directly to the unit from the source junction.
This approach might seem silly, but considering the shallowness of the wall, he wasnt able to put in a 2 gang deep box.
The one thing I do NOT like about his approach, was to keep the grounding to only one wire (i.e. only one of the 12/2 wires going to the unit is grounded, the other ground wire is cut). Theoretically, the unit is grounded, but I agree with Nates remark, all the grounds should be connected.
Raj
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On Apr 22, 10:59pm, snipped-for-privacy@gmail.com wrote:

Only one ground wire is perfectly fine - you have a 20A circuit, therefore if there is current to ground of over 20A the breaker will trip. A single 12AWG conductor is sufficient to carry a 20A load. Now if you have more than one ground, there's absolutely nothing wrong with connecting them all together, just provides redundant paths.
What *isn't* fine is the multiple cables. think about it like this, you'll have a single neutral going to the ceiling unit, but multiple "hot" wires for different functions. The current in the neutral wire will be the sum of all the currents in the "hot" wires, but in the opposite direction. Code requires that the currents sum to zero in every single cable assembly. otherwise you can get induced currents and resultant heating, which isn't good. In practice this is probably insignificant, but "probably" is not a good thing to rely on, and it's against code.
it sounds like you may want to replace your wall switch box with a three or four gang old work box to give you some more wiring space, and either run some greenfield as RBM suggested, or else pull two 12/3wgs and split the neutrals apart at the device - e.g. run the light and night light, say, off one cable and and have the neutrals for those functions connected to the neutral in that cable, and then have the fan and heater on another cable, with the neutrals for those functions connected to the neutral in the second cable.
If you're replacing your wall box, you may want to consider adding a GFCI outlet as well if the switches are near your sink. This is also required by current code and is awful handy for hair dryers, electric razors, etc.
Another thing you may want to think about while you're doing all these mods is running the vent fan off of a timer switch rather than a regular toggle switch, that way you can set it to run on for 15 min. or whatever after you get out of the shower and you don't have to remember to turn it off later (or have to turn it off earlier than you'd otherwise want to if you shower and then immediately leave the house for the day.)
I'd consider using all Decora devices in this instance as that will allow you more flexibility in mixing and matching stuff, and two- and three-switch devices are available in Decora format as well if necessary.
good luck,
nate
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One last thought - if the new location of the fan is above the shower, you should connect the feed for the switches controlling all this stuff from the "load" terminals of the GFCI recep unless you have a GFCI breaker in your panel. If you do have a GFCI breaker and still want to add a recep you can just use a regular one, there would be no point in using a GFCI on a circuit that's already protected.
nate
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wrote:

One last thought - if the new location of the fan is above the shower, you should connect the feed for the switches controlling all this stuff from the "load" terminals of the GFCI recep unless you have a GFCI breaker in your panel. If you do have a GFCI breaker and still want to add a recep you can just use a regular one, there would be no point in using a GFCI on a circuit that's already protected.
nate
These units, having a 1.5 kw heating alone, require a dedicated 20 amp circuit. If it's located over the tub or shower, it is required to be gfci protected, but can't be on the same circuit as the required gfci outlet for the hair dryer
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RBM wrote:

You'd know better than I; I've never installed one. Just the usual fan-only deals, with a separate light on the wall.
nate
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But Nate, there's only one source feed to the unit anyway... so wouldn't it still sum to zero?
Currently, the switch box is geting power from one junction box, and I need to split that line (in the switch box) into the four feeds of the four switches.
Thanks again for all you help, Raj
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On Apr 23, 2:31pm, snipped-for-privacy@gmail.com wrote:

yes, over *all* the cables. but if you have, say, only the light turned on and its feed is in one cable and the neutral is in another, the individual cables no longer sum to zero.
nate

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On Apr 22, 1:12pm, snipped-for-privacy@gmail.com wrote:

The whole thing is incorrect, you should be running one cable from the switch box to the unit. Since that is not possible given that you have three different functions in the unit (unless someone makes a 12/4wg cable?) that is, vent, heat, and light, do any of these functions have their own neutral? If that is the case then you should run a separate cable for the light, say, as a 12/2 w/ground, and then another cable 12/3 w/ground for the vent and heat. Neutrals should be connected to each other at the switch box but NOT in the v/h/l unit. this way the currents in each cable will sum to zero in the absence of a ground fault. All grounds should be connected together and to the box at all locations.
You will have to run new wire from the switch box to the new location to be code compliant.
good luck
nate
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What N8N describes is essentially what I did, except that there are 2 additional lights in the bathroom.
There are 3 switches on the wall - one vertical, the other 2 horizontal.
The vertical switch is wired to control the light in the heat/vent unit as well as the 2 other recessed lights via 14/2wg romex. (The lights are on the load side of the GFCI outlet since one recessed fixture is above the shower stall.)
The horizontal switches control the heat or vent via 14/3wg.
The top horizontal switch controls the vent, because the vent pulls air up, the lower horizontal switch controls the heat because the heat blows down.
Anal? Did I hear someone say anal?
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I mentioned 12/2 and 12/3 because I was assuming a dedicated 20A circuit for the bathroom.
yes, I'm still planning exactly how I'm going to rewire mine.
nate
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Ya know...it's been so long and I'm not home now, but it very possible that everything I said about 14/2 and 14/3 should be 12/2 and 12/3. Either that or I ganged two 15A breakers and ran 2 circuits. I remember how I wired it, now you've got me wondering what I wired it with!
Da*m, now I gotta go home and check.
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