Bathroom Heater/Fan/Light/Nightlight Combos - Questions

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JFletcher

Senior Member
Location
Williamsburg, VA
Customer called about installing a Broan QT model fan (4 function) in place of the old 2 function fan (light and fan). I've been looking over the specs for this fan and have a few questions:

1) I know I'll need a dedicated 20A circuit for this model (1500W), and pulling that is no problem. However, the fan needs 4 switchlegs, a neutral, and a ground. Is there anything such as 12/5 NM? Cant seem to find it - would 2 runs of 12/3 work here (would rather not use MC and conduit is out of the question)? I know if I use 2 cables I have to have 2 neutrals instead of 1, and they cannot be joined together.

2) At what CFM range do standard fans switch from 4 to 6" ductwork? Some of the QT series require 6" (not sure which one customer has). Short of going all the way out there or having the HO pull the existing fan for a measure, is there any way to tell beforehand? Also, if the ducting is mismatched, is there any code (NEC, building, or otherwise) compliant way to install a hub/reducer from fan outlet to the existing ducting?

3) On units 1400W total or smaller, if the mfg says to use a 15A circuit, am I stuck with that or may I use a 20A?

4) Provided I pull a new dedicated circuit (20A) to the fan, may I use more than one circuit to power it? Thought being I could use the existing 14/3 to the old fan/light to power the light/nightlight, and use one new 12/3 from a dedicated circuit to power the fan and heater. I could remove the existing fan and light switches and replace them with a timer control for the heater and a 3 function switch, or a 4 function switch if there is a just a single combination switch there. Does anyone see a problem with this?
 

jstjohnz

Member
You could bring the 20A circuit directly to the fixture, then run 2 12-3s to the switch box, hot and 2 switch legs in each.
 

Smart $

Esteemed Member
Location
Ohio
1) What makes you think you'll need a 20A circuit for a 1500W model? Don't know of any 12/5, but assuming existing is 12/3 and reusable, all you'd have to pull is a 12/2. And no, two cables don't require two neutrals... you can re-identify the white of the second.

2) Don't know.

3) Well hopefully mfg don't say it must be on a 15A circuit. Other than mfg limiting you to 15A, you can put it on a 20A circuit.

4) Why would you want to power with more than one circuit if what you pull is dedicated 20A??? If you do use more than one, you'd have to verify the unit has separable neutrals. If not, you'd have to pull essentially a MWBC.
 

JFletcher

Senior Member
Location
Williamsburg, VA
1) What makes you think you'll need a 20A circuit for a 1500W model? Don't know of any 12/5, but assuming existing is 12/3 and reusable, all you'd have to pull is a 12/2. And no, two cables don't require two neutrals... you can re-identify the white of the second.

Mfg specs, and it is a heater (continuous load). 1500W/120V=12.5A. 12.5>80% of 15.

4) Why would you want to power with more than one circuit if what you pull is dedicated 20A??? If you do use more than one, you'd have to verify the unit has separable neutrals. If not, you'd have to pull essentially a MWBC.

Pulling one 12/2 or 3 cable from the existing switchbox to the fan and using the existing wiring would be easier and slightly less expensive for the customer than pulling 2. The HR from the panel to the box has to be done either way. ty for the point about separate neutrals; hadnt considered that.

thx jstjohnz, tho fan boxes are pretty cramped quarters; getting 11 wires in there from 3 cables may not be possible
 

curt swartz

Electrical Contractor - San Jose, CA
Location
San Jose, CA
Occupation
Electrical Contractor
I usually run a 12/3 and 12/2 together through the same clamp into the fan J-box. 12/3 white = neutral, black = fan and red = heater. 12/2 black = light and white re-identified black = night light.

I have never installed any of these units that recommended 15 amp circuits. All of them have required 20 amp circuits. The 1500 watts is just the resistive heater load. You have to add the blower motor, exhaust fan, and lighting loads for the total circuit load of the unit.
 

jstjohnz

Member
But you are splitting the conductors of a single circuit across 2 cables. The 12/2 has 2 hots feeding loads and no neutral.
 

Smart $

Esteemed Member
Location
Ohio
Mfg specs, and it is a heater (continuous load). 1500W/120V=12.5A. 12.5>80% of 15.
Good point about 125%. The unit is fixed space heating and its circuit is required to be considered a continuous load [424.3(B)].

I looked at the web spec's for one model and Broan didn't really rate the unit by overall watts that is saw, but the rated amps was over 13. I was thinking if a unit was rated 1500W it included the lamp wattage. That would put you just under 12.5 and permit rounding down.
 

peter d

Senior Member
Location
New England
I've always wired these with two runs of 12/3. Yes, it is a nightmare to make up in the tiny junction box they give you the unit itself, and it's certainly no fun in the switch box either. Last one I did, I used three 3.5" deep metal old work boxes ganged with a GFCI receptacle and two stack switches for the unit.

In new construction, I would probably go with a piece of flex or ENT to a 4 11/16" box with 2-gang plaster ring.
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
I've always wired these with two runs of 12/3. Yes, it is a nightmare to make up in the tiny junction box they give you the unit itself, and it's certainly no fun in the switch box either. Last one I did, I used three 3.5" deep metal old work boxes ganged with a GFCI receptacle and two stack switches for the unit.
I bet your fingers haven't fully recovered yet.

In new construction, I would probably go with a piece of flex or ENT to a 4 11/16" box with 2-gang plaster ring.
That's what I did the last time I did it 'cept I didn't use a four and eleven box, but I did used stranded wire so it was fine.
 

iwire

Moderator
Staff member
Location
Massachusetts
Because most home owners we ask don't want it

Maybe it's my own OCD but wasting options on any appliance just to make it easier to instal seems like cheating the customer to me. A little extra effort for gives them that option for the life of the fixture. :)


Like Peter I would use flex.
 
Last edited:
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
We use flex and stranded wire. Most likely the switch box isn't big enough so that would get ganged 3 1/2" boxes.

In my mind I see a first floor, center of the house room, with 2x6 floor above joists going the wrong way, 4" duct snaked past x bracing, and "How much will this cost because we have graduation for Susie this coming Friday...":blink:
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Maybe it's my own OCD but wasting options on any appliance just to make it easier to instal seems like cheating the customer to me. A little extra effort for gives them that option for the life of the fixture. :)


Like Peter I would use flex.


If the customer does not want another switch on the wall should I put it there anyway.... Jeepers.. :p

Anyway, I have only installed about 3 of these since the panasonics have come out with the night lights. We are installing fan / heat this week so it has no light- I don't even know if it has a night light but I am betting this guy does not want it. This is a million dollar home and almost every light is surface mounted with a porcelain keyless and a silver crowned bulb. Ridiculous IMO.
 

JFletcher

Senior Member
Location
Williamsburg, VA
We use flex and stranded wire. Most likely the switch box isn't big enough so that would get ganged 3 1/2" boxes.

In my mind I see a first floor, center of the house room, with 2x6 floor above joists going the wrong way, 4" duct snaked past x bracing, and "How much will this cost because we have graduation for Susie this coming Friday...":blink:

The eternal optimist haha! You forgot spray foam insulation, no attic access (or if it does walkboards are nailed down), and the HO watching you like a hawk. Actually it's a master bath first floor, there is attic access, tho joist size and direction are also unknowns at this point.

thx bigjohn for the 300.3(b)(3) ref which goes to 300.20(b). In this case I'm not terribly worried about inductive heating anyway as the second cable would carry all of half an amp and be right next to the other.

Like was mentioned, I suppose I can use a new switchbox that can take smurf pipe and run that to the fan with stranded. I certainly will if we do a new-con that specs one of these heaters, tho we've got one coming up that is $$$$ and just has typical fans spec'd (so far)

Dennis, how are the Panasonics wired internally? the only problem I see with stranded is the possibility of factory Wago connectors which would be cut off and wirenuts used if the case.
 
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