Nutone 744NT Bath Exhaust Fan

[GerryC]

Anyone out there ever experience a Nutone 744NT (combo exhaust Fan and recessed light fixture) tripping a GFIC circuit breaker after a prolonged hot shower,]. After a couple of hours the circuit can be re set. This not a new installation it has been in for a couple of years, just started happening. Any ideas???

 

[kwired]

Megger is probably your friend to figure this one out.

 

[LarryFine]

Sounds lie excessive condensation. Can you insulate the housing?

 

[hillbilly1]

Could be a stuck damper, allowing cold air to flow back.

 

[kwired]

Could be a stuck damper, allowing cold air to flow back.

Presuming the fan is running when this happens, air should not be flowing back.

Sounds lie excessive condensation. Can you insulate the housing?

Would need to be very excessive and would probably also result in water dripping from the unit. Motor should create enough of it's own heat it is not condensing within the motor itself and windings should be insulated well enough to take a little bit of water dripping on them occasionally. Constant wetness of windings however can result in enough insulation breakdown or even for capacitive leakage current to be an issue, but that has to be pretty severe I would think. Seen this on a spa pump motor once where a fitting in lines had failed seal and was dripping right onto pump motor. Was tripping GFCI. Wasn't sure if it would work or if motor was done, but cleaned it up (inside and out) and let it dry thoroughly for a few days and it been fine for few years since then.

 

[retirede]

Bath fans are designed to exhaust air that’s virtually saturated with moisture. I suspect the insulation is starting to fail and you’ll need to replace it.

 

[kwired]

Bath fans are designed to exhaust air that’s virtually saturated with moisture. I suspect the insulation is starting to fail and you’ll need to replace it.

The "better quality" fans the motor isn't directly in the air stream. And unless there is condensing conditions they won't be subject to much moisture anyway. The motor will heat up enough during operation that it shouldn't promote condensation in/on it.

 

[ptonsparky]

The night light in my Panasonic started to stay on very dim. You could only see it at night. It was designed with incandescent, but I replaced It with LED some years ago. There was enough tracking from moisture/dust that it would glow dimly. Cleaned the tracks out and all is fine. Point being, if mine had been GFCId it would have tripped.

 

[Little Bill]

The night light in my Panasonic started to stay on very dim. You could only see it at night

Hence the name!

 

[ptonsparky]

Hence the name!

Ok. I deserved that.

 

[garbo]

Anyone out there ever experience a Nutone 744NT (combo exhaust Fan and recessed light fixture) tripping a GFIC circuit breaker after a prolonged hot shower,]. After a couple of hours the circuit can be re set. This not a new installation it has been in for a couple of years, just started happening. Any ideas???

Had trouble with a Nutone exhaust fan that had regular lite, night lite and a heater tripping GFCI feed thru device that was only 10' away. Would trip GFCI if you just turned on the fan. If lite was turned on first then paused a second to turn fan on no problem. I replaced it with exact model and even replaced the GFCI device and would still trip. Did not bother customer to turn lite on first so never did find out why it tripped. Even ran a temporary wire from GFCI to fan box but it still tripped proving wire was not the problem. Once fan was on you could turn off lite and GFCI would not trip. Talked to an electronic brain and he was going to make up something to hopefully correct the problem.

 

[kwired]

Had trouble with a Nutone exhaust fan that had regular lite, night lite and a heater tripping GFCI feed thru device that was only 10' away. Would trip GFCI if you just turned on the fan. If lite was turned on first then paused a second to turn fan on no problem. I replaced it with exact model and even replaced the GFCI device and would still trip. Did not bother customer to turn lite on first so never did find out why it tripped. Even ran a temporary wire from GFCI to fan box but it still tripped proving wire was not the problem. Once fan was on you could turn off lite and GFCI would not trip. Talked to an electronic brain and he was going to make up something to hopefully correct the problem.

Sounds like inductive kickback is likely causing the trip. When the light is in the circuit it absorbs enough the kickback to not effect the GFCI.

A filter to help with this is nothing more than a resistor and capacitor network across the inductive load, you have same thing with an incandescent lamp less the capacitor.

 

[ptonsparky]

Sounds like inductive kickback is likely causing the trip. When the light is in the circuit it absorbs enough the kickback to not effect the GFCI.

A filter to help with this is nothing more than a resistor and capacitor network across the inductive load, you have same thing with an incandescent lamp less the capacitor.

I've suggested the solution frequently. Worked for me.