Fan Speed Control & a bathroom fan

[jay80424]

Hello everyone,
I have a quick question, I hope this is the right area.

I have a bathroom vent fan. It's pretty old, and when switched on, runs at a super high and noisy speed.

I installed a 4 speed ceiling an control in the hopes that the speed could be regulated. I figured if the control can regulate a powerul ceiling fan, it should be safe for a bathroom fan.

Heres the deal, it works fine, but when in the lowest setting, does not pass enough power to spin the bathroom fan.

Is this safe, is there any danger of the control or fan motor overheating or anything like that.

Unfortunatelly, I do not know the current draw of the bathroom fan, and it's not marked anywhere, and is probably of the '70 vintage.

Thanks!

 

[tom baker]

Re: Fan Speed Control & a bathroom fan

The bathroom fan motor and the ceiling fan motor are not the same type of motor. The speed control may not be rated to work with the bath fan, check the instructions or call the mfg. Bathroom fans are typically impedance protected so they can overheat even if the rotor is stalled, but the speed control may affect it, don't know for sure.

 

[jay80424]

Re: Fan Speed Control & a bathroom fan

Thanks, I guess I better take that thing out. Any suggestions on how I can regulate the speed? I guess a light dimmer would be a bad idea.

 

[hurk27]

Re: Fan Speed Control & a bathroom fan

Very bad
some motors are not design to have a speed control as this would not allow for the engineered design for cooling of the motor windings. and a shunt field motor is one of them.
You would be replacing the motor real soon as they incorperate a thermal fuse in the winding that when it reaches a set melting point it opens and the motor stops. there is no way to replace them and I don't think the motor would be UL listed afterwards if you could.

If you have ever messed around with an old record player you will notice that they use this same type of motor if it could have been done they would not have used the differant size wheels to change the speed. Instead they had to change the whole design of the played to a DC motor to do this.