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-   -   Attic Fan Question (http://www.diychatroom.com/f18/attic-fan-question-24206/)

clauff 07-24-2008 12:10 PM

Attic Fan Question
 
I am a first-timer, and I appreciate being able to ask a question. I have a single speed, 30" attic fan that I use to exit the warm air from the house. I would like to be able to slow it down once the house has cooled off, and am wondering if it can be done with this type fan with a rheostat, and if so, what type. I cannot imagine that a typical dimmer switch would be heavy enough. Thank you.

clauff

williswires 07-24-2008 01:48 PM

I personnally have a two-speed 30" belt drive whole house fan installed in my bilevel home. I also have the automatic shutters on the living side of the opening which open as the air is drawn into the fan.

I can say that I never run it on low speed because so much of the fan's power is needed just to "pull" the shutters open while running. While on low speed, there's not much air flow because of that. (I noticed the difference when I installed my fan and tested it for a couple of days before installing the shutters. Wow, the automatic really drops the air flow)

Now, if I had the manual shutters I would be inclined to use the low speed.

Yoyizit 07-24-2008 02:17 PM

Quote:

Originally Posted by clauff (Post 142625)
with a rheostat, and if so, what type.



Some motors require a stiff (low impedance) voltage source and if this is the case for your motor in this application, using a rheostat or a 200w bulb in series with the motor would be out.

A Variac, or a 1:1, 120v transformer [capable of handling the power] with multiple taps on the secondary, probably will not damage the motor but to be sure you should e-mail the manu (look on the nameplate) or call and ask to speak to an application engineer. There's a 50-50 chance that they answer you[fear of lawsuits, etc.].

hpp58 07-25-2008 07:56 AM

They make attic exhaust fan thermostats for this application.
When it cools down to a selected temperature it shuts off.

J. V. 07-25-2008 10:19 AM

Quote:

Originally Posted by hpp58 (Post 142865)
They make attic exhaust fan thermostats for this application.
When it cools down to a selected temperature it shuts off.

I agree. We don't need to complicate matters. :thumbsup:

J. V. 07-25-2008 10:21 AM

Quote:

Originally Posted by Yoyizit (Post 142658)

Some motors require a stiff (low impedance) voltage source and if this is the case for your motor in this application, using a rheostat or a 200w bulb in series with the motor would be out.

A Variac, or a 1:1, 120v transformer [capable of handling the power] with multiple taps on the secondary, probably will not damage the motor but to be sure you should e-mail the manu (look on the nameplate) or call and ask to speak to an application engineer. There's a 50-50 chance that they answer you[fear of lawsuits, etc.].

No disrespect meant, but you are an odd fellow.

Yoyizit 07-25-2008 04:25 PM

Quote:

Originally Posted by J. V. (Post 142907)
No disrespect meant, but you are an odd fellow.

No disrespect taken. I think.


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