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Old 07-24-2008, 01:10 PM   #1
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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.

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Old 07-24-2008, 02:48 PM   #2
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Attic Fan Question


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.

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Old 07-24-2008, 03:17 PM   #3
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Attic Fan Question


Quote:
Originally Posted by clauff View Post
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.].
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Old 07-25-2008, 08:56 AM   #4
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Attic Fan Question


They make attic exhaust fan thermostats for this application.
When it cools down to a selected temperature it shuts off.
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Old 07-25-2008, 11:19 AM   #5
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Attic Fan Question


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Originally Posted by hpp58 View Post
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.
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Old 07-25-2008, 11:21 AM   #6
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Attic Fan Question


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Originally Posted by Yoyizit View Post

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.
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Old 07-25-2008, 05:25 PM   #7
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Attic Fan Question


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Originally Posted by J. V. View Post
No disrespect meant, but you are an odd fellow.
No disrespect taken. I think.


Last edited by Yoyizit; 07-25-2008 at 06:10 PM.
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