Whole House Fan Speed Control?

Old 06-12-13, 09:56 AM
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Question Whole House Fan Speed Control?

My house currently has a whole house fan with a on/off switch. I would like to get some form of speed control. It is a direct drive motor system.

The details from the motor are: A.O.Smith, Model F48G72A64, RPM 1050, Rotation CCWLE, Amp 3.4, 60 Hz, SF 1.0, FR 48Y, PH 1, Cap 5.

Is there a way to do this?

Old 06-12-13, 11:04 AM
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There are a couple of possibilities. There are fan controllers that look just like a rotary knob lamp dimmer but with slightly different electronics that sometimes (not all that often) can be successfully used. They cost around fifteen dollars. The biggest problem is that at lower speeds they cause the motor to growl and the slower you go the louder the growl. They are also prone to causing the motor to overheat which will at the very least cause it to have a shorter lifespan.

Then there are variable frequency motor "drives" that change the frequency of the line power from 60 Hz. to higher or lower. Since the motor speed is determined by the construction and the power frequency this method works fairly well. Biggest downside is the cost, generally $150 and up depending on manufacturer and motor size. There is still a chance of the motor overheating as most fan motors are designed to be cooled by the air flow over the motor and slower speeds means less air flow.

The third method is to replace the existing motor with a multi-speed motor. These have additional windings to allow relatively small speed changes by using a switch to select the different windings. Three-speed motors are fairly common, four-speeds a little less common. Generally these motors will not be harmed by the lesser air flow from the slower speeds. Downside here is finding a motor that fits your needs and fan and also that you are left with a single speed motor that is pretty much useless for anything but fan duty. Cost could be anything from maybe $50 on up to $150 for certain motors.
Old 07-10-13, 12:23 PM
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You'll want to determine the type of motor it is (brushless, etc). Then you need to know the amperage since a normal ceiling fan speed control wouldn't be adequate. Lutron has a NTFS line that is for high amperage "unlimited" speed via a slider.
Lutron Nova TŪ Fan Control Model Numbers

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