Whole house fan - possible to add variable speed?

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I always start my fan on high for a couple of minutes to get the air flowing. Then I can turn it to the lowest setting and it works just fine. I like the variable speed and set it according to the needs at the moment.
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That depends on the motor. If it's a universal motor it'll probably work fine. If it's an induction motor, probably not. Induction motors tend to be "constant RPM" or with a given load, "constant power" devices. As the voltage is reduced they'll want to maintain RPM, which requires the same power, thus current increases.
If the fan is belt driven it's probably an induction motor.
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keith wrote:

If you use an AC motor speed controller it will work fine. It does not control speed with changes in voltage, it changes speed with changes in the frequency. This type of speed control also lets the fan run at lower speeds without stalling. The days of the old rheostats are long gone.
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They're a tad expensive for a fan. Have you ever seen one on a whole house fan?
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snipped-for-privacy@att.bizzzzzzzzzzzz wrote:

(Amazon.com product link shortened)
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Those are simple "dimmer" style controls. They are *not* for induction motors.
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keith wrote:

http://www.kbelectronics.com/kbsearch/descriptions/popup_kbwc_115k.htm It says Shaded Pole motors, which ARE induction motors. Unless you can show me a shaded pole motor that is not an induction motor? I'd love to see it!
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Yes, below is the model I am using with the 30 inch belt drive WHF currently being sold by Home Depot (I think its called Master Flow).
http://www.kbelectronics.com/kbsearch/descriptions/popup_kbwc_110kb.htm
Works great but I did want to inform the family to start it on high before turning it lower, but even if they did spin the knob to low from off quickly the motor still starts ok. The off click goes straight to High, turning the knob clockwise keeps getting lower, which is the proper configuration for a motor speed control.
Light dimmers are bad because they force the motor to start on Low and you must quickly crank the knob to get to High. Having the potentiameter go from Off click to High to Low as you move clockwise is the proper configuration for a fan control.
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You won't find a whole house fan that uses a shaded pole motor, but go ahead and smoke your fan.
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keith wrote:

I said those dimmers were indeed for shaded pole motors, someone disagreed, I don't really care who it was. But the fact is that the speed controls I suggested can be used on shaded pole motors.
Hell, I don't even have a whole house fan, so I don't suppose there is much chance of me smoking my fan. Unless it was made of hemp. No not really.
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I didn't see anyone saying that they weren't for shaded pole motors (or universal motors, for that matter), only to *not* use them on induction motors.

The thread is about controlling the speed of whole house fans, idiot.
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snipped-for-privacy@att.bizzzzzzzzzzzz wrote:

Oh, OK. Now show me a shaded pole motor that isn't an induction motor.

So I have to own one to reply? Show me a shaded pole motor that isn't an induction motor.
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Idiot. Not all induction motors are shaded pole. Shaded pole motors are *NOT* used for whole house fans.
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wrote:

Another clueless dolt.
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keith wrote:

No shit. I never said they were, it was your buddies who keep throwing "shaded pole" into the conversation. I just replied that a shaded pole motor is indeed an induction motor. Go back and see who first mentioned shaded pole motors. It wasn't me.
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You kept bringing them up, apparently to show how "bright" you are. Didn't work.
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On Jul 12, 11:20pm, " snipped-for-privacy@att.bizzzzzzzzzzzz"

$39 is not too bad I dont think, I use the 10 amp one at the bottom of this page (my fan only draws 5 amps but I wanted the controller to run real cool so I oversized it): I got this same model for about $25 elsewhere.
http://www.electricmotorwarehouse.com/kbwc.htm
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On Wed, 14 Jul 2010 12:28:36 -0700 (PDT), RickH

That's a "dimmer" style controller. Do *not* use that for an induction motor. Induction motors need a VFD type controller, which is far more expensive.
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On Jul 14, 7:21pm, " snipped-for-privacy@att.bizzzzzzzzzzzz"

Well It's been working great for 3 years now, and it runs cool, the heat sink on the 10 amp controller barely gets warm powering a 4 amp fan.
Here is the wording from their web site (note it says ok for fans):
"The KBWC-110K provides infinitely variable speed motor control for Shaded Pole, Permanent Split Capacitor and Universal (AC/DC) motors. The variable speed motor control contains the following features; an on/off line switch, RFI filter, minimum speed trimpot and a flame- retardant ABS enclosure. Applications include range hoods, vibrators, humidifiers, fireplace blowers, fans, laminar flow hoods, heat tunnels and stirrers."
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Do you notice a "for induction motors" in there? Huh?

Did you notice "whole house fans" in there? <sheesh!>
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