Whole house fan - possible to add variable speed?


wrote:

And of course, back to the oP's question, they sell fan speed controls that mount like wall switches. Often there's a switch there for the light that often comes with a ceiling fan. I presume whole-house fans use more current than ceiling fans, but would the speed control be big enough?
He could use teh toggle swtich for any old thing, including perhaps turning off the fan without changing the speed setting.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You're not listening. Whole house fans often (if not usually) use induction motors. These motor controllers WILL NOT work with induction motors. You'll likely burn up both.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Jon Danniken wrote:

Thanks. Is that something an electrician could tell by looking at the unit? (No point in telling me what to look for, I'm not built for climbing a ladder up into that little trap door to the attic... or worse trying to climb back down!). I got the old fan at Sears and also got the variable speed dial there. I can't remember what I paid for that fan 20+ yr ago, but I know it wasn't a top of the line or anything special. I sort of assumed they all worked the same and was surprised when I encountered this one.
I can't use the fan too often, living in the mid-Atlantic where it's often too humid to suck that wet air in. But we've had a few really pleasant evenings where the humidity was low, and it would be nice to turn off the A/C and feel like I'm saving $.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Lee B wrote:

Yes, an electrician will know in short order what type of motor is in your unit.
Jon
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Lee B wrote:

Yes, it's doable. There are variable AC motor controllers. They are not cheap. Might be cheaper to replace the motor with a 3 speed wound rotor motor or a DC motor with speed controller. Electrician can give you an estimate.
--
LSMFT

I haven't spoken to my wife in 18 months.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Whole house fans are great. Yes you can put on a variable speed controol, but I suggest you over-rate the control amperage you buy by double. For example if the fan draws 5 amps then get a 10 amp control. Also when turning it on make sure the control passes through the higher speed, then you lower it. This is so the motor gets enough starting current. I replaced the Off/High/Low switch on mine with a variable speed. You only use the High speed motor input wire, just cap the low speed wire.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

While a full variable speed controller would be nice, I wonder if it really adds that much to the benefit of the fan. For instance, the louvers of the fans require a minimum amount of pressure differential for the air to open them, eliminating the lowest speeds you could get with the controller. The one I installed in our first house had a 2-speed switch for High/Low operation and we seldom used it in any position other than High. Our second house had two of the fans and again, both were left on High.
If the OP investigates and finds that his fan is a 2-speed one, my suggestion would be to invest first in a DP switch and use the high/low speeds to see if it's worth the added cost of buying a full controller for anything intermediate or lower.
Nonny
--
On most days,
it's just not worth
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I needed a speed adjustor because sometimes you choose to not open enough widows to keep up with the fan draw, so a nice slow fan is nice if you just want one bedroom window open at night. Even on low, may fan was overdrawing most of the time, its a 30 inch belt drive.
Also depending on how much output venting the user has in their roof and eves, a variable speed lets you not overload the amount of air your attic is capable of evacuating. Its cheaper than installing more vents. Also the variable speed saves kilowatts. The louver spring can be easily adjusted to require only a very light amount of air to open them, mine pops open very easily.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

They're a tad expensive for a fan. Have you ever seen one on a whole house fan?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@att.bizzzzzzzzzzzz wrote:

(Amazon.com product link shortened)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Those are simple "dimmer" style controls. They are *not* for induction motors.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You won't find a whole house fan that uses a shaded pole motor, but go ahead and smoke your fan.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.