Whole house fan - possible to add variable speed?

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Lee B wrote:

Hi, Anything is possible. Like infinite speed control tied to the ambient temp. Wonders of electronic engineering....
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Lee B wrote:

What is the voltage and amperage ratings of the motor? Here are some speed controllers to choose from.
(Amazon.com product link shortened)
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Tony wrote:

My fan has a 2 speed motor. The 2 speeds are from separate windings - each speed has a different number of poles in the motor.
You can easily control a "universal" motor - the type with brushes. Not likely that is what is in the fan.
Three phase motors can be controlled by changing the frequency. No possibility there is a 3 phase motor in the fan. The control would be relatively expensive. I have never seen info, but I suspect the new variable speed furnace motors are of this basically this type.
You could probably use a variable frequency control for a standard induction motor, but if the speed falls to where the start switch in the motor turns on you will probably burn out the motor. And probably relatively expensive.
If you use a "phase angle" controller, like a light dimmer, you could control the speed - the motor speed falls farther from the "rotating field" speed. Has the same problem with start switches. I believe the torque falls rapidly as the speed drops, but the power required for a fan, if I remember right, is about the 4th power of the RPM.

Briefly looking at the info for one of the speed controllers, it says it is for shaded pole motors (which are used in clocks and my bathroom fan) and permanent split capacitor motors, which is not likely what is being used for the fan. Not obvious from what I saw that the 10A speed control would work for a typical induction motor, which is probably what powers the fan. These controls are probably "phase angle" controllers - as above.
Outside of a 2 (or more speed) induction motor, I don't know how you reliably control the speed of an induction motor that probably powers the fan. How does the control work? How do you avoid problems with the start switch?
--
bud--

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bud-- wrote:

Uh... hello? A shaded pole motor IS an induction motor. Motor speed controllers will vary their speed by varying the frequency. Try google.
http://www.google.com/search?numP&hl=en&client=firefox-a&hsJG&rls=org.mozilla%3Aen-US%3Aofficial&q=shaded+pole+induction+motor&aq=f&aqi=g1&aql=&oq=&gs_rfai
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Tony wrote:

http://www.google.com/search?numP&hl=en&client=firefox-a&hsJG&rls=org.mozilla%3Aen-US%3Aofficial&q=shaded+pole+induction+motor&aq=f&aqi=g1&aql=&oq=&gs_rfai=

You will not find a shaded pole motor on a fan of any size - like a "whole house" fan that makes too much noise.
The motor controller I commented on (from your previous post) is almost certainly a "phase angle" control (like a light dimmer). It does not change the frequency.
The controller I looked at was also stated to work with a permanent split capacitor motor. If I remember right, they are a 2 winding motor with a capacitor in series with one of the windings. There is no start cap and no start switch. It is basically a 2-phase motor. (I don't remember ever seeing one.)
Neither of the motors that the controller said it was good for has a start switch. A "whole house" fan will almost certainly have an induction motor with a start switch. Using a dimmer-type control, as above, can easily burn out the motor. It is a misapplication according to the limited information provided with the control.
--
bud--

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bud-- wrote:

What is it like to guess instead of going by the facts? Probably everything goes your way, if you don't read the specs.

There is a lot more info out there. I can't do all the work for you, look up KB Electronics and read the specs. And if you look at the picture, you will see that from the "off" position,the first "on" position is "high". Yes it will start the motor.
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LOL....Always worked for me. :)
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Tony wrote:

Guessing?
Facts: a variable frequency drive converts the AC line to DC and then inverts that to variable frequency AC. There is no way the enclosures have enough space for the filter capacitors that would be required. Also way to cheap. And all VFDs I have seen are for 3 phase motors.
They are "phase angle" controls.

I read the specs - "shaded pole" or "PSC motors". Neither of these motors has a start switch. Find me a "whole house" fan that uses either.
Someone else said that shaded pole motors are about 1/4 HP max. In a fast look at Grainger I only saw 1/5 HP max. Find a "whole house" fan that only uses a 1/5 HP motor.

If you set the speed too low will the motor start switch close? If it does the motor is likely toast. The motors in the manufacturer's spec do not have a start switch. There is a reason.
Where in the specs does it say the control is good for an induction motor with a start switch that would be used on a "whole house" fan?
Seems to be a lot of people who disagree with you.
--
bud--


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The biggest I found was 1/6HP, so said 1/4HP to make some wiggle room. The plan worked. ;-)

Only the ones who have a clue about basic electricity.
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bud-- wrote:

I was replying to those who said the speed controls I pointed to would not work on an induction motor. The specs says it does. That's all. I didn't argue that they would work for a whole house fan. My grinder is 1/2hp and it has an induction motor.
Here is a 2HP induction motor. There are many more even larger. http://www.biscuitplantspares.com/index.php?main_page=product_info&cPath &products_id2
http://www.google.com/search?q=1%2F2hp+grinder+induction+motor&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a
Again, the motor speed controllers I posted a link to do work on induction motors. That is a fact. That's all I'm saying. What did I post that is not true?
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Moron, the thread is *about* whole house fans. Induction motor powered whole house fans *CANNOT* be "dimmed".

What an idiot.
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Mine works great, the KB controller I got hooks up in series, I capped the low speed wire on the motor and just use the high speed one.
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The fan in my house was single speed. About the only thing it was practical for was evacuating smoke when my wife burned dinner. I had to replace the motor to get it to operate at lower speeds. Now its 3 speed and I stilll wish it had a slower speed. I am considering mounting some muffin fans in the corners of the chassis for when I want to draw a gentle flow into the house.
Jimmie
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JIMMIE wrote:

Is it belt driven? How about a smaller drive pulley?
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