fan speed

[stenfam]

i was wondering....

If one can put fan speed controls on a condensing unit, (head pressure control),.
( i like the electronic ones that make the motor go ANY speed, compared to the cheaper pressure sensing, ON OFF ones),

Couldn't you do this with a ceiling fan?

I want to put my ceiling fan on a reostat so it would go lower than the LOW speed.

To me, this sounds like it would work.
I used to work with large freq. drives and then THEY were supposed to be a special motor to take the weird voltage / curves, but then later, after installing a device on small condenser motors that weren't DESIGNED for that, and not ever having later problems with them..
?????????

[mattm]

It may be possible but most will burn up on a dimmer switch which is the same thing.

[stenfam]

why don't the condenser motors burn up? Is it the psc / split phase?

[rabram]

I have varible speed switchs on two of the fans in my home,work great,no problems. Go to home depot or lowes and see what they have - may have to go to electrical supply house, but they are out there. The one for my living room fan actually has cooling fins - mounts to a standard 2x4 box.These are not dimmer switches-BIG difference. Do not go CHEAP don't need a fire. Good luck, Ronald

[Diceman]

One thing for sure, those cond fans that go at any speed need to have ball bearings, sleeve motors dry up and die.

[midhvac]

I think the cheapo dimmer switches just add resistance which drops the voltage. The better ones, which are designed for ceiling fans with psc motors come in 2 different types if I recall, one does something to the sine wave of the voltage, and the other lowers the frequency of the voltage without reducing the voltage, which I guess is also modifying the sine wave by reducing the number of positive to negative waves that the current alternates at.

[stenfam]

These are not dimmer switches-BIG difference.


yea, I almost forgot about those! I installed some "soft start" type devices some 5 years ago that had those cooling fins.
They would SOFT START the motors ( 3 phase 4hp cond. mtrs. at the time.) they would be 100% speed in probobly 30 seconds or so, but I think you are telling me they also make something like THAT that is NOT a reostat that just adds resistance?
I will do some homework at the supply houses.
I don't think the soft starts I put in would've fit in a 2" box for a residential app.....

[oil lp man]

Make sure you get the rheostat that is the round dial type and can be pushed on and off. Also is rated for fan motor current.
Don't get the slide type that is next to the switch. These will burn out. I had one burn out already and replaced with the same switch by an electrician then later found out from another electrician that this was the wrong one and is supposed to be used as a light dimmer only.

[midhvac]

I think anymore, the ones that are for incandescent lights have labels on the switch which says "for incandescent lights only."

These are the ones which use resistance to drop the voltage. These are nothing but a glorified potentiometer (volume control). Whatever you use, I don't think it should drop the voltage. Motors have to be run at their rated voltage or they'll overheat and fry.

The ones that vary the sine wave are a bunch more expensive.