Ceiling fans...

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chevyx92

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Can all ceiling fans be speed controlled through a "Fan Rated" rheostat? Say your average fan from home depot or lowes. Or does the fan need to be rated for speed control?
 
A rheostat might be OK, but a light dimmer using a triac will almost certainly cause buzzing, as the chopped waveform from the dimmer causes the fan magnetic compionents to rattle a bit.

The trouble with a (real) rheostat is that it gets hot; most fan controllers use switched capacitors, which reduce the fan speed without buzzing or getting hot.
 
dbuckley said:
A rheostat might be OK, but a light dimmer using a triac will almost certainly cause buzzing, as the chopped waveform from the dimmer causes the fan magnetic compionents to rattle a bit.

The trouble with a (real) rheostat is that it gets hot; most fan controllers use switched capacitors, which reduce the fan speed without buzzing or getting hot.
Click to expand...

Yeah, and sometimes those capacitors trip the AFCI breaker:rolleyes:
 
chevyx92 said:
Can all ceiling fans be speed controlled through a "Fan Rated" rheostat? Say your average fan from home depot or lowes. Or does the fan need to be rated for speed control?
Click to expand...

Most fans can be controlled by a 3 speed fan control. Be careful though because some of the older original Hunters will not work with them.

Had a Ho who had a fancy outdoor fan and the EC used a speed control on it and now the fan has problems. I called the manufacturer and they insisted you need to use their speed controls.

Again I think the basic fans from Home Depot you are okay with the speed control. Avoid the variables because they will make the fan hum.

Also be careful not to put 2 fans on one speed control. The only ones I know of that will work 2 fans are a variable and they will cause humming.
 
dbuckley said:
A rheostat might be OK, but a light dimmer using a triac will almost certainly cause buzzing, as the chopped waveform from the dimmer causes the fan magnetic compionents to rattle a bit.

The trouble with a (real) rheostat is that it gets hot; most fan controllers use switched capacitors, which reduce the fan speed without buzzing or getting hot.
Click to expand...

A (real) rheostat is not Ok since it reduces voltage. You cannot control AC motor speed buy dropping the voltage. In addition to that I have not seen a real rheostat in a long time but I know people always refer to them when they really mean a modern dimmer. I think they feel technical when they use the word even though they could not tell you the difference between a modern dimer, a rheostat, and a Potentiometer.
 
mikeames said:
You cannot control AC motor speed buy dropping the voltage.
Click to expand...

You would not think so but that is essentially what the variable fan speed controls do.

They do not modify the frequency like a VFD.
 
Yea I guess they do but conceptually thats not what you shoot for.(AS you know iwire) In small application the voltage may drop 30% but it does not go 50% for half speed. It is more frequency and waveform rather than Voltage. Changing the frequency and waveform has an impact on voltage.

If this were conceptually true then we could just install a series of transformers and switch between them to get different speeds. Want half speed ????? No problem stick a transformer in.... HA

I only put your name in iwire because I always have to double check what I write when the moderators and some others respond simply because you all know your crap.... I have read your posts for more than half a decade, even on other forums.
 
Changing frequency and wave form has an effect on current not voltage because when you change frequency you change the inductive reactence of the motor. Most VFD's strive to maintain a Vts/Hz ratio that keeps the impedence of the motor the same so you are not letting all the magic smoke out of the motor.
 
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