Dimming a fan

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Geon_W

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Is it possible to control the speed of a fan by using a typical dimmer used to dim light fixtures?

Are there any down sides?
 
Possible, yes. A good method, no.

Most dimmers work by 'cutting off' portions of the sine wave, which isn't good for the motor.

Edit to add:

Pure sine wave:
Sine1.jpg


'Dimmer' sine wave:
Sine2.jpg
 
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Depends on the fan motor used. If it is a Shaded Pole motor, then yes, an old fashioned rheostat can work (but good luck finding one). If it is a motor with a capacitor (Capacitor-Start, Split-Phase etc.) where there is a centrifugal starting switch, then no, you cannot control the speed in any way. If it is a PSC (Permanent Split Capacitor), then you can use a true 1 phase VFD, but that is much more expensive.
 
I don't get it. Are you trying to save a buck by using a dimmer instead of a proper speed control? We're not talking about a ton of money here....
 
Geon_W said:
Is it possible to control the speed of a fan by using a typical dimmer used to dim light fixtures?

Are there any down sides?
Click to expand...

If you use a variable speed dimmer made for fans I will bet that you will get humming from the fan. I suspect you will also have the same problem from a standard dimmer.

Of course, the type of fan comes into play here. The old Hunter paddle fans could not be used with a 3 or 4 speed dimmer but had to be used with a variable speed control. They always hummed.
 
The fan specs as listed by the manufacturer are as follows.

120V,
0.24A,
20W,
RPM 3100
MOTOR TYPE: shaded pole

I've tried a 3 speed control, below are the results

lowest speed - fan stayed off
middle speed- fan ON
High speed - fan on, no increase in speed.

I now want to attempt a fully variable control, before I spent my time and money I want to know what to expext
 
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Geon_W said:
The fan specs as listed by the manufacturer are as follows.

120V,
0.24A,
20W,
RPM 3100
MOTOR TYPE: shaded pole

I've tried a 3 speed control, below are the results

lowest speed - fan stayed off
middle speed- fan ON
High speed - fan on, no increase in speed.

I now want to attempt a fully variable control, before I spent my time and money I want to know what to expext
Click to expand...

Sounds like something isn't wired right, or its a bad fan. Why not just return it and get another one?

If you really want a speed control, look online at Hunter fans and Casablanca fans. They make speed controls made for fans.

Steve
 
Sounds to me like the speed switch on the fan itself was not set on high.

Maybe you should have an electrician take a look at this.
 
most new fans ive installed recently come with a controller and a remote control that allows dimming of the light kit. does the fan company offer one of these kits for your fan?
 
Geon_W said:
The fan specs as listed by the manufacturer are as follows.
........
I now want to attempt a fully variable control, before I spent my time and money I want to know what to expext
Click to expand...

I would contact the manufacturer of th motor and find out what they require for their equipment.
 
electricmanscott said:
Sounds to me like the speed switch on the fan itself was not set on high.

Maybe you should have an electrician take a look at this.
Click to expand...

I thought of that too. Did you check to see if the fan itself is on high speed? Turn the speed control to high, then pull the chain on the fan until it gets going.
 
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