Lesson: AC Fan Controllers

airspirit · 12-03-2002, 10:36 AM

I learned a good lesson last night/this morning:

Ceiling fan controllers DO NOT work right for controlling AC fans. Neither do dimmers. Not potentiometers or rheostats. You cannot cheaply control fan speed without creating crazy fan noise (obnoxious buzzing that is louder than the fan itself).

The only thing that will do this correctly is a Variac Transformer. The ceiling fan controllers and such are Triac based just chop off a portion of the sine wave causing all sorts of chaos and you risk burning your fan up and possibly your house down. A Variac transformer with the correct W load rating can provide a smooth transition from 0-X VAC while keeping the integrity of the the AC sine wave (no chopping). The downside of these controllers is that they are expensive (120 VAC/3A 0-130VAC output at Allelectronics is $45 + s/h).

For all of you considering AC fans to cool your machines, keep this in mind. While there is a solution that will work, it is not a cheap one. Going with a cheaper method such as a dimmer will cause more noise than it will prevent.

Since87 · 12-03-2002, 11:16 AM

I've been doing a little research on AC motors lately and I don't think you can count on a Variac working well either.

Many AC motors are designed to operate in sync with the AC line frequency. Oftentimes the normal RPM of an AC motor will be:

(Line Frequency / 2 ) * 60 seconds/minute = 1800 RPM (@ 60Hz)

The best way to adjust the RPM of these motors is to vary the frequency of the power applied. ( Google VFD controller )

A variac will adjust the amplitude of the drive signal but not change the frequency.

I don't know enough about AC motors to say with any accuracy what happens when the voltage amplitude is lowered. I believe the fan will probably stay at it's normal RPM until the force applied to the blades prevents the motor from staying synced to line frequency, at which point the motor may behave erratically.

bigben2k · 12-03-2002, 11:31 AM

I'm (still) using a light dimmer (round knob) and it works, but I otherwise agree, the IDEAL solution would be to alter the frequency.

My fan seems to work just fine, and it does slow down to whatever level I like.

There is a starting level (or point) that is higher than the minimum setting, but that's ok, I never run it that low.

If anything, there is a buzzing noise coming from the dimmer, at lower settings, but it's barely noticeable.

I can run the fan full speed, and there is no (discernable) difference if I connect the fan directly to the outlet.

Maybe I just got lucky, with a low power fan, and high power dimmer?

airspirit · 12-03-2002, 11:42 AM

That would be correct, assuming that the fan is using an AC synchronous motor (the spinning of the current causes the moving part to spin synchronously with it, if it gets out of sync it stops). Since these are AC induction motors (the spinning current exerts force upon the moving part pulling it along, through by nature it is always in a status of slip, where the stronger the current, the faster the moving part moves and vice versa).

Changing the freak (I love that term) can cause unpredicable side-affects. Changing the voltage with a variac provides you with no distortion to the wave-form.

Since87 · 12-03-2002, 12:02 PM

Quote:

Originally posted by airspirit
Since these are AC induction motors (the spinning current exerts force upon the moving part pulling it along, through by nature it is always in a status of slip, where the stronger the current, the faster the moving part moves and vice versa).

Ok, time for me to do some more research. Most of my experience with magnetics is with inductors and transformers where nothing's moving but the electrons.

BTW, I've got an old panel mount variac that I pulled out of a cabinet I'm using for a project. I don't know the current rating offhand. (I'd guess at least 3 amps.) I'd sell it for $20 + shipping.

airspirit · 12-03-2002, 12:08 PM

If you could confirm the power rating, I may be interested. What type of connectors does it have? What kind of VAC range? I found a new 3A Variac at

http://www.savon-electronics.com/variacs.htm

for $33 + shipping with plugs on it. Can you take a picture of it?

Here is this one:

http://www.savon-electronics.com/sgrc/phcsc.jpg

Since87 · 12-03-2002, 12:21 PM

The variac I have is not enclosed. It is meant to bolt to a panel, with the knob sticking through the panel. There is exposed high voltage on the other side of the panel. It probably has screw terminals for making the electrical connections, but maybe spade lugs or solder tabs. (don't remember)

Probably not the way you want to go, unless you already have some panel space available to mount it conveniently.

If you are still interested let me know and I'll get a picture.

airspirit · 12-03-2002, 12:35 PM

I have tons of places to mount it (about, oh, 8 sq. ft. of space to mount it), so don't worry about that. Gotta pic?

Since87 · 12-03-2002, 01:10 PM

I'll get a pic tonight or tomorrow.

airspirit · 12-03-2002, 01:53 PM

Rock on. I just ordered a replacement pump (the used Gen-X Mak 4 I got is the loudest pump I've ever used ... imagine a large pump running dry, and that's what this sounds like wet ... it is being shipped back to Ft. Collins), so this is the only other component necessary to silence my system. I really can't stand the circular saw noise the fans and pump make any longer.

Since87 · 12-03-2002, 07:39 PM

Meant to take a digital camera home from work, but forgot.

The variac is a Powerstat model 21. This link shows the specs. In brief; 0-140V, 5A.

I snagged the attached picture off the web. The one I have looks cleaner than that. I'd say near mint.

Plus mine has the screws for panel mounting the variac, the big 3 inch knob, and the metal plate for indicating the voltage setting. The indicator plate is a little odd because it goes 0-100 with a dot at 85 which indicates 1:1 input to output. It is missing the hardware to hold the indicator plate to the mounting panel, but that's just some sheetmetal screws, or 6-32 nuts and bolts.

I'll try to remember to get pictures tomorrow.

My Heatware

FuzzyFace · 12-04-2002, 01:44 AM

For the past 18 months I have used 2 Radio Shack 120v fans in my system (12w each) running in parralel off of a fan controller. I have had no problems with it, and it makes no noise that I can hear.

The “speed controller for 115V fans” came from Edmund Scientific’s (http://www.scientificsonline.com). Part #D30347-60 (US$4.95) in their latest paper catalog (C029D) page 62. I could not find it at their internet site.

This controller is about 1.5” (37mm) square. A nice safety feature is the second pot (trimmer pot) which allows you to set the lowest speed the fan will operate at.

I have no idea what the max load is that you can put on the controller. The voltage regulator (or what ever it is called, it has an aluminum tab with a hole on it for heat sink mounting) has two numbers on it 8T24A, and H2581. My electronics knowledge is close to nothing. Maybe one of the electronics experts can tell us what kind of load it can handle. The controller also has a diode and a couple of capacitors.

All the catalog says is “Keep those fans under control! Components protected from dust by clear plastic case. 120VAC, 60Hz.”

airspirit · 12-04-2002, 01:01 PM

Um, I actually picked up a dehummer type triac fan controller (3-spd) last night. When I wired it in, it gave me three speeds: full, 30% (turns 1100 CFM to about 150 CFM), and stall (the fans are audibly popping as they stall too far past the waveguide ... maybe 10 CFM total, if you're lucky and don't kill the fans). I think this'll work, since when my puters are idling, I can set it to 30%, and when I need some killer cooling, I can crank the heat on (though it is about 47-48 dB of fan noise). I think I'll just stick with this for a few months and then look at putting on a variac and do it right.

Unfortunately, there is no such thing as a dehummer circuit for fully variable control. They require a set number of connection settings in order to work. C'est la vie.

Since87 · 12-04-2002, 02:26 PM

So, I take it you don't want to buy my variac?

Good.

$20 was way too cheap anyway now that I looked up the specs and the list price.

Do Mag drive pumps have synchronous motors? (I've noticed that Iwaki's have substantially lower specs for 50Hz vs 60Hz operation, so I suspect they do operate synchronously.)

If not, I'd be tempted to use the variac to put 140V into my Danner Mag 5 and see what happens.

airspirit · 12-04-2002, 02:38 PM

Most all mag drives are induction. You should be able to run it on a variac, but be warned that running it too far under spec can cause damage on that type of drive unit. Synchronous motors are easy to spot because they require an induction based starter in order to get them to synchronous speed. A centrifugal pump with a synchronous motor would be mighty expensive to buy. Since danners are not, I would suspect they are induction. It would not hurt to try running the variac. If you tune the variac down and the speed does not change, or the pump stops spinning, then you know that it is synchronous.

Let us know how it goes.

I would highly suggest not putting it below 80VAC.

12-03-2002, 10:36 AM	#1
airspirit Been /.'d... have you? Join Date: Jul 2002 Location: Moscow, ID Posts: 1,986	Lesson: AC Fan Controllers I learned a good lesson last night/this morning: Ceiling fan controllers DO NOT work right for controlling AC fans. Neither do dimmers. Not potentiometers or rheostats. You cannot cheaply control fan speed without creating crazy fan noise (obnoxious buzzing that is louder than the fan itself). The only thing that will do this correctly is a Variac Transformer. The ceiling fan controllers and such are Triac based just chop off a portion of the sine wave causing all sorts of chaos and you risk burning your fan up and possibly your house down. A Variac transformer with the correct W load rating can provide a smooth transition from 0-X VAC while keeping the integrity of the the AC sine wave (no chopping). The downside of these controllers is that they are expensive (120 VAC/3A 0-130VAC output at Allelectronics is $45 + s/h). For all of you considering AC fans to cool your machines, keep this in mind. While there is a solution that will work, it is not a cheap one. Going with a cheaper method such as a dimmer will cause more noise than it will prevent. __________________ #!/bin/sh {who;} {last;} {pause;} {grep;} {touch;} {unzip;} mount /dev/girl -t {wet;} {fsck;} {fsck;} {fsck;} {fsck;} echo yes yes yes {yes;} umount {/dev/girl;zip;} rm -rf {wet.spot;} {sleep;} finger: permission denied

12-03-2002, 11:31 AM	#3
bigben2k Responsible for 2% of all the posts here. Join Date: May 2002 Location: Texas, U.S.A. Posts: 8,302	I'm (still) using a light dimmer (round knob) and it works, but I otherwise agree, the IDEAL solution would be to alter the frequency. My fan seems to work just fine, and it does slow down to whatever level I like. There is a starting level (or point) that is higher than the minimum setting, but that's ok, I never run it that low. If anything, there is a buzzing noise coming from the dimmer, at lower settings, but it's barely noticeable. I can run the fan full speed, and there is no (discernable) difference if I connect the fan directly to the outlet. Maybe I just got lucky, with a low power fan, and high power dimmer? __________________ WBTA (Water Block Testing Alliance) Nordic Hardware WC 101

12-03-2002, 11:42 AM	#4
airspirit Been /.'d... have you? Join Date: Jul 2002 Location: Moscow, ID Posts: 1,986	That would be correct, assuming that the fan is using an AC synchronous motor (the spinning of the current causes the moving part to spin synchronously with it, if it gets out of sync it stops). Since these are AC induction motors (the spinning current exerts force upon the moving part pulling it along, through by nature it is always in a status of slip, where the stronger the current, the faster the moving part moves and vice versa). Changing the freak (I love that term) can cause unpredicable side-affects. Changing the voltage with a variac provides you with no distortion to the wave-form. __________________ #!/bin/sh {who;} {last;} {pause;} {grep;} {touch;} {unzip;} mount /dev/girl -t {wet;} {fsck;} {fsck;} {fsck;} {fsck;} echo yes yes yes {yes;} umount {/dev/girl;zip;} rm -rf {wet.spot;} {sleep;} finger: permission denied

12-03-2002, 12:08 PM	#6
airspirit Been /.'d... have you? Join Date: Jul 2002 Location: Moscow, ID Posts: 1,986	If you could confirm the power rating, I may be interested. What type of connectors does it have? What kind of VAC range? I found a new 3A Variac at http://www.savon-electronics.com/variacs.htm for $33 + shipping with plugs on it. Can you take a picture of it? Here is this one: http://www.savon-electronics.com/sgrc/phcsc.jpg __________________ #!/bin/sh {who;} {last;} {pause;} {grep;} {touch;} {unzip;} mount /dev/girl -t {wet;} {fsck;} {fsck;} {fsck;} {fsck;} echo yes yes yes {yes;} umount {/dev/girl;zip;} rm -rf {wet.spot;} {sleep;} finger: permission denied

12-03-2002, 12:35 PM	#8
airspirit Been /.'d... have you? Join Date: Jul 2002 Location: Moscow, ID Posts: 1,986	I have tons of places to mount it (about, oh, 8 sq. ft. of space to mount it), so don't worry about that. Gotta pic? __________________ #!/bin/sh {who;} {last;} {pause;} {grep;} {touch;} {unzip;} mount /dev/girl -t {wet;} {fsck;} {fsck;} {fsck;} {fsck;} echo yes yes yes {yes;} umount {/dev/girl;zip;} rm -rf {wet.spot;} {sleep;} finger: permission denied

12-03-2002, 11:16 AM	#2
Since87 Pro/Guru - Uber Mod Join Date: Sep 2002 Location: Indiana Posts: 834	I've been doing a little research on AC motors lately and I don't think you can count on a Variac working well either. Many AC motors are designed to operate in sync with the AC line frequency. Oftentimes the normal RPM of an AC motor will be: (Line Frequency / 2 ) * 60 seconds/minute = 1800 RPM (@ 60Hz) The best way to adjust the RPM of these motors is to vary the frequency of the power applied. ( Google VFD controller ) A variac will adjust the amplitude of the drive signal but not change the frequency. I don't know enough about AC motors to say with any accuracy what happens when the voltage amplitude is lowered. I believe the fan will probably stay at it's normal RPM until the force applied to the blades prevents the motor from staying synced to line frequency, at which point the motor may behave erratically.

12-03-2002, 12:21 PM	#7
Since87 Pro/Guru - Uber Mod Join Date: Sep 2002 Location: Indiana Posts: 834	The variac I have is not enclosed. It is meant to bolt to a panel, with the knob sticking through the panel. There is exposed high voltage on the other side of the panel. It probably has screw terminals for making the electrical connections, but maybe spade lugs or solder tabs. (don't remember) Probably not the way you want to go, unless you already have some panel space available to mount it conveniently. If you are still interested let me know and I'll get a picture.

12-03-2002, 01:10 PM	#9
Since87 Pro/Guru - Uber Mod Join Date: Sep 2002 Location: Indiana Posts: 834	I'll get a pic tonight or tomorrow.

12-03-2002, 01:53 PM	#10
airspirit Been /.'d... have you? Join Date: Jul 2002 Location: Moscow, ID Posts: 1,986	Rock on. I just ordered a replacement pump (the used Gen-X Mak 4 I got is the loudest pump I've ever used ... imagine a large pump running dry, and that's what this sounds like wet ... it is being shipped back to Ft. Collins), so this is the only other component necessary to silence my system. I really can't stand the circular saw noise the fans and pump make any longer. __________________ #!/bin/sh {who;} {last;} {pause;} {grep;} {touch;} {unzip;} mount /dev/girl -t {wet;} {fsck;} {fsck;} {fsck;} {fsck;} echo yes yes yes {yes;} umount {/dev/girl;zip;} rm -rf {wet.spot;} {sleep;} finger: permission denied

12-04-2002, 01:44 AM	#12
FuzzyFace Cooling Neophyte Join Date: Dec 2001 Location: California high desert Posts: 52	For the past 18 months I have used 2 Radio Shack 120v fans in my system (12w each) running in parralel off of a fan controller. I have had no problems with it, and it makes no noise that I can hear. The “speed controller for 115V fans” came from Edmund Scientific’s (http://www.scientificsonline.com). Part #D30347-60 (US$4.95) in their latest paper catalog (C029D) page 62. I could not find it at their internet site. This controller is about 1.5” (37mm) square. A nice safety feature is the second pot (trimmer pot) which allows you to set the lowest speed the fan will operate at. I have no idea what the max load is that you can put on the controller. The voltage regulator (or what ever it is called, it has an aluminum tab with a hole on it for heat sink mounting) has two numbers on it 8T24A, and H2581. My electronics knowledge is close to nothing. Maybe one of the electronics experts can tell us what kind of load it can handle. The controller also has a diode and a couple of capacitors. All the catalog says is “Keep those fans under control! Components protected from dust by clear plastic case. 120VAC, 60Hz.” __________________ Have fun, FuzzyFace

12-04-2002, 01:01 PM	#13
airspirit Been /.'d... have you? Join Date: Jul 2002 Location: Moscow, ID Posts: 1,986	Um, I actually picked up a dehummer type triac fan controller (3-spd) last night. When I wired it in, it gave me three speeds: full, 30% (turns 1100 CFM to about 150 CFM), and stall (the fans are audibly popping as they stall too far past the waveguide ... maybe 10 CFM total, if you're lucky and don't kill the fans). I think this'll work, since when my puters are idling, I can set it to 30%, and when I need some killer cooling, I can crank the heat on (though it is about 47-48 dB of fan noise). I think I'll just stick with this for a few months and then look at putting on a variac and do it right. Unfortunately, there is no such thing as a dehummer circuit for fully variable control. They require a set number of connection settings in order to work. C'est la vie. __________________ #!/bin/sh {who;} {last;} {pause;} {grep;} {touch;} {unzip;} mount /dev/girl -t {wet;} {fsck;} {fsck;} {fsck;} {fsck;} echo yes yes yes {yes;} umount {/dev/girl;zip;} rm -rf {wet.spot;} {sleep;} finger: permission denied

12-04-2002, 02:26 PM	#14
Since87 Pro/Guru - Uber Mod Join Date: Sep 2002 Location: Indiana Posts: 834	So, I take it you don't want to buy my variac? Good. $20 was way too cheap anyway now that I looked up the specs and the list price. Do Mag drive pumps have synchronous motors? (I've noticed that Iwaki's have substantially lower specs for 50Hz vs 60Hz operation, so I suspect they do operate synchronously.) If not, I'd be tempted to use the variac to put 140V into my Danner Mag 5 and see what happens.

12-04-2002, 02:38 PM	#15
airspirit Been /.'d... have you? Join Date: Jul 2002 Location: Moscow, ID Posts: 1,986	Most all mag drives are induction. You should be able to run it on a variac, but be warned that running it too far under spec can cause damage on that type of drive unit. Synchronous motors are easy to spot because they require an induction based starter in order to get them to synchronous speed. A centrifugal pump with a synchronous motor would be mighty expensive to buy. Since danners are not, I would suspect they are induction. It would not hurt to try running the variac. If you tune the variac down and the speed does not change, or the pump stops spinning, then you know that it is synchronous. Let us know how it goes. I would highly suggest not putting it below 80VAC. __________________ #!/bin/sh {who;} {last;} {pause;} {grep;} {touch;} {unzip;} mount /dev/girl -t {wet;} {fsck;} {fsck;} {fsck;} {fsck;} echo yes yes yes {yes;} umount {/dev/girl;zip;} rm -rf {wet.spot;} {sleep;} finger: permission denied

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