Way to slow down box fan?

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Just bought a cheapo box fan, which we use in a window at night to draw in cooler outside air. However, even at the slowest of its 3 speeds, the fan is too noisy. I'd like to make it less noisy, which I think the best way wo uld be to make it turn slower. I'm wondering if it would be possible to wi re in a resistor in series with the motor to accomplish that. If so, what would be the correct specs on the resistor?
thx, H
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On 7/29/2013 1:08 PM, heathcliff wrote:

You could try a regular light dimmer. It's easy to build a unit for what you wish to do rather inexpensively. You can use 4" conduit box, one with the rounded corners, a dimmer, a duplex outlet and a combination 4" metal box cover with a position for a switch and the duplex outlet. You can get a cheep three wire extension cord and cur the outlet end off and use it to supply power to your dimmer. You'll need a cord grip to attach to the 4" box. Another route is to use a regular handy box with rounded corners, dimmer, metal switch cover, cheap extension cord, two cord grips and cut your dimmer into the middle of the extension cord. It's very easy to make. ^_^
TDD
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replying to The Daring Dufas , passerby wrote:

Small AC fans usually have shaded pole motors, RPM of which is frequency dependent. By cutting off part of the phase with a light dimmer you will just make it start even harder than it already is for this type of a motor. There may be *some* RPM control due to torque losses when dimmer is dialed down, but it's only a small percentage point around the designed RPM, not from 0 to the max.
Since the actual complaint is noise, not RPMs per se, I would take the fan apart and try to balance the blades to deal with vibration. You know, disconnect the motor from power and spin the blades by hand. Mark which blade stops at the bottom, do it again. If the same blade stops at the bottom again, file some material off that blade, repeat until no single blade stops at the bottom repeatedly. Hard to say how effective it will be with lightweight plastic blades coupled to a badly constructed motor, but is worth a try. Not much else to do: if you have to look at the motor, you might as well just get yourself a new fan - motor is the bulk of the cost of it, anyway.
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On Mon, 29 Jul 2013 20:45:02 +0000, passerby

Since the actual complaint here is fan-noise and not fan-speed it may help to move the fan to another room, possibly a room that is far enough from your bedroom that fan-noise will be less of a problem. Configure the fan (in the distant room) to exhaust hot air to the outside of the house. Keep the door and windows in your bedroom open, and also keep the door to the fan room open. Then, close windows and doors in the remainder of the house in such a way that the fan draws cool outside air (only) into your bedroom and exhausts hot air out through the distant room that has the fan. You could re-adjust the windows and doors in such a way as to draw cooler outside air into other parts of the house when you aren't using your bedroom.
--
HTH

pilgrim
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replying to pilgrim, JP Huie wrote: Just want to add that a larger fan (blade diameter) will produce less noise for the amount of air moved. So a larger fan (I'd shoot for 20" at least) on a slowish speed might move enough air AND be quieter. Problem may be finding one... I bought earlier model of this from Amazon, but reviews on current model arent' to good. You can check Grainger but they don't seem to give the diameters, so maybe go to mfg's website for that... https://www.amazon.com/AirKing-9166-Whole-House-Window/dp/B0007Q3RQ6/ref=lp_3737641_1_10?s=home-garden&ie=UTF8&qid 67657395&sr=1-10
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On Mon, 04 Jul 2016 19:44:02 +0000, JP Huie

I've been reading this group for maybe 20 years and I don't remember any pilgrim.
But I might have missed say, one lone post.
If he's still reading I have some info, but I'm not going to the trouble of writing it unless someone who is reading wants to know how to slow a fan.

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On Monday, July 4, 2016 at 4:02:57 PM UTC-5, Micky wrote:

If you bothered to go to the link you would see...even TDD is there, from 2 yrs ago! :^(
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On 7/29/2013 3:45 PM, passerby wrote:

My suggestion was about a low cost experiment. I built a variable voltage box using a triac, pot, trigger diode, capacitor, single 120 volt 15 amp outlet, cord, cord grip and sloped project box. I was able to use it for all sorts of things including shaded pole motors, light bulbs and universal AC/DC motors. If he uses a triac type dimmer, it should work. A dimmer using an SCR might not work very well. The link below is about LED dimming but shows the waveform output of a triac type dimmer. ^_^
http://www.digikey.com/us/en/techzone/lighting/resources/articles/Dimming-LEDs-with-Traditional-TRIAC-Dimmers.html
https://tinyurl.com/l655p55
TDD
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On 7/29/2013 9:18 PM, The Daring Dufas wrote:

If you use a triac dimmer control the motor torque falls off pretty rapidly. But as you reduce the fan speed the torque required falls off rapidly also, something like the 3rd power of the RPM. I never used a dimmer to control a fan, but it might work. From mickey, it often does work.
I believe a triac dimmer will maintain torque better than a resistor.
The box fans I have make noise because of the air being moved, not because of balance problems.
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On 7/30/2013 10:03 AM, bud-- wrote:

You don't really have to be concerned about starting torque with a fan but if it's a problem, crank the dimmer wide open to start then back off. ^_^
TDD
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wrote:

I should say that every fan I have except the 4" fan (which is a year old) is over 25 years old. I have a Tintang** (or something like that, 2-speed fan) that is about 25 years old, but I've never used a speed control with it, or with the 4" fan. **Co-workers gave me this when they felt sorry for me when I was using a fan from the '30's. But I liked the older fan more, until it caught fire last summer (fan stopped, overheated, and set fire to too much light oil).
The rest are 30 to 80 years old. I don't think newer fans from the last 10 years are made differently from my older ones, which are all (except maybe one) brushless, induction motors. I guess I could try dimmers on those two newer fans if anyone was curious.
I got the old fans, with iron or heavy steel bases, from my father when he died in 1955 at age 62. They were in his office or our home.

Yeah.
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On Mon, 29 Jul 2013 20:45:02 +0000, passerby

I've put dimmers on fans and all you do it trade off some fan blade noise for increased motor noise because the solid state dimmers just chop the current up and make the motor "buzz". The only way to do it without the buzz is with an old fashioned transformer based dimmer/motor controller.
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On 8/3/2013 3:43 AM, Ashton Crusher wrote:

Otherwise know as a variable autotransformer or Variac. The dimmers using a triac instead of an SCR may be less likely to make the fan motor buzz. I've seen Variac light dimmers used in recording studios because they don't make the lights buss or add noise to the electrical power for the studio. ^_^
https://en.wikipedia.org/wiki/Autotransformer
http://www.variac.com/
TDD
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wrote:

Not in my experience. In one case the dimmer was a foot from my ear when I lie down and the fan was 18 inches. Still heard no humming or buzzing. And since the reason I use the dimmer is mostly to get rid of noise, I would notice.
There is probably a lot of variety in motors and fans, and even maybe dimmers.

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replying to The Daring Dufas, Shawn hill wrote: best thing to do is buy something that will reduce the amps not the volts because the speed is changed by a tapped winding in the motor which reduces the amperage
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On Saturday, September 17, 2016 at 5:44:04 PM UTC-5, Shawn hill wrote:

TDD has gone the way of the Mormon...and is no longer with us. Alas!
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On 2016-09-17 6:52 PM, bob_villa wrote:

--
Froz....

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On Saturday, September 17, 2016 at 8:18:53 PM UTC-5, FrozenNorth wrote:

...you've been had.
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On 2016-09-17 9:46 PM, bob_villa wrote:

confirmed both brothers are two distinct people and are both alive. Quit spreading crap you know absolutely nothing about.
--
Froz....

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On Saturday, September 17, 2016 at 8:59:31 PM UTC-5, FrozenNorth wrote:

I have no reason to believe your story...TDD would not leave without saying something...he was descent person. Nothing like his "brother".
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