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
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
I know exactly what you mean about the noise. Almost any fan, when run slow enough, will be totally quiet.
I don't know if a resistor would work, and rather than get into the possible problems, fire and everything, I'd recommend
either a) getting a fan speed control and finding a box to mount it in, For the most part, the only fan speed controls I've ever found were the kind that fills the same size box that a wall switch or receptacle goes into. Pretty big. I did once come across, at an electronics flea market maybe, one about the size of a brownie, but I couldn't find a box the right size and ended up putting it one that was the right width and depth, but was 4 inches high.
Hmmm,
They didn't have any of this stuff 15 years ago, I think.
Or b) getting a light dimmer, which usually comes already in a box and which also usually has a cord with a combination plug/receptacle, that you can plug the light [or fan] into and plug all of that into the wall.
Whenever I recommend this, I'm certain to get criticism about how light dimmers won't work with motors, and they are correct that they are not designed for the purpose, and once in a while I find a dimmer that will not work with a fan (probably it's the fan that is different from other fans, and less likely that the dimmer won't work with any fan.) but I have 30 years experience here, with about 12 fans and 3 or
4 different kinds of dimmer, and I think only one fan, at most two, would not work with the light dimmer I tried it with. None have shown RF interference with the radio or tv.But you should never turn the speed down so low that the fan stops spinning. There were probably still be some current running through the fan motor, and if the energy in the current doesn't get turned into motion, it will be turned entirely into heat, with the possibility of a fire. (Although I seem to recall that I did test one combination, by turning the speed down just enough until it stopped, and letting it sit where it was always within my view for a
30 minutes and feeling the fan to see how hot it was. And it was only a trifle warm, so I probably decided it couldn't get too hot. But still there is no point to turning the speed down so it doesn't turn, when it's just as easy to turn the fan off.I only use the AC about 10 days a year, fewer now that it has broken, so I have a fan in almost every room, even in the basement (which never gets that hot but on humid days, the fan feels good), and when the house is warm, I use them every day.
In the bedroom I had a small table fan, and sometimes it would get too cold at night, as it cooled off but the fan was still on. So I took a thermostat from a burned-out big box fan, mounted it in a big plastic cap from a large aerosol can, and wired that into fan wiring so the fan turns off completely if it gets colder than where I set it while I'm sleeping.
The dimmer I use the most they sold for maybe 20 years or more, but they don't seem to sell it, at least not in the same case now. It is like this one
When the dimmer didnn't work with the fan, I mean that the fan didn't spin at all no matter what setting the dimmer was on. But the dimmer did work with other fans.
If the fan spun at all, everything else was fine, IME.
You can see this if you rolll the cursor over the slider control and see the enlarged picture of the dimple at one end.
More dimmers
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.
Ken,
Return the fan and try another brand. If you can't find one that's quiet enough look into balancing the blades. That's where the noise is coming from, most likely. Forget the resistor.
Dave M.
A lof of fan noise is not caused by out-of-balance fans but by the air which is moving because of the fan. No matter how good the bearings or how well balanced the blades, if there is too much air moving, one can hear that. Many people may not mind or even notice, since it's the essense of a fan to move air, but I sure mind. Maybe that's what is bothering Heathcliff too.
(My last 3 Chrysler LeBarons had 4 speed fans, and I almost always kept the speed on 2, almost the slowest, because that was the fastest speed I could not hear. After 23 years with LeBarons, I bought a Toyota Solara, which has 5 fan speeds. Sounds better, but only the lowest speed is silent. But the lowest speed moves less air than speed 2 (and maybe even speed 1) of the LeBaron. So I'm forced to use speed 2 and put up with the noise.
(One of twenty reasons so far that the Chryslers (and the GM cars) were better than the Toyota.)
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.
The real solution would be to get a quieter fan, as a resistor in series with the low speed will draw just as much power as the low speed does now, and shed all its heat into the airflow going into your house.
I know, that's not the DIY way, but it's the truth...
If you really, really don't want to do that for whatever reason, I would remove the 3-speed switch, wire everything up so the fan runs on its FASTEST speed, and get a triac based motor speed control so your fan now has infinitely variable speed.
nate
Lamp dimmer control maybe?
. Christ> 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 would be to make it turn slower. I'm wondering if it would be possible to wire in a resistor in series with the motor to accomplish that. If so, what would be the correct specs on the resistor?
Newer box fans are noisy. I have an older kmart box which is very quiet. Many upright fans are very quiet.
NO resistor.
Some motor speed controllers are only for brushed devices. A heavy duty dimmer will probably work, but may introduce buzzing.
Greg
Not a bad idea, except there's no need to remove the 3-speed switch. He can just set it to the highest speed. Then, if he or the next user ever stops using the speed control, he'll still have a 3-speed fan.
However, my experience is that sometimes it's better to use the external speed control with the lowest speed. Frankly, I forget why, but it might have been this: Say the knob and the rheostat is such that one can set the control to any one of 200 physical positions. If the fan has natural speeds of 400, 800, and 1200, then at the low setting, one can control the speed in increments of 2, (2 x 200 = 400) but at the highest speed setting, he can only control the speed in increments of 6. If he's going to use a speed below 400 anyhow, he'll have more control over the speed when the fan is set at
400. (I'm not saying 400 or 1200 what, revolutions per something or other. I don't know what actual speeds these fans run at.)
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. ^_^
TDD
Dang, I forgot all about the dimmer already built on to the cord. The only thing I don't know about them is whether or not they use a triac. Perhaps one made to dim LED lamps would work better but those may use SCR's instead of triacs. I'm so use to building things I forgot about the ready made dimmers on a cord. O_o
TDD
I have an 89 full sized Dodge van that's older than the girls I chase. The poor old guy makes all kinds of noise. I'm looking for a vehicle manufactured in this century like a small SUV and I'll keep the old van since it carries a lot of stuff and has a ladder rack. ^_^
TDD
LOL. This reminds me of when I wanted to build a lid for lidless frypan, but you all convinced me to buy one meant for another pan or pot. (I had to go to 8 thrift shops, but it took only about 5 minutes each and was a lotl easier than making one.)
Good plan.
When I was in college my 80-year old cousin gave me his '50 Olds, in
1968, I noticed a similar car and left a note trying to buy his back-up lights. He wouldn't sell but we became friends. He was 30 or 35 and would drive his '50 olds around campus, saying he thought the college girls might find the car interesting. I'm sure none did, but I didnt' tell the guy since it seemed to be his whole social life.He had two models of the 50 Olds, or a 50 and 51, and he had a whole townhouse stuffed full of electronic parts, etc. on the first floor at least, that he bought in bulk at auctions. He lived somewhere else.
Later, when my brother went to Viet Nam, he gave me his '65 Pontiac Catalina convertible, and when I left town 18 months after that, I couldn't take both. I didn't want to but I gave my Olds to my friend, so he had three!
Man I wish I still had my 1981 Dodge Aries station wagon. It was a neat little car with bucket seats and four on the floor which was unusual for those funky little cars especially in a wagon. I got the roller cam from a later model 2.2L engine and it bolted right in and improved performance but the other thing that really helped was getting the clutch and flywheel off a turbo version of the 2.2L engine and it was a direct bolt in too. The friction surface and disk took up the whole flywheel which gave me the ability to lite up the front tires without any clutch slippage. Darn, I wish I still had the little critter. ^_^
TDD
For "Small SUV" I don't think anyone will ever top the Jeep Cherokee or early Grand Cherokee... everything since has either been too big or not capable enough.
It'll be a sad day when mine dies but I'm hoping to postpone that day as long as possible.
nate
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.