Need a speed control for blower

[Phil Thien]

I purchased a three speed 1/4-horse blower at what I feel is a good price.

I'd like to make an air cleaner. Have some ideas to try.

But I'd like to take advantage of the three speeds, instead of wiring it for just one.

Are there any reasonably priced switches for something like this? I don't need anything fancy, no remote, no timer, nothing. Just off, speed 1, speed 2, and speed 3. I can even do power with a separate switch if it helps.

[Lee Schierer]

I don't know if this will help, 3 position switch (http://www.surpluscenter.com/item.asp?item=11-3227&catname=electric) It seems to have a high enough current rating and it is cheap.

Or watch the trash by the curb for a box fan. Box fans usually have the motors that fail. They have three speed switches, but I can't speak to the amp rating.

[Dan Hintz]

If it's a brush motor, Harbor Freight has a router variable speed controller for about $20 (use your 20% off coupon)... it's what I used on my 1HP HF DC blower.

[Bob Faris]

I'm not sure if this information will help or not...


THREE SPEED MOTOR SWITCH

You may find a 3 speed motor in an old furnace blower. You can get a 3-speed fan switch from the local hardware store for under $5 but chances are it's for a ceiling fan and can't handle the amps on a furnace fan motor. You could plop down $20 or more on a 3-position switch with a higher amp rating, or you could do it with a few 15A switches that you would use in your house for lights. Basically the first switch is your simple SPST light switch that you can get for about $1. That controls ON/OFF, then you need two SPDT (or often called 3-way) light switches for a few dollars each. Those two switches will let you select Low, Medium or High speeds. When the first one is on Low the second switch does nothing, but when the first switch is on Medium/High then the second switch will select between Medium and High speeds. from HappyWoodworking.com

http://www.happywoodworking.com/images/MotorWiringSpeedSwitch.jpg

[Scott T Smith]

I did the same thing about 15 years ago, and purchased my switch from Graingers. It had the proper amp rating on the contacts and has worked well. Probably about 25 bucks back then.

[Phil Thien]

I'm not sure if this information will help or not...


THREE SPEED MOTOR SWITCH

You may find a 3 speed motor in an old furnace blower. You can get a 3-speed fan switch from the local hardware store for under $5 but chances are it's for a ceiling fan and can't handle the amps on a furnace fan motor. You could plop down $20 or more on a 3-position switch with a higher amp rating, or you could do it with a few 15A switches that you would use in your house for lights. Basically the first switch is your simple SPST light switch that you can get for about $1. That controls ON/OFF, then you need two SPDT (or often called 3-way) light switches for a few dollars each. Those two switches will let you select Low, Medium or High speeds. When the first one is on Low the second switch does nothing, but when the first switch is on Medium/High then the second switch will select between Medium and High speeds. from HappyWoodworking.com

http://www.happywoodworking.com/images/MotorWiringSpeedSwitch.jpg

Thanks Bob. If I can't find a purpose-built switch for a good price I can give that a shot.

[Phil Thien]

I did the same thing about 15 years ago, and purchased my switch from Graingers. It had the proper amp rating on the contacts and has worked well. Probably about 25 bucks back then.

$25 fifteen years ago? I'll bet they're $40 now. I was thinking $10 or $15. At least you gave me somewhere to start looking, so thanks!

[Phil Thien]

Can I used one of these?

http://www.grainger.com/Grainger/POWER-FIRST-Rotary-Switch-2VLR8?Pid=search

The contacts are rated for 13A at 125V.

My motor is only 1/4-HP.

But I know inductive loads are different from resistive loads. Just not sure if a switch like this will be reliable.

It's cheap, I like that. :)

[Alan Schaffter]

Phil, go to Lowes or Ace and buy a replacement 3-way pull chain fan switch. You'll find them in the fan section :)

I think most are good for 3A so should be no problem handling the current of a 1/4 hp motor (if it were only 60% efficient it would draw about 2.7A @ 115V). I got a good deal on a Jet 1000B air that had a control circuit board fried by a lightning strike. I pulled out the circuit board, drilled a hole in the bottom of the cabinet for the pull chain switch, and wired it to the motor. Works fine.

Oh, and if you thought ahead when you built your shop, or can still put in a switched ceiling outlet, you can replace the regular wall switch with a timer switch so you can set the air cleaner to run for awhile after you leave the shop.

Less than $5 (http://www.google.com/products/catalog?hl=en&rlz=&q=pull+chain+switch&um=1&ie=UTF-8&tbm=shop&cid=18068986992930974285&sa=X&ei=vS7bTdKNL9KtgQfPua33Dw&ved=0CCgQ8wIwAA&biw=1366&bih=632#) at most retail places or online at Amazon. The contacts for the one at the link are rated for 3A inductive, 6A resistive @ 125V and good for a 1/4 hp motor . . . . . . and only $2.00 somewhere(?)

http://www.minute-man.com/acatalog/PHILMORE30-9158.jpg

Pull string just visible in far corner of the bottom of the air cleaner:

http://www.ncwoodworker.net/pp/data/500/medium/IMG_2759.jpg

http://www.ncwoodworker.net/pp/data/500/medium/IMG_2757.jpg

[Scott T Smith]

Phil, that should work just fine. The one that I bought had a much higher amperage rating, hence the increased cost.

I like Alan's suggestion regarding the fan switch too.


Can I used one of these?

http://www.grainger.com/Grainger/POWER-FIRST-Rotary-Switch-2VLR8?Pid=search

The contacts are rated for 13A at 125V.

My motor is only 1/4-HP.

But I know inductive loads are different from resistive loads. Just not sure if a switch like this will be reliable.

It's cheap, I like that. :)

[Phil Thien]

Phil, go to Lowes or Ace and buy a replacement 3-way pull chain fan switch. You'll find them in the fan section :)


I gave those some thought, but I'm not going to mount this to the ceiling. Bending over to pull the chain might be a little weird.

Apologies for the double entendre.

[Larry Edgerton]

Phil

I posted a pic of the one I built on here some time ago, but can't find it now. It was an octagon with 20x25 filters on each side, and a squirrel cage fan in the middle pulling the air through and blowing it out the top.

I used to race off road and so studied air filtration for extreme conditions, and what you want is to move the air through the filter as slow as possible, hence the large filter area. I used a three speed fan, but set it on the slowest speed, just by selection that wire. I tried it on higher speed, but it did not work any better and the noise was annoying to me.

I originally built this to paint a van in the shop. I hung it over the van, sprayed on three coats, and the floor was clean. All of the overspray went to the filters, they were immediately the color of the paint. The ones sold commercially are useless as far as I am concerned, not enough filter area for what they are being asked to do, and they only draw from one direction. I made mine switched with the lights so that if I was in the shop it was filtering, and I didn't have to remember to turn it on.

I did have 15 foot ceilings in that shop, so height was not an issue, but the same idea could easily be done with a filter arrangement that was not vertical. In my newshop I am considering doing a filter dropped soffit all the way around the room as my ceilings are only 12 feet in this shop. Of they could be splayed on an angle, many possibilities.

But on the question of speed, I don't think it is really important, Find the wire that is the speed that works for you and don't have any unnecessary complications. I am a firm believer in the KISS principal. Parts break by percentage.....

Larry

[Phil Thien]

Thanks for the thoughtful post, Larry.

I found your air cleaner, here:
http://www.sawmillcreek.org/showthread.php?98274-Dust-filtration-experiment&p=991622#post991622

Pretty neat!

I won't be able to go with eight filters. I have low ceilings and this unit will have to sit on the floor. I thought I'd use at least one 4" deep filter and maybe a cheapo 1" in front of it to make the expensive 4" last longer. Maybe I'll adjust things to add a 4" + 1" on two sides.

On the issue of speed, the switch at Grainger is only $8, so for $8 I can be indecisive about speeds. Seems like a bargain to me. :)

[Alan Schaffter]

Phil, something I think you already know, is that what you need is nothing like a DC fan or even a furnace fan. You want max CFM. You don't need to be concerned with SP hardly at all since you are not pushing or pulling through ductwork (just filters). I know you probably got that squirrel cage fan pretty cheap (free?) but if you ever run across anything bigger . . . .

like this 48" beast from Northern Tool :eek: How about 19,500 CFM!?!?!?!


http://www.northerntool.com/images/product/images/251558_lg.jpg

or this little guy- 24" and 7700 CFM?!?!?:

http://www.northerntool.com/images/product/images/250730_lg.jpg

[Phil Thien]

Phil, something I think you already know, is that what you need is nothing like a DC fan or even a furnace fan. You want max CFM. You don't need to be concerned with SP hardly at all since you are not pushing or pulling through ductwork (just filters). I know you probably got that squirrel cage fan pretty cheap (free?) but if you ever run across anything bigger . . . .


LOL, those would blow my aluminum table saw over. :)

I have tried one of those box fans with a filter in front. The filter dramatically cuts the CFM by about 90%. I wonder how one of those fans you linked would handle a filter.

[Alan Schaffter]

Probably depends on the hp. :D I think a typical box fan motor runs in the fractions of hp.

[Larry Edgerton]

Couple of thoughts on design Phil......

If you can figure out a way to use more filter area you will catch more with a lower quality filter, and so less cost to keep up. I use the medium grade furnace filters with a 36 to 1 filter to exaust area ratio. My filters can easily catch the dust, and need to be changed very seldom even in my commercial situation. If I am full time in the shop I have to change them once a month in the extreme.

Two, more filter area does not cost you more money. You are going to replace your filters at exactly the same rate for the amount of air filtered, but with more filters you will replace less often, and as an added bonus, your filters will be more efficient.

I like your double filter idea, using the cheap ones in front of a better on. I will incorporate that into my new one. I have been checking out filter fabrics as another option. When I feel I know enough about them I will get ahold of you. I do have a point collection box fan made for this that has a roll of filter paper that pulls up, but it plugs pretty easily, but the paper is available in different grades. I need to do some more research on that.

Larry