Squirrel cage blower

[David Klink]

I got a squirrel cage blower off eBay. It was listed as "around" 1460 CFM, unknown amps, 4 speed. I get the thing, and maybe I'm just naive, but it's huge! I've got a grip on CFM needs, and he listed the dimensions, but it's one of those cases where you don't really know how big something is until you actually see it in your home.:)

Anyway, the first thing I do is check out the label to see if I can discern how many amps it is. The seller said it was obscured, but maybe he was just lazy. It lists the motor as 8.8 amps, 1050 RPM. I'm supposing that's high speed.

Now, the point. (Finally)

First:I bought it with the intention of making an air cleaner. The thing is, this weighs 30+ by itself without any enclosure I might make. I'm a wee bit leery of hanging something that weight from the trusses in the garage.

Second:What would be anyone's best guess on actual CFM? This person estimated 1460, but at 8.8 amps would that be accurate? I know there's some kind of formula that could be used to calculate this, but I'm far removed from math class, and while I can ace +,-,/,x, algebra's a wee bit beyond me.

Third:How in heck could you wire the thing to take advantage of multiple speeds? That may or may not be worth it to have, and I don't know whether or not it would.

Fourth:I've done some basic wiring before, but if I just said forget it and wired it on high, should I remove the one red connector?

Last, I got it for $50 shipped. If I decided it was a little much for me to deal with and stuck it back up on eBay, what would it actually be worth? I got it for $30 + shipping, and seeing the prices on some lower capacity ones, almost have to believe it would be worth more than that.

Here are some pictures with dimensions:
http://home.comcast.net/~dklink913/blowerin.jpg
http://home.comcast.net/~dklink913/blowerout.jpg
http://home.comcast.net/~dklink913/blowerlabel.jpg
http://home.comcast.net/~dklink913/wiringlabel.jpg
http://home.comcast.net/~dklink913/wiringconnector.jpg

Any input or opinions would be greatly appreciated.

[Dan Stuewe]

I bought a 3 speed from a local A/C shop a few years ago that was a pretty similar size. I built a 1/2" MDF box for it and sized it for the largest 3M Filtreet (sp?) filters at the local Home Depot. The switch I used was a toggle that has three positions: middle=off, up and down. Through trial-and-error I wired the up for the top speed and the down for the middle speed and just don't use the low speed (actually thinking about it, you could probably wire all three postitions to a speed and have a separate on/off - like a timer :rolleyes: ). It took two of us to hang it and I feel pretty secure about that. The main problem is the size, I thought there would be plenty of head room underneath it, but if I'm stepping up when I go under it, my noggin is hitting the bottom of the box. My idea is to someday take it down (I'll use a different friend) and either build a new box or convert this box to a sanding center/outfeed table/ air cleaner.

On the performance standpoint, I am pleased. If I'm running it while making dust and then for a bit afterwards, when we go into the garage there isn't a lingering smell of sawdust, and the flat surfaces seem less dusty - still dusty, but less so.

[David Klink]

I've got you...I helped a friend wire a cooling fan for his son's computer with a toggle switch in a similiar manner. Same principle, smaller scale. I wonder if you could wire the highest speed to a variable speed control?

I have one that I used for a router, but haven't used it for some time. I just happened to think about that.

[Dean Baumgartner]

Dave,

Here's the formula for horsepower on a fan:

Fan Hp = 62.3*p*Q/(n*12*33000)
delta p (inH20) = p
fan efficiency = n
inlet flow CFM = Q

This is for horsepower at the fan shaft not electrical horsepower in so make a few assumptions:

For your motor 8.8 amps x 120 volts x motor efficiency of 70% = about 1 hp output.

Now for the fan:

Fan delta p is 4"
Fan efficeincy is .8

Using these values in the equation above and solving for flow gives about 1300 cfm. I would say with the assumptions used that the flow is +/- 20% of that so the seller's guess isn't bad.

Dean

[David Klink]

Thanks Dan and Dean.(Did you guys ever sing together? :) )

So one filter on the intake side, with possibly some screened slotting on the motor's side for cooling? I did read where you should have it at least 12" from the wall, in the upper third of the ceiling height. I guess I could reinforce the two bottom sections of the truss where they meet for some peace of mind. Oh, and I'm a touch under 5' 7", so head clearance is rarely an issue for me.:D

No go on the v. speed control. Should have known with a fan being a soft start proposition. Runs like a champ, though.

Dean, what is the delta p=4" variable based on?

[Bart Leetch]

Mine is much the same. I mounted mine in a OSB box with the motor on top this made the depth from top to bottom less & used a 3 speed switch from ACE & a bag filter system from Grizzly with a pleated filter on the front. Work like a champ. :) If your case is made so it will span 2 trusses & your only 12" or so from the wall you should have no problems at all.

[Dan Stuewe]

So one filter on the intake side

I have a washable "electrostatic" filter first, than one of the 3M filters (supposed to be really good for small stuff). Then the blower, and finally one more 3M filter. I put the washable one first to take the brunt of the mess. I don't do as much woodworking as I would like (so I don't have much experiance with longevity), but the washable filter does a good job (i.e. it gets really dirty) and the other two are just insurance for the real small stuff.

[David Klink]

That might be the ticket then Dan. Thanks for all the advice guys!

[Bill Turpin]

Motor is probably closer to half HP. A/C's require 400 cfm per ton. Four ton blowers are usually 3/4 HP@ 1600 cfm. The listed cfm is probably pretty accurate. These are true cfm's, HP, and amps, not the inflated statistics of tool manufacturers. Be sure you apply power to only one speed at a time. If you do two you will create an auto transformer and motor will fry in about five seconds. A multiple position rotary switch that will carry amp draw would give all the speeds. You could operate at full speed when making dust and put a timer on lower speed to clean shop after exiting. Do not use a dimmer for speed control. When the small cup of the blower blades gets full of sawdust (x ... at the x, clean it. An 1/8 inch will cut cfm by 50%.

Bill in WNC mountains
NC Refrigeration License #2821

[Jack Wood]

I built a box that sits on the floor mounted on casters. My unit was rated at 220v so it really cranks out the air.:D I use 3 25x25 cheap fibreglass type filters as prefilters with a 25x25 pleated 3m filtrete final. here's a not too good of a picture, if you want better ones I can take some more for you, good luck!

[David Klink]

Motor is probably closer to half HP. A/C's require 400 cfm per ton. Four ton blowers are usually 3/4 HP@ 1600 cfm. The listed cfm is probably pretty accurate. These are true cfm's, HP, and amps, not the inflated statistics of tool manufacturers. Be sure you apply power to only one speed at a time. If you do two you will create an auto transformer and motor will fry in about five seconds. A multiple position rotary switch that will carry amp draw would give all the speeds. You could operate at full speed when making dust and put a timer on lower speed to clean shop after exiting. Do not use a dimmer for speed control. When the small cup of the blower blades gets full of sawdust (x ... at the x, clean it. An 1/8 inch will cut cfm by 50%.

Bill in WNC mountains
NC Refrigeration License #2821
Thanks for the information. This one is from a furnace. Would that make a difference, or are they fairly similiar? I was considering the suggestion of the 3 position toggle switch, but a multiple position rotary switch would be preferable, if I knew where to get one. All I saw at Lowe's and Menard's were dimmer switches, and I didn't give that a second thought.

Jack, is yours fairly efficient on the floor like that? I would prefer that to ceiling mounted and if it worked well enough, I'd probably take that route.

[Jack Wood]

Well this was what I decided to do as I only have an 8ft ceiling and hanging something that big would have really taken up space. This is over in a corner next to my dust collector so that any thing that gets past it gets sucked into the filter. I have another 110 filter in the opposite corner mounted from the ceiling so I get upper and lower air movement. Here's a pic of the "small" one. I used a left over gable fan and a 3m filtrete with a cheap furnace filter as a prefilter, it works really good. With the large one I have a long extension cord so I can move it if I need to, but I never do. I am not an AC guy or electrician, I had a an electrician wire this for me, the big one, I did the 110v, I just built the case around the motor and he juiced it:D I know my limits when it comes to electricity:eek: So there are guys on this site who can tell you more about how efficient this or that is, but when I look at the filters and see the crap in them I figure that it's worth doing. Hope this helps you:rolleyes:

[David Klink]

Thanks Jack..Appreciate it.

[Dean Baumgartner]

Thanks Dan and Dean.(Did you guys ever sing together? :) )

So one filter on the intake side, with possibly some screened slotting on the motor's side for cooling? I did read where you should have it at least 12" from the wall, in the upper third of the ceiling height. I guess I could reinforce the two bottom sections of the truss where they meet for some peace of mind. Oh, and I'm a touch under 5' 7", so head clearance is rarely an issue for me.:D

No go on the v. speed control. Should have known with a fan being a soft start proposition. Runs like a champ, though.

Dean, what is the delta p=4" variable based on?


The delta p = 4" variable is an estimate on what the pressure change accross the fan would be if you are pulling through a furnace type filter or two. It's just my estimate.


Dean

[Chris Padilla]

Check out this web site for some food for thought on these kinds of air cleaners: http://www.cleanshopair.com (http://www.cleanshopair.com/)

[Bob Hovde]

Check out this web site for some food for thought on these kinds of air cleaners: http://www.cleanshopair.com (http://www.cleanshopair.com/)

Along the same lines, http://www.zianet.com/calexander/ makes a fetish out of capturing ALL of the dust at the source. Instead of filtering it, however, he dumps it outside to totally get rid of it. His claim is that all masks, respirators, filter boxes, etc. have the same failing - they only claim to be good down to the level at which dust becomes dangerous. (His stuff may be a bit dated on the filters, but the mods to tools to insure getting all of the dust make sense.

I've been working in an open garage and am now closing in a small shop. It's beginning to worry me.

Bob

[Mac McAtee]

I built a box that sits on the floor mounted on casters. My unit was rated at 220v so it really cranks out the air.:D I use 3 25x25 cheap fibreglass type filters as prefilters with a 25x25 pleated 3m filtrete final. here's a not too good of a picture, if you want better ones I can take some more for you, good luck!

I did the same as you Jack, with an addition. On the top of the box I put 1/4" Masonite pegboard. Drilled out all the holes to 3/8" and made them funnel shape with the big end on the top.

I ran a support across the middle so the pegboard wouldn't sag too much. I put one of those bench top sanding pads that have holes in it on top.

Anytime I am sanding anything I take it to that box, turn the fan on, put the item on top of the pegboard/pad and sand it. It is amazing how much it cut down on the very fine dust in the shop. Hand sanding, belt or random orbit goes on the box with the fan on.

I too used the washable filter as the first one and then a normal filter as the second. I usually wash the washable twice before the toss away needs changing. I put the motor on a timer so I can turn it on and it will turn it's self off. If i must sand something large that I can't put on top then I run the filter, do the sanding and leave it running for an hour or so to circulate all the air in the shop.

[Jack Wood]

The links above will indeed give you some really good info on the dangers of wood dust and collection of it and offer good info on how to do that, but they, if I'm not mistaken take the approach of one system or the other. My 2 cents says use both and in addition a good quality dust mask, not the surgical mask type. The best thing you could do is to run both and vent all DC air out of your shop, not back in to it. But as it gets awfully hot and muggy in Alabama I need my AC, and its chilly in the winter so I want to keep my heat(I know it's nothing like you guys up North have, but that's why I live here:D) Will some dust get past your air filter? Yes but if properly constructed you can get a pretty good seal around the element. Are cyclones good? You bet! But the $2000 estimate from a well known manufacturer is way more than I am going to be able to afford, if I bought it I wouldn't have to worry about dust as I couldn't afford to make any. So where does that leave me? Well I am using both systems and in addition a good dust mask and I can tell a diiference in the dust level in my shop since combining the 2. I have a total of $200-250 total in motors, DC system, aftermkt shaker felt bags, and mask. So if despite all of this I still suck some dust down, well I eat fried chicken and biscuits too and we all know what that toxic stuff does to your insides:D so l feel I'm doing better than most, not as good as others. But I am just a hobbyist who turns out a rocking horse, adirondack chair etc, and turns the occasional salt and pepper shaker. My grandfather was the woodshop foreman at Pullman Standard(they make boxcars) for over 40 years and after retirement spent his time making doodads and toys for his grandkids and I NEVER EVER saw him use a dust mask, and no pictures of him working show any sort of DC system, he died at 83 from a stroke. Never complained about any lung problems. So life is a gamble in all aspects and you can get so caught up counting the flowers, that you forget to smell them. Do the best you can afford and keep working in the shop. No worries mate!:D

[Chris Padilla]

Everyone reacts differently to these things. I started geeting worreid when I started sneezing now and again...just doesn't seem right. I've known people who've smoked for 40-50 years and never had any problems, too! :)

[Bill Turpin]

Most A/C blowers are furnaces. Everything I said about cfm applies. Try www.newark.com for item #92F2740 @$16.39, 6 position 15 amps. They may have others that will work, search: rotary switch. Radio Shack may have something also. I struck out at WWGrainger.

Good luck
Bill in WNC mountains

[David Klink]

Mac, I considered the idea of a sanding station. I thought about making the top with 1/4 inch material and the sides of hte box with rabbited or grooved edges so I could have interchangeable tops. Pegboard for a sanding station, ply for regular filtering.

Bill, thanks for the link to that site. I checked Radio Shack, and I didn't see anthing rated higher than 10 amps that would suit the application. Looks like Newark In One may have something.

I'd forgotten there's a guy up the street who's an electrician. We've never had much of a dialogue, but maybe he could get his hands on something or give me a hand.

Thanks!

[Bob Johnson]

David,

I got a free 3 speed used furnace blower from the AC/furnace guy down the street. I built mine as a floor model on casters. I put doubled up filters on three sides with the exhaust blowing up. I found a two position switch at home depot that handled 10 amps, my blower was rated at 6.1 amps. I wired it to the high and low speeds and have found that I never use the high speed. I would suggest that you try it with a simple on/off switch to the low speed before bothering with the multiple speed switch.

The AC guy stressed checking the amp draw and restricting either the intake or the exhaust to keep the amp draw below the motor rating - he recommended about 1 amp below. He said if you draw over the motor's amp rating it will significantly shorten the motor's life. If you keep below the rating it should run for many years. I had origionally cut the exhaust port the size of the blower exhaust, and had to reduce it about 40% to get the amp draw down.

Bob