# Noobie questions! Beware!



## Itchytoe (Dec 17, 2011)

Once again, my ignorance has got the best of me and I must ask for help. I am greatly in need of some dust collection and air filtration. I have an old AC air handler blower that I'd like to use to set up a home built system. Unfortunately, I can't figure out what kind of CFM to expect from this thing. It likely came from a trailer house AC and has a 240v, 3.9amp 1/2 hp motor. I think a 2 or 2.5 ton AC unit.

I've heard 400 cfm per ton is typical which would put this one at 800-1000 CFM. I've also checked online and found blowers that will put out twice that at the same amperage and hp ratings. Then I read some of the other DC threads in here and found things like a 240v 13amp 1.5 hp DC blower that puts out only 500 CFM. Three times the power my blower has and draws more than three times the amperage! There's also posts about 3 hp units?! That's 6 times the power this blower has, so assuming 4 times the volume, that's 4,000 CFM. That will turn over all of the air in my entire home in 5 minutes. I have a 5 ton 2 stage heat pump in my home, which keeps it at a chilly 70 degrees when it's 95+ outside if I want it to, but I don't think it has a 3 hp blower. Ugh, There's probably something extremely simple that I'm not understanding here.

Anyway, my garage (where my shop is) is 20x30x8 so a total of 4800 cubic feet of volume. At 800 CFM, it takes 6 minutes to filter through the whole volume of air. That's 10 times the shop's volume per hour. Is that typical of a DC system, or am I way off and should look into something totally different?


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## woodnthings (Jan 24, 2009)

*Yes, look for something different...*

Air handlers/blowers are meant to handle filtered air, NOT a collection of dust chips and shavings.

Your furnace blower would be OK to make an Air Filtration Unit, overhead using a series of progressively finer filters to remove particles from the shop air, NOT for a Dust Collector. :no:

There are several threads here on shop built units.

FYI a squirrel cage blower has small blades or fins which the dust and chips clog and settle on as opposed to a blower with a 5 or 6 blade impeller which will not collect dust or chips. 

This site has a wealth of info on dust collection...lots of reading but very useful:
http://billpentz.com/woodworking/cyclone/CyclonePlan.cfm


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## Dave Paine (May 30, 2012)

*Air filtration - lots of information*

I think your message is about what I would refer to as Air Filtration. I used this term to find this link to a potential useful reference site.

http://www.woodworking-news.com/woodworking-tool-reviews/airfiltration.shtml

I cannot help with the air conditioner blower, other than to look at the nameplate as you did. A 1/2HP motor should move a lot of air. You can easily build this into a frame with filters.

How much you want to filter the air is up to you. The more air, the more electricity you will consume.

You may find the air filtration units do not state the motor HP, rather the CFM and particulate filter.

If you also need dust collection, this is a completely different function. An air conditioner blower is not going to work for dust collection. You need more suction than a squirrel cage air conditioner blower can provide.

I would not recommend trying to build your own dust collection.

This link is one site with several dust collectors to give you a feel what to look for.
http://www.pennstateind.com/store/bag-style-dust-collectors.html

Compared to the air filtration, dust collectors do rate the units in HP of the motor. I would expect most people would start with 1 or 1 1/2HP units. Personally I started with 1 HP then wanted more flow and suction so upgraded to 1 1/2HP with bag and cannister. Now considering another upgrade to a cyclone unit.

Note the dust collector max suction is rated at the inlet of the machine, so no pressure loss from ductwork. All units have a "capacity curve" which shows how the flow capacity falls with the rise in pressure drop. Some companies show these curves, many do not. In general terms, the more drops and ducting, the lower will be the flow capacity and suction.


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## Itchytoe (Dec 17, 2011)

I'm looking for something to collect the chips and dust created by the tools I use. Mostly interested in keeping things clean in the shop and cutting down on the dust so I'm not breathing all that wood. To avoid the problem of debris getting to the blower fins, I was planning on a set up more like this:

Tool/whatever - Thein separator trash can collector thingy - a few cheap-o AC filters or a filter bag set up - blower - outside/inside (I haven't figured that out yet)

That way, I'm not sending everything through the blower then filtering it. I'll be filtering it then sending the air through the blower and out the window. The filters and separators will add the same restriction on the suction side as the discharge side so I don't see how putting the blower before the filtering makes any difference.


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## woodnthings (Jan 24, 2009)

*I'll put it simply*

A blower is not an impeller. They are completely different and the only similarity is they "blow" air...
Dust collctors use impellers, air filtration units use blowers.
Blowers are higher volume air movers with very low pressure.
Impellers are lower volume air movers with higher pressures.


1. Buy or make an air filtration unit to get the smallest dust out of the shop air.

2A.) Buy a good shop vac...Rigid... and hook it to your small chip makers like router table, bandsaw, ROS sander etc.
2B.) Buy a 1HP or greater dust collector, hook it to your large chip and shaving maker...jointer or planer and to the base or dust port on your table saw.

Simply put that's it. No short cuts. 2 methods of dust collection are required.  bill


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## Dave Paine (May 30, 2012)

Woodnthings and I are trying to tell you the same thing.

Air filtration and dust collection are two different problems which require two different solutions.

If you want to filter FINE dust out of the air then you use an air filtration unit. Low airflow, and low suction.

If a machine is generating wood dust and chips, then you use a dust collection unit. High airflow and high suction.

Each unit has different requirements. I am not aware of a unit which does both requirements.


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## woodnthings (Jan 24, 2009)

*If you want to go elcheapo*

A box fan with a furnace filter will catch some "dust" out of the shop air, but it won't collect chips. Your furnace blower will also do the same as a box fan but requires a more complex enclosure.  bill


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## Itchytoe (Dec 17, 2011)

woodnthings said:


> A blower is not an impeller. They are completely different and the only similarity is they "blow" air...
> Dust collctors use impellers, air filtration units use blowers.
> Blowers are higher volume air movers with very low pressure.
> Impellers are lower volume air movers with higher pressures.


Ah ok. See that's what I didn't know. I thought they were the same thing. I know plenty about fixed equipment, but rotating equipment is completely foreign to me.


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## dbhost (Jan 28, 2008)

woodnthings said:


> A box fan with a furnace filter will catch some "dust" out of the shop air, but it won't collect chips. Your furnace blower will also do the same as a box fan but requires a more complex enclosure.  bill


Totally agree. However I have used both a box fan with a filtrete filter duct taped to it. (It's proper, I live in the south...), and a full blown air filtration unit. The air filtration unit does the same job, just a whole lot better / faster due to it's MUCH higher air flow rating.

I do have to disagree with one thing Woodnthings said, and it is my personal preference here, but I do NOT consider any 1HP dust collector to be sufficient for collecting dust, just chips and shavings. At a minimum you want a 1.5HP dust collector, preferrably 2HP or better... And 1 micron or better filtration.

An ambient air filtration unit can be built from pull out HVAC blower, a reasonable gauge extension cord with the female end cut off, a switch box, some plywood, some screws and a couple of common household filters. No need to spend hundreds of dollars on a filtration unit unless HVAC blower pull outs are hard to find near you. I was going to go that way but kept getting bad blowers (The gorillas doing the HVAC work around me were damaging them when pulling them out.)

An inexpensive dust collector that meets the minimum requirements and then some is the HF 2HP DC, and add to that a 1 micron either filter bag (cheaper) or a 1 micron pleated filter like a Wynn 35A (flows air much better). Harbor Freight frequently has coupons for this DC for around $149.00... Add a Wynn Spun Bond filter with shipping and you are around $320.00 into it.. Not free, but certainly cheaper than many alternatives, including many 1 HP machines...


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## woodnthings (Jan 24, 2009)

*1 HP is an entry level DC for sure*

There are a few that would work for a one machine at a time DC but as you say the bags are mostly 30 micron, not good enough. Here's a few:
http://www.grizzly.com/products/1-HP-Light-Duty-Dust-Collector/G1163 30 micron bag

http://www.mytoolstore.com/delta/50-720.html 1 micron bag!

http://www.pennstateind.com/store/DC1BXL-1M.html 1 micron bag!

Amazon.com: SHOP FOX W1727 1 HP Dust Collector: Home Improvement



Amazon.com: General International 10-005 M1 1 HP Dust Collector with 2 Micron Filter Bag: Home Improvement


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## Beckerkumm (Jun 4, 2012)

Remember that the finer the filter the larger the collector you need to compensate for the restriction so as other have said go with a 2 hp 12-13" impeller. I'm always surprised at the emphasis on really fine dust filters for dust collection while there seems to be none for overhead ambient cleaners. They typically run MERV 10 or less. If I were limited to a small collector I would run a 3-5 micron filter and put a MERV 14 or MERV 15 nano in the ambient. With enough power I would run MERV 15-17 in both. Dave


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