Dust collector exhaust to outside?

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Forum topic by idahotinker posted 05-11-2020 06:46 PM 2310 views 0 times favorited 24 replies Add to Favorites Watch
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42 posts in 3000 days

05-11-2020 06:46 PM

Topic tags/keywords: dust collector exhaust dust filter air quality heating

I have a Penn State Tempest TEMP142CX 2HP cyclone dust collector, which has a twin/stacked canister .5 micron filter. The unit is mounted in a separate small room, and then I have constructed basically a plenum which opens between the shop space and the DC room. My thinking was that (since I live in central Idaho and it can get very cold) I would pull the air from the shop, through the DC, pass it through the filter into the airtight room, and it would return back into the shop via the plenum without losing much heat. After spending the better part of yesterday cleaning out the filter, I was shocked at the airflow restriction through the filter, which obviously impacts the performance. The mostly-cleaned filter (I gave up after a couple hours) significantly improved things, but I wondered if I shouldn’t just punch a hole in the wall of that room and vent the DC to the outside. I would be giving up 1900 CFM (theoretically) of conditioned air if I did so. My shop is heated, insulated, and about 24×13x10 (3,120 CF). I would need to open a window (I think) to avoid negative pressure (and air leak whistling I assume) inside the shop, which would obviously impact the temp in the shop. If my math is right, theoretically the DC would suck all the air out of that room and to the outside in less than two minutes.

I thought about only using the filter during the winter months, and then quickly attaching to a duct to the outside during the warmer months. I suppose I could also split the air exhaust between the filter and the outside, but assume the path of least resistance would always direct the air to the outside.

I’m worried about the cold air coming into the DC room via a duct to the outside, but only a little since it’s mostly thermally separated from the conditioned shop and living spaces.

Anyway, I’m not sure what the best course is. I’ll have to invest about $100 to do the vent to outside right, but then all the micro-particles will just enter the atmosphere and won’t be clogging up my filter. What would you advise?

Some photos:

-- Making sawdust in Idaho since 1968

24 replies so far

View Madmark2's profile


3096 posts in 1830 days

#1 posted 05-11-2020 06:49 PM

It will pull heated air from your house. Your heating bill will soon exceed your mortgage.

-- The hump with the stump and the pump!

View Fred Hargis's profile

Fred Hargis

7229 posts in 3735 days

#2 posted 05-11-2020 07:19 PM

The filters won’t last forever. On an Oneida I used to own, I replaced the OEM filter after 6 years because it got to the point where cleaning didn’t improve air flow. I actually replaced it with one from PennState made for their cylones, and it was a better filter than the OEM Oneida. What I’m saying is: replace your filter and save your heat. Some other things to keep in mind, a cyclone needs sufficient airflow to do the sensation thing. If you have inadequate ductwork or some other circumstance reducing that air flow…more fines than normal will get to the filter.

-- Our village hasn't lost it's idiot, he was elected to congress.

View idahotinker's profile


42 posts in 3000 days

#3 posted 05-11-2020 10:52 PM

@Madmark2, your point is well taken. The house is not impacted, the shop stands alone but I realize it would not be ideal.

@Fred Hargis, since Penn State got out of the business, and you aren’t sold on Oneida, are there other brands? I found this, but not sure about the quality or reputation of this brand:

I’ve looked at Wynn of course…

-- Making sawdust in Idaho since 1968

View natgas's profile


55 posts in 2231 days

#4 posted 05-11-2020 11:04 PM

I vent to the outside in my woodshop—a separate building from my home; no more than I run the DC, I haven’t noticed a real difference in either heating or cooling

-- Randy

View Fred Hargis's profile

Fred Hargis

7229 posts in 3735 days

#5 posted 05-12-2020 10:32 AM

Penn state got out of the DC business, but the last time I looked they still sell filters. This is the one I bought. These filters are very high quality, made in USA by Clark Filters in Pensylvania. The price has went up significantly…it was $160 the last time I bought one. If you don’t wnat that one, I would look for something from Wynn Filters.

-- Our village hasn't lost it's idiot, he was elected to congress.

View clagwell's profile


387 posts in 1034 days

#6 posted 05-12-2020 01:32 PM

Just in case anyone else likes to see numbers as much as I do…...

First, CFM. 1900CFM is the free fan rating of the blower. That number is obtained by testing the blower by itself, no cyclone or filter. A variable speed booster fan is connected to the test fan and the speed adjusted to force zero pressure drop across the test fan. The CFM measured is the free fan rating. It’s only vaguely related to actual system performance. A Wood Magazine test from 2003 shows an actual 800CFM maximum with no ducting. I see quite a bit of what looks like 4” hose in the photos so likely no more that 500CFM.


Air weighs about .075 lb/cuft so 500CFMx.075lb/cuft = 37.5lb/min. Air heat capacity is about .24 BTU/lb/F, so you are losing at most 37.5x.24 = 9 BTU/min per degree of temperature difference. It’s usual to use BTU/Hour so 540 BTU/Hour per degree.

I don’t know what your average winter temperature is but Google tells me that Boise averages about 30F through the winter months. For an inside temperature of 60F we have 540 x (60-30) = 16,200 BTU/Hour while the DC is running.

Check your energy supplier for average temperature and cost per BTU. Using a fairly high value of $40.00 per million BTU gives about $0.65 per hour. Electricity cost to run the DC motor might be as much as $0.30 per hour.


If you try to use your shop when it’s 0F outside it will cool off quickly, as you pointed out. There is a lot heat stored in the mass of your shop so it won’t get as cold as you might think but yes, you could experience some discomfort. At a 60F difference you’re losing as much as 32,400BTU per hour. I doubt if your heating system can match that.

-- Dave, Tippecanoe County, IN --- Is there a corollary to Beranek.s Law that applies to dust collection?

View ibewjon's profile


2641 posts in 4035 days

#7 posted 05-12-2020 01:39 PM

+1. The new filter is much cheaper than the lost heat.

View idahotinker's profile


42 posts in 3000 days

#8 posted 05-13-2020 02:20 PM

Thanks everyone. I’ve been reading other sources and I’m thinking some of my trouble was due to letting the dust barrel overfill. At least one source said that’s a sure way to force all the dust into the filter and clog it up. I’m very grateful for all the feedback, thank you.

I’ve decided to put a “wye” at the DC exhaust and add a duct to the outside with a damper and blast gate. That way in the “not extreme cold days” I can dump the air outside. And I’ll start setting my quarters aside for some new filters, although I’m startled how much difference the good cleaning made. I can leave multiple blast gates open and get pretty good suction, although that is not my habit.

@clagwell, thank you so much for taking the time to run the numbers. Yes, I do like to see them. Facts trump anecdotes.

-- Making sawdust in Idaho since 1968

View Ocelot's profile


3396 posts in 3880 days

#9 posted 05-13-2020 09:25 PM

Have you looked at large diesel truck filters? They are considerably cheaper than filters sold for dust collectors, since there is a huge market and good competition between manufacturers. Consult Shipwrights’s blogs for details.

-- I intended to be a woodworker, but turned into a tool and lumber collector.

View pintodeluxe's profile


6488 posts in 4055 days

#10 posted 05-13-2020 10:14 PM

I run a very similar D.C. unit, the older Red 2 HP Tempest cyclone. Frankly I’m surprised to hear you complain about the filter getting clogged with fines, or that cleaning the filter made an appreciable difference.
I clean my filter once every 18 months (if I remember). Nothing ever appears in the filter cleanout, and no visible dust settles after I blow it out with compressed air.

As long as the last pipe heading into the cyclone is straight, and at least 5’ long, you will get fantastic separation. I empty my 50 gallon dust bin when it’s 3/4 full.

On a side note, I was trying to measure CFM and air velocity with a digital anemometer on my 6” metal mains. I just about lost my grip on it! That anemometer was nearly sucked up for good.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View idahotinker's profile


42 posts in 3000 days

#11 posted 05-14-2020 02:48 PM

@Ocelot, no I hadn’t thought of that. I’ll take a look.

@pintodeluxe, that’s both interesting and alarming. I do think I need to empty my dust bin more often. I’m also looking to replace the cleanout can on my unit (which I bought used). The blast gate has a very sharp fastener of some kind top and bottom and I can’t get in there easily. That fine dust just cakes when it accumulates and it’s actually kind of hard to get out the way it’s set up. I’ve seen some mashups that use a 5-gallon bucket clamped to the bottom filter. I’m leaning toward something like that. My last section into the unit may be a bit less than 5’. I’ll take a look at that. Thanks so much for responding!

-- Making sawdust in Idaho since 1968

View TexaCali's profile


6 posts in 513 days

#12 posted 05-29-2020 08:04 AM

Yes, letting the bin fill up will cause all sorts of problems. I vent my cyclone (ClearVu) to the outside, but my shop is in the garage and I live in a mild climate, so I run with the garage door open and the vent out the other end of the garage. I think your idea of venting out side during good weather and using the filters during cold months will serve you well. But heads up, the one time I forgot to empty my bin and got carried away with the planer, my exhaust ducting “exploded” and it took me months to clean up the mess.

View Notw's profile


1097 posts in 2995 days

#13 posted 05-29-2020 04:16 PM

Vent outside, can’t put a price tag on your lungs. Also, everyone i know who has vented outside has not had enough of an increase in heat loss to make it matter

View fivecodys's profile


1761 posts in 2878 days

#14 posted 05-29-2020 05:01 PM

I vent outside after running through the Oneida Super Dust Deputy. My garage shop is neither heated or cooled so there was no issue at all. I am still surprised how well the SDD works. There are bushes in the flowerbed where I exhaust to and I have yet to see any saw dust on them. I did use insulated flex duct to vent to the outside via a 6” dryer vent assembly. Originally I used regular old HVAC ducting but it sounded like a jet engine running outside. The insulated flex duct really calmed that down. If you walk past it outside now it sounds like a clothes dryer is running. I call that neighbor friendly. :)

-- A bad day woodworking is still better than a good day working.

View Woodknack's profile


13584 posts in 3622 days

#15 posted 05-29-2020 06:03 PM

There is a years long thread on this subject around here somewhere but I’ll give you my feedback based on knowing 2 people who vent outdoors.

Guy 1 has a small-medium shop and spews dust, chips, everything out the side and down an embankment. He’s been doing it for years and loves that he never has to change filters, empty bags or barrels. He is a hobbyist so the machines + DC are only running a few minutes at a time.

Guy 2 has a fairly good size shop with all the common machines, and 2 dust collectors (3hp & 5hp), is a hobbyist that sometimes makes cabinetry, and vents outside. I’ve spent all day in his shop more than once with snow on the ground outside and never felt a temperature change. The reason is the dust collectors come on and shut off with machines so they aren’t running constantly and all the thermal mass (floor, walls, cabinets, machines) preserve the heat.

I’ve been planning on switching to venting outside for a couple years but just never set aside the time to make the change. Even if I do lose some heat (I have a separate shop) it’s worth it for the convenience. Also I heat with infrared which heats objects, not air, so a draft (and my shop is already drafty) doesn’t make much difference.

-- Rick M,

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