# Dust collector exhaust to outside?



## idahotinker (Aug 2, 2013)

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:


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## MadMark (Jun 3, 2014)

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


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## wapakfred (Jul 29, 2011)

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.


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## idahotinker (Aug 2, 2013)

@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:

https://dustcollectorwarehouse.com/products/penn-state-tempest-cyclone-filter

I've looked at Wynn of course…


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## natgas (Sep 11, 2015)

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


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## wapakfred (Jul 29, 2011)

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.


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## clagwell (Dec 20, 2018)

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.

*COST*

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.

*COMFORT*

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.


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## ibewjon (Oct 2, 2010)

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


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## idahotinker (Aug 2, 2013)

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.


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## Ocelot (Mar 6, 2011)

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.


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## pintodeluxe (Sep 12, 2010)

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.


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## idahotinker (Aug 2, 2013)

@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!


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## TexaCali (May 25, 2020)

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.


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## Notw (Aug 7, 2013)

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


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## fivecodys (Dec 2, 2013)

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.


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## wormil (Nov 19, 2011)

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.


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## AndyJ1s (Jan 26, 2019)

I would be wary of Penn State filter efficiency. They specify MERV 15, which is defined as 85% - 94% efficiency at 0.3 - 1.0 Micron. This is nowhere near HEPA standard (99.97% efficient at 0.3 microns, in the USA).

A MERV 15 filter can pass between 167x and 500x as much 0.3 - 1.0 micron dust as a HEPA filter.

Wynn's website claims 'there is no such thing as a "Cleanable HEPA" here in the United States', on their "Misleading HEPA Claims" page.

ClearVue DC filtration is MERV 15 & "Efficiency: 99.999% at .5 micron". Their filters are supplied by Wynn. That rating is interesting because by the time you include the average over 0.3 to 1 micron, the efficiency drops all the way to less than 95%, otherwise it would be a MERV 16 rating.

Oneida, on the other hand, offers several dust collectors with HEPA filters that have a "non-stick membrane for easy cleaning".

I suppose "easy cleaning" is in the eye of the beholder, but it certainly indicates they are at least cleanable, contradicting Wynn's statement. The only filters Oneida sells are replacement filters for their DC's, so they may not have one that fits someone else's DC, and not every filter is HEPA rated.

BTW, dust bin level sensors are a good idea for DCs in closed closets, that may not be checked that often.


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## AndyJ1s (Jan 26, 2019)

deleted…


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## bondogaposis (Dec 18, 2011)

I have to agree that venting outside would be the best option. But the reality is if you live in a northern state like Idaho, that is not practical in the winter if you are spending good money to heat your shop. Sure the guys in southern states can do it, they don't experience the short days and long nights and prolonged cold spells and are not spending that much to heat their shops in the first place.


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## idahotinker (Aug 2, 2013)

Well, I went ahead and created the bypass with a blast gate to be able to direct through the filter when I don't want to lose a lot of heat (long stretches with dust collector in very cold weather). Here's what it looks like:










I am stunned by how much air is moving, yet there are some strange things going on, and some new frustrations. For whatever these are worth:


When I close the blast gate (since technically it's installed backwards to normal airflow), there is significant air leakage at the gate due to the pressure, which means that any escaping air is not filtered and could be returning back into the shop. I don't want to take it all apart, but it occurs to me there's like some kind of damper that might work better.
There is significant noise to the outside through the duct and the wall jack when I run the collector. For the sake of the neighbors I feel like I need to do some mitigation. Open to ideas. It's a short 5' x 6" metal duct to the outside. Duct insulation help at all, or make it worse? I could also run the air into a plenum of some kind and try to isolate the noise that way.
Venting to the outside means a significant amount of makeup air that is not returning to the shop from the filter, so a door or window needs to be open (not much of a problem, but it does mean equipment noise for neighbors). I wonder about pulling makeup air from somewhere else, but the only thing that makes sense is from the outside.
Even when the gate is open to the outside, there is still some air finding it's way back into the shop (which makes little sense to me since this is the path of almost zero resistance). There are no direct leaks that I know of. I taped every seam, even in the adjustable elbows. Maybe it's because the air direction to the filter is more direct? Do I need turning vanes? A second blast gate ahead of the filter outlet? (This was my original design.) I've contemplated eliminating the filter altogether…
And this is the strangest thing, at least to me. I had disconnected the collector dust bin, and when I turned it on just to test the airflow, I noticed tremendous suction at the duct from the cyclone down to the dust bin. Maybe that's just normal and I don't understand the physics of it. How is the dust and particulate dropping down into that bin unless it is absolutely airtight and pressure neutral? I'm dying to know. The suction up into the cyclone was striking.

I got what I wanted…this thing really sucks (yes, I know…old pun). But I didn't anticipate all the complications. I'm hoping you experts can help me get more creative. The wife saw it and said, "never run the filter again" as she's worried about my health, more than the heating bill. What I have is fairly elegant, but I'm still not sure it's the perfect solution.

And now that I'm done writing this, I'm thinking I have a solution: create something of a "maze duct" using 2" rigid insulation inside an airtight plywood plenum attached to the ceiling. Eliminate the duct. Devise two "airtight diverters" which control airflow to the filter and/or the outside. Thoughts? Eliminate the filter entirely?

Thanks everyone. You're all so helpful!


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## wapakfred (Jul 29, 2011)

Blast gates leak, they just don't have the really tight tolerances to stop air flow, when they are on the other side of the system you don't notice it except maybe if it whistles. When in normal use and closed the slide is sucked against the body of the gate sealing it reasonable well. You could make a home made gate that seals a little better, or try to cobble together a damper as you surmised. The noise is what it is, you might be able to fashion a muffler of some type to put over the end. Some of these are just some foam wrapped around the discharge end. I think I'd try to measure the noise level first, it drops off quickly as you move away from it, so stand by the neighbors house and see how it sounds. Duct insulation might help inside the shop, but not outside, it's the air flow at the outlet making the noise. You are correct about makeup air, the only thing that makes sense is from outside. Be aware if you have vented gas appliances (water heater, gas log, some furnaces) you might draw air back through their vent, and the CO that's with it. Q 4 seems to me to be the same, or related to, Q2. If your intent on keeping the convertible feature, the blast gate ahead of the filter might help, it will also be another gate that leaks air. As to the last question, look closely at the cyclone and how air moves through it. When you disconnect the bin that's becomes the path of least resistance for the air to flow. Be aware, even a tiny leak at the dust bin will allow dust to go through the system winding up outside or in the fllter.


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## ibewjon (Oct 2, 2010)

You're lucky only the heat bill went up. If you heat with oil or gas, you could have pulled enough CO from the furnace to make you ill or dead. Why are you having ducts cleaned that often?


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## ibewjon (Oct 2, 2010)

You're lucky only the heat bill went up. If you heat with oil or gas, you could have pulled enough CO from the furnace to make you ill or dead. Why are you having ducts cleaned that often?


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## CaptainKlutz (Apr 23, 2014)

If want to reduce the exhaust noise outside, WWW search for dust collection mufflers or silencers. 
They are easy to build DIY, but several folks sell them. Here is spec sheet from US duct showing typical construction.

Best Luck.


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## tingaling (Jul 10, 2017)

Your dust collector is an air cleaner. It can make the shop safer than the outside air. I live in Northern California and due to the recent wild fires, our air quality has suffered. Recently I measured a PM 2.5 reading of 240 (safe levels are 35 or less). I opened several gates on collector and ran it for 15 to 20 minutes and measured a PM of 40 compared to the outside level of 240.


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