I’m planning my Dust Collection system…
My shop is arranged so that I can put my dust collector in a large closet (about 4′ x 5′). This closed is in the corner of a room so it has two outside walls. Does it make sense to vent the DC outside? My assumption is that normally DC’s feed a “filter bag” (is that correct)
——>from shop—->cyclone—–>DC—->bag or outside?
Thanks for your thoughts.
Mark
Replies
I don't have your answer, but I am looking forward to seeing the advice you receive. I have my dust collector in a small room beside my shop. I leave the door to the shop (from that room) open when the collector is running , otherwise it would back up air pressure in the room. it is my intention to cut a window in the outside wall and put in some sort of screen. This will allow pressure to vent outside, but fine dust passing through the filter bags will still be able to collect in the room. I could not simply vent the dusty air directly outside or it would coat my house walls, plants etc. (not to mention possible problems with the neighbours).
Keith
It is possible to vent your DC to the outside. The 2 issues I've heard about regarding this kind of configuration are:
1) Depending on your climate, it may increase your heating/cooling cost since you will also be venting conditioned air (either heated or cooled on your dime) to the outside. This may or may not be a big deal to you if you only run the DC for short bursts or you live in a relatively mild climate. Something to consider.
2) The other issue (and the one with the most potential danger) is that a DC that takes inside air and moves it outside could create a condition that would not allow gas appliances (e.g. water heater, gas furnace) to vent their gases up their vents. The result can be your gas appliances exhausting CO in the living areas of your house and exposing you to CO poisoning. Now this would only apply if you have gas appliances and they are in the same general area as your DC (basement perhaps). This can be easily mitigated by opening a window in the shop while running the DC so that the makeup air is pulled in the window and not down the vent stacks used by your gas appliances.
The other popular configuration is to use a filter on the exhaust side of the DC to "recycle" the air back to the shop. You don't have the downside of the above issues but you need to use high-quality filters to clean the dust out of the air picked up from the tools.
Check out Bill Pentz's web site for additional information on dust collection http://cnets.net/~eclectic/woodworking/cyclone/
--Rob
Yes I do have the "makeup air" problem. The closet is next to the furnace and water heater. The furnace and WH are open to the shop for the same reason you describe, they need makeup air and they draw it from the large room...M.
I am considering installing a dust collection system for my 600 sq ft one man shop. I am planning on a 2HP dust collector with a filter bag the is rated at 30 micron. I plan to install the unit in a closet inside my shop. I then plan to install a couple or three hig efficiency furnace filters into the wall between the shop and the closet so the return air will pass through the filters as it returns to the shop. I am also considering installing a fan from a large window air conditioner to force additional air into the closet in order to use it as a plenum for additional air purification when the dust collector is not running. I plan to install a swinging door over the opening between the closet and the additional fan that will shut and seal when the dust collector is running.
Do you think this will work?
Warren
Warren;
Hmmm. Let's see. First the dust goes through a 30 micron filter, then through furnace filters? Why? furnace filters are FAR less efficient than 30 micron filters. They will collect nothing!
Just make kind of a return plenum lined with rigid insulation in the closet to remove some of the D/C noise. About 2.5 - 3.5 sq. ft. free area should be adequate, based on about 1200 cfm air quantity.
Can't quite see the window A/C "thingie". Doesn't make any sense to me. Remember that a window A/C has no air delivery ability once the air is released from the unit. You cannot add any resistance to the air flow for those things.
Brian
(Retired HVAC Engineer)
Brian:
In regards to the discussion on the dust collection/venting outside, would it be possible for a cyclone to be installed outside, and still have the exhaust air from the DC to go back into the shop? Would the area below the cyclone need to be sealed off, to mitigate a negative air space? I was always taught that air takes the path of least resistance, so I am guessing that if the area under the cyclone is not sealed the fan will draw it's air form the bottom of the cyclone and will by pass the shop. Is this correct?
Steve
Steve,
"In regards to the discussion on the dust collection/venting outside, would it be possible for a cyclone to be installed outside, and still have the exhaust air from the DC to go back into the shop?"
Yes this is possible and many do just this to save space in their shop. You still need a good quality filter since the air is coming "back in" the shop. Since you aren't really removing any air from the shop, you don't have to worry about make-up air issues .
Would the area below the cyclone need to be sealed off, to mitigate a negative air space?
The cyclone will not work if you do not seal the bin under the cone. Separation will not occur and you run the risk of over heating the motor. The bin is often required to keep enough resistance in the system to keep the motor from drawing to many amps. So you'll still have to empty the bin. Of course if the cyclone is outside you could make the bin VERY large. Just make sure it is air tight.
--Rob
Sorry but I don't understand what you are trying to describe.
If you just follow where the air is going you will answer your own question. How does the air get back to the shop after it leaves the final filters at the DC? Is it still the same temperature or is it outside air that is getting back into the space?
We often put the DC in a concrete block enclosed "closet" outside the shop and provided an opening for air to return to the shop at low velocity (low pressure drop) once it left the DC and was in the "closet". We also provided noise isolation in this return air path.
Brian
Brian:
What I was trying to do was to put the DC outside of the shop, with a return duct back into the shop. That way I can collect the main sawdust, chips etc. outside of the shop area, and then have a return back into the shop with cartridges. I just needed to know if the area below the cyclone needed to be sealed or not.
Thanks for your help.
Steve
Let me see if I follow your plan. The cyclone is outside but the DC fan discharges into filter bags located back in your shop. The air then returns to the shop through the bags. In that case you don't need to enclose the area below since the chip collector is sealed and the air has a direct path back to the shop.
Brian
Thanks, that what I needed to know. I thought I saw a show on Woodworks that showed David Marks setup and it looked like the sawdust and chips dropped right to the ground. Couldn't figure out how that worked??!?
Thanks again
Steve
What you propose to do will work. I am trying to follow your logic as to WHY. Blowing the air back into the shop is just returning the fines so that you can breath them. As far as saving room - the big bags or cannisters would still be in the shop. Would you not lose airflow in the needed piping to run it outside and back in again? I can only see that it could make dumping the cyclone easier. Do you have some other reason that I have missed. I posted earlier, saying that I was moving my sysyem outside and I have done that now. The whole system is under a shed roof to keep it dry otherwise it is completely outside. I have a vent on the other side of the shop for make up air so that it does not create a vacuum in the shop. So far I am very pleased. It is now much quieter. I have more room in the shop, no dust in the shop from recirculating fines and it is better for dumping the collector bags. There may be a slight disadvantage in the winter for heating, but the climate here is pretty mild, so in total it has been a good change for me.
Keith
Keith:
thanks for the input. I want to move the DC outside to lower the noise and make more room in the shop. It will also be easier to dump the sawdust, and I can put a bigger bin under it so I don't have to dump so often. I also wanted to get it outside in case there is ever a fire in the system. I have a 100 year old schoolhouse that I am turning into the shop. It is 22'x32' with 8 windows, so there is not a lot of wall space. I am in Kansas so the winter is an issue. I was planning on putting the DC next to the outside wall with a shed roof over it, and running the return air with a cartridge back into the shop. I am seriously looking at the Penn State cyclone. Thanks for your input, sounds like your system works great.
Steve
It looks like you are after all the advantages that I saw in putting the system outside, however I did not need to deal with make up air, (one of the benefits of the west coast climate). I would however point out one other observation.
I used to live in a cold climate - the Canadian prairies. If you sucked air out of the room, through outside ducts and a cyclone then return it, I think it will be chilled to outside air temperature by the time it gets back into the shop. You could think of insulating it, but the only sure way would be to run it through a heat exchanger. This brings up the problem of the exchanger plugging up.
Here is my solution in more detail. I did just what you propose and I don't have heat in the shop so make up air is just outside air, it works great. I also have a small shop just inside the heated house that I use for "clean" work. I can do my layouts, organise, glue and clamp, carve or work with hand tools in the small inside shop and endure a bit of cold in winter months to do the dirty work. It is a luxury. Maybe you could add a wall to do something similar. Occasionally, I use a portable electric heater in the bigger shop, just to take the chill off, if I really need to work there when it is really cold. I have been quite happy to trade off some drawbacks for the clean air. Since setting up the system, the complaints from my wife have stoppoed, my lungs are better and I am not covered in dust. The shop is also much cleaner.
Keith:
I thought a little about the heat exchange issue of the air running out to the DC and then back into the shop. The DC will be right next to the outside wall, in it's own enclosure and then the return air will come back in through the wall. If I have to I will insulate the enclosure, but I dont think the air will cool that much to notice.
Now all I have to do is come up with the cash for the DC, ducting etc. and will test it out.
Thanks for your help and input.
Steve
kieth....I saw a shop near winterpeg where the dust collector was enclosed in it's own little seperate and insulated closet at one end of the shop, the door to which had insets for furnace filters.The heated air was filtered through the dust collector, and then filtered through the furnace filters. It was described as effective. Back then they didn't have the room hepa air cleaners, so that would be an improvement. No heat loss, clean air.Eric
in Calgary
Yes! That would work, I had thought about doing that and putting a really large filter in the wall between the shop and the little room. A large filter area would slow the return air current so that it would not stir up dust that was already in the shop. In the end, I just decided to get it out altogether. Perhaps the money saved on replacing filters will pay for some heat, That may not work so well in Calgary in January.
Keith
As I've read this thread, I've learned that outside venting (unless you live in the tropics and have all the windows open (or no windows)) is a lousy idea.I do like the idea of a passthru from your closet to the shop - my biggest concern with the passthru is the noise. The closet was built in my shop specifically to hold the DC and keep the noise down (it even has a hung ceiling in it with double ceiling panels to keep the room upstairs from experiencing the racket.On the other hand, if the vac pipe through the wall is 6" or 8" diameter, then the return need only be the same size and If I put it near the floor, noise should be controllableIf the 30 micron bag is sufficient then filtering the return is not an issue, though it is easy to do... (duct tape and a filter over the hole :-)M.M.
Warren,
30 micron bags are no good. Consider upgrading the bags to a quality cartridge or bag rated at 1 micron or less filtration. I believe particulate in the 1 to 5 micron range is the most dangerous. Regardless, sub 1 micron filter is what you want. 30 microns bags will just turn your DC into a dust pump.
Placing the DC in a "closet" like structure in the shop is a great way to mitigate the noise. To allow the closet to breath, your idea of using a pass-through is on the right track. Consider the following:
- Make sure the opening is large enough so that as the air returns to the shop from the closet, the velocity of the air is slow. This will prevent the return air from stirring up other dust in the shop. A diffuser filter (kind of like those 3M scrubber pads) is a good way of doing this.
- Try to locate the opening pointing in a direction that isn't directly at the main shop where you will normally be. This should help reduce the noise also.
- Don't make the opening a straight shot for the air. Make offsets. Noise doesn't turn corners very well. This will enable you to have a return without as much noise if it were a plain hole. Lining this plenum with noise insulation material (similar to what is used in HVAC) sounds like a good idea.
- Leave yourself enough room in the closet to change the bag out.
- I light in the closet is a good idea to help you see what you are doing.
Instead of pulling unconditioned air from the outside (don't remember your climate), might you be able to use that air conditioner motor/fan to build an air scrubber unit you could hang in the shop? (I am not sure of the size or type of motor/fan from such a unit) I would think that an air filter hung in the shop would more useful. It would also allow you to more easily located it so that a circulatory pattern could be established to allow for more efficient air filtration.
Sorry for the winded response,
--Rob
I am also upgrading my dust collection. After reading numerous articles and opinions, one thing becomes obvious, - it is not easy. You need a lot of airflow for good pick-up, this means a lot of air to filter and if that air is returned to the shop it means a lot of air currents to stir up dust. I have about given up and because I live in a mild climate, I think I will vent it outside.Currently my collector is in a separate closet and I just leave the door ajar when the collector is running. Reading your question and some of the other answers gave me an idea. If your closet is dedicated to the dust collector, how about using normal dust filter bags and placing a fine micron size filter over quite a large return air "window"to the shop. The large window should slow the return air and while fine dust from the filter bags may get into the closet it would not get back into the shop. The slow speed of the return air through the micron filter cloth "window" may improve its efficiency.
This is all speculation and theory, but I would like to see others comment on it.
Keith
Sounds reasonable to me. My home furnaces (one in the attic, one in the basement) have 4.5" wide Honeywell pleated filters (not electrostatic) and they catch 98% of 5 micron particles for a year - I live in MA so that's a lot of air going through the filters - one of those in the wall between the shop and the vac closet would knock down the breeze and catch much of what a bag might miss...Mark
Measure it with a micrometer, mark it with chalk, cut it with an ax.
Kieth,
You understand what I am trying to do. It sounds like it should word. I'll post the results after I have it installed. It will be a few weeks though.
Warren
I've seen this question a number of times on this and other forums and I have to wonder why we would want to take our mess and spread it around the country. People are their own worst enemies, some times. If you live in a residential area, why should neighbors have to put up with your mess? If you live out in the country, why would you want to create a fire hazard outside your own shop? I'm lucky enough to live in a very cold climate so venting outside is a non-issue. I have to keep my pollution (both air and noise) confined. Very few people even know that my hobby is woodworking and, to tell you the truth, is the way I like it. I don't like people interfering with my business and, by the same token, I don't want to interfere in theirs.
Just my opinion.
Venting. (Pun intended). LOL
If I was going to vent anything, saw dust seems reasonably desirable - certainly better than VOCs put out by body shops or chemical manufactures...The noise has to be better than the AC systems that are always on ...M.
Venting outside does not mean just blowing the sawdust and chips outside. There would still be collector bags and only the fine particles that pass through the filter cloth would escape. These are the ones that are hardest to remove with a filter and the ones that do most damage to your lungs. I think they would be a non issue when outside.
Keith
OOPS. Sorry!
I was going by stuff I'd seen posted elsewhere. Believe me, they were NOT using any bags or filters.
Nuff said.
Mark;
(From a retired HVAC Engineer, for what it's worth).
I used to design ventilation systems for school shops. We NEVER vented from the DC to outside. You need to have an air balance in your shop. What goes out MUST come back - from wherever. Where we exhausted to outdoors (e.g. for welding hoods), we provided a conditioned makeup air source. In a cool climate there is a high heating cost to condition the makeup air. Often we used an open duct from outdoors into the welding booth so the untreated air would go from the duct straight through the welding area to the hood. So it would be a little cool in there - they were welders!
In the case of DC's, we usually located them in a brick enclosed closet, often with door access to outdoors for removal of dust. The air was always allowed to return to the shop via a duct connecting the closet to the shop. Usually we provided some form of sound lining in the duct to limit the sound returned to the shop.
Of course we always provided a ventilation system for the shop. We usually put a filter directly on the inlet to the return system to remind the users that the filters needed regular attention.
We NEVER located a gas-fired appliance in a shop that could be under a negative air pressure due to exhaust systems. This is an invitation to asphyxiate the occupants.
Brian
One other consideration: In the winter, even without the makeup air problem, you will be taking heated air out and drawing cold air in, causing quite a fuel deficit!
Just my $0.02 worth!
Regards,
Don
I do my venting outside. My DC is mounted high, I move the four inch pipe around as I need it in my 9 by 13 foot workshop, it hangs from the ceiling. However, I am only a light user, a month can go by and I don't use it. With my level of use I see it no worse than if I were using the tools outside anyway which houseowners and carpenters do as a matter of course. Also the outlet is sheltered from the wind.
I hope this is of some use to you, regards Steve
Steve, how do you handle the makup-air problem discussed above - or is it not an issue in your shop?Best,
Mark
Measure it with a micrometer, mark it with chalk, cut it with an ax.
I don't understand what you mean by "The make up air problem". However. my DC is not directly connected to any machine, for that I use a domestic vacumm cleaner connected through a Triton dust collection bin. Not perfect but it works more or less and I make improvements as I go along.
All the best regards Steve
Essentially, running a vaccuum that vents outside creates negative pressure in the shop. That makes it hard for the furnace to vent - especially if it's on a passive vent (like up a chimney). That could mean CO that should be venting is coming back into (or not leaving) the shop.When I originally went to close in my furnace into it's own little "machine closet" the HVAC guys said it could not be done without providing a makup-air supply.Traditionally, Furnaces are designed to draw their combustion air from the surroundings, usually a big room like a basement. The basement has enough "leaks" to feed the furnace. Put the furnace in a little room and it potentially starves for air causing the same CO backup that the shop DC might cause.HTH,
Mark
Measure it with a micrometer, mark it with chalk, cut it with an ax.
As a firefighter (spare time, woodworker full time), I've set my 3hp dust collector to exhaust to the outside, no bags. This is for the same reason that floor sanders ALWAYS place their bags of sawdust outside after a job: any sparks generated are in there, and can lead to a fire. And I've seen plenty of sparks generated off my TS just cutting plywood. In addition, by not using a bag, the flow is substantially increased.
However, many of the other concerns need consideration, such as make up air, and especially negative pressure around a boiler or furnace. I'm about to install a new boiler, and it will have it's own air supply, sealed from the shop air. I'm in CT, and my solution has been to heat using radiant in the slab, the source being solar energy (water drainback system). With radiant heat, there's much less of an issue of heating the air, then blowing it all outside, as radiant is way more stable due to the thermal mass. I also hate emptying the bags.
The downside, of course, is this is really an entire system, not easy to retrofit, but better suited for new construction.
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