Venting DC Outside

[Andrew Kertesz]

As I'm trying to figure how to set up my DC I'm thinking about venting outside. What does everybody use to cap off the exhaust? Obviously you just can't leave a hole in your wall.

Thanks,
Andy K.

[Dan Friedrichs]

I just have a 45 degree elbow pointing downward. I should probably cover it with some chicken wire (to keep animals out), but.....there's really nowhere for them to go, so I'm not too worried :)

[eugene thomas]

I use 8" dryer type flapper fitting got off Amazon. And if forget to change the barrel in my shop it allows sawdust to escape outside.....

[Marty Schlosser]

Andy,

Please ensure you do your homework and research options for returning the exhausted air back into your shop. There's several different ways to acheive this and you should be able to find one that'll meet your needs.


As I'm trying to figure how to set up my DC I'm thinking about venting outside. What does everybody use to cap off the exhaust? Obviously you just can't leave a hole in your wall.

Thanks,
Andy K.

[Keith Outten]

Andrew,

Eugene's suggestion about using a dryer vent is just the ticket. I have used a 4" dryer vent for a laser engraver in the past. In my current shop I have a 4" PVC pipe going straight through the wall from my dust collector into an exterior chip box. No filters, no bags to empty and no flow restrictions so the performance is great. If you have a heat pump your all set, if you have a different heating system you will have other issues to consider that may involve exhaust gases.
.

[Ray Newman]

If your shop is heated and cooled, would not a DC exhaust into the outside remove the warm/cool air from the shop?....

[Mike Cutler]

If your shop is heated and cooled, would not a DC exhaust into the outside remove the warm/cool air from the shop?....

Yes, exhausting it will place a load on your heating/cooling system.
In the end, it's a tossup between the cost of heating/cooling the shop versus the cost of installing an enclosed system, over time.

[Ian Moone]

Venting outside the shop will avoid the urea formaldehyde gasses that outgass from cut / sawn / machined, "man made panel products" made with urea formaldehyde glues from giving you esophageal / lung cancers - so is a good idea. Yes you will lose shop heat! That can be an issue in some cold environments BUT would you sooner be warm or dead?

http://www.cancer.gov/about-cancer/causes-prevention/risk/substances/formaldehyde/formaldehyde-fact-sheet

Please familiarize yourself with the dangers of formaldehyde & make an informed decision.

Obviously those who only work with natural sawn lumber - this is no issue and heat retention then is an acceptable priority!

BUT - I suggest most of us revert to use of man made MDF/chipboard/Melamine panel products which contain Urea Formaldehyde - so the question of heat retention shouldn't come into the decision process if health/safety priority over rides it!

Lost my father to esophageal cancer - its not a joking matter... it seldom if ever rates a mention in dust collection threads on this forum for some reason?.

The formaldehde gas passes straight thru dust filters where DC systems vent inside the shop!.

OMMV.

[Charles Lent]

There are also the dangers of putting negative pressure in your shop because your dust collector is exhausting inside air to the outside this is a danger if your source of heat is a wood stove, gas or petroleum sourced furnace. By putting negative pressure on your shop you could reverse the flow on your heat source, bringing carbon monoxide, smoke, and other products of combustion into the air in your shop. You might be better off breathing the sawdust than these gasses. You probably only need to worry about this if your shop is tight so no outside air can get in to replace that lost through the dust collector, but you should at least consider this. For a well made, tight building it's a real possibility.

Charley

[Keith Outten]

If your shop is heated and cooled, would not a DC exhaust into the outside remove the warm/cool air from the shop?....

Ray,

The heat loss isn't as dramatic as you would think because most of the heat in your shop is in the walls, floor, tools and machines not the air. I use a mini-split heat pump in my 24 by 36 foot shop, it doesn't have any problem keeping things comfortable winter or summer. If you are in an area that has extreme cold weather your experience may be different.

Ian is right though, the air in my shop is much cleaner because I exhaust outside. You could spend a fortune in filters and other components to try to scrub the air and get it anywhere near the air quality in my shop not to mention the gas problems that filters rarely are able to deal with.

My Laser Engraver is just three feet away from my CNC Router and although I never run both machines at the same time I don't have problems keeping my laser engraver clean or the computer (PC) that sits between the two machines.

We have had this discussion many times here and a lot of our Members are now exhausting outside into chip boxes and happy with their less expensive and more powerful systems that produce cleaner air.

[Robert Delhommer Sr]

Dryer vents work great.

[William C Rogers]

Since I have a 7" exhaust, I have a plastic mesh cover over mine like this. 326703 I had birds build a nest in my house dryer vent with a flapper before, but that would be unlikely in a DC system. I built a homemade blast gate just inside the wall.

[Martin Wasner]

Ray,

The heat loss isn't as dramatic as you would think because most of the heat in your shop is in the walls, floor, tools and machines not the air.

For some maybe. You're not heating much space and your delta isn't that great being in the south. When it's 62º in the shop and -35º outside you'll spend a fortune pumping heat outdoors.

Another thing to consider is not having an air make up, you're pulling air through places you shouldn't, pulling moisture into places you shouldn't and potentially creating mold problems. Not an issue if your space isn't sealed up well, but most new homes need an air make up for just a hood liner. I think the cut off in Minnesota is 500cfm. Square footage of the house also comes into play.

Our new shop will have the baghouse outside, when the doors are open in the building there will be a gate in the return air to dump the clean air outside. It should help keep the shop a bit cooler not cycling that hot air from the machines back into the shop.

[Keith Outten]

Ray,

If you are in an area that has extreme cold weather your experience may be different.

Ian is right though, the air in my shop is much cleaner because I exhaust outside. You could spend a fortune in filters and other components to try to scrub the air and get it anywhere near the air quality in my shop not to mention the gas problems that filters rarely are able to deal with.



Martin,

Note that I mentioned that if you are in an area that has extreme cold weather your experience may be different.
If your shop has a garage door it will most likely take care of the makeup air issue along with other places in the structure. Its pretty rare, even in areas up North that buildings are air tight. I think that its significant that exhausting outside is probably an acceptable technique for at least 75% of the country and the health benefits are beneficial to 100% of those who use the system.

[Scott Wigginton]

In my current shop I have a 4" PVC pipe going straight through the wall from my dust collector into an exterior chip box.

Keith, could you share some pics/advise on your exhaust setup/box? I keep struggling with a design that contain most of the chips but still be easy to clean out.

Thanks,

[Keith Outten]

Scott,

My first chip box was a simple 4 by 4 by 8 foot long plywood box with a top that a flange around the edges. I cut two 6" holes in the end opposite the intake and covered both holes with a baby diaper. I used this box for several years until the plywood disintegrated and then built a second box identical to the first.

When I started the sign shop at Christopher Newport University I converted the shipping box that the ShopBot CNC Router came in to a chip box. The design was much the same as the two chip boxes that I made for my personal shop except the height of this one was only about two and a half feet tall. I put three coats of paint on this one so it is still in use at CNU.

The chip box that I am using in my shop right now is an old 3000 gallon steel tank that I purchased as scrap. I don't have a top on the steel tank, been on my list of things to do but haven't found the time. The exhaust line from my shop goes straight though the wall into the steel tank, the pipe is about 4 foot long. Since I don't have a top there isn't any need for a filter and the tank is so big the dust and chips don't fly out of the box. Several people have asked me how I intend to dump the tank when it fills up, I have two plans to accomplish the task. The first one is to use several 30 gallon trash cans and shovel the chips into the cans then take them to the local recycle center, this would take an unknown number of trips in my truck. The second option is to just wait for the next hurricane or Noreaster, the box should be empty in just a few minutes :)

[Allan Speers]

Regarding Ian's point about formaldehyde:

First, of course, the amount of formaldehyde in modern MDF, etc, is vastly lower than in the old days. It's still something to think about, though.

With an enclosed system, maybe it would be possible to build some kind of charcoal filter on the DC filter's output. You'd have to enclose the filter (s) in a box first, but it could be done. Heck, this would also cut down on the noise a little.

If you already have you full DC system enclosed in a sound- dampening enclosure, then this becomes a bit simpler.

Activated charcoal is easy to buy in bulk, online. Just figure a way to pass the air through it.