Piping the dust collector outside

[blanning]

I was thinking to collect the larger stuff with a cyclone, then send the fine stuff outside.  I think I remember reading somewhere that this causes problems with heating and cooling because it would suck outside air in from other places to equalize the pressure.

Does anyone do this?

[fredhargis]

I do not, for the reason you mention. But there are a number of things to consider. How long you run the DC, where your shop is located (basement versus detached building versus garage, etc.), how much DC do you have (actual CFM discharge) and some others (like where you're located) I can't remember at the moment will determine how much heat/cool loss you'll have That said, I would love to vent outside...not having a filter on the DC would increase airflow and give me one less thing to tend to and I suspect (but do not know) it may lower some of the noise in the shop. But I live in the country and blowing a small amount of fines outside wouldn't be a problem...if I covered a neighbor's car with dust I think it might be.

[Splinter Puller]

I do. I have infloor heat which has a lot of thermal storage so if I run my DC in the winter for a long time, i just crack an outside door. I only run my DC when using dusty tools so that helps. In the warmer months, I have an overhead door open all the time so pressure does not matter.

[blanning]

I do not, for the reason you mention. But there are a number of things to consider. How long you run the DC, where your shop is located (basement versus detached building versus garage, etc.), how much DC do you have (actual CFM discharge) and some others (like where you're located) I can't remember at the moment will determine how much heat/cool loss you'll have That said, I would love to vent outside...not having a filter on the DC would increase airflow and give me one less thing to tend to and I suspect (but do not know) it may lower some of the noise in the shop. But I live in the country and blowing a small amount of fines outside wouldn't be a problem...if I covered a neighbor's car with dust I think it might be.

I'm in the country so no one to annoy.  I'm likely to dump the sawdust on the ground outside my shop anyway where it will await other uses.  Why not just have the DC dump it there.  Maybe I can do some kind of test to see how it goes.

[blanning]

I do.  I have infloor heat which has a lot of thermal storage so if I run my DC in the winter for a long time, i just crack an outside door.  I only run my DC when using dusty tools so that helps.  In the warmer months, I have an overhead door open all the time so pressure does not matter.

I'm actually more worried about a/c than heat.  The summers here can be oppressive.  

I thought about using multiple smaller dust collectors.  So eject the fines outside.  But for something like a planer that makes chips, keep that one inside.

[fredhargis]

If you're more worried about the AC, it seems to me like there's another advantage to venting out. The air that comes out of my DC is quite a bit warmer than room temp. In fact in the summer if I'm running AC (small window unit, doesn't get too terribly hot here) the DC can overpower it if run for some time.

[jteneyck]

I was thinking to collect the larger stuff with a cyclone, then send the fine stuff outside.  I think I remember reading somewhere that this causes problems with heating and cooling because it would suck outside air in from other places to equalize the pressure.

Does anyone do this?

I've been running my DC outlet outdoors for over 5 years.  Wouldn't have it any other way.  I have a cyclone inside that spins out everything except the really fine dust.  Unless I'm doing hours and hours of veneer sanding with my drum sander there is never enough accumulation of dust outside to do anything about it.  The rain and wind takes care of it.  When I do run the drum sander hard, I go out and blow away the dust with a leaf blower.  

Venting outside with no filter or bags gives the maximum flow your system can generate, and it never changes because there are no filters/bags to load up.  However, if your current system does not have a cyclone and you add one, the static pressure will increase.  You have to look at the static pressure increase by adding the cyclone minus the static pressure reduction from removing the filters or bags to see how performance is affected.  In my case it was a win.  

You have to provide makeup air or the DC will either get starved for air if you shop is really, really tight, or it will suck the air down your chimney, hot water heater flue, etc, often from somewhere that you don't want.  I have a window on the other side of my shop that I open when I run the DC.  I can't remember the numbers off the top of my head how large the makeup air opening has to be, but would guess it's on the order of 25 in^2 / 100 cfm.  

I'm in a basement shop, with heat but no AC.  There is a LOT of thermal mass in the walls, floor, and everything inside my shop.  In the winter, even on days that are 10F outside, my shop might drop a couple of degrees after I run the DC for an hour or so.  The furnace does not run for long to get the shop back to its normal 68F.  In the summer, the temp. goes up a similar amount, maybe a little more on 90 deg days; the bigger issue is the rise in humidity, which can easily be 5 to 10%. However, it quickly returns to near normal after I close the window and the dehumidifier does its thing.  I said near normal because the dehumidifier will raise the temperature a degree or two as it works.  

Another benefit of venting outside is air as clean as outside air w/o needing expensive HEPA filters for an indoor unit.  I guess this might not be good if you live somewhere with lousy air quality, but for me it's good.  

John

[blanning]

I've been running my DC outlet outdoors for over 5 years.  Wouldn't have it any other way.  I have a cyclone inside that spins out everything except the really fine dust.  Unless I'm doing hours and hours of veneer sanding with my drum sander there is never enough accumulation of dust outside to do anything about it.  The rain and wind takes care of it.  When I do run the drum sander hard, I go out and blow away the dust with a leaf blower.  

Venting outside with no filter or bags gives the maximum flow your system can generate, and it never changes because there are no filters/bags to load up.  However, if your current system does not have a cyclone and you add one, the static pressure will increase.  You have to look at the static pressure increase by adding the cyclone minus the static pressure reduction from removing the filters or bags to see how performance is affected.  In my case it was a win.  

You have to provide makeup air or the DC will either get starved for air if you shop is really, really tight, or it will suck the air down your chimney, hot water heater flue, etc, often from somewhere that you don't want.  I have a window on the other side of my shop that I open when I run the DC.  I can't remember the numbers off the top of my head how large the makeup air opening has to be, but would guess it's on the order of 25 in^2 / 100 cfm.  

I'm in a basement shop, with heat but no AC.  There is a LOT of thermal mass in the walls, floor, and everything inside my shop.  In the winter, even on days that are 10F outside, my shop might drop a couple of degrees after I run the DC for an hour or so.  The furnace does not run for long to get the shop back to its normal 68F.  In the summer, the temp. goes up a similar amount, maybe a little more on 90 deg days; the bigger issue is the rise in humidity, which can easily be 5 to 10%. However, it quickly returns to near normal after I close the window and the dehumidifier does its thing.  I said near normal because the dehumidifier will raise the temperature a degree or two as it works.  

Another benefit of venting outside is air as clean as outside air w/o needing expensive HEPA filters for an indoor unit.  I guess this might not be good if you live somewhere with lousy air quality, but for me it's good.  

John

Thanks for the info.

I'm still in the planning stages for the shop building.  So I can make it whatever.  But it's likely to be largish with 12' ceilings.  Heating and cooling is going to need something big.  So maybe I can just overestimate it to make up for the cracked window.

I had been planning to get a Harvey G-700.  But if I can vent outside, it would be a lot cheaper to get just a motor and a cyclone.  Maybe I can get a small portable DC I can use if I really want to spend all day sanding when it's 110 outside.

[jteneyck]

Thanks for the info.

I'm still in the planning stages for the shop building.  So I can make it whatever.  But it's likely to be largish with 12' ceilings.  Heating and cooling is going to need something big.  So maybe I can just overestimate it to make up for the cracked window.

I had been planning to get a Harvey G-700.  But if I can vent outside, it would be a lot cheaper to get just a motor and a cyclone.  Maybe I can get a small portable DC I can use if I really want to spend all day sanding when it's 110 outside.

Why use a DC for sanding?  I would use a Fein or Makita dust extractor with a HEPA filter and a Dust Deputy in front of it.  More than enough suck for sanding, much quieter than a DC and the air is returned, clean, to your shop.  My advice is to use a hybrid approach.  Use a DC for the big stuff that only requires short term use, and an extractor for the rest.  I've been using a Fein/Dust Deputy system on my CNC for the past year.  It sometimes runs 12 hours/day, several days in a row.  It never complains.  After a year, the filter barely has anything in it.  It does add heat to my shop, but not humidity.  An AC system would easily handle the added heat load.  

John

[Stwood_]

My system is under the concrete floor. Blower sits outside on a concrete pad.
Everything get blown outside. I've never noticed any heat loss.