Piping the dust collector outside

[rwe2156]

I vent outside, but my shop is not climate controlled. I think you have to balance the size of the shop (cubic feet) vs. the maximum CFM's of the blower, climate and season of the year.

If you have a small shop, say 3200 cu. ft. (20x20x8) and you are running a blower at say, 500 CFM's at a machine, would I be correct saying in less then 7 minutes you've theoretically exchanged all the air in the room? And the make up air has to come from somewhere, right?

I don't know how that actually translates to reality. It all depends on how hot or cold the make up air is, and how efficient your HVAC system is.

Even with my system, I'm anal about not leaving it running, tempting as it is to do that when jumping around from machine to machine.

[jteneyck]

I vent outside, but my shop is not climate controlled.  I think you have to balance the size of the shop (cubic feet) vs. the maximum CFM's of the blower, climate and season of the year.

If you have a small shop, say 3200 cu. ft. (20x20x8) and you are running a blower at say, 500 CFM's at a machine, would I be correct saying in less then 7 minutes you've theoretically exchanged all the air in the room? And the make up air has to come from somewhere, right?

I don't know how that actually translates to reality.  It all depends on how hot or cold the make up air is, and how efficient your HVAC system is.

Even with my system, I'm anal about not leaving it running, tempting as it is to do that when jumping around from machine to machine.

My shop is about 25 x 25 x 8ft, so not much different than your example, and my DC is rated at 1200 CFM, but realistically more like 800 ACFM.  As I said earlier, the temp. in my shop never changes by more than a degree or two even if I run it for an hour straight, summer or winter.  There is so much mass in the foundation and contents that there is a huge thermal mass to overcome.  Wherever the limit is on how much air can be exhausted/make up air enters, I'm not there yet and I suspect it's a big number.  Thermal mass is a wonderful thing.  But if you are in a stick-built garage, etc. with little thermal mass, the capacity of the HVAC system becomes much more important to the discussion.    

John