another dust collection question

[Greg Visser]

I'm in the process of designing a dust collection system for my shop. I like the idea of exhausting outside for the health benefit as well as maybe a noise reduction. But, I've got the same considerations as most for the heated space exhausting outside. In Northeast Tennessee, there are about 3 months a year that I work with the heat on in the shop. Has anyone ever fashioned a system that can switch back and forth between outside exhaust and filter? Maybe a diverter of sorts that would let me choose based on the temperature? It doesn't seem like it would be that difficult.

Thanks,
Greg

[Ken Fitzgerald]

Greg,

It wouldn't be hard to use or make a couple blast gates to divert the dust/air flow to one or the other but....I think there are folks here that exhaust outside in cold climates with no noticeable problems related to heat though in theory a negative pressure could effect furnace operation.

[Gary Salisbury]

Ken has a good suggestion but I would add to that to install some additional filtering if the air is coming back into the shop. Furnace filters are cheap. Make use of them!

[Greg Visser]

Well, then that leads to a second question. How many guys have experience exhausting directly outside from heated space? What has been your experience with heat loss?

thanks,
Greg

[Dan Friedrichs]

I believe Alan Schaftter has a system with the ability to switch between a filter and outside exhaust, although I couldn't immediately find a link to his write-up. As I recall, it wasn't tremendously more elegant than just a Y fitting and 2 blast gates, though.

Here is an extraordinarily long thread on the topic of heat loss:
http://www.sawmillcreek.org/archive/...t-131889.html?

The take-home message is that the heat capacity of air is very low (relative to things like metal tools and concrete floors). For a hobbyist running a DC intermittently, the cost of the heat lost is probably less than the cost of filter replacements, so it's generally preferable to exhaust outside. If you already own the filter, I'd build a way to switch it in for particularly cold days (and that way, you capture the heat energy "wasted" by the DC for some additional shop heating, as well). If you don't already own the filter, depending on your location and usage patterns, it might be better to just forgo it and always exhaust outside.

[Lornie McCullough]

Well, then that leads to a second question. How many guys have experience exhausting directly outside from heated space? What has been your experience with heat loss?

thanks,
Greg

Hi Greg....

I vent outside, and I feel it is a non-issue. You've probably already read the reasons why.

Lornie

[William C Rogers]

Greg, I just set up my DC system to vent outside. I am in southern Indiana. I would agree with Lornie that it is a non issue for heating. I converted my twin bigger to a cyclone (eBay cyclone) and kept the filters for a while just in case to do what you suggested. I sold the filters recently as I will never need them. AC may be a different story.

edit: I do not have any visible dust at the DC outside and it is fantastic having full performance every time I use the DC.

[Greg Visser]

Does anyone know if any of the cyclone manufacturers will price their units without filters, or do you just have to buy the "stock" unit? It seems like that may present a savings.

Thanks,
Greg

[John K Jordan]

Greg, I use a ClearVue and I think they will sell without the filters, connection, and cleanout box. As for your earlier question about switching I saw pictures of a big valve someone devised: turn a handle and a metal flap would switch exhaust from one duct to the other. I think I saw this on the ClearVue forum. Lots of good DC ideas there.

JKJ

[Tom Hyde]

I have the dust collector outside (Oneida Cyclone V-3000). In addition to dust and noise benefits, I don't have to mess with a filter. When I run the collector, I open the garage door a foot or two. Obviously, having an air inlet is very important, especially if you have some type of combustible heating in the shop (including gas appliances). All of that said, I don't think it's a big issue and the benefits well outweigh the negatives. Having radiant heat floors helps a bit, and I have a wood stove (with its own outside air inlet) that I'll get going if I'm going to be doing a lot of work with the collector going. I've checked, and with the door open a bit, I'm not sucking stove exhaust into the shop. Even in subfreezing temps, hasn't been an issue.

[Dan Friedrichs]

The benefit of a cyclone is that it separates more dust from the air before the air hits the filters, prolonging filter life. But if you don't have filters, you don't need a cyclone, because you don't care about fine dust in the air. Just use a trash-can type chip separator to collect the big pieces, and the fine dust can just blow away in the wind.