building DC closet

[newtonc]

I have had so many priorities/distractions in setting up my shop with my last relocation.And up til now I considered that a bad thing.But it has allowed me a second opinion on all my original intentions.And that has proved to be a good thing.
And I am now rethinking my floor plan and have decided on building a closet for my dust collector.I plan on having external ventilation for the closet,which I also plan on filtering.
Some of the recent posts have been about getting the DC out of the shop and I have at last been sold.
So I would like to ask...
without me hurting my head with numbers...if anyone has the answer or equation for determining the needed vent(s) diameter(and/or)number of vents to adequatley vent a 700CFM dust collector??
All advise is welcome and thanks in advance.

[JimmyC]

I too, am waiting for an answer. This is a question that greatly interests me.

Jimmy

[Jim Murphy]

Go here:

http://www.cambridgefilterusa.com/pr..._industry=HVAC

Pick a filter type, and open the PDF datasheet. Scroll down to see the CFM and size. The "tighter" the filtration, the larger the filter needs to be (that should be obvious). For example, for the Absolute Filter 1 (a HEPA filter) the CFM ranges from 80 CFM to over 2000 CFM, depending on filter type and dimensions. Less "effective" filters pass much larger CFM values through smaller filters. Again, that's a no-brainer concept.

For general purpose uses, assume that a home HVAC system needs approximately 400CFM per ton of air conditioning. (source: http://americanstandardair.com/HomeO.../Glossary.aspx scroll down to definition of CFM)
Look at the tonnage of your home AC system (where one ton of AC is 12000 BTU) and measure the size of the air filter you have on the return. That should give you some ideas to work with.

Note that this is the result of Google searching and not MY personal knowledge of such things. I intend to return approximately 1800CFM from the Clearvue through a 12X15 window. So there.

[Gotcha6]

Help me with your math here, Jim. 1800 cfm through a 12 x 15 opening (assuing no friction loss) would result in a velocity of 1440 fpm (1800/12*15/144). That's 24 fps or approx. 17 mph. Is that too stiff a breeze for you going back into the shop or are you venting it outside?
BTW, ALL my closets are dust collectors.

[Jim Murphy]

Dennis,

While you can safely ignore the friction losses, you cannot ignore the fact that the DC closet floor is PT 2X6 with the inevitable shrinkage gaps and that I built the closet adjacent to the shop with no help and there are multiple unplanned exit locations for the breeze. That is, it ain't exactly tight. Beside, I kinda doubt that we're really gonna see 1800 CFM out of the system.

Here's what Ed's site says: CV 1800 18" Diameter x 48" long with inclined rectangular intake chute. 3/4" MDF top. 6" long piece of Flex hose connected to bottom of cyclone. Max CFM through a 6" pipe 1442

CV 1800 MAX Re-designed 18" Diameter x 48" long with inclined rectangular intake chute. 3/4" MDF top. 6" long piece of Flex hose connected to bottom of cyclone. Max CFM through a 8 " pipe 1935

Honestly, I don't know if I have the 1800 or the MAX, but I don't have the 8" pipe, so it's probably more like 1442. Or less.

If it is breezy, I'll just fabricate a deflector to shoot the breeze upward and circulate the conditioned air. Suck from down low and return up high seems to be the right direction winter or summer.

Also, since I make sawdust when I want to, not because I have to for a living, if it's 35° outside, I may decide to post quirky comments here and wait until it's 60° outside to make dust. Then I can open the door and not worry about the breeze.

[Alan in Little Washington]

Good decision to put your DC outside- gets the noise and dust outside.

I can't tell by your post what your DC configuration is, but sounds like a basic blower and bag setup. Technically, unless you are going to have a long pipe run to vent your closet/enclosure, all you need for a vent is the same size pipe/opening as the one that enters DC, though I would go with a little larger pipe/opening. Are you still going to use a bag or are you going to be discharging dust/chips directly into an open bin outside with no filter bag? If you can get away with it where you live, that will yield the most effective/efficient DC system CFM wise. The next best is a cyclone venting to the outside w/o filters.

I recycle the air from my DC/cyclone (though I am considering possibly a direct vent)- after the air leaves the cyclone it goes to two cartridge filters connected in parallel in an enclosure. The filtered air is returned from the enclosure to the shop via a standard HVAC return/filter register, I think it is 14" X 20" (I use a HVAC filter just in case I get a cartridge filter blow-out).

[newtonc]

Alan
It's a .01 felt bag on top/garbage bag on the bottom,kinda dust collector.
The closet will be within the shop,but vented outside through the wall.I do plan on still using the bag.And with adhesive and caulk and a weather strip door,I don't see any reason why the closet can't be sealed up tight.
Thanks for all the advice, everyone.

[Alan in Little Washington]

Originally Posted by newtonc

Alan
It's a .01 felt bag on top/garbage bag on the bottom,kinda dust collector.
The closet will be within the shop,but vented outside through the wall.I do plan on still using the bag.And with adhesive and caulk and a weather strip door,I don't see any reason why the closet can't be sealed up tight.
Thanks for all the advice, everyone.

.01? How many microns is that? Most typical fabric filters are rated at 30 microns, some down to 5 microns, while the good cartridge filters stop particles as small as .5 microns.

That will work, keeps the dust that always escapes from fabric bag filters out of your shop. You should see a noticeable reduction in dust on everything. The only thing to made sure is that you don't make the space too small- you need a little air circulation to keep the motor from overheating. Is it that you have the luxury of space why you aren't putting the whole mess (literally ) outside?

I guess I'll throw in here that I made an improved version of the original Wood Magazine cyclone (added a spiral inlet ramp) that worked superbly well- which to took to the dump a few years ago- nobody wanted a FREE cyclone!?!?!?!

[toolferone]

The first thing I want to ask is, are you runing heat/air in your shop. If you are then you will be throwing $$$ out the door. You need to vent it back into the shop if you are heating/cooling your shop.

[Alan in Little Washington]

Originally Posted by toolferone

The first thing I want to ask is, are you runing heat/air in your shop. If you are then you will be throwing $$$ out the door. You need to vent it back into the shop if you are heating/cooling your shop.

Tom, true, but only to a certain extent- the mass of the floor and shop structure hold a lot of heat and (cool). It won't be too noticeable on your body, but you may notice it a little in your wallet.

The BIGGEST problem with discharging outside is if you have an oil or gas fired furnace or hot water heater. Unless you have one of the new "closed" systems where the furnace/water heater draws combustion air from outside and the combustion chamber and flue are sealed, discharging your DC outside will cause a reverse flow in the flu, and can be VERY DANGEROUS due to carbon monoxide be sucked into the shop.

This was a problem in my prior shop before I returned the air. In this shop, I still return the air but have a heatpump system. I think the advantage gained from getting a fabric bag DC out of the shop, outweighs any disadvantage of heat/cooling loss.

[newtonc]

Sorry... it's a 1 micron upper bag.
And it's not that I see dust,I don't see a thing,but I know it's floating around.Your not really seeing 1 micron add up that quickly.
All the units are self contained and seperate,not an issue.
I do have a lot of space.But it's never enough.I do hate to cut in to it with the closet,but the look of it on the outside is out of the question.
I have the shop's humidity controlled.Right now I don't have it heated or air'ed.I don't consider it a real problem.It will probably be hooked up in the next year or so,but I doubt I will use the heat much.It's pretty cool in the shop as it is and I would prefer the cold anyway.I lived for many years in the Colorado Rockies.This is my second winter here and I can count on 2 hands how many times I have needed long pants.
And just a thought,you can also add an intake vent if the furnace,etc. are an issue.
thanks everyone for the feedback.it all helps.

[Cuprousworks]

I'm on the fence whether I should be placing my DC in a closet. Since I'm building the partition walls in my shop right now it ought to be quick and easy, right?

I started with an idea of a partition wall in the corner, with the hope that as a baffle it might lower some of the DC noise. Then I got thinking about fire. For some reason I've always worried about a spark off my impeller smoldering in the dustbag for a couple of hours after I leave the shop. Since the shop is in my basement of my house... (no, I don't have a floor sweep or ever use it as a floor vac, but an irrational fear isn't easily swayed)

So the thinking moved to a closed closet, maybe with double drywall layers or possibly firecode drywall and an exterior or fire-rated door. But there's the need for venting - which I was thinking would be a 16x20" vent in the wall, mitigating likely protection from both noise and fire. Now thinking about some sort of an offset inlet/output or baffle arrangement, maybe incorporating another filter for final-stage filtering of any blow-by dust.

Has anyone considered this or am I just over-engineering? I have one of those simple Delta bag DCs (older) with the shaker felt bags. Probably upgrade to a cannister and plastic bag operation sometime after the shop is finished. (And after all that the DC will probably be sitting out in plain sight in the corner)

Mike

[Alan in Little Washington]

My recommendation is to get the DC out of the shop. On a similar note- we had a central vac put in our new house with the vac stuff in the garage. It is so nice not have the noise and recycles dust of a regular vac in the house.

[newtonc]

Originally Posted by Alan in Little Washington

My recommendation is to get the DC out of the shop. On a similar note- we had a central vac put in our new house with the vac stuff in the garage. It is so nice not have the noise and recycles dust of a regular vac in the house.

Good point Alan.
I wish that would work in my circumstance.
But I like your point.