Dust Collection - Did I miss one important thing.....

[Justin Jump]

Hello All,

So, My plan for DC was going to be a 2HP, from Grizzly, 6" PVC to all the machines and one floor sweep, and I was going to locate it in the lower half of my 2 story addition, garage on the bottom, workshop on top.....

However, after some additional reading, I realized one thing. My shop is seperated and sealed from the house, it had no incoming air, if the door and windows are closed, its sealed....

I read that I should be replacing the same amount of air into the room, that the DC is pulling out. I guess this could be easily accomplished by opening a window or two a bit, to let some outside freash air in, but in the middle of Winter, not sure this is the best practice.

Has anyone solved this? Should I just located the DC in the same room? Or, just live with the windows cracked open. In the Summer, unless it's extremely too hot - I plan on working with the door and/or windows ope, so I dont think it will be an issue.

THX

[Rick Potter]

I don't think I would put a return vent to the garage below, even though it might be legal since the shop is separate from the house. Despite the assumption that the garage has proper venting for vapors, you might be sucking in unhealthy air.

My shop (3hp collector, outside vent) has to have the window open for the dust collector or the DC will starve within a few minutes. I am planning to put in a vent like you would put around an exhaust fan, only backwards to allow air to come in when needed, and be closed normally. Someday.

One oddball idea I had for mine was to make an insert the size of the window opening out of that 1/4" poster foam, cut a hole in it about 15" square, put duct tape on the top side for a hinge, and insert the whole thing where the window screen goes. This would automatically open when needed and close (sorta) when not needed. This is possible in my shop because I have a window in the rear where no one (read wife) can see it. This would be my temporary fix till I do a proper vent. Temporary in my house is a very vague word.

Rick Potter

[Andy Fox]

Just another hobbyist here who is planning to use the same 2 HP DC, but located in my basement shop....

Two things I see going on here:

1. Your shop pressure will be negative, meaning sucking air in. That might be from outside, the garage, or a room/basement where there are combustion appliances. The source is unknown, and might vary with other conditions.

2. Your garage pressure will be positive, meaning trying to get rid of air. If a car, generator, or other source of combustion is there, it could blow carbon monoxide into your shop or house. Despite being sealed, no seal is perfect.

I'd guess it would probably be ok if you can vent [edit: discharge] the DC outside (no neighbors) and open a window in your shop. Or, build a very well-sealed and insulated closet for your DC in the garage, and put a vent in between that and your shop. But, that vent could still leak carbon monoxide into your shop from the garage because your closet won't have a perfect seal. It might be a building code violation too, but I'm not sure. A carbon monoxide detector in both your shop and your house would be a good idea.

[John Lanciani]

How about leaving the DC in the garage below and putting the filter in the shop? You could even put a wye in the return line with blast gates and duct one leg of the wye outdoors. That way you could vent outside when the weather allows and vent back to the filter in the shop when it doesn't.

[Robert Payne]

Justin:

One thing in your description is unclear: How do you access the workshop in the upper level of the addition? If you have access through a weathersealed door from your house and no stairs down to your garage, then you might need to follow John Lanciana's advice an put your filters for the DC in your shop through a floor duct, thus equalizing the pressure in both spaces. But if you access the shop from the garage through stairs, then a stairwell to the upper level shop would suffice for return air to the shop; I'd add a grille in the doors (if present) to insure adequate return airflow. Check Alan Schaffter's posts about his upper level garage shop.

[Michael W. Clark]

John and Robert have good suggestions. Also the concern about gas-fired appliances is valid if applicable. Not sure about CO build up in the garage? My garage is not vented, but I don't run combustion engines in there without the door open either...Our cars are in their and I work in there some without the door open and have never had a CO issue that I know of.

Another idea would be to bring in make-up air from outside into the shop near the point of dust collection. The principal is that the unconditioned air is sucked into the collector and exhausted instead of the expensive conditioned air. This is becoming more popular in industrial systems where the work area is conditioned. Another option along these lines, would be to bring in make-up air either in a location where you are not typically working or up high. Bringing it in up high (and being cold air) it will settle but will mix with the other conditioned air and temper. If you bring it in low, it will stay low and not mix as well with the other conditioned air.

If you do not replace the air, the collector will be starved but it will still suck air, just a lower volume. I seriously doubt your shop is "air-tight". If it was, the collector would operate at the fan max SP and move 0 CFM of air. The fan max SP is probably in the 15-20"wg range. A noticably negative room is in the tenths of an inch negative (0.1 to 0.2"wg) relative to its surrounding areas. Doors get dangerous and stick, etc.

Mike

[Justin Jump]

Just some clarifications....

I access from the outside, through a set of french doors off the deck.

I wouldnt say i am completely air tight, i just have no ductwork or returns.

Lastly, the bottom half of the addition, though attached to the house with a breezeway, is still seperared by a firewall and fire door, and seperated from the combustables.

[Jim Neeley]

Justin,

I saw some pictures on the ClearVue Cyclone gallery where someone built a "closet with a removeable panel" around the filters (with 4-5" of clearance for filter cleaning and access) and then used insukated HVAC ducting (for further muffling) to route the air back into the shop. They had mounted the whole cyclone with filters in a larger closet for noise abatement. With or without the outer closet, this would be a way to recycle the filtered air back into the shop without picking up <much in> garage vapors. It concurrently removed the need to exhaust from the "garage" and provide makeup air to the shop room. Make sense?

Just one thought..

Jim

[David Hostetler]

I am not sure I understand the problem. You have an "addition" that is 2 stories, a garage below, a shop on top. Do they not share air space? If they do, no problem at all. I am a little curious. Why not keep the dust collector in the actual shop where your runs would be shorter, and exchange air won't be a problem?

[Justin Jump]

@ Dave....

They do not share air space, no access to the shop from the garage, just the french doors off the deck....

The simplest solution is most likely what I am going to have to do, but I wanted the DC, along with the air compressor which is already down in the garage, to be below for noise and to save on floor space. I am still cleverly trying to come up with a solution to keep the DC below.







245663245664

[Justin Jump]

I was going to put air and DC in the room woth the toilet - but I thought a toilet would be better.....

[Michael W. Clark]

I would keep the toilet and sink, major convenience. Why not do like Jim referred to? If you want to vent to the garage in the summer, put a panel on the filter enclosure that can be opened. No need for anything in the flex duct going to the shop, the air will take the path of least resistance. I think you would still want to run through the filter if discharging in the garage, otherwise you will get a layer of dust on everything (may still happen depending on the filter, dust PSD, etc). If you want to divert outside, then branch off before the filter to increase your flow, save on filter wear/tear, and filter cleanings.

Mike

[ian maybury]

Not familiar with the unit you have in mind, but think Justin that you may be living a little dangerously re. low airflow by using a 2HP fan and (if I read it correctly) hoping to push air up to the second floor before distributing it around a workshop to your machines. 2HP is marginal - maybe capable of doing a fairly reasonable job if the ducting is 6in and not too long - and everything else is very highly optimised. Very sensitive to any additional restriction though.

The 6in ducting will help, but it still accounts for about 4.4.in WG pressure drop per 100ft of run at the sort of airflow you need. (add 7ft or so for every 90 deg bend, and about 18in WG/100ft for 6in hose) A bag filter would likely add 4in WG and above as it cakes. Not only do they not filter properly until well until caked, they block quickly as result of having minimal area shoving the resistance number rapidly higher. A cartridge filter should reduce the filter pressure drop to less than 2in WG, but will blind quickly without plenty of area (2 cartridges) and a dust separator/cyclone.

A cyclone or a baffle will add more pressure drop - maybe 2 - 4in depending on the airflow and the design.

Then there's the question of how restrictive your machine hoods are - unless heavily modified it's almost inevitable that they will be restrictive compared to your 6in ducting. Any restriction/reduction in open area in the duct (even a short one) restricts airflow as though the rest your ducting was of that size or a little larger too i.e. a short restriction of 4in diameter will probably double the resistance/pressure drop.

A 2HP fan probably has a 13in impeller at most, and that's likely (depending on the exact blade type - BC or not) to stop delivering an acceptable say 800CFM by a bit over 9in WG, and below the 400+ CFM needed to pick up chips effectively in another 1 - 2 in WG or so.

The above numbers are pretty rough (you could do better or worse depending on the specifics), but the basic issue is that at this end of a fan curve the effect of adding even small amounts of additional pressure drop/resistance to flow is to very rapidly reduce the CFM/airflow....

ian

[Ole Anderson]

If you are going with the G0440, it has a 7" inlet, you are already starting out compromised with 6" duct. I would recommend going with steel duct and staying with a 7" size for your main run. As Ian states, you will get 4.4" of loss per 100 feet of 6" duct, but I see you only get 2.05" of loss per 100 feet of 7" pipe. To avoid flow issues, don't use 7" up vertically, the velocity may be too small to carry chips up, assuming 800 cfm of airflow, 7" down is fine.

And, Ian, I see from the Grizzly website that the 2 hp G0440 has a 14 1/2" impeller. Wish I would have measured my 2 hp Oneida impeller before I installed it. Still not sure which Grizz the OP is using.

[Jeff Monson]

1st off, what style 2HP dc did you buy?? Is it a cyclone or a bag style? If you have a cyclone, I'd second the advice for returning the air with the filter mounted in your shop. If you have a bag style then that scenario is out. I have a bag style dc unit located in another part of my garage (wall seperating the two), I return the air through a vent in the wall studs. I made a frame that houses a filter that I can change easily. Not sure I need that filter but I use it anyways.

[Howard Acheson]

I can't tell from your description--are you going to vent your dust collector to the outside? If yes, then you need makeup air. If no and you plan to recirculate, no make up air is required.

[Ole Anderson]

Justin,

I saw some pictures on the ClearVue Cyclone gallery where someone built a "closet with a removeable panel" around the filters (with 4-5" of clearance for filter cleaning and access) and then used insukated HVAC ducting to route the air back. They had mounted the whole cyclone with filters in a larger closet for noise abatement. With or without the outer closet, this would be a way to recycle the filtered air back into the shop without picking up <much in> garage vapors. It concurrently removed the need to exhaust from the "garage" and provide makeup air to the shop room. Make sense?

Just one thought..

Jim

Tagging onto this idea, if you are using a cyclone, leave the blower and cyclone in the lower garage, but run an 8" duct elbowing up through the floor, a vertical piece to the top of your duct and then a 180 back down into your filter which would be located in your shop. That way you eliminate the circulation problem and gain some space in your garage with a small penalty of space allocated for just the filter in your shop. And with 8" duct on the pressure side of the blower, losses would be minimal. Taking this a step further, come up into the bottom of your filter, still in the shop, eliminate the 180 at the top, and put a short 8" sump piece (possibly a wye) with a cleanout at the bottom of the vertical run down in the garage for a cleanout when cleaning the filter.

[ian maybury]

I'd been thinking of the Cincinatti fan curves/tables Ole. Maybe the 14 1/2in dia impeller Grizzly uses has very low vanes, or presumes a high level of pressure drop or something. Looking at the CF curves again the data suggests that a 14 1/2in impeller is likely to draw way above 2HP unless its heavily restricted or neutered in some way - e.g. by a pressure drop of maybe 9in or more. I guess in the end that (whatever the impeller ) fan HP is proportional to pressure drop x airflow, and radial impeller efficiencies tend to be fairly similar. The thought is just that this installation is asking a lot from 2HP...

Even if the ducting layout can be finessed into doing better one concern is that machine hoods etc seem likely to be highly restrictive which risks swamping anything that can be done with duct sizes...

ian

[Justin Jump]

OK - so chime in here where needed......

I did not plan to vent outside, I could, but that would mean routing electrical and everything else to the other side of the garage, and lose some "parking" area. Not ideal for me, I got 2 cars, 4 ATV's and one tractor, it's pretty full.

I did not purchase the dust collector yet - this could be a good thing.

The DC would be in a seperate floor, so make up air, whether returned air from the DC, or fresh outside air is needed.

@ Ian....Not familiar with the unit you have in mind, but think Justin that you may be living a little dangerously re. low airflow by using a 2HP fan and (if I read it correctly) hoping to push air up to the second floor before distributing it around a workshop...

I don't plan on pushing air up, rather sucking air, chips and dust down. Workshop is on the top, and all the ducting will go through the floor, similar to Alan S.'s setup...

Therefore, I see the easiest solution being, keep a bag style, maybe upgrade to 3HP, and open windows for makeup air. Possibly even design/build something for the top panes of one of my windows that sort acts like a reverse louver system, letting air in when needed.

The above allows me to keep the DC below, and save floor space and noise.

Another solution I read is to upgrade to a Cyclone, and return ductwork back up into the shop, and locate the filter in the upper half.

I notice though that it appears that most Cyclones empty into the top of the cartridge

The Cyclone option, now with a bit more understanding, seems appealing, but much more expensive....

[Michael W. Clark]

Justin,
As Ian said, the 2HP could be marginal, especially if doing a cyclone. Ian was referring to pushing the clean air back into the shop from the filter. You could use the bag type or cyclone type with the open window concept your describe. The benefit of the cyclone is that it keeps your cartridge filter cleaner for longer resulting in a more uniform flow. You pay for it with additional HP required to overcome the losses in the cyclone. The cartridge filter on the bag type (without some type of pre-filter) can plug fairly quickly and reduce your flow and collection at the tools. The other benefit to the cyclone systems is that the fan is on the clean side, so you don't have to worry about larger peices tearing up the fan, they will drop out in the cyclone.

The cyclone after filters are made to go in from the top to make the cyclone filter arrangement as compact as possible. There is little performance reason to go into the top or bottom. In fact, most industrial collecters go from outside to inside and have an upward flow. On some, the filters lay on their side (Torit Downflo), but these are not good in high load applications.

Long story short, you could get the cyclone option and install the filter at or near the floor of your workshop. The elbow out of the fan could be rotated 90 upward and go into the bottom of the filter. The filter media does not care if it is right side up or not. The one downside to this I see if the fine dust that may fall off of the filter and back down toward the fan. For this reason, you may want to throw away the outlet elbow and put in a tee. The bottom of the tee could be made to accept the dust bin that would normally be located at the bottom of the cartridge filter. You can make the duct bigger on the outlet of the fan to reduce pressure losses.

Mike