Smaller DC with Direct Outside Exhaust?

[John Newell]

I've been following the threads on dust collection and have been thinking about purchasing one of the smaller DCs...either something like the Delta 50-760 or even one of thr 1hp models and going with a direct exhaust. My shop is small, and the DC would be wheeled around to the relevant machine, hooked up with a short hose, and then hooked up to an external vent.

Does this sound practical?

If I do this, I should have good suction at the tool...how sensitive is the design (esp size of ducting) on the exhaust side? If I use something like 8" round galvi (or the ~4x10 rectangular), will I have flow problems? (In other words...I read that you can over-size DC ducting - is that true only on the suction side?

What am I missing? (I'm sure I have overlooked something...)

Many thanks for your input.

[Kyle Kraft]

Are you referring to removing the filter bag on the top, adapting the opening to fit an 8" pipe then routing the pipe outdoors? The only problem I could see might be if the duct was so huge that fine dust particles would settle out in the pipe instead of being shot outdoors. A smaller pipe would cause a greater velocity of airflow with some increase in static pressure, whereas a larger pipe would have less SP and less velocity. Make sense??

[John Newell]

Are you referring to removing the filter bag on the top, adapting the opening to fit an 8" pipe then routing the pipe outdoors?

Yes, exactly!


The only problem I could see might be if the duct was so huge that fine dust particles would settle out in the pipe instead of being shot outdoors. A smaller pipe would cause a greater velocity of airflow with some increase in static pressure, whereas a larger pipe would have less SP and less velocity. Make sense?

Yes, that does make sense - although would the worst case there be that the fine dust would (mostly? - would depend on how the duct runs are set up) settle back into thr plastic bag?

[Phil Thien]

If it wouldn't create too much of a mess and you don't have any problems with the types of dust you emit (I guess some wood dusts can be toxic to certain plantings, for example, and walnut dust is bad for horses and dogs I read), then I would go for it. If possible (if there is room) you could even extend the exhaust pipe away from the shop wall a little.

If you have any problems w/ plants or animals, you could always build one of my separators:

http://www.cgallery.com/jpthien/cy.htm

and exhaust the fines outside. This separator, because it is so well sealed (compared to commercial offerings), doesn't put that much of a "hit" on your DC (much, much less than a seasoned bag or filter). It will keep all the chips and most of the fines in your garbage can, and you won't be able to even tell it is exhausting outside except for the sound of the exhaust (when it is running).

[Phil Thien]

Oh, and one more thing. If I were going to do what you're contemplating, I would try to figure out a way to put the blower outside, too. Maybe in a small enclosure attached to the outside of the shop. You can do this with or without my cyclone separator. But it would cut down on the noise in your shop appreciably.

[M Toupin]

John,
There's no free lunch, at least with DC. The more piping you have the more air flow and SP you loose. Flex pipe exacerbates the problem and it doesn't matter if the piping is on the front end or back end, there's still loss. Unfortunately you can't rewrite the laws of physics. Adding all that piping to get the dust outside is going to seriously impact the performance of an already marginal DC and reduce the performance.

Single stage DCs are notorious for not being very efficient in removing the chips and dust from the air stream. That means all that dirty air has to go through the filter and the filter clogs much faster. A cyclone on the other hand is much more efficient in removing the fine dust from the air stream thus your filters stay clean longer. The reason I mention this is all that dirty air (dust and chips) has to go somewhere. Some folks do exhaust their cyclones directly outside, but there is still a film of dust directly around the outlet and a cyclone is a clean system. If you duct your single stage outside your going to have a LOT of dust and chips around to deal with. This might not be a problem if your out in the woods, but close to the house or in an urban environment it's going to be a problem.

Bottom line - if your going to go with a low power, single stage DC, stick with the roll a round and a short flex hose to get the maximum performance out of it.

Mike

[John Newell]

Thanks for the replies so far - I guess I wasn't clear about my (current) idea. I'm thinking about a "portable" (roll-around) 2-stage unit (like the ones mentioned above) that I could connect via a short pipe to the tool. The DC would, I assume, keep the larger waste in its bag. On the exhaust side, I'd replace the bag or filter with an adapter that would connect to hard duct of some kind - 6" PVC or 6", 8" or rectangular HVAC metal duct for what would be a pretty short run up to ceiling height (basement shop) and then 90 degrees out the wall.

Seems like it would work? I suppose I could put a relatively coarse bag on the outside exhaust if working with material that's especially troublesome, like walnut? It could be pretty high-flow/low-restriction, given that it's outside, without compromising performance?

Basically the idea is to replace the internal exhaust with an external exhaust. I did briefly consider the 3/4hp true portable single-stage units but I'm guessing they just don't move enough air.

I do realize that I could buy/build a blower/cyclone setup, but adapting a unit like one of those I mentioned seems like a lost less work, which translates into getting it running sooner.

[glenn bradley]

I would be leary of the Rube Goldberg adapter that would be required for smaller DC's that exhaust right into the bag as opposed to via a hose. You may want to go with a different format where a length of 4" hose could be used: http://www.pennstateind.com/store/dc5.html

[John Newell]

Thanks, Glenn. That looks similar to the Delta and Sears single-stage DCs...the question would be how to handle the larger stuff. Also, these units seem to be much lower powered than the 2-stage DCs...

:confused: :confused: :confused:

[David Giles]

John, I've been playing around with using a 1.5Hp Jet blower/motor for outside venting with varied success. What worked well was to replace all 4" ducting and connections with 6" size. Increasing the blower outlet duct size won't help significantly if the suction hooks to a 4" port. Larger pipe requires larger airflow to keep the chips moving in a vertical rise. The small blower/motor works, but only if the suction is 6" all the way without restrictions.

What didn't work (so far) was a good method of chip/dust collection. Trash can collectors take a lot of pressure drop and aren't big enough for 6" ducting. I discharged into a 3'x6'x6' shed and it didn't work very well either. Chips all over the yard. The 5" blower discharge was so powerful that the chips never settled out inside the shed.

At one point, I tried taking off the upper filter and leaving the lower bag on the DC. A whole bunch of chips and dust escaped the tangential inlet from the Jet DC. Much more than I had anticipated.

[John Newell]

David, which Jet DC?

I was wondering about rigging up what would be essentially a giant cone-shaped adapter from where the filter or bag attaches on the top to whatever the exhaust duct would be to avoid the problem you mention.

For clarity, on the suction side, I envision running a short 5" or 6" hose (can be kept short because the DC can move some) from the DC to the tool, with a 4" stepup at the tool.

[Matt Schroeder]

What about something like on Mr. Pentz' site, with the complete DC enclosed in a cabinet in the shop (or outside) with all of the filters or bags in place, and then that cabinet vented to the outside in whatever manner you choose? Maybe the DC you are looking at doesn't have the power for a long enough hose to reach all of your tools, so this may not work, but it might give you other ideas.

http://billpentz.com/woodworking/cyclone/DCConversion.cfm

This idea is outlined in the "Good Solutions" section about halfway down.

[Matt Meiser]

I'd still go with a larger blower than one of the 1HP models use. Used blowers come up on Ebay from time to time.

[John Newell]

I'd still go with a larger blower than one of the 1HP models use. Used blowers come up on Ebay from time to time.

The Delta 50-760 is a 1.5hp and I agree, that (or a similarly-sized DC) seems like a better choice. It doesn't cost much more, either.


What about something like on Mr. Pentz' site, with the complete DC enclosed in a cabinet in the shop (or outside) with all of the filters or bags in place, and then that cabinet vented to the outside in whatever manner you choose?

I've spent hours and hours trying to digest and assimilate Bill's website. Frankly, I don't have room for a stationary cyclone, and I'm not sure I need it, either - I've got a very compact area and the runs will be quite short. Also, if I try to do this from scratch, I will still be working on it next year, which is suboptimal. :(

[David Wilhelm]

John I have some info if you'd care to email me i will FWD it to you. you may find it helpful. Will2Day@aol.com. I'm looking at mounting a blower on the wall and ducting to my lathes then ehausting everything outside not box no filter, just a mulch pile for the garden....

[John Newell]

John I have some info if you'd care to email me i will FWD it to you. you may find it helpful. Will2Day@aol.com. I'm looking at mounting a blower on the wall and ducting to my lathes then ehausting everything outside not box no filter, just a mulch pile for the garden....

David, thanks - email sent.

[David Wilhelm]

nothing here yet..........

[David Giles]

David, which Jet DC?

I was wondering about rigging up what would be essentially a giant cone-shaped adapter from where the filter or bag attaches on the top to whatever the exhaust duct would be to avoid the problem you mention.

For clarity, on the suction side, I envision running a short 5" or 6" hose (can be kept short because the DC can move some) from the DC to the tool, with a 4" stepup at the tool.


John, it's a Jet DC-1100CK with 1.5Hp and a canister filter. Supposedly rated at 1100cfm, I doubt that it does 1/3 of that with 4" ports or pipe. I've tried a number of configurations. For a while, it was located in a shed with the canister and bags attached plus a trashcan preseparator. In search of higher air flow, first the canister disappeared. It was a big improvement and the big chips were still collected as long as the preseparator wasn't too full. Bypassing the presep put a lot of chips into the shed. I like your idea of a cone shaped filter. Maybe just a cloth transition piece?

But the biggest improvement was getting rid of the 4" ports on the jointer and saw. I'm convinced that unless the machine ports are replaced, larger ducting doesn't make much improvement. The minimum choice seems to be a big DC with small ports or a 110V DC with big ports. My current setup is adequate for air flow, but has poor chip collection. Anything that conveniently improves chip collection also adds pressure drop and reduces air flow. So a 2-3Hp cyclone is probably still in my future.

Want to buy a DC-1100CK with lightly used canister?

[John Newell]

But the biggest improvement was getting rid of the 4" ports on the jointer and saw. I'm convinced that unless the machine ports are replaced, larger ducting doesn't make much improvement.

Even with an immediate4 transition to 5" or larger, right at the tool???



Want to buy a DC-1100CK with lightly used canister?


I might, if you are local-ish (New England area?)....it'd be a first step.

[John Browne]

Oh, and one more thing. If I were going to do what you're contemplating, I would try to figure out a way to put the blower outside, too. Maybe in a small enclosure attached to the outside of the shop. You can do this with or without my cyclone separator. But it would cut down on the noise in your shop appreciably.

What Phil said. I plan to put the whole DC outside the garage, in a little box with sound insulation. Then the fine dust that escapes the filter bag can just go wherever it wants to go, and I can empty the lower bag every week or so.

Frankly I can't quite see why everybody doesn't do it this way, unless their shop is in a basement or the noise would annoy their neighbors (I live in the country, so that's not an issue).

[John Newell]

Frankly I can't quite see why everybody doesn't do it this way, unless their shop is in a basement or the noise would annoy their neighbors (I live in the country, so that's not an issue).

That's my problem. If I put the DC outside, the duct run will be so long it'll be in a different area code... :(

[Marty Schlosser]

[quote=M Toupin;737830]John,
There's no free lunch, at least with DC. The more piping you have the more air flow and SP you loose.

Mike, I think you meant to state that more piping increases the SP...

Marty

[David Giles]

Even with an immediate4 transition to 5" or larger, right at the tool???
Exactly. An analogy would be a water faucet. There can be a small pipe or a big pipe before and after the valve, but the tiny valve opening controls the flow rate. Same with air flow in a dust collector system. That 4" port acts as a flow restricting valve to the rest of the large ductwork. Think of it this way, pretend that you have a 6" slide gate on 6" ducting connected to the small blower. What happens when the slide gate is half closed (the equivalent of a 4" port)? The flow will be greatly reduced. It's not exactly proportional because the blower sucks a little harder when the flow rate is lower, but it's pretty close.

I've got a 4" port on the side of a 6" vertical line. With only the 4" line in service, chips will settle out onto the 6" blast gate below the 4" entry point. Not enough velocity to pull them up the 6" riser. But cracking an upsteam blast gate adds enough air to sweep them through the vertical riser.

I think that's why so many guys like the 3-5Hp cyclones. They generate a lot more suction pressure to pull air through the 4" ports.

[Steven Wilson]

Removing the filter bag and venting outside should lower the resistance of your setup unless you have a bunch of duct work going from the machine to outside. Doing this will not really improve the CFM at the tool, so you won't be picking up anymore dust. For that you will need a larger motor and more importantly a larger impellor.