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Thread: DIY air filtration unit for <$200

  1. #331
    Any sneaky hacks for extending the furnance filter life? My hardwood engraving is real rough on them. Thinking I may increase the amount of sacrificial Merv 8-9's in the front to help slow down the wear on the Merv 13. I also vacuumed a good amount of gunk off one and stuck it back in just to see how it performs. Curious if anyone ever did anything similar. Man I'm glad I didn't go with an Atmos or something similar. I'd bleed $ in filters with what deep hardwood engraving produces, gunk-wise.

  2. #332
    Question guys:

    I''ve chosen 8" ducting to run from my laser to my extractor and my extractor to my blower. But I'm exhausting out the blower with 4" duct. Is that an issue? Didn't think it was, but wanted to make sure.

  3. #333
    Only an issue in that you need to find/create some adapter to connect the 8" ducting to the 4" duct outlet on your machine. Mine is like that, a 4" duct outlet on back of machine and 8" ducting run to the filter (8" for the reduced air flow resistance it allows compared with everything 4"). I actually just started by putting an 8" cap on the end of the ducting, cut a 4" hole in the center, and cemented in the final 4" diameter connector to mate with the back of the machine. The abrupt transition from 4" to 8" undoubtedly creates some turbulent friction losses (but presumably less than having the full run and turns all 4" diameter) and I intended to locate/make a funnel type of adapter to smooth the transition, but that hasn't happened yet :^/

  4. #334
    Quote Originally Posted by Glen Monaghan View Post
    Only an issue in that you need to find/create some adapter to connect the 8" ducting to the 4" duct outlet on your machine. Mine is like that, a 4" duct outlet on back of machine and 8" ducting run to the filter (8" for the reduced air flow resistance it allows compared with everything 4"). I actually just started by putting an 8" cap on the end of the ducting, cut a 4" hole in the center, and cemented in the final 4" diameter connector to mate with the back of the machine. The abrupt transition from 4" to 8" undoubtedly creates some turbulent friction losses (but presumably less than having the full run and turns all 4" diameter) and I intended to locate/make a funnel type of adapter to smooth the transition, but that hasn't happened yet :^/
    Hey Glen,

    You can't just use one of these? http://www.homedepot.com/p/6-in-to-4...R6X4/100111736
    Then have that fit into one of these and you're done http://www.homedepot.com/p/8-in-to-6...R8X6/100142122

    My question had more to do with duct gauges at different spots in the system. Ultimately my hose run from the blower to outside is only 4 feet. I was trying to figure out the impacts of having 8" ducts upstream (so laser to blower) and then 4" duct downstream (blower to window). From my testing the duct size makes a dramatic difference upstream in terms of the power of the suction. Even from a draw perspective, my blower draws way more power and moves way more air when I hook up an 6" or 8" duct to the intake while testing it. But I haven't noticed any dramatic change based on the diameter of ducting on the outflow. I just wanted to see if I'm missing a key concept there since I'm obviously novice at best on these.

    Btw Glen how tall is your extractor? I'm rebuilding vertically this week, and I keep coming up with something like 5 feet tall to accommodate 8" ducts. Is yours that tall? I guess I should ask how tall it is in total, including whatever you're feeding into below.
    Last edited by Raphael Weil; 05-25-2016 at 7:15 AM.

  5. #335
    Hi Raphael,

    Yes, could use those two adapters, or similar, but I'm inclined to go with a single stage if I ever get around to "fixing" it.

    As for impact of duct sizes, moving more air is expected with larger duct sizes but I'm surprised that your blower would draw more power with the larger duct because it should have less resistance than with smaller ducting.

    When putting my filter unit together, foot print was far more important than height and, as it turns out, mine unit is 5 feet 2 inches tall (plus casters add another couple inches of height). The cabinet is set up for down flow, with a good bit of the top allocated to smoothly turning the air downward and spreading it evenly across the filter bed, then 4 filter trays, the fan, and then the exhaust chamber. I was originally going to exhaust straight down but thought it would be too restrictive because the bottom was only a couple inches off the floor (located in a carpeted area when I built this, but just moved into my new digs this last week and the flooring is smooth planking so would have been less an issue), and I didn't want the air blowing out the front. So, I side vent instead and have a curved baffle to help smooth the 90 degree turn.

  6. #336
    Join Date
    Aug 2006
    Location
    Suwanee, GA
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    3,686
    Quote Originally Posted by Glen Monaghan View Post
    I'm surprised that your blower would draw more power with the larger duct because it should have less resistance than with smaller ducting.
    The odd thing about the dust collectors we use is that they are more efficient with less airflow. If you restrict the airflow completely then you'll see a lower current draw vs completely unrestricted.

  7. #337
    Quote Originally Posted by Glen Monaghan View Post
    Hi Raphael,

    Yes, could use those two adapters, or similar, but I'm inclined to go with a single stage if I ever get around to "fixing" it.

    As for impact of duct sizes, moving more air is expected with larger duct sizes but I'm surprised that your blower would draw more power with the larger duct because it should have less resistance than with smaller ducting.

    When putting my filter unit together, foot print was far more important than height and, as it turns out, mine unit is 5 feet 2 inches tall (plus casters add another couple inches of height). The cabinet is set up for down flow, with a good bit of the top allocated to smoothly turning the air downward and spreading it evenly across the filter bed, then 4 filter trays, the fan, and then the exhaust chamber. I was originally going to exhaust straight down but thought it would be too restrictive because the bottom was only a couple inches off the floor (located in a carpeted area when I built this, but just moved into my new digs this last week and the flooring is smooth planking so would have been less an issue), and I didn't want the air blowing out the front. So, I side vent instead and have a curved baffle to help smooth the 90 degree turn.
    Oh cool, I came to within a few inches in height to yours when I engineered mine. Glad to hear I got close. I just need to make sure the damn thing can't topple over now.

  8. #338
    The footprint on my stack is just a bit less than 18"x21" (mainly driven by the size of the filters and diameter of the fan) and it's perfectly stable sitting flat on the floor. But I put it on 3" casters because I needed to move it at times, and had to be a bit careful repositioning it on carpet when pushing/pulling with the handles I have mounted on the door at about 4' height. Biggest mass is the fan, which sits low in the case, but the case is heavy MDF and the weight caused the wheels to nestle into the carpet, so the stack would start to tip rather than roll when pushed/pulled without care. However, even on casters, I've had no problem with positioning or stability on the new plank flooring.
    Last edited by Glen Monaghan; 05-25-2016 at 7:08 PM.

  9. #339
    I'm almost done the new design, put in a solid 5 hours on it today. Just have to do the door and weather stripping. Was a challenge to find 8" flex duct but I found it. Can't wait to see this baby in action, although I may need my blast gate to cut airflow. That's a problem I look forward to having.

    Thanks again to all in here helping me along the way. I mean it when I say I couldn't do it without you. And with how much gunk my engraving process produces, I don't think a pro machine would have worked. I tear a massive strip off hardwood, it produces way more residue than your typical job.

  10. #340
    Well I did it, sort of. I'm now engraving with so little smoke and odour that I'm basically not worrying about it right now. With a lot of messaging help from Glen I was able to absolutely not fix my door, lol. I tried and tried to get the gasket to work perfectly, but something in my clamping force is uneven. So I decided to stick a diy carbon filter right at the outlet to catch the last of what I was missing, and that did the trick. It killed my air flow, but with how much smoke I produce in my process, low flow is actually a must to scrub the smoke. When I've got a bit more time on my hands I'll show the pics, the thing is pretty damn well built all things considered.

    My single greatest contribution to this page is now with filtering. My local dollar store sells a product made for covering plants to protect them from the frost. I pay $3 CDN for a big bunch of it, so $20 buys me a ton of it. From what I can tell this stuff:

    1) Filters darn near Merv 11-12 levels
    2) is totally washable and pretty strong

    I've covered all my filters with it. I've also stuck a Merv 13 over each of my carbon shelves (with that stuff coating it). My filters are honestly getting exponentially more life out of them. I've been clocking the minutes on the machine to see when I hit various change time since my engraving is a very consistent kind. My next plan is to go straight to a distributor to pay 100 filters, as it turns out there's one near me that I think will probably wholesale me stuff.

    So I'm finally in production now, it was a long road. Thanks Dan and Glen and all those who helped, you don't know how much it means to me.

  11. #341
    Join Date
    Sep 2015
    Location
    Nelson, BC Canada
    Posts
    3
    Dumb question, but why a 3.5" cap for a 4" pipe?
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