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Thread: How long do you keep your dust collection system "on"?

  1. #1
    Join Date
    Jan 2018
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    Vancouver Canada
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    490

    How long do you keep your dust collection system "on"?

    I bought a 2HP cyclone style collector with cartridge which use at this point, only with my table saw. While I'm reconfiguring the work area I'll be adding the appropriate 6" ducting. Besides the TS, I use a 735 planer and a 6" floor mounted jointer. I will be making collector boxs for the sliding mitre saw, bench top mortiser and drill press. Everything else are portable tools which usually get hooked to a Dust Deputy via the Rockler adapter fittings. I also tend to do much more hand work excepting for dimensioning, so, joinery saws and hand planes.
    The wife ordered up a ceiling mounted air cleaner as a present.
    I work in an unconditioned space - my 2 car garage of ~400 sq.ft., with open ceilings to the roof, and almost always with the entry door and and the 16' roll-up doors open (well, not in deep winter...). I also wear and Elipse respirator when using any of the machines and for at least 10 minutes afterwards.
    My question is about the length of time one keeps the big dust collector "on". Obviously, while using the machine and I keep it on for about 10-15 minutes afterwards, but realistically, with blast gates closed except to the just-used machine, would there be any significant air quality improvement when it's just sucking from the one machine?
    Young enough to remember doing it;
    Old enough to wish I could do it again.

  2. #2
    Join Date
    Apr 2013
    Location
    Black Oak Ark.
    Posts
    179
    I turn on and off quickly , but I try to make a milling session TS - jointer - planer when feasible . Thats when I will leave the DC running . Doesn't happen real often , honestly .

  3. #3
    If you are going to leave it on for air quality control, I would open all blast gates. Or at least the ones on the opposite end of shop to the filter.

  4. #4
    Join Date
    Mar 2003
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    SE PA - Central Bucks County
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    57,354
    I leave it on for the duration I'm using the tool(s) that it's collecting from. I don't usually turn it off and on with any frequency, but occasionally that does happen. I've also had it running for an entire day when using my CNC machine for continual jobs or long cuts. There likely is some small benefit to running it beyond when the cutting stops to clear out some additional stuff, but unless it's an unusually huge system for the space, it's not going to process the ambient air all that much. That's where an air cleaner helps beyond the DC.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  5. #5
    The math is pretty easy. The dust collector filter has some efficiency which you probably have, but I’ll assume 99%. The garage volume is area times height of walls plus area times half height from the top of wall to peak of roof. I’ll assume your garage walls are 8’ and the peak is 6’ above that. The volume is 400*(8+6/2)=4400 ft**3. A typical 2hp collector connected to a table saw via 4” flex might draw 400 cfm. In 11 min, the collector would complete one air change. Now let’s see what that does to air quality. This is more complicated, but we will do some estimates. Let’s just assume that at the moment you turn the saw off, the air concentration of dust particles is like my shop about 2000 particles/m**3. This is tolerable but not healthy in my experience. If air entering the dc is perfectly mixed with all the air in the shop and there are no other sources in the shop generating dust, you would reduce that concentration by 99%, down to 20 particles/m**3. This is excellent. Our estimate is overly optimistic. The air is not perfectly mixed. That means the air near the DC and TS gets drawn through the filter more times than air farther away. Dust that is in stagnant little eddies in the corners of the room does not get cleaned. Anything that improves mixing like a fan would help. Even worse than lack of mixing, is the other sources of dust generation Walking around on dust on the floor grinds it up and generates a lot of airborne dust. The open garage would mix in outside air which could easily have dust and pollen count higher than 1000 particles/m**3. The net result is that the air in the garage would equilibrate at a level that balances the dust generation and dust removal.

    Bottom line, an open garage door with a box fan will probably be the most effective/$ in bringing dust down to equilibrium.

    If you want to do some spray finishing, close the doors, turn on the fans and air cleaner, and leave the room.

  6. #6
    Join Date
    May 2018
    Location
    Lancaster, Ohio
    Posts
    794
    My dust collection starts automatically when certain tools are started and runs until they are turned off. Also have a switch that will turn it, on this gets used when jumping from machine to machine to eliminate to many start/stops in a short time.
    Have a old furnace fan pulling thru two 24x24 " filters. Pre filter is 2" thick, main filters is are 18" bag filters, this gets turned on before any machines start and turned off a day or two later
    Ron

  7. #7
    Quote Originally Posted by Thomas Wilson View Post
    The math is pretty easy. The dust collector filter has some efficiency which you probably have, but I’ll assume 99%. The garage volume is area times height of walls plus area times half height from the top of wall to peak of roof. I’ll assume your garage walls are 8’ and the peak is 6’ above that. The volume is 400*(8+6/2)=4400 ft**3. A typical 2hp collector connected to a table saw via 4” flex might draw 400 cfm. In 11 min, the collector would complete one air change. Now let’s see what that does to air quality. This is more complicated, but we will do some estimates. Let’s just assume that at the moment you turn the saw off, the air concentration of dust particles is like my shop about 2000 particles/m**3. This is tolerable but not healthy in my experience. If air entering the dc is perfectly mixed with all the air in the shop and there are no other sources in the shop generating dust, you would reduce that concentration by 99%, down to 20 particles/m**3. This is excellent. Our estimate is overly optimistic. The air is not perfectly mixed. That means the air near the DC and TS gets drawn through the filter more times than air farther away. Dust that is in stagnant little eddies in the corners of the room does not get cleaned. Anything that improves mixing like a fan would help. Even worse than lack of mixing, is the other sources of dust generation Walking around on dust on the floor grinds it up and generates a lot of airborne dust. The open garage would mix in outside air which could easily have dust and pollen count higher than 1000 particles/m**3. The net result is that the air in the garage would equilibrate at a level that balances the dust generation and dust removal.

    Bottom line, an open garage door with a box fan will probably be the most effective/$ in bringing dust down to equilibrium.

    If you want to do some spray finishing, close the doors, turn on the fans and air cleaner, and leave the room.
    Stop the presses, my equation for cleaning is wrong. For a perfectly mixed volume, the removal is an exponential decay. The time constant is volume divided by volumetric flow, TC=4400/500 minutes= 8.8 min. If C is initial concentration, the final concentration CF after time interval t=11min is CF=C*exp(-t/TC)=2000*exp(-11/8.8)=573 particles/m**3.

  8. #8
    Join Date
    Feb 2013
    Location
    Tippecanoe County, IN
    Posts
    790
    Quote Originally Posted by Thomas Wilson View Post
    Stop the presses, my equation for cleaning is wrong. For a perfectly mixed volume, the removal is an exponential decay. The time constant is volume divided by volumetric flow, TC=4400/500 minutes= 8.8 min. If C is initial concentration, the final concentration CF after time interval t=11min is CF=C*exp(-t/TC)=2000*exp(-11/8.8)=573 particles/m**3.
    True for a perfect filter. To include the filter efficiency simply divide the time constant you calculated by the filter efficiency to get the actual time constant. That is, replace the flow rate with an effective flow rate that equals (actual flow rate) x (filter efficiency).

    If you're familiar with the AHAM AC-1 air cleaner spec you'll recognize that as similar to CADR or Clean Air Delivery Rate.
    Beranek's Law:

    It has been remarked that if one selects his own components, builds his own enclosure, and is convinced he has made a wise choice of design, then his own loudspeaker sounds better to him than does anyone else's loudspeaker. In this case, the frequency response of the loudspeaker seems to play only a minor part in forming a person's opinion.
    L.L. Beranek, Acoustics (McGraw-Hill, New York, 1954), p.208.

  9. #9
    Join Date
    Oct 2015
    Location
    SW Florida
    Posts
    137
    The DC runs while machines runs (remote control) and the air purifier runs the entire time I'm in the shop (garage) and a timer is set to run for two hours after I leave. Not scientific by any stretch, but it seems to work for me, but I'm just a weekend warrior.
    A wannabe woodworker!

  10. #10
    Join Date
    Oct 2008
    Location
    Columbus, OH
    Posts
    2,331
    I see no benefit to running the big collector for more than 5-10 seconds after completing the operation. You have an air cleaner coming. That will do the bulk of trapping air borne dust. I have about 500 sq ft shop space. I run the air cleaner during operations and then for ~1/2 hr after finishing operations for the day. Usually about same amount of time it takes to do other general cleanup.
    Brian

    "Any intelligent fool can make things bigger or more complicated...it takes a touch of genius and a lot of courage to move in the opposite direction." - E.F. Schumacher

  11. #11
    I recommend getting a PM tester. I finally broke down and bought one and have been able to get my shop air cleaner than the air in my living room air. Now my sanding station will spike 0.5 PM counts, but I simply put on a respirator and crank the speed on my DIY air filter (four furnace filters and a fan) and in a few minutes I can remove the respirator. I run the tester at all times.

    I can verify what Mr Wilson is saying above.....that "mixing" is critical to clean air. I was initially hesitant about a strong fan blowing air everywhere in my shop. I thought circulating the dust sitting in the corners of my shop was BAD. It's actually good as it is exchanged with clean air, which I can verify with the tester.
    Thanks,
    Fred

  12. #12
    Join Date
    Jul 2016
    Location
    Lebanon, TN
    Posts
    1,304
    Cycling the DC On/Off with power tools, multiple times an hour, is one of the reasons I have not moved away from a reasonably cheap 1.5HP DC to something that may work a little better, e.g. CV1800 or Oneida.

    I don't have the space to build a sound proof closet for the DC, so I don't want to operate where I leave the DC running when not using a power tool, just to minimize the start/stop cycles.

    Trying to clean/scrub the air through a couple of open 4" blast gates from 9000cu/ft (30x30x10) seems like trying to drain a swimming pool through garden hose, it'll probably do it eventually, but the noise level, electricity use and wear on the DC doesn't seem worth the effort.

  13. #13
    Quote Originally Posted by ChrisA Edwards View Post
    Cycling the DC On/Off with power tools, multiple times an hour, is one of the reasons I have not moved away from a reasonably cheap 1.5HP DC to something that may work a little better, e.g. CV1800 or Oneida.

    I don't have the space to build a sound proof closet for the DC, so I don't want to operate where I leave the DC running when not using a power tool, just to minimize the start/stop cycles.

    Trying to clean/scrub the air through a couple of open 4" blast gates from 9000cu/ft (30x30x10) seems like trying to drain a swimming pool through garden hose, it'll probably do it eventually, but the noise level, electricity use and wear on the DC doesn't seem worth the effort.
    I also stayed with the 1.5 HP collector and 4" PVC configuration. I did however convert to two duel stage with a SDD vented outside. When I spoke to Oneida's tech about which SDD to buy he asked about my configuration. I was amazed when the tech he did not try to sell me a collector....he said I'd be fine adding a SDD to my existing config and likely even gain CFM. He was 100% right. Once I was able to test with a counter, I set out to address ambient air which I detailed above.

    I should have added above that I DO NOT own a CNC or thickness sander AND I and a hobbyist in a 14x28 basement shop. My tools are TS, Jointer, Planer, DP, BS, and sander center with Belt Sander, OSS, and Disc Sander.
    Thanks,
    Fred

  14. #14
    Join Date
    Feb 2008
    Location
    E TN, near Knoxville
    Posts
    10,862
    Quote Originally Posted by Aaron Rosenthal View Post
    I bought a 2HP cyclone style collector with cartridge which use at this point, only with my table saw. While I'm reconfiguring the work area I'll be adding the appropriate 6" ducting. Besides the TS, I use a 735 planer and a 6" floor mounted jointer. I will be making collector boxs for the sliding mitre saw, bench top mortiser and drill press. Everything else are portable tools which usually get hooked to a Dust Deputy via the Rockler adapter fittings. I also tend to do much more hand work excepting for dimensioning, so, joinery saws and hand planes.
    The wife ordered up a ceiling mounted air cleaner as a present.
    I work in an unconditioned space - my 2 car garage of ~400 sq.ft., with open ceilings to the roof, and almost always with the entry door and and the 16' roll-up doors open (well, not in deep winter...). I also wear and Elipse respirator when using any of the machines and for at least 10 minutes afterwards.
    My question is about the length of time one keeps the big dust collector "on". Obviously, while using the machine and I keep it on for about 10-15 minutes afterwards, but realistically, with blast gates closed except to the just-used machine, would there be any significant air quality improvement when it's just sucking from the one machine?
    Aaron,

    Sorry if this was covered - I didn't have time to read the entire thread.

    There is another issue to consider unrelated to your air quality question: the health of the DC motor. I use a 5hp ClearVue cyclone with 6" ducting. The motor manufacturer recommends to not cycle the power more than, I think, 6 times per hours to avoid overheating and damaging the motor. This may not be the case with a smaller motor.

    I control the DC with keyfob remotes placed at key machines. If I move to another machine I leave the DC running, close the blast gate, then open the other blast gate. If I expect to use the DC again within about 5-10 minutes I leave it running with all the blast gates closed. (Closing the blast gates significantly reduces the power used.) Note that with the blast gates closed and the cyclone in a sound insulated closet the noise is not a problem. If I expect the pause in use to be longer than 10 minutes or so I turn the DC off.

    As for the air quality, I haven't tested but I don't think the air moved with one blast gate open would have a significant effect in the fine dust floating around the room. I use a Dylos DC1100 Pro Air Quality Monitor to see how effective my dust collection is:
    https://www.amazon.com/gp/product/B004AWEG0Y

    dylos_particulate_monitor.jpg

    If concerned about fine dust floating around the room, I found a air cleaner that hangs from the ceiling (such as the Jet) works well if given a little time. A good respirator is always recommended even with the dust collection system. With a history of asthma and other lung issures I use these from 3M with P100 filters:

    respirator.jpg

    These are effective, light weight, and comfortable although their newer 7000 series respirators are a bit more comfortable.

    I also have a couple of the full-face versions which give some additional protection:

    respirator_full_face2.jpg

    JKJ

  15. #15
    Join Date
    Apr 2013
    Location
    Okotoks AB
    Posts
    2,800
    I leave it running if I'm going to be using it within a few minutes in order to keep the hourly cycles down. I also keep an eye on the particle counter & will leave it running to get the counts down. They usually stay low, but if there's a bunch of dust that gets away, it doesn't take long to clean the air. I also leave the furnace fan, which has a HEPA filter, running when I'm working in the shop.

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