Page 2 of 3 FirstFirst 123 LastLast
Results 16 to 30 of 36

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

  1. #16
    I try not to turn it on and off often. If there will be more than about 5 mins between tool changes I will shut it off.

  2. #17
    Quote Originally Posted by David L Morse View Post
    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.
    As usual, David is correct. I was in a hurry and doing the derivation in my head. The corrected formula is TC= 4400/(.99*500)= 8.889, CF=2000*exp(-11/8.889)=580.2 particles/m*3.

    I am not familiar with AHAM AC-1 or CADR. I just know basic physics.
    Last edited by Thomas Wilson; 06-07-2021 at 3:39 PM.

  3. #18
    interesting topic. I just switched from a Harbor Freight/thein baffle that I vented outside, to a CV. I live in FL, so cant vent outside (with the CV), so I went with the WENN filter system, and immediately started building an enclosure for noise control - as I no longer could just "cycle" my dust collector multiple times an hour. I had 4" piping with gates all wired to a 24v actuator to start/stop the DC. With the new system, and 6" piping to a 5hp motor that hates multiple cycles, that would not work, now I have two switches located at strategic locations to turn on/off the DC, so I don't overcycle it by accident.

    So now I plan my machine ops a bit better so I can run the DC in 15 minute or so increments. No misgivings, as before I had "chip collection", and now I have "dust extraction". There is a big difference.

  4. #19
    Join Date
    Jul 2016
    Location
    Lebanon, TN
    Posts
    1,303
    So what part of the motor, in a DC like a CV1800, is prone to damage with multiple start stop cycles per hour?

    Nearly all my tools, from battery powered drills and routers to larger motor AC powered tools like to my 240v Sawstop and J/P and Shapers, all use electric motors, so what causes the damage in these larger motors?

    I understand there is a massive electrical load down on initial startup, but isn't that the job of the capacitor to handle that.

    Is it just the heat generated during this start period that is hard to dissipate on large motors? If so, why aren't these vented better for cooling or have larger heat sink casings?

    I've not seen these restrictions on my cutting tools, i.e. you can only turn your table saw on 5 fives and hour, or what about electric cars, how do they handle stop and start traffic with their electric motors?

    Please educate me, thanks

  5. #20
    Join Date
    Apr 2013
    Location
    Okotoks AB
    Posts
    2,800
    Short cycling is hard on all motors, but the bigger ones don't dissipate the heat as quickly. In a single phase motor it's the start windings & capacitor that suffer most. the capacitor is not there to "handle" the starting current. It's job is to provide a phase shift for the start winding. The reason why you can start a 3 HP table saw more times per hour than you can a 3 HP blower is that the blower is a much higher inertia load, with a much longer start time.

  6. #21
    Join Date
    Feb 2013
    Location
    Tippecanoe County, IN
    Posts
    789
    Frank is exactly right. It's the startup time that causes a problem. While spinning up, the motor is drawing close to it's Locked Rotor Current. That's generally in the area of about six times rated current. Since heat generation is proportional to the square of current that means the motor is producing thirty six times the amount of heat it generates at full load.

    Another way to look at it, imagine jamming the blade on your table saw so it can't rotate. Now, turn it on and count out the four or five seconds it takes for your DC to spin up before turning it off. Not something you want to do too many times in an hour.

    There's another failure mode than's usually associated with large, multipole three phase motors. I have, though, seen it at least twice and perhaps three times on forum posts about failed DC motors. It's the failure of the rotor bars caused by the high rotor currents during startup. They actually get hot enough to soften the Aluminum and the shorting ring breaks away from the bars where there's a high stress corner. Too many starts too close together appears then to also cause that failure in small single phase motors with the high inertial load of a big fan.
    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.

  7. #22
    Join Date
    Feb 2008
    Location
    E TN, near Knoxville
    Posts
    10,859
    I put an amp meter on my 5hp Clearvue cyclone and watched the numbers. The current draw at startup was significantly higher at startup even with all blast gates closed. With all the blast gates open the current at startup wasn't much different, I presume because it still had to bring the heavy impeller up to speed, but after startup the current while running with all the blast gates open was higher. (ClearVue says to NEVER test or run the motor without the ducting in place which adds a lot of resistance or the motor may be damaged from overheating.) With all blast gates closed the current is lower after startup since the motor has to do less work to spin the impeller in partial vacuum.

    Quote Originally Posted by David L Morse View Post
    Frank is exactly right. It's the startup time that causes a problem. While spinning up, the motor is drawing close to it's Locked Rotor Current. That's generally in the area of about six times rated current. Since heat generation is proportional to the square of current that means the motor is producing thirty six times the amount of heat it generates at full load.

    Another way to look at it, imagine jamming the blade on your table saw so it can't rotate. Now, turn it on and count out the four or five seconds it takes for your DC to spin up before turning it off. Not something you want to do too many times in an hour.

    There's another failure mode than's usually associated with large, multipole three phase motors. I have, though, seen it at least twice and perhaps three times on forum posts about failed DC motors. It's the failure of the rotor bars caused by the high rotor currents during startup. They actually get hot enough to soften the Aluminum and the shorting ring breaks away from the bars where there's a high stress corner. Too many starts too close together appears then to also cause that failure in small single phase motors with the high inertial load of a big fan.

  8. #23
    I tend to use machines in batches, so I will turn on the 3HP cyclone at the start of the batch, and then (if I remember) turn it off at the end of the batch. I think I'm not supposed to do more than 6 or 10 starts an hour, but I rarely remember to turn it off fast enough to hit 6 starts an hour.

    I don't leave mine on for air quality reasons though, only to minimize starts (or because I forgot to turn it off at the end of a step). I have two ceiling mounted air filters that pull much more ambient dust out of the air than the cyclone. That setup is optimized for point of generation dust reduction.

  9. #24
    Join Date
    May 2015
    Location
    Morocco IN
    Posts
    1,289
    If I'm breaking down and sizing a lot of wood I might have it running all day. But like others I try to batch things to minimize the on/off. And if I just need to joint one edge I don't turn it on at all - just sweep the shavings it a can. Like Andrew, I have air filters mounted above the bench that clean the air pretty quickly.
    You know, the worst ain't so bad when it finally happens.
    Not half as bad as you figure it'll be before it's happened.
    - Bob Curtin

  10. #25
    Commercial shop rule are different. Some want to turn the thing off if no one is using planers, moulders,etc., so that they can hear their
    radio. But the systems had to be started a certain way ,and it could be damaged by bad timing. So some shops have a rule that it runs all
    day except lunch time.

  11. #26
    Quote Originally Posted by ChrisA Edwards View Post
    So what part of the motor, in a DC like a CV1800, is prone to damage with multiple start stop cycles per hour?
    The insulation will be damaged by excessive heat. The heat build up is influenced by numerous factors: #starts/time interval, the starting load, the motor's size, speed, etc..

    Most are intuitive, but as we add larger and larger motors to our shops, this may interest some: The larger the motor, the better it 'self-insulates' :: it takes longer for the heat to transfer out of windings into the surroundings. If the heat does build up, generally the first thing to degrade will be the internal insulation. It is a logarithmic decay, too (damage gets 'worser' AND faster with each cycle).

    You can mitigate the temperature rise in several ways -
    - Limit the #starts/time.
    - Disengage the load until motor is up to speed (i.e. a clutch). Impractical maybe, but you don't have the combined inertia of rotor and load (impellor) all at once.
    - Soft Start controller (generally got to go 3ph to get it).
    - Run larger motors on a VFD. This controls the inrush current, and limits heat rise. You can even use current switches from tools to a DC on a VFD to let the DC run at low speed (30%?) until the tool starts - then kick DC to 100%. DC should easily be at speed before the load hits the tool (=start of dust generation).
    - Add a smaller HP blower with flow ducted around the problem motor's cooling ribs. Let the blower run anytime the problem motor will be cycling on/off. Should keep it somewhat cooler.

    We run a few 6000hp motors. We pay careful attention to numerous thermocouples embedded in the motor interior. They are on VFDs and have 50HP supplementary blowers on top.
    Last edited by Malcolm McLeod; 06-09-2021 at 10:24 PM. Reason: typo, clarity

  12. #27
    Join Date
    Dec 2010
    Location
    NW Arkansas
    Posts
    1,789
    Blog Entries
    1
    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.

    Worthless to think that you are cleaning the room air by pulling air through a tablesaw. It AIN'T happening.
    You might get the air 'clean' in hours, but not anywhere near 9 minutes or even 90 minutes. Just ain't happening, you are moving the air from one small area you aren't moving it from one side of the room to the other. And our saws, routers, sanders, etc, are slinging dust way farther than a 4 inch opening will pull it back into.
    I turn my cyclone on, use tool and back off a few seconds later. Maximum air cleaning that the cyclone will do. Get another filter system that MOVES the room air.
    Woodworking, Old Tools and Shooting
    Ray Fine RF-1390 Laser Ray Fine 20watt Fiber Laser
    SFX 50 Watt Fiber Laser
    PM2000, Delta BS, Delta sander, Powermatic 50 jointer,
    Powermatic 100-12 planer, Rockwell 15-126 radial drill press
    Rockwell 46-450 lathe, and 2 Walker Turner RA1100 radial saws
    Jet JWS18, bandsaw Carbide Create CNC, RIA 22TCM 1911s and others

  13. #28
    Join Date
    Feb 2013
    Location
    Tippecanoe County, IN
    Posts
    789
    Quote Originally Posted by John Lifer View Post
    Worthless to think that you are cleaning the room air by pulling air through a tablesaw. It AIN'T happening.
    You might get the air 'clean' in hours, but not anywhere near 9 minutes or even 90 minutes. Just ain't happening, you are moving the air from one small area you aren't moving it from one side of the room to the other. And our saws, routers, sanders, etc, are slinging dust way farther than a 4 inch opening will pull it back into.
    I turn my cyclone on, use tool and back off a few seconds later. Maximum air cleaning that the cyclone will do. Get another filter system that MOVES the room air.
    John, your analysis has some errors.
    ...pulling air through a tablesaw...
    You can't "pull" air through a table saw. You can't "pull" air. It has no tensile strength. You can only push it. The pressure in the room caused by the outflow of the DC pushes air into the saw.
    ...you are moving the air from one small area you aren't moving it from one side of the room to the other...
    No, you can't very easily remove air from just a small area, you would have a vacuum "bubble". That air you remove has to be replaced by air from somewhere else. In a typical DC setup that air is coming out of the filter. And, if that filter is on the other side of the room from your tool you are indeed moving it from one side of the room to another.

    A typical ambient air cleaner has it's inlet and outlet separated by maybe two feet and gets good enough mixing to clean the air efficiently. A typical DC system has a much larger separation and will also get good mixing. 500CFM of clean air being pumped into a room will clean the air at a rate that's independent of the type of air mover it's coming from. The only real problem with the DC is the higher energy cost per cubic foot of clean air compared to an ambient air cleaner.
    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.

  14. #29
    Join Date
    Jul 2016
    Location
    Lebanon, TN
    Posts
    1,303
    This thread finally prompted me to buy a Dylos 1100 Pro.

    Right now, while it's still a bit of a novelty, I've been watching the readouts after using several power tools.

    It's located on my laser cabinet, about 40" off the floor and about 15' away from my tablesaw.

    My small particle count hovers in the 250-350 range when everything is off and the air is relatively still.

    Making a few rip cuts and planing raised the count to about 1500. My DC cycles down about 15 seconds after I power off the cutting tool. Even with the DC running those few extra seconds, you can see count coming down.

    I did a lot of bandsaw cutting, routing and drilling, for about an hour. My DC sucks off all these tools and I didn't see any real increase in the particle count during this operation. These three tools are about 20' away from the Dylos.

    With my overhead Jet 1000 running, the particle count gets down to the 300's in about 3-4 minutes.

    I did have a bonfire, in my back yard, yesterday. Even though all my garage doors were shut, when I went into the garage to grab something, the count was hovering around 3600.

  15. #30
    Join Date
    Feb 2013
    Location
    Tippecanoe County, IN
    Posts
    789
    Quote Originally Posted by ChrisA Edwards View Post
    This thread finally prompted me to buy a Dylos 1100 Pro.

    Right now, while it's still a bit of a novelty, I've been watching the readouts after using several power tools.

    It's located on my laser cabinet, about 40" off the floor and about 15' away from my tablesaw.

    My small particle count hovers in the 250-350 range when everything is off and the air is relatively still.

    Making a few rip cuts and planing raised the count to about 1500. My DC cycles down about 15 seconds after I power off the cutting tool. Even with the DC running those few extra seconds, you can see count coming down.

    I did a lot of bandsaw cutting, routing and drilling, for about an hour. My DC sucks off all these tools and I didn't see any real increase in the particle count during this operation. These three tools are about 20' away from the Dylos.

    With my overhead Jet 1000 running, the particle count gets down to the 300's in about 3-4 minutes.

    I did have a bonfire, in my back yard, yesterday. Even though all my garage doors were shut, when I went into the garage to grab something, the count was hovering around 3600.
    Are you saying that the DC1000 was able to take the count from 1500 to 300 in 4 minutes in a 9000 cubic foot shop? That would require about 3600 CFM of clean air Seems a bit ambitious for the DC1000.

    Did you try turning on the DC1000 to clear the smoke from the bonfire? That would be interesting data.
    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.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •