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Thread: How often do you turn your DC on and off

  1. #1
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    How often do you turn your DC on and off

    Malcolm started a thread about an A/C energy monitor which got me to thinking about turning some equipment on and off, mainly the DC. All of our power equipment have motors which, if I recall correctly, have a high startup current. When I work in my shop, like most of you I presume, we try to plan as much of the work at one time at a particular machine like a jointer or table saw and leave them running.

    Then I started to realize that I turn my dist collector on and off a fair amount, even if it's only going to be a minute or two before I have to turn it on again. It's a 3 HP cyclone and it sits on the other side of an insulated wall so the noise isn't too bad. But it's just a habit I got into years ago with a smaller DC.

    I was wondering if anyone has done even a basic analysis to determine if the DC were going to be off for some minimal time would it be better energy use wise to just leave it on. I know places like millworks and cabinet shops leave their's on for the whole shift but what about us hobbyists. I'd like to hear what others do.

  2. #2
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    I turn on my 3HP gorilla when I need it and turn it off when done. Sometimes it is only on for a few minutes. Even so, I doubt I have ever turned it on more than the recommended 6 times per hour.

    The longest times are during long drum sanding sessions when it may be on an hour or maybe two at a time.

    It's about 6 years old, and my only problems are the crummy remote receiver that came with it.
    Rick Potter

    DIY journeyman,
    FWW wannabe.
    AKA Village Idiot.

  3. #3
    I have all my machines tied to one central dust collector with automatic gates. Any machine powered up starts the dust collector and there is a programmable shut down time for dust collector after machine is shut off. I set the 5hp collector to shut off 1 minute after last machine is turned off. 1 minute is usually more than enough time when I'm hopping from machine to machine. I did not set that time so much for energy savings but rather reduce the strain of starting and stopping the dust collector so often when I'm on a run of series of different cuts.

  4. #4
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    There was a thread about this not long ago, not about the energy use but the health of the motor. Apparently turning DC on too often in a short period of time can cause a large motor to overheat. I don't remember the numbers or the sources of these warnings but you might try a forum search or maybe someone will remember the details.

    I personally leave mine running if I will use it again in a few minutes. (5hp ClearVue cyclone) Mine is in a sound insulated closet so most of the noise in the shop is from the air rushing though tool intakes so I close the blast gates until needed. This, BTW, reduces energy use since the motor doesn't have to work so hard to spin the impeller in a partial vacuum/reduced pressure. (I used an amp meter on mine to verify this.)

    JKJ

    Quote Originally Posted by John Ziebron View Post
    Malcolm started a thread about an A/C energy monitor which got me to thinking about turning some equipment on and off, mainly the DC. All of our power equipment have motors which, if I recall correctly, have a high startup current. When I work in my shop, like most of you I presume, we try to plan as much of the work at one time at a particular machine like a jointer or table saw and leave them running.

    Then I started to realize that I turn my dist collector on and off a fair amount, even if it's only going to be a minute or two before I have to turn it on again. It's a 3 HP cyclone and it sits on the other side of an insulated wall so the noise isn't too bad. But it's just a habit I got into years ago with a smaller DC.

    I was wondering if anyone has done even a basic analysis to determine if the DC were going to be off for some minimal time would it be better energy use wise to just leave it on. I know places like millworks and cabinet shops leave their's on for the whole shift but what about us hobbyists. I'd like to hear what others do.
    Last edited by John K Jordan; 12-24-2018 at 11:05 PM. Reason: grammar

  5. #5
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    John

    There are lots of studies done on this and it becomes somewhat situational. In other words, what work is the motor performing?
    A table saw just spinning isn't going to have near the amperage draw as once it starts cutting, which is the same with most of the other wood working machines in your shop. The dust collector is one of the exceptions. It is always under some type of load due to the dynamics of the system.
    Starting and stopping motors isn't so much an energy saving strategy, though it does accomplish that, it is more to extend the life of a motor in a given application. The more starts and stops on a motor, the shorter the life of the motor will be, all things being equal. The start up current on a motor is much higher than while it is running, but that inrush current is only there for a few seconds.
    I tend to leave my dust collector running until I know I'm done with it. I don't start and stop it with each machine. Rarely though is it on than more than a 1/2 and hour at a time. Generally this is the time I'm running material through the Jointer and the planer. I think the longest I remember it running continuously was 4-5 hours when I was cutting parts for an ultralight airplane wing. The band saw was running that whole time also. That was fun.
    "The first thing you need to know, will likely be the last thing you learn." (Unknown)

  6. #6
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    Quote Originally Posted by Mike Cutler View Post
    ...I think the longest I remember it running continuously was 4-5 hours when I was cutting parts for an ultralight airplane wing. The band saw was running that whole time also. That was fun.
    Not on the topic, but do you have pictures of the ultralight wing (and plane) somewhere, perhaps in a thread here?

  7. #7
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    John
    Sadly, no. Everything left my house as "parts". Kind of like a giant RC model kit.
    I don't fly but a friend does/did? and was making his own ultralight. He had a cut list from the plans, and we started out with four, 22' long, sitka spruce beams, maybe 4"x8"? and started making the parts. It was pretty cool, we had to bring the band saw into the garage and run the boards through a side door and then out the front of the garage. I like doing stuff like this.
    Last edited by Mike Cutler; 12-24-2018 at 9:48 AM.
    "The first thing you need to know, will likely be the last thing you learn." (Unknown)

  8. #8
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    I do not turn my cyclone on and off with any frequency and often keep it running as I move from tool to tool and just change blast gates. And with the CNC in the shop now, my cyclone runs almost all day some days with only a few times being shut down. That's using less energy this year with the MiniSpilt in my shop than just the resistance heater did one year prior without the CNC in play. And since my cyclone is in a sound reduced closet, keeping it running isn't really an issue with sound level. The music over-powers it quite nicely.
    --

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

  9. #9
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    I believe compressor duty motors are designed for more starts per hour then standard motors. Of course most of them do not have a nameplate horsepower rating. So Sears can lie about how much horsepower you have.
    Bil l.

  10. #10
    My DC turns on automatically each time I start my TS. For other shop tools such as the planer, I have to manually move the plugh for the DC to a live outlet, set up the duct work and then start the planer.

    As far as the efficiency question. The start up current is a very short duration spike so it shouldn't take very long for it running continuously to equal the start up surge. It is likely that running it for just a few seconds would use as much as the start up spike.
    Lee Schierer
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  11. #11
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    I tend to leave mine running, unless I know I won’t be at/using a machine within the next 15 minutes. The DC also tends to help circulate the heat in the shop which is a nice two-fer when leaving it running.

  12. #12
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    Santa Fe, NM
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    My DC is in the garage next to my shop, so ambient noise is pretty low. I tend to leave it running if I know I'll be doing any machine operations within a half hour or so. Otherwise I turn it off.
    Semi-retired, teaching CNC for Fine Woodworking at the local community college. FineLine Automation Saturn 2, EnRoute Pro, Aspire, Mach3.

  13. #13
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    I tend to leave mine running if I am actively machining wood. Since I don't have an air filter, I figure it might help a little to clean the air in the shop.

  14. #14
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    My dust collector is connected to start when I manually open a blast gate.

    I must move slower than most of you guys. I close the gate after doing what I need to do at that tool and the dust collector motor shuts down.

    When I get to the next tool, and open the blast gate when I am about to start that tool, the dust collector starts again.

    As a homeowner, power factor issues are no concern. My slow moves between each machine makes leaving the DC running a waste of energy.

    Oh! To be young and fast again like you guys! Guys that can leave the dust collector running because you move so fast!

    I would gladly leave my DC running all day if I could return to those days...
    Too much to do...Not enough time...life is too short!

  15. #15
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    Quote Originally Posted by Lee Schierer View Post
    My DC turns on automatically each time I start my TS. For other shop tools such as the planer, I have to manually move the plugh for the DC to a live outlet, set up the duct work and then start the planer.

    As far as the efficiency question. The start up current is a very short duration spike so it shouldn't take very long for it running continuously to equal the start up surge. It is likely that running it for just a few seconds would use as much as the start up spike.
    I think the biggest issue with frequent starts on induction motors is heat rather than electricity use. There's quite a bit of heat created in a short time on start and the motor doesn't run long enough and isn't off long enough for the heat to dissipate. Lower quality motors have lower quality insulation in the windings so they're more of an issue. At least that's my understanding.

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