Do you leave your D/C running ??? [Archive] - Sawmill Creek Woodworking Community

Dewey Torres

01-13-2009, 8:29 PM

I'm with you, Dewey. Maybe they think the ideal thing is x times per hour, but I can't see how the motor would care.

I know.... I am sure they had a reason but I just question the reason.

Shampoo instructions tell you to wash rinse and repeat!!! Who does that?

Now we all know that one is to sell more shampoo so it surly doesn't apply. I was just making the point that the manufactures recommendations are not always to make the tool last longer. There may be something I am not aware of but...

Like my band saw: I think it has a VERY similar motor as my DC. Maybe I should go run and check that:confused:. Ah what the heck, we are talking Oneida here so my findings will not apply.

Tom Veatch

01-13-2009, 9:02 PM

...aren’t those motors similar to table saw motors (just with a plenum air fan attached)?....

I'm with you, Dewey. Maybe they think the ideal thing is x times per hour, but I can't see how the motor would care.

The motors are similar in that they are usually both induction motors. The difference is that the startup load on a DC motor with a high inertia blower wheel is much higher than that on a table saw motor with a low inertia saw blade. Therefore the time to reach full speed and drop the amperage in the motor to the much lower running current from the high startup current is much less in the table saw than in the DC.

The heat generated in the motor is a direct function of the amperage flowing through the motor. The high amperage, high heat input, startup phase of a DC motor lasts appreciably longer in a DC than in a table saw due to the higher startup load. This causes the DC motor to heat more during startup than the table saw motor.

High temperature damages the insulation on the wire in the motor coils. Therefore the potential for damaging heat buildup in the DC motor from frequent on/off cycles is much higher than in a table saw. When the motor is running at its design speed, the amperage draw is somewhere around 15% to 25% of the startup amperage, so heat is generated at a rate that allows it to dissipate before temperatures reach damaging levels.

Hence the recommendations of the manufacturers to limit the number of start cycles. This allows the motor to cool between the blasts of heat generated by the high amperage start up current.

Of course this all assumes the motor is operating within its load and environment design specifications.

To accommodate this, I installed a variable time delay in the circuit that energizes the coil in the contactor which switches my cyclone motor. When the tool shuts down, the cyclone continues to run for 5 to 6 minutes before it shuts down. There is also a manual override so I can manually shut the cyclone down prior to the end of the time delay if I know I won't be needing it for an extended time.

Dave Verstraete

01-13-2009, 9:08 PM

Rick
I'd be taking a different thought on this one. Country music or DC "music" HMMMM...I'm not sure which I like better!

Jim Becker

01-13-2009, 9:18 PM

The whole time? No. But I'll go for a period of time bouncing between machines sometimes, just adjusting the gates in use.

Dan Friedrichs

01-13-2009, 9:21 PM

Tom,

I did consider that - I'm not sure I buy that the I^2R heating losses are significant enough to damage the enamel on the windings, though. It certainly makes sense, but it would take a LOT of heat to damage anything, and running the motor continuously will also generate heat, so maybe the manufacturer has decided that running the motor continuously makes as much heat as turning it on 5 or 6 times an hour. I reluctantly suppose that it's possible, but still feel that the amount of heat generated would have to be awfully large to actually pose any risk.

My intuitive feeling would be not to turn the thing on, say, 15 times an hour if you're working outside in 100F weather. But otherwise, this is probably not something worth worrying about.

Dan

Tom Veatch

01-13-2009, 9:39 PM

...My intuitive feeling would be not to turn the thing on, say, 15 times an hour if you're working outside in 100F weather. But otherwise, this is probably not something worth worrying about.

Dan

Dan, you may well be right. I've never had the ambition to test or measure the heat loads on my electric motors but figured that in the absence of specific reasons to disregard mfg. recommendations the better part of valor would be to adhere to them. In a prior life as a design engineer, I never specified limiting recommendations without some technically justifiable reason for doing so. Of course by the time it was in the customer's hands, there's no telling what stickers, placards, and/or other "lawyer-speak" had been applied.

Bruce Wrenn

01-13-2009, 9:51 PM

Mine is controlled by a sensor mounted in the panel box. A machine cuts on, so does DC. When machine cuts off, DC runs for an additional 10 sec. to clear pipes. Sometimes it will ge over twenty starts per hour. Been doing that since 2001

Rick Peek

01-13-2009, 10:23 PM

Rick
I'd be taking a different thought on this one. Country music or DC "music" HMMMM...I'm not sure which I like better!
Ha! Thats funny Dave. I'm really a rock & roll guy,but for some weird
reason I listen to country when workin wood.
Seriously...I bought it with a remote. The concern was that Onieda says
not to stop & start more than 6 times an hour. Last night while working
I realized that I start & stop my currant D/C quite often. I really find the
added noise of the D/C annoying.

Dan Friedrichs

01-13-2009, 10:38 PM

Very valid point, Tom - they probably didn't just make that "5 or 6 times an hour" number up.

In all friendliness, I think putting a 555 in your contactor box to make sure it doesn't exceed that is probably something I would make fun of you for doing, though :D

Sonny Edmonds

01-13-2009, 10:50 PM

The answer would be...
It depends.
Usually I will leave it on for any period when it will be picking up dust or chips when I move from one operation to a different one.
But not "on with the lights, off with the lights". That would be ridiculous.
But when changing a blade or bit, I will let the DC run, but close the gate(s) to the machine I'm changing on.
It in no way hurts or overloads a DC systems blower to run statically closed. In fact, it actually unloads the motor. The motor is cooled by it's own external fan on the tail end of the motor.
Just like when you put your hand over a shop vac's hose and it speeds up because it is in an unloaded state (not working, idling).
DC's induction motors do not speed up because they are synchronous motors. But they unload and the amperage drops.
Then when they begin to move air again, the amperage draw climbs back to what it takes to do the work. And by design that is less than the FLA (full load amperage) rating of the motor.
I have started and stopped my motors (2) more than 5-6 times an hour. But never had any ill effects or burned out a motor.
But I don't start and stop my DC with every time I move from one machine to another.
After all, when it is on it is filtering air.

It is true that some motors are short lived if they have excessive starting and stopping. And for the reasons Tom tried to explain. The starting current is usually 5 to 8 TIMES the full load current on the nameplate. And it not only heats the windings each time, it can also weaken the bonds of the varnish and insulation in the stator of the motor.
If you've ever heard a metallic whack in a conduit when a heavy load is started, that is the wires literally jumping from the massive current being drawn for several milliseconds as the motor becomes magnetized.
Our old air conditioning unit would do that when it started. It was rather unnerving to my trained ear. The wire, fuses, and supply was all correct. But the 23 year old unit took a big punch to roll it. Ping! The conduit would ring going up from the panel to the attic. And I'd cringe.
It did finally stop one day, when the compressor died. The new one uses 25% less ampereage to do the same heat load. 30 amp fuses Vs: the old 40 amp ones for the old unit.
That is graphic inrush current. Making the wire jump inside the conduit.

But different motors will have different amounts of magnetic slip engineered into them. That allows then to survive in extreme conditions, like crusher duty motors with a 40% slip factor built into the stator to winding. So they won't burn out quickly from the starting loads imposed on them.
Even with the gear reduction, it is designed that a conveyer belt be able to start and move the belt it runs fully loaded. Talk about a load on a poor motor! They can do it with out burning out, or ripping the guts out of the gear reducers, because of the slip factor in the motor itself.
So the efficiency isn't great, but the machinery or motor isn't killed either.

If yours is a bother, then build an enclosure around it and control the noise. Or relocated it outside to an enclosure.

And if you can't hear your music, it isn't loud enough. :D
Or you need to get your priorities straight. Go sit and listen to music and drink beer. Or go do some woodworking in the shop. ;)
90% of you have no clue about what I, and Tom, have told you here. :)

Dewey Torres

01-14-2009, 1:09 AM

The answer would be...
It depends....90% of you have no clue about what I, and Tom, have told you here. :)

Sonny,
How about you explain to a Southerner What the difference in start up load is between a plenum air fan and a band saw with a blade a two big wheels. I may be an idiot to some but I am (not bragging just credentials) a US Navy graduate in the advanced electronic field and fully understand ohms law, special circuits, resistance, power, voltage, amperage, induction, alternating and direct current, propagation.... yada yada yada... and these are just what I call the basics. I also understand electronic physics to an extent.

Even still... don't buy it. And I am still not sure why:confused: Maybe I am dumber than I think.

John Keeton

01-14-2009, 7:26 AM

Here is the problem as I see it. Tom, Sonny and Dewey, and others, have significant knowledge about all this electronic stuff, and apparently are truly concerned about the overall efficiency of the motors, etc.

Then, there are the unknowing idiots like me, that simply go out to the shop to escape the myriad of mundane minutiae with which one typically deals with on a day to day basis. I just want to make sawdust, make reasonable assurance it gets sucked up, leave with all my body parts, have fun - and, if all works out right - build a respectable piece of woodwork.

The question was really not WHY you either leave the DC on or not, but WHETHER you do. I leave it on while I am milling, etc., and turn it off if it is not going to be in use for 15 - 20 minutes. But, I don't go further in the analysis than - "it is getting hot in here and that dang thing makes too much noise." Good enough for me.

And, Sonny is right, I don't understand that stuff - but, more importantly, I don't care.

But, that is not to say that my attitude lessens the importance of the knowledge that has been imparted. I just don't want to go there when I am having fun. If it is your cup of tea - I enjoy you posting about it! It is good to see others enjoying what they do in life.

Joe Chritz

01-14-2009, 7:32 AM

At at extreme I believe it completely.

Subject, non statistically important example: I was doing a project which involved cutting the corners off a lot of blocks. Just a quick notch, 4 times per block a couple hundred blocks in one sitting. I found it was faster to use a stop and a chop saw than a bandsaw so I went to work.

About 25 or 30 blocks into it the motor on the Dewalt SCMS was hot to the touch. Hot enough for me to worry and cool it off and rethink the process into something else. Granted that was about 100 or so starts/stops in short order but it does give an example.

For the DC. I use a remote and want to wire blast gates with micro switches and a time delay but really haven't had that much shop project time. Perhaps a time delay like Tom talks about is a good alternative if it is relatively cheap. To counter for now I generally leave it on if I am in milling processes and think I will be using it again within a few minutes.

If I have to turn it off and on in close proximity I don't worry to much.

Joe

Jim Kountz

01-14-2009, 8:14 AM

Ok down boys, down. Thats it easy now. Ah thats better! I think most of the replies here make sense in their own right, but Im with John on this one, I just really dont care about my DC motor that much to worry about it the whole time Im in the shop. Its not that I want to burn it up or anything its just when Im out there doing something my DC motor is the last thing on my mind, least I hope so. If it burns out then I get a new one if it doesnt even better! Enjoy your time in the shop fellas, dont sweat the small stuff!!

Rod Sheridan

01-14-2009, 8:28 AM

The issue isn't the winding temperature only, it's also a factor for the aluminum bars in the rotor.

Slip causes currents to be induced in the rotor bars (hence induction motor). Starting with high inertia loads causes very high currents in the bars for a relatively long length ot time, and of course heat.

The heat in the rotor bars can actually melt the aluminum, causing an open bar. It's all downhill from there as the motor is now permanently missing a rotor bar.

regards, Rod.

Prashun Patel

01-14-2009, 8:36 AM

I spend about 95% of the time planning, measuring, and setting up the operation, and 5% of the time executing it. Oneida's way more educated than I am, but I find it hard to believe that a few more stops and starts are harder on the motor than leaving it running for all that time.

The exception is when I'm making repeated cuts or ops that require less than a minute or two between turn on; then I just leave it running.

My router and miter saw are connected to a shopvac, and I heard those motors are not designed for long continuous running. So I definitely turn that off between ops.

Rick Hubbard

01-14-2009, 9:07 AM

In the interest of full disclosure, I’m a bona fide card carrying cynic when it comes to statements that are not self-evidently true made by commercial businesses. I also subscribe to the proposition that NOTHING is ever said without a purpose.

So here is the situation: the DC manufacturer advises users not to energize the motor more than X times per hour. The reason for this proscription is not self evident (therefore, in my mind, is suspect). Since nothing is ever said without a purpose, why would the manufacturer say such a thing?

Here is one scenario: imagine that the motor on your DC fails in 3 months. You make a call to the DC manufacturer and at some point in the conversation the rep might ask an innocent sounding question such as, “Do you leave the DC running all the time”? You answer, “No I just turn it on when I need it.” “AHA!” The manufacturer asks, “Do you ever turn it on and more than X times an hour”?

There’s no point in saying anymore- you can see where this is heading, can’t you?

Rick

Eric Gustafson

01-14-2009, 4:43 PM

.To accommodate this, I installed a variable time delay in the circuit that energizes the coil in the contactor which switches my cyclone motor. When the tool shuts down, the cyclone continues to run for 5 to 6 minutes before it shuts down. There is also a manual override so I can manually shut the cyclone down prior to the end of the time delay if I know I won't be needing it for an extended time.

I did pretty much the same thing. I think I bought the time delay at McMaster Carr. However, I wanted to make it so it would start and commence countdown with each tool's start up, but gave up when I figured the cost. So I am using the remote with the time on delay in the circuit.

What did you use to sense tool start-up and shut-down, Tom?

Mine is controlled by a sensor mounted in the panel box. A machine cuts on, so does DC. When machine cuts off, DC runs for an additional 10 sec. to clear pipes. Sometimes it will ge over twenty starts per hour. Been doing that since 2001

I guess I'll ask you what you are using, Bruce. Since you are also doing at least part of what I had in mind.

I guess this exposes me as a believer of excessive inrush/over heating! :o I just do not want to replace that 5hp motor! $$$ :eek:

Tom Veatch

01-14-2009, 6:27 PM

Eric,

I built a control system based on the article "Automate Your Dust Collector" in Vol 91 of Woodwork Magazine. More details are in this thread (http://www.sawmillcreek.org/showthread.php?p=955593)- see post #28. The delay timer shown in the schematic referenced in that post is one of these (https://www.alliedelec.com/Images/Products/Datasheets/BM/ARTISAN_CONTROLS_CORP/519-0007.PDF) (Artisan 4710A-8-B-3) from here (https://www.alliedelec.com/Search/ProductDetail.aspx?SKU=5195185&MPN=4710A-8-B-3&R=5195185&SEARCH=5195185&DESC=4710A-8-B-3). Note that the price of that unit has almost doubled since I built my system.

Note also, the the description in the link calls it an "On Delay" but it's actually a "Delay On Break" relay. It does what I think you wanted - "start and commence countdown with each tool's start up". The countdown to turn off the cyclone begins when the tool is powered off. If another tool is started during the countdown, the countdown restarts when the last tool is turned off.

Jim Eller

01-14-2009, 7:57 PM

I went right to the horse's mouth and asked them.

Here is Oneida's response:

Hi Jim,
I consulted with our electrical engineer just to double check my facts, and this is the reason we advise customers they should start their single phase motor no more than 4 to 10 times an hour (the 3hp Gorilla manual has been updated to reflect the change from just 5):
Single phase motors use a combination of a start capacitor with a centrifugal switch. Turning the motor on and off sends the locked rotor inrush across the contacts of the centrifugal switch, doing so multiple times in a short period of time will eventually cause the switch to fail.
Just to clarify this point as well, turning the motor on and off more than 5 times an hour is usually the last thing that will cause the motor itself to fail, but it is possible... our warning is more to lessen the burden on the centrifugal switch contacts.
I'm a contributor at Sawmill myself, so I can post this there if you think it will help, or you can copy and paste it yourself if you'd like.
Thanks,
Oneida Air Systems

I have removed the name of the Oneida representative.

Another great job of customer service by a great company to work with.

Jim

Jim Becker

01-14-2009, 8:51 PM

Well, that's good advice from Jamie! :)

Dewey Torres

01-14-2009, 9:03 PM

Ah Ha!!! I knew it!

Go ahead and revisit that remote idea I posted above. Now that we have the facts. Heck, 6 times off and on per hour is once every ten minutes without fail. You may achieve that once in a while but probably not often so who cares. I bet that switch is a cheap fix anyway so load up those country tune and let r' rip!

Carl Babel

01-14-2009, 9:12 PM

Shampoo instructions tell you to wash rinse and repeat!!! Who does that?

You mean you don't?;) I suppose the next thing you're going to tell us is that you rip the labels off of those mattresses, too.:D

Sonny Edmonds

01-14-2009, 9:15 PM

Dewey, I worte you a very elongated reply last night.
Maybe too long.
Because when I tried to post it, IE froze up and couldn't find the web site. :mad:
No bother though, why drag a dead cow around.

I know more than I care to remember about electicity and industrial motors, circuit design and maintenance.
You name it, I've had my fingers in it or my electrical brain wrapped around it in some way.
Just know that a motor can be beaten to death by the operator.
Usually the engineer designing the process or circuitry will take into consideration the duty and how severe it may be.
If Onieda (just for example) sez no more than 6 starts per hour, and someone beats their DC to death (those of us who maintain motors and have repaired them can tell) they might replace one. But asking for more is eventually going to raise a bigger stink than the smoked motor.
There is a lot more I could impart about motors, but what the hell? ;)

Bruce Page

01-14-2009, 9:21 PM

Shampoo instructions tell you to wash rinse and repeat!!! Who does that?

OMG, you don't? :eek:

I turn my DC on & off as needed.

Dan Friedrichs

01-14-2009, 9:49 PM

The heat in the rotor bars can actually melt the aluminum, causing an open bar. It's all downhill from there as the motor is now permanently missing a rotor bar.

regards, Rod.

Rod, I ask this in all seriousness: Have you ever seen a sub-5HP induction motor that has gotten hot enough to melt a rotor bar? I'm curious - I've never seen it at all, but I agree that it's possible. I think it's much more likely in a very large motor that's been stalled, though. Also, I somewhat doubt that a motor of this size would have a Al squirrel cage rotor - I imagine it's more likely to be copper windings on the rotor, as well.

Bruce Wrenn

01-14-2009, 10:02 PM

[quote=Jim Eller;1019634]I went right to the horse's mouth and asked them.

Single phase motors use a combination of a start capacitor with a centrifugal switch. Turning the motor on and off sends the locked rotor inrush across the contacts of the centrifugal switch, doing so multiple times in a short period of time will eventually cause the switch to fail. Start switch is OPEN when motor is running. It only closes after motor drops in speed. It's a centrifical (sp?) switch, and opens upon motor reaching a predetermined speed, generally less than full speed. The start capacitor can only stand so many in rushes per hour though. The better the capacitor, the more starts per hour. Look at the compressor on your AC / heat pump. How many starts per hour does it do?

Jim Kountz

01-14-2009, 10:17 PM

Dewey Torres

01-14-2009, 10:22 PM

Dewey, I worte you a very elongated reply last night.
Maybe too long.
Because when I tried to post it, IE froze up and couldn't find the web site. :mad:
No bother though, why drag a dead cow around.

I know more than I care to remember about ...

Sonny,
Thank you very much for not posting your "elongated reply".
Every tool in our shops can be beaten to death by the operator. If you give a rat enough red m&m's it will cause cancer. I think you get my point.

All Rick wants to do is listen to his country music in between cuts. According to "the horses mouth" He should be able to do that without worrying about his motor.

We beat this thing to death ... hey, even YOU SAID SO!

PS. I know you are a diver but I am not so where the heck is Saugus, Kelpafornia? I thought you had to put where you actually live when you registered:confused: Maybe I am wrong. It has been a while since I registered so I forget.;)

Bruce Page

01-14-2009, 10:22 PM

Wow.........Can we beat this horse anymore, the poor thing is dead already folks.......I think if Edison himself replied to this thread someone would still disagree with him....
For what its worth heres some advice from ol Jim.
Do what ever turns you (or your motor) on.

:confused::confused::confused::confused:

It seems like a legitimate question with good information to me.
Isn't that why we're here?

Dewey Torres

01-14-2009, 10:29 PM

:confused::confused::confused::confused:

It seems like a legitimate question with good information to me.
Isn't that why we're here?

thread steal on...
Hey Bruce...new avatar. Very nice...can I ask why? It's the second one in a month or so.

thread steal off...

Sorry Rick:o

Chris True

01-14-2009, 10:30 PM

Sonny,
How about you explain to a Southerner What the difference in start up load is between a plenum air fan and a band saw with a blade a two big wheels. I may be an idiot to some but I am (not bragging just credentials) a US Navy graduate in the advanced electronic field and fully understand ohms law, special circuits, resistance, power, voltage, amperage, induction, alternating and direct current, propagation.... yada yada yada... and these are just what I call the basics. I also understand electronic physics to an extent.

Even still... don't buy it. And I am still not sure why:confused: Maybe I am dumber than I think.

Bandsaw has inertia but no load on startup - unless you start to cut wood before it reaches speed. The DC has the inertia but also the air load it's designed to run at. That load starts low but keeps getting higher and higher until the motor reaches it running RPM and the full load at the same time.

Dewey Torres

01-14-2009, 10:35 PM

Bandsaw has inertia but no load on startup - unless you start to cut wood before it reaches speed. The DC has the inertia but also the air load it's designed to run at. That load starts low but keeps getting higher and higher until the motor reaches it running RPM and the full load at the same time.

hmmm.... I guess that makes since but seems a negligible difference.
Anyway, the manufacturer already answered and stated it has nothing at all to do with our hunches. It's the switch. Thanks for the reply Chris. A short one too. I like that.:)

Bruce Page

01-14-2009, 11:01 PM

thread steal on...
Hey Bruce...new avatar. Very nice...can I ask why? It's the second one in a month or so.

thread steal off...

Sorry Rick:o

No reason, just an eagle shot from Kodiak.

Sonny Edmonds

01-15-2009, 12:34 AM

North of L.A. a bit off of Interstate 5.
Ever hear of an amusement park called Magic Mountain? (A Six Flags Park)
I can see their fireworks from my winder.
My Mom always said I lived on the edge of where ever I was. So I'm close to the mountains, but still close enough to walk to the 7-11 to get beer. :rolleyes:
California is known for it's kelp forests in the ocean. So me being me, I coined Kelpafornia for the State I come from, and yep, took up scuba diving.
(The Governor calls it Kally-fornia with his Austrian accent. Sounds like Cauliflower.)
We have a nephew who is a diving instructor who got me certified to dive.
California water is cold though, so it requires a lot of gear and a heavy wetsuit.
Whole different world under the sea. Beautiful world! :) But I'm almost too old to do the gear anymore. Done wore out parts too soon, dang it!
I'd be proud to buy you a beer and sit and jaw about things if we ever got the chance. We could chew on jerky from dead cows. :D ;)

Chip Lindley

01-15-2009, 12:37 AM

All cynicism aside, turning on your DC 5 or 6 times per hour gives a duty cycle of 12 or 10 minutes (or less). I can certainly see heat build-up in the motor, with many start cycles and little time to *just run* and cool down. But, in my most likely planing/joining/shaping/sawing sessions, my duty cycle is more like most of an hour, once I have my work laid out. I do believe someone would have to be very OCD to flip the switch every 10 or 12 minutes!! Of course, those handy dandy remotes do make it much easier.

On a monetary note, those power surges at FLA will all add up on your electric bill. Starting a 2 or 3 or 5hp induction motor repeatedly uses lotsa JUICE, compared to just letting it RUN!

Steve Rozmiarek

01-15-2009, 1:24 AM

You all are missing the forest for the trees... Rick has a serious question, and to this point, no one has answered correctly, so let me take a shot.

Leave the dust collector on, it drowns out that awful country music racket!

J/K, but it is what I'd do...

Chip Lindley

01-15-2009, 1:53 PM

I don't think this thread missed the point at all. You ask 50 woodworkers the same Q. you get 35 different A. New Oneida V3000 Owner Rick will just have to make up his own mind! Much information has been presented here as Pros and Cons of constantly flipping that DC switch.

Personally I kinda like the sound of MY Oneida 3hp!! It sounds **Industrial**!! Building a closet for your DC would help the noise level Much! Put your air compressor in there too!

IF you gotta have your C&W, and are now Freaked to turn your Oneida on and off more than the manufacturer recommends, ther ARE those ear protectors with built in AM-FM!! You can even tune in your iPod to a vacant FM freq and listen to your own compilation--COMMERCIAL FREE!! YeeHaw!!

Rick Potter

01-15-2009, 2:07 PM

For what it's worth, I turn my 3 HP gorilla on when I need it, and unless I am going to use it within the next few minutes I shut it off. My previous one is still running fine after 10 years of this kind of (ab)use.

Rick Potter

John Schreiber

01-15-2009, 2:44 PM

As one of the few people who have not yet expressed an opinion here, I'll give mine.

I understand the reasons why it is bad for a DC motor to be started too frequently. I'd guess that if I start it more frequently than the manufacturer recommends, it will cause some damage. If I start it 100 times per hour, that will cause more damage than if I start it 11 times per hour.

The other factor is why do you want to turn it off at all. If it is very annoying and keeps you from enjoying your music (to me that excludes country music - it's best with the DC and compressor on at the same time), I'd be willing to take some loss in the life of my DC motor, but if I had it in a sound proof closet where it didn't bother me too much, I'd leave it on any time I thought I'd be using it again soon.

It's a cost benefit decision. Long motor life vs. loud annoying noise.

Chris Padilla

01-15-2009, 3:50 PM

Personally, I'd like to see a cost-analysis of power of the guise of: leave it on if you plan to use within 10 minutes or shut it off if you plan to use it 11 minutes+.

Being a non-pro, my motor doesn't run all that much and so I'm more concerned about keeping PG&E's spinning wheel at its minimum....

But, yeah, it sure is loud and I don't know if I have the room to quiet it down more by building around it....

John Hedges

01-15-2009, 4:18 PM

I think I'm the only one on the forum not on this thread yet (cant let that happen).

One interesting note is that when I was shopping cyclones recently, one of the companies I talked to touted that their Asian Motors were better than Oneida's Baldor's. His reason is because of Oneida's statement to not start and stop the motor more than x times an hour. Needless to say I did not buy from that vendor.

Getting back to the initial question, I don't think any of us hobbiest are going to run into a problem with this, due to our light usage. At least that's how I look at it. I don't think I start and stop it more than 6 times an hour anyway. One of the few advantages to being a slow woodworker I guess.

Oh and if I did have Coutry Music playing in the shop I would definitely keep it on all the time.:D

Rick Peek

01-15-2009, 5:55 PM

Wow,what a bunch of country haters:D And here I thought all
woodworkers were hillbillys! I think I have my answer though. The
answer is, do whatever the heck you want & live with it. I more or
less leave my current d/c on if I'm going to use it within about 10
minutes. Other than that, I turn it off. It's good to hear that a few
guys do the same with no real affect after many years of service.
Cheers, Rick

Brian Kincaid

11-12-2009, 9:26 AM

Bandsaw has inertia but no load on startup - unless you start to cut wood before it reaches speed....

That's my favorite way to trip a breaker. :mad:
-Brian

Mitchell Andrus

11-12-2009, 1:28 PM

Hence the recommendations of the manufacturers to limit the number of start cycles. This allows the motor to cool between the blasts of heat generated by the high amperage start up current.

It took five years, but I did finally fry my 3 hp Jet DC motor. I took it to a rewind shop and the first question he asked... "How often do you cycle it per hour and per day?"

Heat cooked the starter cap and the motor's windings developed a short. Don't know which came first though. Doesn't matter.
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Mitchell Andrus

11-12-2009, 1:36 PM

I do believe someone would have to be very OCD to flip the switch every 10 or 12 minutes!!

Nope, not OCD. I've got an Ecogate system and the timer is (was) set to turn the DC off 2 minutes after the tool was stopped. So, if I had a few pieces of wood to get from the miter to the jointer, then TS, back to the miter saw, over to the drum sander.... With a 2 minutes pause to check notes, set the cut, etc..... I can easily turn the DC on/off 5 or 6 times in HALF an hour.

My bad, see my other post.

I've now got it set for 15 minutes... but boy, making a 5 second cut turns the DC on for 15 minutes now. Sometimes I turn the Ecogate off to make a quick cut just so the DC isn't pestered.
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Greg Portland

11-12-2009, 2:58 PM

Since we're bringing this thread back from the dead...

I have a 5HP collector. IMO, I'll save more $$$ on my electric bill turning it on/off then I would by having to rebuild the motor every few years. Having said that, most of my operations are continuous (stock prep on the jointer & planer, drum sanding, ripping rails/stiles, etc.) so the DC will be running for long periods of time. Smaller tools (routing, hand sanding, etc.) are connected to the shop vac.

Does anyone have a work pattern than would result in you turning the DC on/off >10 times an hour? It's rare for my work pattern to have 1 cut, wait 10min, 1 cut, wait 5 min, etc. I'm either making a bunch of different cuts with <1 minute between them, running a batch / continuous operation (rip 50 rails, sand 20 doors, etc.), or planning the next set of cuts.

Keith Outten

11-12-2009, 11:35 PM

Does anyone have a work pattern than would result in you turning the DC on/off >10 times an hour?

I''m guilty. My DC is used for both my workshop tools like most of you and it serves my laser engraver in my shop office. When I am engraving small projects it isn't uncommon to have to turn the DC on and off every minute or so depending on the job. When the DC is running I can't open the lid on the engravers cabinet and it would cause problems trying to get thin material situated on the engraving table so the DC has to be turned off. Its not uncommon for me to start and stop my DC every 60 to 120 seconds, eight hours per day for jobs that last a month engraving plaques, glass and making wooden business cards.

I use the same DC for my CNC router, it runs intermittently sometimes for a couple of minutes to several hours per session depending on the job. I stop the DC when I change router bits and when I am changing material on the table.

My DC is about 18 years old, if the motor dies tomorrow I wouldn't be surprised. I can't even imagine how many hours it has run just planning lumber through the years. I attribute the life of the DC to the fact that I threw away the bags the first week I got it and built my first chip box. I expect that the start-up load being so low since there are no filters or bags that add resistance has a lot to do with motor life. I must admit that this is just a hunch since I have absolutely no electrical or electronics experience.

For the record my DC is a 1.5hp Grizzly rated at 600 CFM. It has one of those cheap Asian motors that probably won't last more than two decades :)
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Tom Veatch

11-13-2009, 1:23 AM

... I expect that the start-up load being so low since there are no filters or bags that add resistance has a lot to do with motor life...
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I know it's counter-intuitive, Keith, but the fact is, high resistance lowers the flow rate which actually reduces the load on the motor. Low flow resistance = high motor load, high flow resistance = low motor load.

Now, if it were a positive displacement pump like an actuated piston compressor or hydraulic pump, the situation would be quite the opposite, and low resistance would reduce the motor load.

Mitchell Andrus

11-13-2009, 8:16 AM

For the record my DC is a 1.5hp Grizzly rated at 600 CFM. It has one of those cheap Asian motors that probably won't last more than two decades :)
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That's good enough to keep up with a CNC router? I'm surprised. I've always seen much larger units sitting next to the cool tools. Do you have a decent dust skirt at the business end?
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Kenneth Whiting

11-13-2009, 9:45 AM

I'm one of the people that doesn't know/care about the specifics of how/why electric motors work/get destroyed. I figure if Keith can put his DC through what some would consider major abuse for 18 years then you probably don't need to worry too much if that was 5 shots or 6. (Are you feeling lucky punk?)

If you put your DC in a contained area so the noise isn't as bad, would there be a problem with leaving it on most of the day?

Mitchell Andrus

11-13-2009, 10:44 AM

If you put your DC in a contained area so the noise isn't as bad, would there be a problem with leaving it on most of the day?

If the filter is also in there (with an air escape vent or similar) I'd thing the airflow caused by the DC would be more than enough to provide cooling.
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Keith Outten

11-13-2009, 7:19 PM

That's good enough to keep up with a CNC router? I'm surprised. I've always seen much larger units sitting next to the cool tools. Do you have a decent dust skirt at the business end?
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Mitchell,

I use the stock dust skirt that came with my ShopBot. One of these days I hope to find the time to build a new dust skirt that will improve my access when changing router bits.

The flow rate of my Dust Collector probably exceeds the original specs because I removed the bags and blow chips directly into a chip box, it probably performs more like a 2 to 3 hp DC. Even though I don't have the best DC system design my 4" PVC pipe system functions really well if I only run one machine at a time.
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Alan Bienlein

11-13-2009, 9:01 PM

Yes I'll let my home built Bill Pentz design cyclone run. I always have one blast gate open besides the one or two that I have connected to other machines while I work. It does an excellent job of keeping the air in the shop clear when I use tools that I can't connect to my ductwork.

jeff kratz

11-14-2009, 6:16 AM

Hey guys---just wanted to comment on a subject that is kinda old no but never saw the thread before. Im an electrician down here in Wash DC and 2 years away from my EE degree-

if we are afraid of our motors burning up by hard starts why not see if a variable frequency drive will work on a dust collector. It will not only take away inrush current but will also be easier on the centrifugal switch if the switch will take differences in frequencies (hz)... for those of u that have high hp motors a freq drive is what u might want...most penthouse electrical motors in commercial buildings have freq drives.
It will save money in the long run on electrical bills also(less startup current)

while we are on the subject of power saving how many of u guys have a cap farm for all the high inductive loads in the work shop?

jeff