Run versus Start Capacitors - How to tell

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I have a 9" Craftsman (Sears) drill press that just smoked the motor capacitor. I call Sears about a replacement and they want to sell me the whole motor (of course). I'm trying to replace just the capacitor but I don't know if it's a run or start. Here's what labeled on the cap:
CBB60 SH 16mF +/- 5% -25/70C 250VAC 50//60Hz Wenling Star &Fire Capacitors Factory E215152
The model of the drill is 137.219090 if that helps
How can I determine if it's a run or start cap?
thx
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stoneattic wrote:

If there's only one capacitor it will be a "run" one.
It would be highly unusual for a small drill press to have a motor with a "start" capacitor, but there really isn't any difference between a "run" and a "start" capacitor, the term comes from the application, not the design.
You'll be able to purchase a 16 mfd 250VAC motor capacitor at lots of places. Getting one the correct size and shape will be the more challenging part.
Jeff
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I seem to recall that start caps are smaller and less expensive and rated for less ripple current than run caps. For instance, Grainger's 4CU61 and 2GU30 caps have similar values and voltage ratings, but the 4CU61 costs $8.26 vs $15.12, and it's only rated for 20 3-second starts per hour, ie a 2% vs 100% duty cycle.
Nick
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snipped-for-privacy@ece.villanova.edu wrote:

YOU GOT A POINT THERE JUDGE! *
I'll stand corrected on the ripple current rating thing, which seems to make sense.
If the OP really can't find the value he needsk he could get one of these monsters which comes with jumpering instructions to replace anything from a 12.5 to a 67.5 mfd capacitor, but it might be bigger than the motor itself. <G>
http://www.motor-rundirect.com /
I'm betting the OP's motor has a cylindrical paper covered cap under a sheet metal "hump" on it's side.
Jeff
* From "Bad Man's Ballad" - Kingston Trio - ca 1960
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--
But it could be (and w/ a drill press it\'s what I\'d expect) just a
capacitor-start motor to provide the starting torque. I\'m w/ John G
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I wouldn't expect to see a capacitor-start motor in a drill press. Drill presses start up under no load (except some friction from the bearings and belts) so they don't need much starting torque. A capacitor-run motor provides a positive starting direction and better running torque than a split-phase motor, without any need for a starting switch or starting relay.
I have a Sears drill press with a capacitor-run motor. One bench grinder is also capacitor-run.
Besides, starting capacitors are often in the range of hundreds of uF, while run capacitors are usually tens of uF.
    Dave
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stoneattic wrote:

There is no run or start specific caps. It depends where in the circuit. Just get a same spec. cap. If you can't match it little bigger value is OK on capacitance and voltage.
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Thanks guys! I'm having a tough time locating a replacement locally. The only two places that I'm aware in the area are Grainger and Johnstone Supply and neither seem to have any 250VAC or 16mf. Are you aware of any online sources? My Google searches have so far yielded no luck.
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wrote:

Try looking for a motor repair shop (or electric motor repair) in your phone book. They may only charge a few bucks to fix it.
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On Wed, 18 Apr 2007 12:49:21 -0400, "John Grabowski"

I prefer the phone book myself, but sometimes it confuses me, like, Is there still a Business to Business Yellow pages and would this category be in that one.
There is also in the US yp.yahoo.com which is a lot like the yellow pages, but when I was trying to find the major electric motor repair store in Baltimore, that I've been to, it didn't seem to come up in yp.yahoo.com .
Probably not necessary here, but if one can find the right kind of store somewhere else, the Electric Motor Repair in Baltimore, even if they are not a mail order store, if you pay them extra they'll often be glad to put what you need in a box and ship it to you. "Extra" might not even be that much. They have boxes, tape, pens, and they get deliveries all the time via ups etc.
For example, not electric motors but Eliot's Hardware in Dallas isn't mail order, or at least wasn't 14 years ago, but they'll still mail things out if one asks. I think they charged, for an envelope of shelf pins, 32 cents to ship them. That was the cost of the stamp. No other shipping or handling charge. A great store.
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Tony Hwang writes:

You're mistaken. Please, nobody listen to that ignorance.
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wrote:

No normal electric motor has a 16 MF start capacitor. And, most run capacitors are 370 volt. You can replace it with a 16 MF 370 volt run capacitor. They are available at W.W. Graingers or Johnstone. Or, why not try Sears parts?
Al
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On Wed, 18 Apr 2007 11:05:18 -0400, Jeff Wisnia

I guess a motor store would be better, but you could also check out www.mouser.com and www.mcmelectronics.com I think I have the second url right.

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wrote:

I've used both Mouser & MCM for years for electronic items. Good sources. Also I bet the 21ufd cap here would work: http://www.action-electronics.com/capac.htm
This is the kind of thing that in most areas is easier to obtain through the mail.
Dan
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Jeff Wisnia writes:

No, these are "different same" items.
Both are typically electrolytics which are compact but lossy. The start type is rated for a low duty cycle so they can be made very compact and very lossy (i.e., cheap). The run type must be physically bigger and more expensive for the same capacitance to make it less lossy, so that it doesn't overheat in a 100 percent duty cycle.
Weren't they past the phlogiston and ether theory when you studied EE? Start vs run types vary in the real component of their impedance, which is reflected in the resistive component of the lumped element model. This is usually explained in dumbed-down terms of "ripple" for the non-engineer.
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Richard J Kinch wrote:

Hey Richard, I admitted yesterday that I screwed up by wording it that way, but go ahead and beat on me if it feels good to you, I've got thick skin. <G>
Peace,
Jeff
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You may have trouble finding a generic 16mfd, but 15's are very common and will work fine. You have a 10% +/- tolerance anyway. Larry
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You sound like a hack. Lossy is an audio or compression term. Maybe you are after...lousy?
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snipped-for-privacy@gmail.com wrote:

No, I don't think Richard is a hack. He was right to pounce on me over that mistake.
I stand corrected. I either never learned or never thought about the operating requirement differences for "start" and "run" capacitors, but it now seems obvious, especially since supply houses list them for one or the other purpose.
Though, if push came to shove I'm sure one could use a run capacitor of the correct capacitance rating to do a start capacitor's job, but not the other way around, huh?
Jeff (Looking forward to attending his 50th MIT class reunion in less than two weeks. <G>)
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Probably. The run capacitor would be too large to fit the space provided for a start capacitor of the same voltage and capacitance rating, but it ought to work fine electrically. The start capacitor used as a run capacitor would soon overheat.
    Dave
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