Start capacitor for the motor

by Kevin
(Ware,Ma)

Can you tell me where i would look for the start capacitor for the motor, And how to test it?

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Kevin, typically the start capacitor, or motor start capacitors (sometimes there is a start and a run capacitor rather than just one) are found attached to the side of the motor, a tube like thing, sometimes 1 1/2" or so in diameter and 2-3 inches long.

But, since you don't tell me what kind of compressor you have, make, model or size, then all bets are off in terms of identifying yours.

To test the capacitor, please see that page on this site.

Bill


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Motors

by Simon
(Brooklyn, NY)

Hey Bill

Great site! I'm thinking of building my own compressor for a number of reasons and I have a motor question. I've noticed that the 5 HP motors I am looking at fall broadly into two RPM categories - 1750 and 3400

a) Is there are reason to purchase one over the other other? I haven't seen any pumps that would seem to be able to handle the higher RPM so what gives?

b) Is there a formula for matching pumps and motors?

c) Should I just shut up and buy your book?

SM

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Bill says....

Chuckle! Simon, I'd tell you to buy the eBook, but the info you seek isn't in there. My eBook, The Home Compressor, is for folks that want to know more about buying an already built air compressor, and then, when they do so, it offers tons of tips on using it to it's fullest.

As far as I'm concerned, good on you for going to a 240 volt power supply. You really cannot good performance for most air compressors running on a 120 volt circuit. That voltage just doesn't have the oomph to run a powerful enough compressor pump.

I don't know why the 240 volt motors have two speeds. Nor would I much care. I would select the motor that the compressor pump specs called for.

"Is there a formula for matching pumps and motors?" I would expect so, but not being electrically inclined, haven't had the need.

I am happy to post this for you in the hopes that someone can offer more info on your questions than I!

Cheers,and thanks for your kind words.

Bill

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Hot air compressor motor?

by Simon
(Brooklyn NY)

Bill - any idea how often you're supposed to grease your motor - I have a 5 HP and it's running hot but I don't know if it's supposed to be that hot or if something else is up. I know it's a bad idea to over grease the motor but how do you tell if it's lacking grease on the bearings? After some sustained use the mag starter is tripping now.
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Simon, whenever I have had to lube an electric motor, it was 2-3 drops of motor lube oil once every year!

Anyone else have experience with compressor electric motor lubrication?

It could just be wear on the motor that is increasing the temperature, as long as your electric supply to that motor has not varied.

Could you add a comment letting us know how old this motor is, and if it is well used or not?

Cheers,

Bill

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Thermal cut out on compressor motor failed?

by Mike
(East Yorkshire UK)

OLD compressor 2.5hp on about 200ltr tank

OLD compressor 2.5hp on about 200ltr tank

OLD compressor 2.5hp on about 200ltr tank
OLD compressor 2.5hp on about 200ltr tank

I have a large OLD compressor 2.5hp on about 200ltr tank, has been great, but last problem was either the start OR run capacitor failed... can't remember which but that was changed and all has been great.

OK for about a year of occassional light use but now the it runs fine for anything up to 4 or 5 mins then the thermal cut out pops.

it will restart again within a matter of seconds but trips again after about 1 min.

I have done the troubleshooting checks and tests and proved ok, the mains supply 20 amp feed, no leaks on dump valve, pressure switch ok, still trips with the compressor belt removed, will with repeated resets (possibly 3 reset) will get up to 140 in main tank, there also appears to be no excessive heat anywhere on motor or coils so am I right in assuming it could simply be the thermal tripswitch that is poorly?? if so is it the black button itself that is the switch. Can I test it off the comp?? what rating will I need??
Many thanks for any help. Mike (UK)

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May 03, 2014
caps
by: Doug in s.d.ca

Testing caps is discussed on these pages.
It's not real easy to find, so try this link:
http://www.about-air-compressors.com/testing-capacitors.html

Follow the directions carefully.
Pretty much any meter (V.O.M.) will do the job, if it has a resistance function.

Most everything is covered, you want to use the site map to actually find some of it.


May 03, 2014
question
by: Anonymous

Excuse my ignorance but can you tell me in laymans terms how to test the capacitors, do they need to be tested/ checked in situ or will they test the same if removed from the compressor. Also is there any way to test /measure the thermal switch?
Thanks, Mike.

Apr 27, 2014
motor n stuff
by: Doug in s.d.ca

Did you recheck the caps?

The thermal cutout may also be measuring overcurrent, which could be caused by bad run cap...

If that's not it, then can we get pix of the blue box, inside and out (label)?

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