Adding start & run capacitor to split phase motor w/o one?

[ching0n]

I've got an old split phase grinder w/o a cap and a spare capacitor from another project that I ended up not using thinking I had a bad one. I believe it's both start & run can (have to find it). I can hear a centrifugal switch going off inside the grinder.

Is this a conversion that's routinely done? How would I go about figuring out if the sizing is appropriate or not (cap was for 1/2 drill pres motor, grinder rated as 8A (3/4?).

 

[BillK]

Im confused, does the grinder run now as it is ??

 

[The Cobbler]

if the motor wasn't originally designed with a capacitor, leave it alone. find another use for the capacitor .

 

[micromind]

If a motor uses a capacitor, it has to be designed for it. Adding one will make it draw more current and thus, run hotter.

 

[Bert_]

Leave it alone

 

[KenC]

I've got an old split phase grinder w/o a cap and a spare capacitor from another project that I ended up not using thinking I had a bad one. I believe it's both start & run can (have to find it). I can hear a centrifugal switch going off inside the grinder.

Is this a conversion that's routinely done? How would I go about figuring out if the sizing is appropriate or not (cap was for 1/2 drill pres motor, grinder rated as 8A (3/4?).

OK, I', curious about the red above. What would be the purpose of such a switch with no cap in the motor???

 

[Bert_]

OK, I', curious about the red above. What would be the purpose of such a switch with no cap in the motor???

It still has a start winding. A single phase motor has no way to get spinning without one.

A small motor will often have no capacitors and just uses a higher resistance winding to create a phase shift compared to the more inductive run winding.

 

[ching0n]

Im confused, does the grinder run now as it is ??

yes but I've added quite a bit of drag w/a belt attachment so though of improving the start up w/a cap (it's not bad as is but may as well use it if I have it sorta scenario).

 

[ching0n]

If a motor uses a capacitor, it has to be designed for it. Adding one will make it draw more current and thus, run hotter.

I checked and it's just a start cap, not run cap so if it would only come in during start up.

 

[micromind]

OK, I', curious about the red above. What would be the purpose of such a switch with no cap in the motor???

A split-phase motor has a centrifugal switch, just like a capacitor-start one. Works the same way but no start capacitor, the phase shift is accomplished mechanically rather than electrically by a capacitor.

 

[ching0n]

OK, I', curious about the red above. What would be the purpose of such a switch with no cap in the motor???

protects the starter winding which is thinner gauge and only meant for short use and not continuous duty.

 

[wyliesdiesels]

Dont add one if it doesnt have one. Leave it alone

 

[nadogail]

If it works, it doesn’t need fixing.

 

[ching0n]

If it works, it doesn’t need fixing.

but then hotrods wouldn't be a thing....

 

[The Cobbler]

but then hotrods wouldn't be a thing....

you asked some questions, you got answers you didn't want to hear.
what more discussion is there, other than have you figure out how to do it yet?

 

[ching0n]

you asked some questions, you got answers you didn't want to hear.
what more discussion is there, other than have you figure out how to do it yet?

I had questions that weren't really answered (is this routinely done? and how would I go about doing it?)....but yes, I have figured out how to size a start and run cap now.

 

[RonRock]

I just stumbled onto this thread. Actually I was going to ask the same question. I have a very old Red Devel paint shaker that I have reconditioned and use in my homeshop. The motor is original to the unit and has a Red Devel tag on it. Too cool to replace. It runs fine, but usually needs a "bump" to get the shaker in motion. I was wondering if I could ad a start capacitor to give it that little bit of a bump on it's own. Looks like that is not a good idea. Bummer. But still a helpful thread.

 

[ching0n]

I just stumbled onto this thread. Actually I was going to ask the same question. I have a very old Red Devel paint shaker that I have reconditioned and use in my homeshop. The motor is original to the unit and has a Red Devel tag on it. Too cool to replace. It runs fine, but usually needs a "bump" to get the shaker in motion. I was wondering if I could ad a start capacitor to give it that little bit of a bump on it's own. Looks like that is not a good idea. Bummer. But still a helpful thread.

Have you cracked the motor open yet? I've seen the centrifugal sw get sticky in 2 or 3 motors I've redone. Either they had very few hrs and the wear wasn't there to make it engage/disengage or they were dried out (some had felt pads to keep a bit of oil). helps to clean & regrease the contact points too.

 

[whateg01]

I had questions that weren't really answered (is this routinely done? and how would I go about doing it?)....but yes, I have figured out how to size a start and run cap now.

The answer is no.

I just stumbled onto this thread. Actually I was going to ask the same question. I have a very old Red Devel paint shaker that I have reconditioned and use in my homeshop. The motor is original to the unit and has a Red Devel tag on it. Too cool to replace. It runs fine, but usually needs a "bump" to get the shaker in motion. I was wondering if I could ad a start capacitor to give it that little bit of a bump on it's own. Looks like that is not a good idea. Bummer. But still a helpful thread.

Fix the start issue, like a dirty centrifugal switch.

 

[RonRock]

Thanks guys for the replies. I did not get notice so figured this was of no interest. I'll take the motor apart and clean the start switch. She's an oldie so could use a good cleaning and lube. Thanks for the suggestions.