Is this a defective capacitor?

[dilalio]

Hi all,

I'm usually found in the plumbing and heating or combustion chamber forums.

I've a powerflushing machine (basically a pump) which is having issues.

The motor has a start up capacitor which is showing a blob of what looks like blue tack on the side, but it's rock hard.

Should this be there or is it a bulging capacitor? I can't tell.

And can it cause the motor to overheat? I had to start it by manually spinning the fan and after an hour there was a funny electrical burning smell, lots of vibration and a red hot motor. So had to shut it down.

Pics attached of existing cap with bulge. Data label and a potential replacement cap I found on ebay but is not 'exact' same details on label... Although very similar.

Can a failed cap like this cause motor to overheat when running or is it purely for start up and should not cause motor to overheat if manually started, as I did?

TIA
Dean

 

[just pumps]

Yes that is sign of a blown capacitor. Being only the start capacitor I dont think it has anything to do with the motor getting hot.

 

[RandomGrinch]

Example from elseware, a little more extreme than yours!:

New capacitor time I think!
Although there may be further issues, that led to the cap failure.

 

[AdrianUK]

There are several types of single phase motor which use a capacitor to get a phase shift.

Does your pump motor have a centrifugal switch that cuts out the start winding when the motor gets upto speed?

If not it could be that the aux winding is intended to stay in circuit full time & hence why things are not behaving with the cap being missing - without the aux winding in circuit, the machine will be under-powered for the mechanical work to be done, the main winding will pull more current & the motor will get hot.

Its quite common for 'cheap' motor caps to fail in the way you have seen. I don't recommend that you source a replacement from Ebay!

Some general rules for substitution:

i). A 'motor run' capacitor can be used to replace a 'motor start' capacitor but NEVER the other way around.
ii). A higher voltage rating cap can be used to replace one of a lower rating, but never the other way around.
iii). Don't assume that the maximum voltage that the capacitor is exposed to is the supply voltage - it can be exposed to higher voltages.
iv). A capacitor of a smaller tolerance can be used to replace one with a greater tolerance.