Electric motor help please?

What causes a capacitor to do this?

Can duration of running be detrimental to a capacitor, or is it just cheaply made?

this motor needs to run eight hours a day, and as I can be away for days at a time, I am not happy this might happen again - is there a bomb-proof marque that I can fit instead of cheap replacement does anyone know?

What causes it? Capacitors degrade with age, and manufacturers often fit ‘that’ll do’ components rather than the best components in order to save money/meet a price point.

Rubycon are generally reckoned to be very good, and they’re available from RS Components.

If it were me, I’d look for a replacement of the same capacity but perhaps go for a higher voltage rating. You should be able to read the current device’s rating assuming that it hasn’t been obliterated!


Electrolytic caps just degrade, especially cheaper versions.

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So much for buying what is meant to be reputable products for the job, if they just fit junk that degrades.!

Here is what printing on the capacitor exists. What do you recommend for ordering a new, decent one?

See if you can find a 20μF capacitor rated at 500V…

It looks as if pool pump capacitors have their own category on Amazon. Perhaps @Corona has some advice?


Thanks again. And you say that Rubycon is the way to go? I will ask RS. In the meantime, I will have to buy what I can from Rexel to keep the thing going.

You know what my next question will be… what does a capacitor actually do?

No not really, I endorse your recommendation for quality make though.

Stores an electrical charge.

Whatever you do, don’t replace the cap with a direct equivalent. That is a P0(S0) cap, with absolutely no inbuilt protection from short circuit or overheating. Find an equivalent P2 cap, which will safely fail and won’t melt or burst or set on fire.



:grinning: Thanks - but I was hoping for a couple of lines on its function! But ok now, I found a very good tutorial on Youtube…

Very co-incidental that you posted this! I went to Rexel who then pointed me to a nondescript concrete building and told me to ask in there. Well, inside it was a place that specialised in re-conditioning motors of every size. I would say an aladins cave to someone who knew electric motors!

Anyway, a huge chap took me in hand and chastised any and all modern motor manufacturers who make for pretty looks and size, and said I was lucky the whole thing did not properly explode and set fire to the box it was in along with all the wiring. Still muttering and swearing obscenities at the Haywards of this world, he delved into a parts bin and pulled out a huge capacitor and told me to mount it externally. And then come back and do the same for every electric motor that I have in the place!

All fitted now and purring away. I just have to make a bracket to hold the thing off the ground.

So thanks for confirming all this! Obviously you fit into the world of my huge, and now, friend :rofl:


I’m a man of few words, not always in the right order :rofl:

I personally would go for Mundorf which is a premium German made capacitor. They are about €40 rather than €15 for a Kemet P2 one (which are also good). The time clock on my pool filtration pump died about 2 years ago, so mine runs 24/24. I noticed how much cleaner my pool kept after this happened so have not replaced the time clock. The pump is in my cellar with 70cm thick concrete walls so don’t hear it up on ground floor unless you are right outside the cellar door. Mine is a big pool (100 M³) so takes a lot of keeping clean and at my age of 78 and very arthritic, it needs to be mostly mechanised cleaning.

Been saying this for years, its because of the dilution principle of the filtration 4 turnoves is filtration of about 98% of the water, 5 turnovers 99%. Its the cost of running 24/7 that stops most from doing so. That issue has been resolved and I run mine on 95% less electricity than a std setup. Add to that Dryden aqua’s AFM ng filter media and management of the water gets so much easier. Thank you for the helpful post on which capacitor you recommend.

I run ground glass filter medium which not only lasts almost indefinitely but filters a lot better than sand. I have a new extra bag, which I must get round to adding as the medium is a bit low in the chamber.


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Excellent, you are doing almost all you can to make life easier, well done!

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