help with submersible pump

[adrian polley]

hi all. hoping to get a bit of advice/help.
im a tradie trying to fix a submersible site pump that stopped working last week. ( i usually fix about 60% of my own tools if its the simple problems)
it was pumping quite clean water. moved it from one spot to another to pump out, then smoke suddenly came from the top of it and the main switch at the house meter box tripped.(which suggests a short)
so i packed it up and now its weekend i decided to see if i can see whats up.
so ive pulled it apart and inside looked good as new. there is no smoke or overheat smell at all. the leads all test out so cant see any obvious place for a short or the source of the smoke.
and being a completely sealed unit, for smoke to be visible on the outside there must have been a lot more inside it. but there is no sign of it.

one part that is beyond my limited knowledge is the motor start capacitor.
generally when a capacitor fails it will swell but this one hasnt. like everything else inside it looks new.
i dont know how to test/investigate problems of a start capacitor and dont even know how they work. ive tried watching a few you tube vids but the ones i can find are very bad at explaining things.


any ideas advice would be appreciated.

 

[Martaine2005]

The start capacitor assists the motor during initial start-up!. Some have a bleed resistor to discharge the capacitor when the unit is powered down. They don’t always show signs of failure. However, they do normally fail open. Again, not all the time. You could remove the capacitor and try the pump again, listening for motor hum. If it hums and wont start, then replace with a new capacitor. If it trips the breaker straight away, the motor is more than likely shorted. This sealed unit (potted) cannot be repaired. (Can be but not worth it).

Martin

 

[Martaine2005]

Forgot to mention, might be worth checking the flex cable for continuity or shorts. I have seen people pull their pumps around ponds or flooded basements using the flex. Don’t ask me how I know !.
Doesn’t explain the smoke though. Should have just tripped straight away.

Martin

 

[Bluejets]

Bit confusing how one can see smoke coming out of a submerged pump.
Guessing the top was above water in which case it might just be the lead.
They cop one hell of a hammering where the flex enters the top of the gland.
Can't see a main switch tripping unless it is a circuit breaker and earth leakage into the bargain given it's a work site.