I have a Mitsui 1.1kW downhole pump, it hangs around 52meters down, working great for around 3 years.

But now it trips the RCBO in the distribution board!

I got the installers in to service the pump, and they ran it in a water tank for 30mins, no problems. when it was put back into the borehole it was still tripping the RCBO, they of course blamed the RCBO / Control panel/ anything but the pump!

 

It seems the water level in the borehole is much higher than past years (tide mark on the pipes) and the electrical joint was under water, this was remade, no difference, still the same. I have now lifted the pump up up to 44 meters, so the cable joint is out of the borehole and made the connection in a junction box but it is still tripping.

Is it possible that the static head of water is too much for the electrical sealing system on the motor?

ie the pump is now totally immersed in at least 30meter of water?

Does anyone know the 'hydrostatic' rating of these pumps (I think that is the right term)

What does a megger test show...?

Is the pump tripping on earth leakage or on over current?

 

Has an inplace load check been done?

 

Apart from that, why immerse 30 metres to begin with, even though any seal should withstand what could be regarded as a reasonable depth.

23 hours ago, bignbad said:

they ran it in a water tank for 30mins, no problems. when it was put back into the borehole it was still tripping the RCBO,

Was the water tank grounded? 

I would guess probably not.

If not then there would be no leakage to earth but the bore hole is most certainly grounded so any leakage would trip the RCBO.

I don't suppose any of the installers checked to see if the water in the test tank was live 

As already said. The proper test is an insulation test with a megger.