Volts drop - 3 phase delta pump supply

[raithrovers1]

We really need the data off the pump.
As mentioned before, the cable seems to be underated. Johnboy has done the calculation and it came out at 10mm.
As to why the MCB & RCD were destroyed?- could be harmonics if a drive is fitted although I don't see why a drive is required for a pump that does not need the speed changed.
Could be loose connections.
2.5mm cable is rated for about 20A. After this it heats up. If the pump is drawing more than 20A then this will cause the terminals on the MCB and RCD to heat up and could cause failure after a prolonged period of time.

 

[leolec]

With you there have sent a text to my brother to find out what the model is should have that info in the next couple of days will post as soon as

 

[Engineer54]

Out of interest, ...How long has this pump been installed, or been in service??

 

[leolec]

I think it was about 12 months ago

 

[malcolmsanford]

Chr!s quite rightly was refering to regulation 525.4 concerning the possibility that the motor would work without undue affect on start up with a larger % VD, but that is just on the start up, and it also as Chr!s states you need to refer to the makers technical data.

If though once the motor was runing and it was still getting an above accepted volt drop, which would impair the performance of the pump, then the pump would labour and take high amps, as the 2.5mm is such a long run I would be amazed if it was not producing high amps due to volt drop, but that does not explain why if it was labouring the MCB did not activate on overload, or indeed the pumps overload protection be it external or internal.

I can only assume that the volt drop was just keeping the pump running at the MCB tripping tolerance and therfore the protection device was at full or just above maximum demand for that 12 months, and with the conductor heating up on the load enough to take out both RCD/MCB.

I would definately be contacting the installers and getting them involved, it maybe over a warrenty period but with what you have said so far I think you would have a good case for them to come out and rectify this problem FOC.

 

[Knobhead]

To be honest it looks like your brother will be getting the cheque book out and the spade.
You’ll have to brush up on your cable jointing skills. ¼ mile of 10mm 4C is one hell of a cable drum if you haven’t got the gear to handle it. I’d put it in sections and through joint.