Even though a few weeks back I found the burnt out electronics board in the failed water pump, something just did not seem right and it has been troubling me ever since. Why did it randomly cause a 32A and even a 63A circuit breaker to occasionally trip and not the RCD. A couple of you said a similar thing. Other previous failed water pumps did not trip out anything. I was just happy that the thing was running ok again but I don't like it if I cannot explain what happened.
But now I have found the REAL problem with the MCB tripping, the failed water pump was probably a symptom of the real problem.
The heat pump tripped the 32A MCB again this morning with the same water pump failure. Hmmmmmm, well I swapped the pump out again and the new pump was all over the place, but generally LED flashing, pump restarting again, LED flashing again. Depending on the interval of flashing tells you what's wrong but it was sort of random flashing.
I gave the mains connector to it a waggle and heard a fizzing sound. OK, sounds like the connectors loose, so back in the house to trip the MCB myself but found the whole house off as the upstream 63A breaker had tripped as well as the 32A breaker.
Took the connector apart and found this,
Its about the worst designed plug I have ever seen in my life, the wires are held in place with a very weak spring. The wires actually go in the other side to the photo and have to be bent 90 degrees to get them into the holes, but a lot of the time the spring does not hold them and they pop out. After much faffing and a fair bit of swearing, managed to get them in and funny enough the water pump now works. Hopefully the one I removed this morning probably works too.
Checked the other 3 connectors and they are still OK, so now I am happy in my own head that everything that happened is now fully explained, especially why the RCD did not go as it was just the live and neutral in the connector shorting out. And also explains why I checked the water pumps after the first trip out and I was sure all 4 water pumps were working. The intermittent supply to the water pump probably caused it to fully fail a week later.