Pulsacoil 2000 Blowing Chip UF2

Hi All! I really need your help and advise.
The fuse on my PCB recently blew. There was no evidence of anything untoward so I replaced the fuse. It blew again after 10 minutes, so decided to call out an engineer. When the engineer arrived, we replaced the fuse and all was well. He stayed for 45 minutes and all was well. The pump was turning over well.
Within about 30 minutes of him going, I could smell burning and saw that one of the legs on the chip on the top left hand corner of the PCB was glowing red and smoking. It is marked as UF2.
I naturally turned everything off. There is continuity through both heater elements and all the connections seem fine. I replaced the whole PCB and turned on. After 10 minutes, another fuse blew.
We disconnected the pump and ran it on it's own, via a safety block. It span freely and all was well until it blew the fuse in the safety block. So I have now bought a new pump, by Grundfos, the 15/50 (as it states in the spares catalogue). This worked well for about 20 minutes, then the chip on the PCB started to heat up and smoke, so again we switched everything off.
We then found out about the water tank on the top, which was empty, so I filled it with water and started again. Again, everthing worked for about 10-20 minutes, then the chip gets very hot and starts to smoke. The red light flashes in the sequence to indicate the board is working.
Any ideas what is going on? HELP!
Thanks, David B

Check the sensors and the connections to the Pump PCB.
The pump will take out the PCB as a rule.
Did you get the right pump?
Mike
MGC/H2O
Norfolk

Thanks Mike. THe sensors are probably the only things left, so yes, I'll give them a check. The pump should be OK. It was to the spec in the instructions. I'm going to be away for a week (so at least I can have a shower in a hotel!), but I'll let you know how I get on when I'm back. Many thanks.

What colour pump have you?
Mike
MGC/H2O
Norfolk

Hi Mike. It is red. The old one was black, but I was told it was no longer made. What do you think?

Wrong pump.
See my post.
Warning 15/50 pumps
Mike
MGC/H2O
Norfolk

Thanks Mike. I'll call them now and try to order another one. I'll let you know how it goes.

15-50X18 modulating Grundfos pump. Going back to the fuse blowing, this indicates a faulty pump but I have come across a job where the PCB just burns due to the printed circuit board becoming faulty with time.