the engineer did not know what the problem was.that was why he fitted the kit which is a honeywell.the boiler is an myson apollo.we had a new pump about two years ago so dont think that would be the problem.
we have had problems with the 3 amp fuse tripping but only when the heating is on it doesn't do it when the hot water is on.we had a plumber/electrician come and he replaced the valve,thermostat,hot water and heating controls and the box with all the wiring in . basically it was a kit which...