I have had to replace the immersion switch 3 times in the last year as it seems to overheat and eventually melt the relay part of the switch. I know a bad contact can cause this overheating but it has happened 3 times now so I dont think that was the cause (The switch was replaced bu a plumber twice). I'm now gonna replace the actual element to see if that improves it. Anyone come across this and find the solution ? My gut feeling tells me its an electrician I should be consulting rather than a plumber.