Mick

I don’t profess to be a plumber or Electrician, not my forte, however, I’ve spent many a times watching my dad fix his boiler, hot water systems, over many years when I used to live there.

By the sounds of it, you have a Conventional Boiler system, e.g not a Combi boiler that heats water instantly on hot tap flow.

The switch you mention is to power on the immersion heater. Immersion heater should only be used, as a fast source of heating water in the tank. A number of potential issues can occur, bad heating element, bad wiring, blocked or dead pump, which would affect water pressure. You could try turning thermostat down, see if that stops the tripping.

I’ve witnessed my dad over the years, strip whole water tank system down upstairs, replace pump, new heating element. Self repair is inexpensive if you know what you’re doing, parts can be obtained from screw fix, B&Q etc. Bear in the mind that it is illegal to tinker with the Boiler systems, by anyone not certified as Gas Safe Registered, what used to be classed as CORGI. But this issue you’re having, is more electrical than gas.

There is lots of arguments about either having a Conventional Boiler or Combi system, I have been used to both, the pros to conventional is there is a back up to having heated water, if boiler packs in. Back in the day, when I lived with my parents, their conventional boiler was about 40 years old and it had a few minor issues like air pockets forming, pump having to be replaced a few times.

I moved in to a new property in 2018 and the Combi boiler has broke down twice. First time it was an internal valve, £150 to fix, then two months ago, it was the PCB, the brains of the boiler, that needed to be replaced, that was another £250, though this is relatively cheap, I’ve seen £300 and upwatds, for that kind of job.