Cooeyswell

@TerryE Many thanks for the detailed response(s). My water here is extremely soft, with no furring in the kettle after 5 years of use. My assumption is that whatever is causing the thermal hat to trigger it is unlikely to be due to furring. Unfortunately I have intimate knowledge of the Sunamp PV internals. Over the last two years I have replaced :- - The thermal cutout (2021) - The control board (2021) - The immersion heater (2023) Like you this is after approximately 6 years use. The thermo trip fired again last night so I now have a completely cold unit after this mornings showers. @Nickfromwales mentioned the Y-Strainer which I have not yet looked at. That's probably my next thing to try.

@TerryE Have you any further insights as to the cause of the heater thermo hat tripping ? I am getting this fault fairly frequently at the moment. I suspect there may be an issue with the pump - it seems a bit noisy but still operational. FWIW - I recommend mounting a mains neon/LED across the immersion feed after the trip, It at least makes the failure visible without taking the unit apart.

Many thanks for this post. A fan in my unit is getting noisy after 7+ years, this looks like the solution