PulsaCoil III corroded rod thermostat

Hi
A few weeks ago my Pulsacoil III started "running out" of hot water very quickly (within a couple of minutes). Switching on the boost switch resolved the problem, so, having read some posts on this forum I thought the issue might be with the lower rod thermostat. When I pulled it out it was extremely corroded (compared to the upper rod which was perfectly shiny copper). To test if it was the thermostat, I replaced the corroded (lower) rod with the clean (upper) one and turned off the boost electric supply and the unit worked perfectly. However, after buying a new rod thermostat I went to put it all back together and found that the thermostat that was clean a few day ago is now corroded. I tested the lower immersion element and it measures 18 ohms so it doesn't seem faulty and there is no evidence of a leak on the outside of the unit but somehow it must be leaking to make the thermostat wet.

Does anyone know if this means I need to replace the immersion heater element? If so, do I need to drain the whole thermal store first?

Thanks

Hi sgw,

Yes the heater element needs replacing as the copper tube the thermostat fits into is leaking. It's a common fault. And yes you have to drain the whole store to do it, then re-fill it afterwards.

Good luck with it!

Cheers, Mike

I would agree with Mike, replace it before it becomes worse and starts touching the electrical conductors.