Question about immersion heater

[lenny]

I would be grateful if anybody can help me. I have an unvented domestic hot water cylinder sourced by solar and immersion heater as back up. What I don't understand is the immersion heater is wired to another thermostat. Is this necessary when the immersion heater has its own stat or is could the other stat been installed as just a fail safe 😕😕😕

 

[Puddle]

It will be the over heat therostat, which is a very important part of the safe operation of the immersion heater,protecting equiptment should normal thermostat fail,it should have a manual reset

 

[lenny]

Thanks for that.....