Immersion Heater Thermostat

[AndyPRK]

I have an vertical Immersion heater on a vented cylinder. No boiler.
Wickes immersion. ~10 yrs old

The flat had been empty for a few days over xmas, and was concerned the water was too hot and was surprised the heater would still draw current when the water was hot.

It also sounded a bit like water simmering in a kettle when on, but I guess it would.

The stat was set at 60C.

I decided the stat was faulty as

a) It needed turning down to about 40C for it to switch off (when the water was much hotter)
b) When I put a new stat in set at max, it switched off straight away.

After some time it did start to work at the correct temperature.

Anyway I replaced the thermostat. And now the question at last.....

Do these stats have hystersis ?

As with the new stat, when the water is hot the stat/heater click on and off every minute or so. I would have expected there to be hystersis. Is this normal ?

I am happer as at least it is switching off now and hear the stat working.

 

[Axel]

Yes, they need to have some hysteresis to stop them clicking on and off every minute or so!! I believe, from my research in the internet in the last minute, that the "differential" should be about 10 deg C. If yours is clicking on and off then it is either losing a lot of heat very fast (water running through it?) or the stat is faulty. BTW, it should have a 96 deg safety permanent cutout, to stop it boiling plastic water tanks, as per some recent legislation.