Which size thermostat for my immersion heater Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[splinternet]

Wasn't sure whether this was a question I should put in the Electrical forum (there doesn't seem to be one dedicated to hot water supply). In the course of renewing the thermostat in the bottom immersion heater of my Economy 7 tank, I've come to know about two sizes of thermostat, 7" and 11". (mine is the shorter one). What are the pros and cons of switching to the 11" size?

[stoneyboy]

Hi splinternet,
If you can fit the 11" one it may place the thermocouple in the main heating zone resulting in intermittent switching.
Regards S

[splinternet]

OK thanks

[ericmark]

The length of the immersion is only important when fitted on the top of the tank, years ago we would fit duel length immersion heaters long one for bath and short for hand washing, the Irish use an immersion outside the main tank, the Willis system, and that uses time to work out how much water is heated.

But with off peak systems the bottom thermostat runs when on cheap rate, and the higher on set to a lower temperature only when boost button is pressed.