COTHERM thermostat on a megaflo tank

[bexy]

My sister has a Heatrae Sadia megaflo hot water tank with two immersion heaters for her hot water. Heating is separate, by storage heaters (no gas supply to flats). She has had some problems, and an electrician has been called a couple of times. Last time, he told her how to reset the thermostat if it tripped. However, there are a couple of things I'd like advice on, please.

From my reading so far, I think that the lower immersion heater is the overnight timed one, and the upper is the boost one - is this always the case?

The thermostats are "COTHERM type: TSE T115". There is a little red plastic switch labelled SAFETY which the electrician told her to "pop out". However, using a small screwdriver to press this switch does not release it out again. Should it, in fact, be pushed in?

I ask both questions because I took the cover off the lower stat and the switch is level with the blue surround, whereas the top one (which the electrician adjusted last time) is depressed. However, the boost currently works and the main water heating does not.

Finally, if this happens again, is it most likely to be a dodgy stat, or will the whole element need replacing?

Sorry for the long post, thanks in advance for any advice.

 

[wetshoes]

It's likely that the stat's failing, but just resetting the safety cut out wont fix the problem.
If the electrician can't work out whats causing the safety stat to trip then your sister might be wise to call someone who is familiar with unvented cylinders.


regards

 

[Hugh Jaleak]

Lower immersion is always connected to the Economy 7 circuits, it allows the whole contents of the tank to be heated overnight at cheap rate electricity. Upper (boost) is there for emergency use, should you run short of hot water it can be switched on at anytime to heat top end of tank to provide some hot water until the next E7 period. The boost does use electricity at normal tariff, so works out more expensive.

Sounds like the safety reset has popped out, I would change the stat first and see what happens. Ideally the bottom immersion needs to be working, constantly using the boost will give you a big eleccy bill! You can buy the immersions and stats seperately, should it need a new immersion you already have a stat.

 

[Boilerman2]

Anybody working on an unvented Cylinder be they a plumber, heating engineer or electrician, must hold an unvented hot water G3 certificate, otherwise they are working illegally