Tesla 7" dual safety thermostats failing

[YorkshireMidge]

@AdrianUK Weird!

 

[Johntheo5]

Is this stat from a different manufacturer?

 

[Johntheo5]

Yes - well, the modern equiv of E7 anyway. It's a five terminal smartmeter now (which replaced one of those old radio control Economy 7 switches).
There is second immersion heater and circuit which I referred to as boost which is wired off the nomal supply via a switch in the kitchen. That hardly ever needs using so I haven't seen the same problem on the stat for that.

The cylinder is either the 117L or 140L (can't recall which) bought from these guys https://www.plumbnation.co.uk/economy-7-copper-vented-cylinders-397-0000

Not so big that it would cause problems I wouldn't have thought.

That looks as if it possibly could have a dual element top mounted Immersion, if so, these have one stat switching the common neutral, like shown below, except that this has a separate hi limit stat in series with the control stat. In your set up, the "bath" would be the Economy 7 and the "sink" the boost.

 

[AdrianUK]

That looks as if it possibly could have a dual element top mounted Immersion, if so, these have one stat switching the common neutral, like shown below, except that this has a separate hi limit stat in series with the control stat. In your set up, the "bath" would be the Economy 7 and the "sink" the boost.

Well no. The Eco7 & Full time tariffs CAN'T share a common neutral - since they are fed from different consume units. (I agree that they share a common neutral in the sense that there is only one supply into the building BUT after that is split to the two consumer units, E7 & normal rate, you CAN'T recombine them again).

 

[YorkshireMidge]

That looks as if it possibly could have a dual element top mounted Immersion, if so, these have one stat switching the common neutral, like shown below, except that this has a separate hi limit stat in series with the control stat. In your set up, the "bath" would be the Economy 7 and the "sink" the boost.

Two holes in the tank, two immersion heaters, each wired off their own consumer unit and operating independently of each other - as per @AdrianUK description. Thanks.

 

[Johntheo5]

Maybe worth trying a different manufacturer's stat, I have replaced a few relation's stats which seem to last up to 7 or 8 years. I have a 52 year old Santon dual element (3 wire) with the c/o switch on top of the immersion!! but only use the "sink" element, still working perfectly.