Weirdly high energy Bills- faulty meter?

Robin9

@Dommyb   With respect this is not a DIY job for you.  Call a plumber 

QrizB

Dommyb said:

Resumably this one?

Yes, that one!

What does the label on the side of it say? I think it's telling you how to reset the thermal cut-out?

The heater looks to be a TIH 476, one of these:

https://www.unventedcomponentseurope.com/tesla-1-3-4-incoloy-immersion-heater-14-tih-476.html/

This should be the instructions:
https://www.teslauk.com/pdf/downloads/v18 September 2021.pdf

Which includes this paragraph:

The Dual Safety Thermostat fitted to this appliance
The temperature control on this unit is variable between the temperatures shown on cap of the thermostat.
The new EN standard states that secondary protection should be incorporated within the rod thermostat. The Tesla secondary protection acts by means of a snap disc (a bi-metallic disc) located beneath the head of the thermostat which is normally ‘at rest’ in the convex position.
In the unlikely event that the system overheats, the snap disc will sense abnormal temperatures and will activate itself pushing the small square reset button flush with the top of the thermostat face, shutting off the electrical circuit. Reset can only be made by depressing the reset button again.
Nuisance Trip-outs: There are many causes of nuisance trip-outs, but they can often be cured simply by reducing the temperature setting on the thermostat. If this does not produce satisfactory results, please see the FAQs on our website or contact our technical helpline above.

TheHareBear

Random thread reader here, and I don't have an immersion heater so this isn't my area of expertise either...

Looking at the photo of the immersion heater switches does the wire coming from the top plug go to the top heater in the tank? It almost looks like the top plug wire goes to the bottom heater, and if that is the case then possibly the wrong switch has been turned off unless I'm misunderstanding things.

QrizB

TheHareBear said:

Random thread reader here, and I don't have an immersion heater so this isn't my area of expertise either...

Looking at the photo of the immersion heater switches does the wire coming from the top plug go to the top heater in the tank? It almost looks like the top plug wire goes to the bottom heater, and if that is the case then possibly the wrong switch has been turned off unless I'm misunderstanding things.

It definitely wants checking. I can't tell from the photo.

The OP has (I think) confirmed that the bottom switch is the one controlled by the E7 circuit, and the top one is permanently live.

Dommyb

Robin9 said:

@Dommyb   With respect this is not a DIY job for you.  Call a plumber 

I completely agree, i can definitely see myself breaking something and definitely do not want to have to cover costs that come with that🤣

coffeehound

Something seen on here a couple of times before with tanks in rented properties is the connections to the immersion heaters being transposed in order to make the top IH the one powered by E7.  

I would guess this happens when the lower IH fails and the tenant doesn't want the hassle of a maintenance visit.  So they just live with the reduced hot water capacity until moving out.

In one case they had taken the thermostat out of the circuit so that the IH was always on during E7 - a dangerous situation

EssexHebridean

The thermostat cover should literally be a case of removing a single screw to lift off that plastic cover - as others have said, you need to kill the power to the immersion (both halves) before doing it.

 coffeehound said:

Something seen on here a couple of times before with tanks in rented properties is the connections to the immersion heaters being transposed in order to make the top IH the one powered by E7.  

I would guess this happens when the lower IH fails and the tenant doesn't want the hassle of a maintenance visit.  So they just live with the reduced hot water capacity until moving out.

In one case they had taken the thermostat out of the circuit so that the IH was always on during E7 - a dangerous situation

We discovered the hard way that the thermostat in the original tank here when we moved in was faulty. Got woken up in the middle of the night with a flat full of steam - the immersion had reached such a temperature that it had vented back into the header tank and that in turn was dangerously hot. We were incredibly lucky that the cat we had at the time was freaked out by it and woke us up - the people who’d sold us the flat had to have known but just chose not to tell us, completely irresponsible. And THIS is why I said to the OP if resetting that thermal link, to do it first thing in the morning while the E7 circuit is still active, not at night then just leave it to run! 

coffeehound

EssexHebridean said:

We discovered the hard way that the thermostat in the original tank here when we moved in was faulty. Got woken up in the middle of the night with a flat full of steam - the immersion had reached such a temperature that it had vented back into the header tank and that in turn was dangerously hot. We were incredibly lucky that the cat we had at the time was freaked out by it and woke us up 

That is frightening @EssexHebridean.  Apparently two people in Britain have been killed by that type of fault, which is why secondary overtemperature trips have been mandated since the mid noughties.  Well done, Felix.