E7 Hot Water Tank - over heating

[tudor85uk]

Hi,
We have an EU setup in the house. Our hot water tank has the two thermostats, one for off peak and one for peak. Has bee. Working fine untill a few days ago. Woke up to see the smart meter registering 3.5kw in use where normal is none in the morning just before EU stopped. Went to have a shower and the water was boiling hot from hot and cold taps. Investigated the cold water tank in the lost and this felt hot to the touch also. So turned off the e7 switch and waited a few days for it to cool. After some further tests it appears the the E7 switch is heating tank as per normal but not cutting off and just continuously heats untill the E7 stops in the morning. Has something stopped working in the thermostat to stop heating when hits a certain temperature?

 

[Murdoch]

That could be dangerous and needs investigating asap.

Sounds like the thermostat has failed and also the thermal override too

 

[tudor85uk]

That could be dangerous and needs investigating asap.

Sounds like the thermostat has failed and also the thermal override too

Thank you for the reply, what would be the best course of action in this case - an electrician to look at thermostat or plumber to replace with new?

Thanks

 

[Richard-the-Ninth]

Which ever one can get there first and not charge the earth.

 

[ProDave]

Yes definitely leave it turned off until fixed. Your thermostat is probably the old sort that is just a single thermostat and does not have the second over heat cut off (which does not automatically reset) Any new thermostat fitted should be the new type with the secondary cut out, and in a few cases that may mean replacing the whole immersion heater.

It was such a fault that led to the mandatory safety cut out. In that case the failed thermostat caused the water to boil in the hot tank, then overflow into the plastic header tank, and the scalding hot water ruptured the tank dumping scalding hot water through the ceiling onto a childs bed killing him.

That is why this is very serious and must remain turned off until properly fixed.