New Flat new EM2000 problem

I've just moved next door and taken on another EM2000, this one is generally in better condition but in the last week it's been playing up.

Symptoms where :
No Heating - adjusting the room stat to call for heat did not give any response on the ACB, odd thing is it usually happens only in an evening ?
Switch off an dback on the 45A supply solved the problem

Yesterday we had no hot water either and I found that the store was at 20 degrees due to both the store and heater assembly overtemp trips being open.
I've rest both and so far its behaving, I have found that the PHE return sensor is intermittent could this cause the over heating issue ??
What does T2 do ?

B@man wrote:I've just moved next door and taken on another EM2000, this one is generally in better condition but in the last week it's been playing up.

Symptoms where :
No Heating - adjusting the room stat to call for heat did not give any response on the ACB, odd thing is it usually happens only in an evening ?
Switch off an dback on the 45A supply solved the problem

Yesterday we had no hot water either and I found that the store was at 20 degrees due to both the store and heater assembly overtemp trips being open.
I've rest both and so far its behaving, I have found that the PHE return sensor is intermittent could this cause the over heating issue ??
What does T2 do ?

Hi
T2 and T3 are the hot water sensors, the temperature difference ( i.e. difference in resistance on the sensor) between T2 and T3 is used on the pcb to adjust the speed of the hot water pump ( i.e. the voltage passed to the pump).
But all this has nothing to do with your overheat problem. This sounds more like a fault on your relays. ( most probably one is bypassing at this time, could also be intermittent fault). On those events, the pcb is stopping the relays passing power to the immersion elements and after a pump overrun also the boiler pump stops. As there is still power going to at least one heating element ( i.e. immersion) first the boiler overheat reset trips ( bottom one), and occasionally also the store over heat reset.
I hope this is helping you a bit
kind regards Mario at Mario's Boiler Service at Fareham / Hants

Thanks Mario,

It looks like you are correct the relay for the boiler element is intermittently sticking closed. Last night I got woken up by a kettle boiling / Gurgling noise (the boiler is located opposite my bedroom) and the only way to stop it was to open the main 45A isolator, switching off the off peak made no difference so the ACB was no calling for heat meaning that the boiler pump was not running, so I guess water was boiling inside the heater and then passing to the heatstore via thermosiphon.

Anyway I've reported it to may landlord along with the T2 sensor fault until he gets someone to look at it we are leaving it switched off unless we are at home, a couple of neighbours have had these things catch fire in the last 12 months.