Biasi 24s

[q0ij0p]

Biasi 24s is overheating on central heating and cutting out after 85c as expected.
Temp thermistors showing resistance around 11000 when cold
Initially it was sometimes blowing out of the expansion pipe
However not recently, but still needing a top up almost every time
cannot find any leak or signs of whatsoever and its had a lot of top ups most walls are exposed plaster so it should show.
Flummoxed... I've tried lowering the rad dial and had no response still heading up to 85+ even on summertime setting...
Could this be the PCB ignoring what the thermistors are telling it.... or something else
All rads throughout are getting very hot and no signs of obvious blockage, no air in system.
Ideas please
Ah, just found now (seems recent development) that the timer is now not turning it off neither...
1 So timer not turning off
2 Rad dial setting not stopping it heading north of 85c
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[Agile]

Sounds like it is responding to an apparent demand for hot water.

If so the hot water temperature knob is likely to control the temperature rather than the CH knob.

Tony

 

[q0ij0p]

Sounds like it is responding to an apparent demand for hot water.

If so the hot water temperature knob is likely to control the temperature rather than the CH knob.

Tony

Thanks Tony, I considered this and once the boiler heads for 85 even if I turn the timer off, turn the timer dial to an off portion, turn the rads to lowest and taps, and even if I turn it to 'summer' it still keeps running and heading for a blow.. The only thing that stops it is turning it off on the winter summer dial to 0 or as you can guess, isolating the switched fused spur.

 

[Agile]

I dont think that you have understood what I have suggested to you!

Nothing you have said above indicates it!

Tony