Boiler turns on even when controller is off (Baxi Solo 3 60)

[Fleetwoood]

Hi,

I have a Baxi 3 60 PF with a Lifestyle LP522 controller installed just before I bought the house (around 2001), it has generally worked well.
However, the last few months I have occasionally woken up in the night to here the pump going and the boiler running full blast. When I go downstairs to check, the controller is off for both Water and CH (check the programme and everything is on/off at the right time).

Last night I had to turn the controller/boiled off at the mains switch to stop it. The strange thing is that it does not happen all the time (it is well behaved right this second for instance and everything is off as it should be).

What has changed?
Well the only possible thing I can recall is that my son has a penchant for switches and switched on the immersion heater the other month (wondered why the water was so scolding hot and replaced the thermostat before I caught a glimpse of the immersion switch!).
So is there anything he could have fiddled with to cause the tank to call for heat irrespective of the settings on the controller?
or is it just a faulty PCB on the BAXI?

Just remembered, I drained the system and used restorer, flushed then inhibitor about a year ago. Can't think this will affect anything tho?

Cheers

Alistair

 

[nickso]

pcb's on these have a habit of leaving the pump live on for extended periods or permanently. probably one of the valves stuck on if its firing though.

check the valves first, assuming you have 2 valves, find the wiring centre and remove and individually check the orange wires for 240 volts when its playing up, if you have one valve there is only one orange. pcb can be checked by removing the outer cover and checking for 240 volts at the pump live. there is a wiring diagram on the case to help you iirc.

 

[Lower]

i had the same problem. Replaced the circuit board and its fine again.

 

[nickso]

i had the same problem. Replaced the circuit board and its fine again.

check the valves first

 

[Agile]

Presumably its fitted within the house proper?

Not in the garage or loft with a frost stat?

If not then most likely the PCB as suggested. Although I have yet to encounter a PCB which brings on the heat. Plenty that leave the pump running though.

Tony

 

[nickso]

Presumably its fitted within the house proper?

Not in the garage or loft with a frost stat?

If not then most likely the PCB as suggested. Although I have yet to encounter a PCB which brings on the heat. Plenty that leave the pump running though.

Tony

check the valves first