Boiler running despite programmer and roomstat not connected to CH valve

[Rogeranerley]

Had a problem with system not working. Replaced 35 year old tempus 7 with Drayton LP25476 which changed nothing despite RF Horstmann calling for spring based CH valve to open. All resulting in boiler laying dead.

Realised the CH valve likely problem. At 78 lacked experience to tackle this myself, I called my regular servicing plumber who changed the solenoid motor. All seemed OK. But last night waken by boiler running. Turned off CH at programmer. Made no difference. Have since checked RF stat receiver connections and no live showing despite boiler continuing to run.

Could it be a duff solenoid that's jamming the valve open thereby trigging the boiler? If not what else might it be, before I call my plumber back. As far as I know there were no wire changes made by him in the junction box.

Many thanks

 

[Rogeranerley]

PS to my call for help above.

The system is two Honeywell sprung valves with CH & DHW separate.

Thanks

 

[oldbutnotdead]

First one- did you tell plumber you thought the motorised valve was US? (Can lead to confirmation bias- plumber may not have done any fault finding)
Second, is the hot water working, have you set timed periods on the controller (the one you reference has control circuits for heating and dhw).
Third, if you were checking for live at the thermostat receiver with a multimeter you have enough knowledge to do some proper faultfinding (with a bit of guidance)

 

[Rogeranerley]

Thanks oldbutnotdead

Yes, I'd concluded that having found the live feed from the junction box to the valve showing no power. However, I recall him carrying out his own tests and reaching the same conclusion. He changed the solenoid. When attempting a restart , the stat receiver was failing to acknowledge the transmitter request. To check whether the valve would function the plumber wired the live feed from the programmer into the same receiver terminal as the white (demand?) terminal which feeds to the brown lead causing the valve to open. He then remade the stat live back to the LN terminal. When switching off and then back on, everything seemed to be running OK.

I've had the programmer set twice daily for HW with the CH on constant, being controlled by 4 different stages. Breakfast, daytime, evening and night time at a lower temp to avoid due point issues.

I've just refitted the programmer on the constant CH. The stat red light appears with current to LN, but no green light (which I assume is the live feeding through to the valve as it was doing following the plumbers visit. When I now programme to off the light on programmer and stat are off with no live feed to stat's LN. However, boiler remains running. All checks being made with standard £1 screw driver tester.

As to system cleanness, this was thoroughly undertaken 24 month ago (3 days with cleaner, followed by 4 flushes).

Might the valve be jammed open inside - it's 35 years old. Would a manual closing confirm such jamming?

Hope this not too much detail, but loath to take chance on an unwarranted
call out charge.

What do you think?
PS. I've just done a final check. Turned whole system off and the on again with programmer on constant. Now have red light on stat....but boiler not relighting??