Hi all - my heating system has developed a bit of a strange fault which has stumped both myself and - although he only had a brief look - my boiler service engineer.
My system is a Glowworm Micron 70FF, gravity fed with F&E and cold water tanks. System is Y Plan with Drayton 7 day programmer, 3 port valve and rotary thermostat controls.
Most of the time the system runs exactly as expected. However, occasionally when the heating is running, it has a tendency to go into a state where the heating stays on permanently.
In this situation, nothing stops it from running except for a system switch-off and on at the mains. Until I power down, the pump runs continuously, boiler cycles and the house overheats. Reducing the thermostat or switching off the HW/CH at the controls has no effect. The 3 port valve is energised to the heating position and stays there regardless of inputs. Only a switch off at the mains gets things working normally again.
I've changed the synchronous motor in the valve with no success (I had a spare and know that a faulty motor is a common problem). After this, I ran a multimeter on the Y plan wiring and all seems in order (I have reasonable electrical experience to fault diagnose). The valves grey/white wires were energised the last time the fault occurred, even when I turned off HW & CH.
This all leads me to the thinking that either the programmer or the boiler's PCB may be faulty - mainly because I can't imagine there's much else to replace! - but wondered if any here have experienced this before I go replacing things for the sake of it.
My system is a Glowworm Micron 70FF, gravity fed with F&E and cold water tanks. System is Y Plan with Drayton 7 day programmer, 3 port valve and rotary thermostat controls.
Most of the time the system runs exactly as expected. However, occasionally when the heating is running, it has a tendency to go into a state where the heating stays on permanently.
In this situation, nothing stops it from running except for a system switch-off and on at the mains. Until I power down, the pump runs continuously, boiler cycles and the house overheats. Reducing the thermostat or switching off the HW/CH at the controls has no effect. The 3 port valve is energised to the heating position and stays there regardless of inputs. Only a switch off at the mains gets things working normally again.
I've changed the synchronous motor in the valve with no success (I had a spare and know that a faulty motor is a common problem). After this, I ran a multimeter on the Y plan wiring and all seems in order (I have reasonable electrical experience to fault diagnose). The valves grey/white wires were energised the last time the fault occurred, even when I turned off HW & CH.
This all leads me to the thinking that either the programmer or the boiler's PCB may be faulty - mainly because I can't imagine there's much else to replace! - but wondered if any here have experienced this before I go replacing things for the sake of it.
