Danfoss programmer

[MickyP10]

With stunning timing, my heating system's started to play up.

Oil fired boiler (Firebird 90S), keeps running when the programmer has switched off. This had started intermittently. Nothing's changed, so I figured the Danfoss programmer FP715 wasn't shutting off the power to the boiler and pump. Stuck a new one on (Danfoss FP715 Si) and it's exactly the same. Only way I can turn the boiler/pump off is with the isolating switch on the wall, or by turning the boiler thermostat down (but the pump still runs).

Clearly it's getting a feed from somewhere, but doesn't it all go through the programmer's electronics? I have the three wires on each Neutral and live (which I guess are: pump, boiler and isolating switch) and one each on terms 3 and 4 (hot water on and heating on).

Didn't alter wiring on wallplate because a) it had worked before and b) it's the same one as supplied with the new programmer.

Any ideas?

 

[Lectrician]

Is their a frost stat anywhere?

Likely cause is a zone valves either sticking open, or the microswitch within the valve sticking open. This would keep the pump and boiler running.

 

[MickyP10]

Re:
Likely cause is a zone valves either sticking open, or the microswitch within the valve sticking open. This would keep the pump and boiler running.

No frost stat. Are the zone valves the motorised valves? I have two two-port Danfoss HPA2s. I can hear them working (although the sticky out end doesn't move. Think that's a manual override for refilling system). Tried disconnecting them from junction box (only one wire, mind. Getting nervous!) and the pump kept running. Maybe I wasn't brave enough. Should I disconnect the whole thing and any tips on finding which one's playing up?