I have installed a new Grant Euroflame condensing central heating boiler.
I have wired it up to a Danfoss heatplan controls pack containing:
1-FP715 Si Programmer,
2-HP22 2 Port Valves,
1-RMT Room Thermostat RMT 230,
1-AT Cylinder Thermostat,
1-WC4B Wiring Box.
I am having a problem in that the boiler will fire up even when the programmer is switched off on both the central heating and domestic hot water buttons. The problem seems to be with the AT cylinder thermostat. When the temperature falls below the ambient setting the boiler will fire up even when it is switched off. I have to turn the thermostat down to near zero to knock the boiler off.
I have followed the wiring diagram attached. I am not an electrician but the wiring diagram seems pretty straightforward to me.
Any suggestions as to what might be causing this problem.