My central heating and hot water is governed by a Danfoss FP715 Si. Using this I can set the time each day when the central heating and the hot water come on and off. When the central heating is on it is further governed by a Honeywell DT92E wireless room thermostat in the living room. This was working fine until a few months ago. Now the central heating only listens to the room thermostat. It does not matter what the Danfoss programmer is set to, if the temperature in the living room falls bellow the value set on the thermostat the heating clicks on, even at 3 in the morning.

What's gone wrong? How do I diagnose the problem? How can I fix it so that the heating only comes on when the Danfoss says it can?


sounds like the room stat is a new addition? If so may have been functioned to switch on boiler and pump at same time ? If boiler is newish then will only heat water when tap is used. therefor room temp controlled by room stat and turn it down at night or programme when to come on?

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.