Central Heating will not switch off

[dugit]

My central heating will not switch off although the heating thermostat and programmer are switched to off ie pump/heating carries on,just started today. If I then switch off the mains and switch on again then the pump will finally stop. When I start the heating again for a short while and then turn thermostat down and programmer heating and water to off the same thing happens again.
I have Glow Worm 80FF / Danfoss HSA3/ Danfoss cp715.
Any suggestions please.

 

[Slugbabydotcom]

It might be running on a frost stat

You say glow worm 80 ff ..... Is there a model name ie. ultimate, micron, express etc

 

[dugit]

Yes Gloworm Ultimate 80ff

 

[dugit]

I have never bothered about the frost Stat which I find is situated on outside garage wall and with a Honeywell l641B on boiler pumped return pipe. Is problem caused by colder weather?