Underfloor heating thermostat triggers heating even when system is switched off

[Scotty Gordon]

Hi I have a Mitsubishi ecodan ASHP. I have the heating switched off and hot water on timed. When I increase the thermostat on the underfloor heating the system fires up and heats the room. I am surprised about this as I have the heating switched off. Any thoughts would be welcome.

[JohnMo]

Are you sure you have the heating fully switched off? Your making the thermostat call for heat, so its asking the system to switch on, depending how its wired in it may just over-ride. If you don't want it to come on, why make it call for heat, just wind to down to 16 so it doesn't call for heat