I can’t seem to edit the original post so I will add a bit more detail here.
The boiler is a valiant combi boiler - only commissioned today for heating although its been working for hot water for 3 months already. The thermostat was installed by an electrician about 1 month ago. Today was the first time that both the boiler and thermostat have been working (kind of working as per the problem). The heating engineer says the boiler is working fine. I can see this ending up in a debate between electrician and heating engineer to who’s problem it is!!! Hence why I am looking for possible solutions myself.
I have re-set both the heat link and thermostat several times. And the boiler was switched on and off too by the mains. The heating remains off until either turning it on via the heat link or turning the heating demand on via the thermostat. Switching it off using the thermostat is not possible.
It's been a while since this thread was last updated so I'll go ahead and lock this thread. If you're still experiencing problems, please feel free to start a new thread and we'll be happy to help.
I'm having a similar problem. Our radiant heat turns on even though the thermometer is off. I did find out that when I turn on then off the heat turns off for about 10 seconds then turns back on.