I have just had installed a Baxi duotec 40 combi boiler and it is controlled with a Honeywell wireless thermostat( DT92E). I have been told that the boiler has a frost free setting and will fire if the temperature of the incoming water is below a certain temperature, 5 degrees Celsius I think. My question is do I have to set the Honeywell thermostat to frost free as well?