In my grandsons room which has a radiator,and is always very hot room even with out heating on,there is a problem,the radiator which is set at the individual thermostate setting on frost as we do not want it to come on at all.still comes on very hot and is becoming unbareable for him at night as too hot to sleep.Can you tell me why this radiator comes on,how can we turn it off completely.Thank you please help