Frost Thermostat Causing Heating To Run All Night

Throughout the last couple of winters I've had numerous customers complaining that their central heating has bee running excessively throughout the night even though the central heating is turned off. The usual cause of this  is their boiler being in the garage is protected by a frost thermostat. Frost thermostats are installed to protect vulnerable parts of the heating system from freezing and can be set to come on usually between 3 and 20 degrees. It is likely that if the temperature drops below freezing outside and the garage also drops to this temperature that the frost thermostat will run until the location has warmed up.

The frost thermostat should be wired to override all time and temperature controls. In the case of a three-port motorised valve system the boiler will then supply heat to the valves last position. So if the central heating has been on until late in the evening but goes of at bedtime, and then the temperature outside drops overnight, the central heating will come on.

One solution to this problem is to fit a pipe thermostat such as the Honeywell L641B. This can be wired in conjunction with the frost thermostat. If the temperature in the garage drops below the set temperature of the frost thermostat the boiler will come on until the temperature on the pipe thermostat is satisfied. Therefore, the pipes will be protected but the boiler should not run excessively throughout the night on particularly cold nights as we have been having the last few winters.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.