Patent ID: 6851948
Filing Date: 2005-02-08
Classification: F23D,F23N,F24C

Abstract:
1. In a gas furnace that is responsive to a thermostat, and which contains a power supply, a gas valve, and an autoresettable thermal switch having a thermal switch probe that is responsive to an over-pressure condition, and a microprocessor responsive to said thermostat and said thermal switch for controlling said power supply and said gas valve, and wherein said gas furnace includes a furnace vent system, a process for detecting a blockage in said furnace vent system, comprising the steps of: mounting said autoresettable thermal switch adjacent to an entrance to said furnace vent system so that said thermal switch opens due to a flue pressure exceeding a certain level and causing hot flue gasses to pass over said thermal switch probe; electrically connecting said thermal switch in series between said power supply and said thermostat; programming said microprocessor to carry out the following steps upon said thermostat calling for heat;