Heating control system

Claim 2

A control system for use in a heating system for controlling the temperature in a space to be heated including a furnace having a plenum chamber and burner apparatus disposed in the furnace, said control system comprising a control device having inlet means adapted to receive fuel from a source, outlet means for supplying fuel to the burner apparatus, main valve means for controlling fuel flow between said inlet means and said outlet means, and safety valve means for controlling fuel flow between said inlet means and said outlet means; recycling control means including a thermostat adapted to be disposed in the space to be heated for thermostatically cycling said main valve means open and closed in accordance with the temperature in the space to be heated, a recycling limit switch adapted to be disposed in the plenum chamber and actuated in response to a recycle limit temperature in the plenum chamber, and a main operator for controlling said main valve means in response to said thermostat and said recycling limit switch to close said main valve means when the space temperature is above a set point for said thermostat or when the plenum chamber is above said recycle limit temperature and to open said main valve means when the space temperature is below the set point of said thermostat if the plenum chamber temperature is below said recycle limit temperature; and non-recycling control means including an abnormal limit switch adapted to be disposed in the plenum chamber and actuated whEn the temperature in the plenum chamber exceeds an abnormal limit temperature greater than said recycle limit temperature, said non-recycling control means closing said safety valve means when said abnormal limit switch is actuated and being inoperative to automatically open said safety valve means whereby the heating system is shut down and cannot be automatically recycled after the temperature in the plenum chamber exceeds said abnormal limit temperature.

Claim 3

The control system as recited in claim 1 wherein said non-recycling control means includes flame sensing means disposed adjacent the burner apparatus and a safety operator for controlling said safety valve means in response to said abnormal limit switch and said flame sensing means to close said safety valve means when either no flame is detected by said flame sensing means or the temperature in the plenum chamber exceeds said abnormal limit temperature.

Claim 4

The control system as recited in claim 2 wherein said control device includes reset means for manually opening said safety valve means and said abnormal limit switch includes contact means movable to a closed state below said abnormal limit temperature and to an open state above said abnormal limit temperature.

Claim 5

The control system as recited in claim 3 wherein said non-recycling control means includes a thermocouple for sensing a flame at the burner apparatus and an electromagnet operator having a coil connected in circuit with said thermocouple and said abnormal limit switch contact means, said electromagnet operator holding said safety valve means open when current from said thermocouple is supplied to said coil but being inoperative to open said safety valve means.

Claim 6

A heating system comprising furnace means for heating air in a plenum chamber and supplying the heated air to a space to be heated including burner apparatus having a main burner and a pilot burner; a control device having inlet means adapted to receive fuel from a source, main oultet means for supplying fuel to said main burner, pilot outlet means for supplying fuel to said pilot burner, main valve means, safety pilot valve means, reset means for manually opening said pilot safety valve means, a main flow passage from said inlet means to said main outlet means through said main valve means and said safety pilot valve means in series, and a pilot flow passage from said inlet means to said pilot outlet means through said safety pilot valve means; main circuit means including a thermostat disposed to sense the temperature in the space to be heated, a recycling limit switch disposed to sense the temperature in said furnace plenum chamber and a main operator controlling said main valve means, said thermostat and said recycling limit switch being connected in circuit with said main operator to open said main valve means when the temperature in said furnace plenum chamber is below a recycling limit temperature and the temperature in the space to be heated is below a set point for said thermostat and to close said main valve means when either the temperature in said furnace plenum chamber exceeds said recycling limit temperature or the temperature in the space to be heated exceeds said thermostat set point; and non-recycling pilot circuit means including flame sensing means for sensing a flame at said pilot burner, an abnormal limit switch disposed to sense the temperature in said furnace plenum chamber and a pilot operator controlling said pilot safety valve means, said abnormal limit switch including a pair of contacts movable to an open state when the temperature in said furnace plenum chamber is above an abnormal limit temperature greater than said recycling limit temperature and to a closed state when the temperature in said furnace plenum chamber is less than said abnormal limit temperature, said flame sensing means and said pair of contacts of said abnormal limit switch being connected in circuit with said pilot operator to hold said safety pilot valve means open When a flame is sensed at said pilot burner and the temperature in said furnace plenum chamber is below said abnormal limit temperature, to close said safety pilot valve means when either a flame is not sensed at said pilot burner or the temperature in said furnace plenum chamber exceeds said abnormal limit temperature, and to prevent said safety pilot valve means from opening after closure in response to the temperature in said furnace plenum chamber exceeding said abnormal limit temperature even if the temperature in said furnace plenum chamber decreases below said abnormal limit temperature whereby said heating system cannot automatically recycle after said abnormal limit temperature has been exceeded in said furnace plenum chamber.

Claim 7

A heating system comprising furnace means for heating air in a plenum chamber and supplying the heated air to a space to be heated including burner apparatus having a main burner and a pilot burner; a control device having inlet means adapted to receive fuel from a source, main oultet means for supplying fuel to said main burner, pilot outlet means for supplying fuel to said pilot burner, main valve means, safety pilot valve means, reset means for manually opening said pilot safety valve means, a main flow passage from said inlet means to said main outlet means through said main valve means and said safety pilot valve means in series, and a pilot flow passage from said inlet means to said pilot outlet means through said safety pilot valve means; main circuit means including a thermostat disposed to sense the temperature in the space to be heated, a recycling limit switch disposed to sense the temperature in said furnace plenum chamber and a main operator controlling said main valve means, said thermostat and said recycling limit switch being connected in circuit with said main operator to open said main valve means when the temperature in said furnace plenum chamber is below a recycling limit temperature and the temperature in the space to be heated is below a set point for said thermostat and to close said main valve means when either the temperature in said furnace plenum chamber exceeds said recycling limit temperature or the temperature in the space to be heated exceeds said thermostat set point; and non-recycling pilot circuit means including flame sensing means for sensing a flame at said pilot burner, an abnormal limit switch disposed to sense the temperature in said furnace plenum chamber and a pilot operator controlling said pilot safety valve means, said abnormal limit switch including a pair of contacts movable to an open state when the temperature in said furnace plenum chamber is above an abnormal limit temperature greater than said recycling limit temperature and to a closed state when the temperature in said furnace plenum chamber is less than said abnormal limit temperature, said flame sensing means and said pair of contacts of said abnormal limit switch being connected in circuit with said pilot operator to hold said safety pilot valve means open When a flame is sensed at said pilot burner and the temperature in said furnace plenum chamber is below said abnormal limit temperature, to close said safety pilot valve means when either a flame is not sensed at said pilot burner or the temperature in said furnace plenum chamber exceeds said abnormal limit temperature, and to prevent said safety pilot valve means from opening after closure in response to the temperature in said furnace plenum chamber exceeding said abnormal limit temperature even if the temperature in said furnace plenum chamber decreases below said abnormal limit temperature whereby said heating system cannot automatically recycle after said abnormal limit temperature has been exceeded in said furnace plenum chamber.

Claim 8

The heating system as recited in claim 5 wherein said flame sensing means includes a thermocouple and said pilot operator includes a magnet having a coil wound therearound and receiving current from said thermocouple.

Claim 9

The heating system as recited in claim 5 wherein said main operator includes a coil opening said main valve means when energized and closing said main valve means when not energized, and said recycling limit switch includes a pair of contacts connected in series with said thermostat and said main operator coil, said contacts being opened when the temperature in said furnace plenum chamber exceeds said recycling limit temperature to deenergize said main operator coil and being closed when the temperature in said furnace plenum chamber is less than said recycling limit temperature to energize said main operator coil if the temperature in the space to be heated is less than said thermostat set point.