Gas pressure control for warm air furnaces

Abstract

Systems, methods, and controllers for controlling gas-fired appliances such as warm air furnaces are disclosed. An illustrative furnace system can include a burner unit in communication with a combustion air flow conduit and heat exchanger, a variable speed inducer fan or blower adapted to provide a flow of combustion air to the burner unit, a furnace controller and motor speed control unit adapted to regulate the speed of the inducer fan or blower, and a pneumatically modulated gas valve adapted to variably output gas pressure to the burner unit based at least in part on the combustion air flow.

1 . A furnace system, comprising:
 a burner unit in communication with a combustion air flow conduit and a heat exchanger;   a variable speed inducer fan or blower adapted to provide combustion air flow to the burner unit;   a furnace controller and a motor speed control unit adapted to regulate the speed of the fan or blower; and   a pneumatically modulated gas valve adapted to variably output gas pressure to the burner unit based at least in part on the combustion air flow.   
   
   
       2 . The system of  claim 1 , wherein the burner unit includes a gas manifold and a burner box. 
   
   
       3 . The system of  claim 1 , wherein the furnace controller is in communication with one or more thermostat units. 
   
   
       4 . The system of  claim 1 , wherein the motor speed control unit is an integral part of the furnace controller. 
   
   
       5 . The system of  claim 1 , wherein the motor speed control unit is a separate component from the furnace controller. 
   
   
       6 . The system of  claim 1 , wherein the gas valve is pneumatically driven via one or more pressure signals received at one or more locations within the combustion air flow conduit. 
   
   
       7 . The system of  claim 6 , wherein said one or more pressure signals includes:
 a first pneumatic signal received from a first conduit in fluid communication with the input side of the heat exchanger; and   a second pneumatic signal received from a second conduit in fluid communication with the output side of the heat exchanger.   
   
   
       8 . The system of  claim 7 , further comprising a pneumatic amplifier coupled to the gas valve, the pneumatic amplifier adapted to amplify a differential pressure control signal fed to the gas valve based at least in part on said first and second pneumatic signals. 
   
   
       9 . The system of  claim 1 , further comprising a sensor or switch for sensing the rotational speed of the inducer fan or blower. 
   
   
       10 . The system of  claim 1 , further comprising a circuit for measuring the voltage and/or current within the inducer fan or blower. 
   
   
       11 . The system of  claim 1 , wherein the furnace system comprises a warm air furnace system. 
   
   
       12 . A controller for regulating a gas-fired appliance, the gas-fired appliance including a burner unit, a heat exchanger, a gas valve, and a multi or variable speed fan or blower adapted to produce a combustion air flow to the burner unit, the controller comprising:
 a processor adapted to compute the temperature of the combustion air flow at the burner unit; and   a motor speed control unit adapted to regulate the speed of the fan or blower based at least in part on the computed temperature of the combustion air flow.   
   
   
       13 . The controller of  claim 12 , wherein the controller is adapted to receive thermostat signals from one or more thermostats. 
   
   
       14 . The controller of  claim 12 , wherein the controller is adapted to receive a speed signal from the fan or blower. 
   
   
       15 . The controller of  claim 12 , wherein the controller is adapted to receive a voltage or current signal from the fan or blower. 
   
   
       16 . A method of controlling a gas-fired appliance including a burner unit, a heat exchanger, a gas valve, a multi or variable speed inducer fan or blower adapted to produce a combustion air flow to the burner unit, and a heated air blower adapted to provide heated air to one or more warm air ducts, the method comprising the steps of:
 receiving a heat request signal and activating the fan or blower to provide a combustion air flow to the burner unit;   activating the gas valve to provide fuel to the burner unit and igniting the air/fuel mixture within the burner unit;   adjusting the speed of the inducer fan and/or heated air blower based at least in part on heat demand signals received from one or more thermostats;   sensing or measuring the mass air flow of the inducer fan and/or heated air blower and calculating the supply air temperature fed to the warm air ducts; and   adjusting the speed of the inducer fan or blower to modulate the gas pressure outputted by the gas valve.   
   
   
       17 . The method of  claim 16 , further comprising the step of sensing the presence of a flame within the burner unit after said step of igniting the burner unit. 
   
   
       18 . The method of  claim 16 , wherein said step of sensing or measuring the speed of the inducer fan or blower is accomplished via a sensor or switch. 
   
   
       19 . The method of  claim 16 , wherein said step of sensing or measuring the speed of the inducer fan or blower is accomplished by measuring the voltage and/or current of the inducer fan or blower. 
   
   
       20 . The method of  claim 16 , wherein said step of adjusting the speed of the inducer fan or blower based on heat demand signals received from one or more thermostats is accomplished with a motor speed control unit.