Digital modulation for a gas-fired heater

Abstract

A gas-fired heater includes a plurality of burners and one or more valves corresponding to one of the burners and operating between a closed position and an open position. A fuel supply is in fluidic communication with at least one of the burners when the one or more valves are in the open position. A modulator receives a temperature signal and computes, as a function of the temperature signal, and emits at least one control signal. The modulator then operates the one or more valves between the open position and the closed position as a function of the at least one control signal and controls the one or more valves to either activate or deactivate the burners for incrementally modulating a heat input to the gas-fired heater.

What is claimed is:  
     
         1 . A gas-fired heater comprising: 
 a plurality of burners, at least one valve, each said valve corresponding to one of said burners and operating between a closed position and an open position;    a fuel supply in fluidic communication with at least one of said burners when said at least one valve is in said open position;    a modulator receiving a temperature signal, said modulator computing as a function of said temperature signal and emitting at least one control signal, said modulator operating said at least one valve between said open position and said closed position as a function of said at least one control signal, and said modulator controlling said at least one valve to one of activate and deactivate said burners for incrementally modulating a heat input to the gas-fired heater.    
     
     
         2 . A gas-fired heater according to  claim 1  further comprising a plurality of heat exchange tubes each accepting heat transfer from a corresponding burner of the burners.  
     
     
         3 . A gas-fired heater according to  claim 1  wherein said at least one control signal is a digital signal.  
     
     
         4 . A gas-fired heater according to  claim 1  wherein said burners have approximately equal firing rates.  
     
     
         5 . A gas-fired heater according to  claim 1  wherein each of said burners has a different firing rate.  
     
     
         6 . A gas-fired heater according to  claim 1  wherein at least one of said burners has a constant firing rate.  
     
     
         7 . A gas-fired heater according to  claim 1  wherein at least one of said burners has a variable firing rate.  
     
     
         8 . A gas-fired heater according to  claim 1  wherein said at least one valve is a solenoid valve and said modulator independently operates each said solenoid valve.  
     
     
         9 . A gas-fired heater according to  claim 1  wherein each said burner is an in-shot burner.  
     
     
         10 . A gas-fired heater according to  claim 1  wherein said open position is a partially open position of each said valve.  
     
     
         11 . A gas-fired heater according to  claim 1  wherein said temperature signal is generated from a thermostat.  
     
     
         12 . A gas-fired heater according to  claim 1  further comprising a main valve positioned between said fuel supply and said at least one valve and in communication with said fuel supply and at least one of said burners with each said valve in said closed position.  
     
     
         13 . A gas-fired heater according to  claim 1  wherein a tube burner proximate to all said burners operates as an intermittent pilot burner.  
     
     
         14 . A method for operating a gas-fired heater, the method comprising: 
 a plurality of burners, at least one valve, each said valve corresponding to one of said burners and operating between a closed position and an open position;    supplying fuel to at least one of a plurality of burners when at least one valve is in an open position;    operating each said valve between said open position and a closed position as a function of at least one control signal received at said at least one valve;    emitting a temperature signal to a modulator;    computing at least one control signal as a function of said temperature signal and emitting said at least one control signal from said modulator to said at least one valve;    operating said at least one valve between said open position and said closed position as a function of said at least one control signal; and    incrementally modulate a heat input to the gas-fired heater by controlling said at least one valve to one of activate and deactivate said burners.    
     
     
         15 . A method for operating a gas-fired heater according to  claim 13  wherein each said burner is dedicated to a corresponding one of a plurality of heat exchange tubes of the gas-fired heater.  
     
     
         16 . A method for operating a gas-fired heater according to  claim 13  wherein each said at least one control signal is a digital signal.  
     
     
         17 . A method for operating a gas-fired heater according to  claim 13  wherein said at least one valve is a solenoid valve and said modulator independently operates each said solenoid valve.  
     
     
         18 . A method for operating a gas-fired heater according to  claim 13  wherein said temperature signal is emitted by a thermostat.  
     
     
         19 . A method for operating a gas-fired heater according to  claim 13  wherein a main valve is operated to provide a fuel from the fuel supply to said burners and said main valve is positioned between said fuel supply and said at least one valve.