Premix air heater

Abstract

A gas-fired heater includes a gas supply line, an air supply line, a valve coupled to the gas supply line and a controller coupled to the valve. The controller is configured to control the valve to control a gas-air mixture. The gas-fired heater also includes a burner configured to receive the gas-air mixture and burn the gas-air mixture, and a heat exchanger coupled to the burner. The heat exchanger is configured to perform a heat exchange process and output heated air. The gas-fired heater further includes a combustion fan located downstream of the heat exchanger, the combustion fan being configured to pull or draw flue gases through the heat exchanger.

1 . A gas-fired heater, comprising:
 a gas supply line;   an air supply line;   a valve coupled to the gas supply line;   a controller coupled to the valve, the controller configured to control the valve to control a gas-air mixture;   a burner configured to receive the gas-air mixture and burn the gas-air mixture;   a heat exchanger coupled to the burner, the heat exchanger configured to perform a heat exchange process and output heated air; and   a fan located downstream of the heat exchanger, the fan being configured to draw flue gases through the heat exchanger and provide negative pressure to draw the gas-air mixture through the burner and the valve-venturi system.   
     
     
         2 . The gas-fired heater of  claim 1 , further comprising:
 an enclosure to house the burner and heat exchanger, wherein the enclosure includes no secondary air inlets such that no air other than air included in the gas-air mixture is provided to the burner.   
     
     
         3 . The gas-fired heater of  claim 1 , further comprising:
 a collector box coupled to the heat exchanger and the combustion fan.   
     
     
         4 . The gas-fired heater of  claim 3 , further comprising:
 a condensate drain coupled to the collector box, the condensate drain being configured to drain condensation from the gas-fired heater.   
     
     
         5 . The gas fired heater of  claim 1 , wherein the fan comprises a variable-speed fan that does not affect the gas-air ratio provided to the burner. 
     
     
         6 . The gas-fired heater of  claim 1 , wherein the controller comprises:
 a pressure regulator configured to:
 measure a pressure drop of air in the air supply line across a venturi, and 
 control the valve to release an amount of gas based on the measured pressure drop. 
   
     
     
         7 . The gas-fired heater of  claim 6 , wherein when controlling the valve, the pressure regulator is configured to provide a gas pressure corresponding to or in a fixed relationship to the measured pressure drop. 
     
     
         8 . The gas-fired heater of  claim 1 , further comprising:
 a venturi coupled to the burner and gas valve, wherein a pressure drop is measured over the venturi.   
     
     
         9 . The gas-fired heater of  claim 1 , wherein the controller is configured to:
 provide a constant gas-to-air mixture to the burner.   
     
     
         10 . A system, comprising:
 a gas-fired heater, the gas-fired heater comprising:
 a gas supply, 
 an air supply, 
 a valve coupled to the gas supply, 
 a controller coupled to the valve, the controller configured to control the valve to control a gas-air mixture, 
 a burner configured to receive the gas-air mixture and burn the gas-air mixture, 
 a heat exchanger coupled to the burner, the heat exchanger configured to output heated air, and 
 a fan located adjacent the heat exchanger, the fan being configured to pull flue gases through the heat exchanger and the gas-air mixture through the burner, the valve and a venturi coupled to the air supply. 
   
     
     
         11 . The system of  claim 10 , wherein the gas-fired heater further comprises:
 an enclosure to house the burner and heat exchanger, wherein the enclosure includes no secondary air inlets.   
     
     
         12 . The system of  claim 10 , wherein the gas-fired heater further comprises:
 a collector box coupled to the heat exchanger and the fan, and   a condensate drain coupled to the collector box, the condensate drain being configured to drain condensation from the system.   
     
     
         13 . The system of  claim 10 , wherein the fan comprises a variable speed fan that does not affect the gas-air ratio provided to the burner. 
     
     
         14 . The system of  claim 10 , wherein the controller comprises:
 a zero pressure regulator configured to:
 measure a pressure drop of air in the air supply across a venturi, and 
 control the valve to release an amount of gas based on the measured pressure drop. 
   
     
     
         15 . The system of  claim 10 , wherein the gas-fired heater further comprises:
 a venturi coupled to the burner.   
     
     
         16 . The system of  claim 10 , wherein the controller is configured to:
 provide a constant gas-to-air mixture to the burner.   
     
     
         17 . The system of  claim 10 , further comprising:
 an air handling unit coupled to the gas-fired heater.   
     
     
         18 . The system of  claim 10 , wherein the heat exchanger comprises a plate heat exchanger. 
     
     
         19 . The system of  claim 10 , wherein the heat exchanger comprises a combination tube and plate heat exchanger.