Leak Sensors for a HVAC System to Detect Fuel Leaks and Methods of Operation

Abstract

A method of operating a HVAC system is provided. The method includes moving airflow out of a duct system using a blower. A heating element is configured to receive a fuel and ignite the fuel to heat the heating element. The method includes measuring a change in at least one gas property value of the airflow in the duct system using a leak detection sensor, where the change in the at least one gas property value is indicative of a gas leaked into the duct system. The method includes determining a concentration of the leaked gas based at least in part upon the change in the at least one gas property value and determining that the concentration as measured by the leak detection is indicative of the leaked gas comprising fuel.

What is claimed is: 
     
         1 . A heating, ventilation, and air conditioning (HVAC) system configured to regulate a temperature of a space, the HVAC system comprising:
 a blower configured to move airflow out of a duct system;   a heating element, wherein the blower is further configured to move the airflow across the heating element to heat the airflow in the duct system, wherein the heating element is configured to receive a fuel from a fuel source, and wherein the heating element is configured to ignite the fuel;   a leak detection sensor configured to measure at least one gas property value of the airflow in the duct system;   a processor communicatively coupled to the leak detection sensor and the blower, and configured to:
 measure a change in at least one gas property value of the airflow in the duct system using the leak detection sensor, wherein the change in the at least one gas property value is indicative of a gas leaked into the duct system; 
 determine a concentration of the leaked gas based at least in part upon the change in the at least one gas property value; 
 determine that the concentration of the leaked gas indicates that the leaked gas comprises fuel, wherein in conjunction with determining that the concentration of the leaked gas comprises fuel, the processor is configured to:
 turn off the heating element; and 
 initiate the blower to move the airflow through the duct system for a duration to reduce an amount of the leaked gas in the duct system. 
 
   
     
     
         2 . The HVAC system of  claim 1 , wherein the fuel comprises natural gas. 
     
     
         3 . The HVAC system of  claim 1 , further comprising an indoor coil through which an A2L refrigerant flows. 
     
     
         4 . The HVAC system of  claim 1 , wherein after determining that the concentration of the leaked gas comprises fuel, the processor is configured to trigger an alarm. 
     
     
         5 . The HVAC system of  claim 1 , wherein the at least one gas property value comprises at least one of a speed of sound or thermal conductivity. 
     
     
         6 . The HVAC system of  claim 1 , wherein the processor is further configured to:
 measure a change in a speed of sound of the airflow in the duct system using the leak detection sensor, wherein the change in the speed of sound of the airflow is indicative of the leaked gas in the duct system;   determine a concentration of the leaked gas based at least in part upon the change in the speed of sound, wherein the concentration is determined as a percentage of a lower flammability limit of the leaked gas;   compare the concentration of the leaked gas to a control setpoint for a maximum allowable concentration of leaked gas in the duct system, wherein the control setpoint is from −1.5% to −4% of the lower flammability limit of the leaked gas as measured by the leak detection sensor, wherein after determining that the concentration falls within the control setpoint, the processor is configured to:
 turn off the heating element; and 
 initiate the blower to move the airflow through the duct system for a duration to reduce an amount of the leaked gas in the duct system. 
   
     
     
         7 . The HVAC system of  claim 1 , wherein the processor is further configured to:
 measure a change in a thermal conductivity of the airflow in the duct system using the leak detection sensor, wherein the change in the thermal conductivity of the airflow is indicative of the leaked gas in the duct system;   determine a concentration of the leaked gas based at least in part upon the change in the speed of sound, wherein the concentration is determined as a percentage of a lower flammability limit of the leaked gas;   compare the concentration of the leaked gas to a control setpoint for a maximum allowable concentration of leaked gas in the duct system, wherein the control setpoint is from −2% to −6% of the lower flammability limit of the leaked gas as measured by the leak detection sensor, wherein after determining that the concentration falls within the control setpoint, the processor is configured to:
 turn off the heating element; and 
 initiate the blower to move the airflow through the duct system for a duration to reduce an amount of the leaked gas in the duct system. 
   
     
     
         8 . A controller of a heating, ventilation, and air conditioning (HVAC) system, the controller comprising:
 an interface communicatively coupled to:
 a blower configured to move airflow out of a duct system; 
 a heating element, wherein the blower is further configured to move the airflow across the heating element to heat the airflow in the duct system, wherein the heating element is configured to receive a fuel from a fuel source, and wherein the heating element is configured to ignite the fuel; 
 a leak detection sensor configured to measure at least one gas property value of the airflow in the duct system; and 
   a processor communicatively coupled to the interface and configured to:
 measure a change in at least one gas property value of the airflow in the duct system using the leak detection sensor, wherein the change in the at least one gas property value is indicative of a gas leaked into the duct system; 
 determine a concentration of the leaked gas based at least in part upon the change in the at least one gas property value; 
 determine that the concentration of the leaked gas indicates that the leaked gas comprises fuel, wherein in conjunction with determining that the concentration of the leaked gas comprises fuel, the processor is configured to:
 turn off the heating element; and 
 initiate the blower to move the airflow through the duct system for a duration to reduce an amount of the leaked gas in the duct system. 
 
   
     
     
         9 . The controller of  claim 8 , wherein the fuel comprises natural gas. 
     
     
         10 . The controller of  claim 8 , wherein in conjunction with determining that the concentration of the leaked gas comprises fuel, the processor is configured to trigger an alarm. 
     
     
         11 . The controller of  claim 8 , wherein the at least one gas property value comprises at least one of a speed of sound or thermal conductivity. 
     
     
         12 . The controller of  claim 8 , wherein the processor is further configured to:
 measure a change in a speed of sound of the airflow in the duct system using the leak detection sensor, wherein the change in the speed of sound of the airflow is indicative of the leaked gas in the duct system;   determine a concentration of the leaked gas based at least in part upon the change in the speed of sound, wherein the concentration is determined as a percentage of a lower flammability limit of the leaked gas;   compare the concentration of the leaked gas to a control setpoint for a maximum allowable concentration of leaked gas in the duct system, wherein the control setpoint is from −1.5% to −4% of the lower flammability limit of the leaked gas as measured by the leak detection sensor, wherein after determining that the concentration falls within the control setpoint, the processor is configured to:
 turn off the heating element; and 
 initiate the blower to move the airflow through the duct system for a duration to reduce an amount of the leaked gas in the duct system. 
   
     
     
         13 . The controller of  claim 8 , wherein the processor is configured to:
 measure a change in a thermal conductivity of the airflow in the duct system using the leak detection sensor, wherein the change in the thermal conductivity of the airflow is indicative of the leaked gas in the duct system;   determine a concentration of the leaked gas based at least in part upon the change in the speed of sound, wherein the concentration is determined as a percentage of a lower flammability limit of the leaked gas;   compare the concentration of the leaked gas to a control setpoint for a maximum allowable concentration of leaked gas in the duct system, wherein the control setpoint is from −2% to −6% of the lower flammability limit of the leaked gas as measured by the leak detection sensor, wherein after determining that the concentration falls within the control setpoint, the processor is configured to:
 turn off the heating element; and 
 initiate the blower to move the airflow through the duct system for a duration to reduce an amount of the leaked gas in the duct system. 
   
     
     
         14 . A method of operating a heating, ventilation, and air conditioning (HVAC) system, the method comprising:
 moving airflow out of a duct system using a blower;   transferring heat between the airflow in the duct system and a heating element, wherein the blower is configured to move the airflow across the heating element, wherein the heating element is configured to receive a fuel from a fuel source, and wherein the heating element is configured to ignite the fuel;   measuring a change in at least one gas property value of the airflow in the duct system using a leak detection sensor, wherein the change in the at least one gas property value is indicative of a gas leaked into the duct system;   determining a concentration of the leaked gas based at least in part upon the change in the at least one gas property value;   determining that the concentration of the leaked gas indicates that the leaked gas comprises fuel, wherein in conjunction with determining that the concentration of the leaked gas comprises fuel:
 turning off the heating element; and 
 initiating the blower to move the airflow through the duct system for a duration to reduce an amount of the leaked gas in the duct system. 
   
     
     
         15 . The method of  claim 14 , wherein the fuel comprises natural gas. 
     
     
         16 . The method of  claim 14 , further comprising flowing an A2L refrigerant through an indoor coil of the HVAC system. 
     
     
         17 . The method of  claim 14 , wherein in conjunction with determining that the concentration of the leaked gas comprises fuel, triggering an alarm. 
     
     
         18 . The method of  claim 14 , wherein the at least one gas property value comprises at least one of a speed of sound or thermal conductivity. 
     
     
         19 . The method of  claim 14  further comprising:
 measuring a change in a speed of sound of the airflow in the duct system using the leak detection sensor, wherein the change in the speed of sound of the airflow is indicative of the leaked gas in the duct system; 
 determining a concentration of the leaked gas based at least in part upon the change in the speed of sound, wherein the concentration is determined as a percentage of a lower flammability limit of the leaked gas; 
 comparing the concentration of the leaked gas to a control setpoint for a maximum allowable concentration of leaked gas in the duct system, wherein the control setpoint is from −1.5% to −4% of the lower flammability limit of the leaked gas as measured by the leak detection sensor, wherein after determining that the concentration falls within the control setpoint, the method further comprises:
 turning off the heating element; and 
 initiating the blower to move the airflow through the duct system for a duration to reduce an amount of the leaked gas in the duct system. 
 
 
     
     
         20 . The method of  claim 14  further comprising:
 measuring a change in a thermal conductivity of the airflow in the duct system using the leak detection sensor, wherein the change in the thermal conductivity of the airflow is indicative of the leaked gas in the duct system; 
 determining a concentration of the leaked gas based at least in part upon the change in the speed of sound, wherein the concentration is determined as a percentage of a lower flammability limit of the leaked gas; 
 comparing the concentration of the leaked gas to a control setpoint for a maximum allowable concentration of leaked gas in the duct system, wherein the control setpoint is from −2% to −6% of the lower flammability limit of the leaked gas as measured by the leak detection sensor, wherein after determining that the concentration falls within the control setpoint, the method further comprises:
 turning off the heating element; and 
 initiating the blower to move the airflow through the duct system for a duration to reduce an amount of the leaked gas in the duct system.