System and Method for Detecting a Refrigerant Leak in an HVAC System Using a Saturated Suction Temperature

Abstract

A method operating an HVAC system is provided. The method includes receiving a concentration of refrigerant from a sensor. The method includes operating the HVAC system in a leak diagnostic mode if a concentration of the refrigerant exceeds a gas concentration threshold. During the leak diagnostic mode the method includes turning on a compressor to compress a refrigerant in a first refrigerant circuit. The method includes receiving a first saturated suction temperature from a sensor. The method includes turning off the compressor for a predetermined duration. The method includes turning on the compressor after the predetermined duration has elapsed. The method includes receiving a second saturated suction temperature of the refrigerant from the sensor. The method includes determining that the first refrigerant circuit includes a refrigerant leak if a difference between the first saturated suction temperature and the second saturated suction temperature exceeds a saturated suction temperature threshold value.

1 . A heating, ventilation, and air conditioning (HVAC) system, the HVAC system comprising:
 a condenser;   an evaporator;   a leak detection sensor;   a first refrigerant circuit comprising:
 a first compressor configured to receive a refrigerant; 
 a first loss of charge sensor configured to acquire a measurement indicative of a saturated suction temperature of the refrigerant in the first refrigerant circuit; 
   a controller comprising a memory and a processor, the memory operable to store a saturated suction temperature threshold value, a gas concentration threshold, and a first predetermined duration, the processor operatively coupled to the memory and configured to:
 receive, from the leak detection sensor, a measurement indicative of a concentration of the refrigerant; 
 compare the concentration of the refrigerant to the gas concentration threshold; 
 determine that the HVAC system should operate in a leak diagnostic mode if the concentration of the refrigerant exceeds the gas concentration threshold, wherein during the leak diagnostic mode the controller is configured to:
 turn on the first compressor to compress the refrigerant; 
 receive, from the first loss of charge sensor, a first measurement indicative of a first saturated suction temperature of the refrigerant; 
 turn off the first compressor for the first predetermined duration; 
 turn on the first compressor to compress the refrigerant after the first predetermined duration has elapsed; 
 receive, from the first loss of charge sensor, a second measurement indicative of a second saturated suction temperature of the refrigerant; and 
 determine that the first refrigerant circuit includes a refrigerant leak if a difference between the first saturated suction temperature and the second saturated suction temperature exceeds the saturated suction temperature threshold value. 
 
   
     
     
         2 . The HVAC system of  claim 1 , wherein the controller is further configured to:
 cycle the first compressor on and off for a plurality of cycles;   receive, from the first loss of charge sensor, a respective measurement indicative of the saturated suction temperature of the refrigerant for at least a first cycle and at least a second cycle in the plurality of cycles while the first compressor is turned on; and   determine that the first refrigerant circuit includes the refrigerant leak if a difference between the saturated suction temperature for the first cycle and the saturated suction temperature for the second cycle exceeds the saturated suction temperature threshold value.   
     
     
         3 . The HVAC system of  claim 1 , further comprising:
 a first circuit of condenser coils positioned in the condenser, the first circuit of condenser coils configured to receive the refrigerant from the first compressor;   a first expansion valve configured downstream of the first circuit of condenser coils, the first expansion valve configured to receive the refrigerant from the first circuit of condenser coils;   a first circuit of evaporator coils positioned in the evaporator, the first circuit of evaporator coils configured to receive the refrigerant from the first expansion valve, and wherein the first compressor is configured to receive the refrigerant from the first circuit of evaporator coils;   wherein the first loss of charge sensor is at least one of:
 a first temperature sensor positioned in or adjacent to the first circuit of evaporator coils; or 
 a first pressure sensor positioned between the first compressor and the first circuit of evaporator coils. 
   
     
     
         4 . The HVAC system of  claim 1 , further comprising:
 a first controllable valve configured downstream of the condenser, and   a first pressure relief valve positioned upstream of the first controllable valve and downstream of the first compressor, the first pressure relief valve configured to vent the refrigerant from the first refrigerant circuit if a predetermined pressure threshold is exceeded.   
     
     
         5 . The HVAC system of  claim 4 , wherein in response to determining that the first refrigerant circuit includes the refrigerant leak, the controller is further configured to:
 determine that the HVAC system should operate in a pump down mode, wherein during the pump down mode the controller is configured to close the first controllable valve, and wherein closing the first controllable valve causes the refrigerant to vent from the first pressure relief valve as the predetermined pressure threshold is exceeded.   
     
     
         6 . The HVAC system of  claim 1 , further comprising a second refrigerant circuit comprising:
 a second compressor configured to receive the refrigerant;   a second loss of charge sensor configured to acquire a measurement indicative of the saturated suction temperature of the refrigerant in the second refrigerant circuit;   wherein during the leak diagnostic mode, the controller is configured to:
 turn on the second compressor to compress the refrigerant; 
 receive, from the second loss of charge sensor, a third measurement indicative of a third saturated suction temperature of the refrigerant; 
 turn off the second compressor for the first predetermined duration; 
 turn on the second compressor to compress the refrigerant after the first predetermined duration has elapsed; 
 receive, from the second loss of charge sensor, a fourth measurement indicative of a fourth saturated suction temperature of the refrigerant; 
 determine that a difference between the third saturated suction temperature and the fourth saturated suction temperature is below the saturated suction temperature threshold value, and 
 in response to determining that the difference between the third saturated suction temperature and the fourth saturated suction temperature is below the saturated suction temperature threshold value, the controller is configured to end the leak diagnostic mode for the second refrigerant circuit and initiate a normal mode of operation for the second refrigerant circuit, wherein in the normal mode of operation, the controller is configured to turn on the second compressor. 
   
     
     
         7 . The HVAC system of  claim 1  further comprising:
 a blower configured to move airflow across the evaporator; 
 wherein in response to determining that the concentration of the refrigerant exceeds the gas concentration threshold, the controller is configured to operate the HVAC system in a mitigation mode prior to operating in the leak diagnostic mode, wherein during the mitigation mode the controller is further configured to:
 turn the first compressor off; 
 turn the blower on; 
 receive, from the leak detection sensor, a measurement indicative of the concentration of the refrigerant; and 
 determine that the concentration of the refrigerant is below the gas concentration threshold, and in response end the mitigation mode and initiate the leak diagnostic mode. 
 
 
     
     
         8 . A method of operating a heating, ventilation, and air conditioning (HVAC) system, the method comprising:
 receiving, from a leak detection sensor, a measurement indicative of a concentration of a refrigerant;   determining, using a controller, that the HVAC system should operate in a leak diagnostic mode if the concentration of the refrigerant exceeds a gas concentration threshold, and wherein during the leak diagnostic mode the method further comprises:
 turning on, using the controller, a first compressor to compress the refrigerant in a first refrigerant circuit; 
 receiving, from a first loss of charge sensor, a first measurement indicative of a first saturated suction temperature of the refrigerant; 
 turning off, using the controller, the first compressor for a first predetermined duration; 
 turning on, using the controller, the first compressor to compress the refrigerant after the first predetermined duration has elapsed; 
 receiving, from the first loss of charge sensor, a second measurement indicative of a second saturated suction temperature of the refrigerant; 
 determining, using the controller, that the first refrigerant circuit includes a refrigerant leak if a difference between the first saturated suction temperature and the second saturated suction temperature exceeds a saturated suction temperature threshold value. 
   
     
     
         9 . The method of  claim 8 , further comprising:
 cycling, using the controller, the first compressor on and off for a plurality of cycles;   receiving, from the first loss of charge sensor, a respective measurement indicative of a saturated suction temperature of the refrigerant for at least a first cycle and at least a second cycle in the plurality of cycles while the first compressor is turned on; and   determining, using the controller, that the first refrigerant circuit includes the refrigerant leak if a difference between the saturated suction temperature for the first cycle and the saturated suction temperature for the second cycle exceeds the saturated suction temperature threshold value.   
     
     
         10 . The method of  claim 8 , further comprising:
 a first circuit of condenser coils positioned in a condenser, the first circuit of condenser coils configured to receive the refrigerant from the first compressor;   a first expansion valve configured downstream of the first circuit of condenser coils, the first expansion valve configured to receive the refrigerant from the first circuit of condenser coils;   a first circuit of evaporator coils positioned in a evaporator, the first circuit of evaporator coils configured to receive the refrigerant from the first expansion valve, and wherein the first compressor is configured to receive the refrigerant from the first circuit of evaporator coils;   wherein the first loss of charge sensor is at least one of:
 a first temperature sensor positioned in or adjacent to the first circuit of evaporator coils; or 
 a first pressure sensor positioned between the first compressor and the first circuit of evaporator coils. 
   
     
     
         11 . The method of  claim 10 , further comprising:
 a first controllable valve configured downstream of the condenser, and   a first pressure relief valve positioned upstream of the first controllable valve and downstream of the first compressor, the first pressure relief valve configured to vent the refrigerant from the first refrigerant circuit if a predetermined pressure threshold is exceeded.   
     
     
         12 . The method of  claim 11 , wherein in response to determining that the first refrigerant circuit includes the refrigerant leak, the method further comprises:
 operating the HVAC system in a pump down mode, wherein during the pump down mode the controller is configured to close the first controllable valve, and wherein closing the first controllable valve causes the refrigerant to vent from the first pressure relief valve as the predetermined pressure threshold is exceeded.   
     
     
         13 . The method of  claim 8 , further comprising a second refrigerant circuit, the second refrigerant circuit comprising:
 a second compressor configured to receive the refrigerant;   a second loss of charge sensor configured to acquire a measurement indicative of a saturated suction temperature of the refrigerant in the second refrigerant circuit;   wherein during the leak diagnostic mode, the method further comprises:
 turning on, using the controller, the second compressor to compress the refrigerant; 
 receiving, from the second loss of charge sensor, a third measurement indicative of a third saturated suction temperature of the refrigerant; 
 turning off, using the controller, the second compressor for the first predetermined duration; 
 turning on, the second compressor, to compress the refrigerant after the first predetermined duration has elapsed; 
 receiving, from the second loss of charge sensor, a fourth measurement indicative of a fourth saturated suction temperature of the refrigerant; 
 determine that a difference between the third saturated suction temperature and the fourth saturated suction temperature is below the saturated suction temperature threshold value, and 
 in response to determining that the difference between the third saturated suction temperature and the fourth saturated suction temperature is below the saturated suction temperature threshold value, the method further comprises:
 ending, using the controller, the leak diagnostic mode for the second refrigerant circuit; and 
 initiating, using the controller, a normal mode of operation for the second refrigerant circuit, wherein in the normal mode of operation, the controller is configured to turn on the second compressor. 
 
   
     
     
         14 . The method of  claim 8 , further comprising:
 a blower configured to move airflow across an evaporator; wherein in response to determining that the concentration of the refrigerant exceeds the gas concentration threshold, the method further comprises:   operating, using the controller, the HVAC system in a mitigation mode prior to operating in the leak diagnostic mode, wherein during the mitigation mode the method comprises:
 turning off the first compressor using the controller; 
 turning the blower on using the controller; 
 receiving, from the leak detection sensor, a measurement indicative of the concentration of the refrigerant; and 
 determining, using the controller, that the concentration of the refrigerant is below the gas concentration threshold, and in response ending the mitigation mode and initiating the leak diagnostic mode. 
   
     
     
         15 . A controller of a heating, ventilation, and air conditioning (HVAC) system, the controller comprising:
 a memory operable to store a saturated suction temperature threshold value, a gas concentration threshold, and a first predetermined duration;   a processor operatively coupled to the memory and configured to:
 receive, from a leak detection sensor, a measurement indicative of a concentration of a refrigerant; 
 compare the concentration of the refrigerant to the gas concentration threshold; 
 determine that the HVAC system should operate in a leak diagnostic mode if the concentration of the refrigerant exceeds the gas concentration threshold, wherein during the leak diagnostic mode the processor is configured to:
 turn on a first compressor in a first refrigerant circuit to compress the refrigerant; 
 receive, from a first loss of charge sensor, a first measurement indicative of a first saturated suction temperature of the refrigerant; 
 turn off the first compressor for the first predetermined duration; 
 turn on the first compressor to compress the refrigerant after the first predetermined duration has elapsed; 
 receive, from the first loss of charge sensor, a second measurement indicative of a second saturated suction temperature of the refrigerant; and 
 determine that the first refrigerant circuit includes a refrigerant leak if a difference between the first saturated suction temperature and the second saturated suction temperature exceeds the saturated suction temperature threshold value. 
 
   
     
     
         16 . The controller of  claim 15 , wherein the processor is further configured to:
 cycle the first compressor on and off for a plurality of cycles;   receive, from the first loss of charge sensor, a respective measurement indicative of a saturated suction temperature of the refrigerant for at least a first cycle and at least a second cycle in the plurality of cycles while the first compressor is turned on; and   determine that the first refrigerant circuit includes the refrigerant leak if a difference between the saturated suction temperature for the first cycle and the saturated suction temperature for the second cycle exceeds the saturated suction temperature threshold value.   
     
     
         17 . The controller of  claim 15 , wherein the first loss of charge sensor is at least one of:
 a first temperature sensor positioned in or adjacent to a first circuit of condenser coils positioned in a condenser of the HVAC system; or   a first pressure sensor positioned between the first compressor and a first circuit of evaporator coils positioned in an evaporator of the HVAC system.   
     
     
         18 . The controller of  claim 15 , wherein in response to determining that the first refrigerant circuit includes the refrigerant leak, the processor is configured to:
 operate the HVAC system in a pump down mode, wherein during the pump down mode the controller is configured to close a first controllable valve, and wherein closing the first controllable valve causes the refrigerant to vent from a first pressure relief valve as a predetermined pressure threshold is exceeded.   
     
     
         19 . The controller of  claim 15 , wherein in response to determining that the HVAC system should operate in the leak diagnostic mode, the processor is configured to:
 turn on a second compressor in a second refrigerant circuit to compress the refrigerant;   receive, from a second loss of charge sensor, a third measurement indicative of a third saturated suction temperature of the refrigerant;   turn off the second compressor for the first predetermined duration;   turn on the second compressor to compress the refrigerant after the first predetermined duration has elapsed;   receive, from the second loss of charge sensor, a fourth measurement indicative of a fourth saturated suction temperature of the refrigerant;   determine that a difference between the third saturated suction temperature and the fourth saturated suction temperature is below the saturated suction temperature threshold value, and   in response to determining that the difference between the third saturated suction temperature and the fourth saturated suction temperature is below the saturated suction temperature threshold value, the processor is configured to end the leak diagnostic mode for the second refrigerant circuit and initiate a normal mode of operation for the second refrigerant circuit, wherein in the normal mode of operation, the controller is configured to turn on the second compressor.   
     
     
         20 . The controller of  claim 15 , wherein in response to determining that the concentration of the refrigerant exceeds the gas concentration threshold, the controller is configured to operate the HVAC system in a mitigation mode prior to operating in the leak diagnostic mode;
 wherein during the mitigation mode the controller is further configured to:
 turn the first compressor off; 
 turn a blower on; 
 receive, from the leak detection sensor, a second measurement indicative of the concentration of the refrigerant; and 
 determine that the concentration of the refrigerant is below the gas concentration threshold, and in response end the mitigation mode and initiate the leak diagnostic mode.