# US 2019/0170415 A1 · Diagnostic mode of operation to detect refrigerant leaks in a refrigeration circuit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0170415 A1 - Document ID: US20190170415A1 - Status: Published application - Kind: A1 - Application number: 15/876,408 - Filed: 2018-01-22 - Published: 2019-06-06 - Earliest claimed: 2017-12-01 - Assignees: Johnson Controls Technology Company - Applicants: Johnson Controls Technology Company - Inventors: Jay C. Walser; William F. McQuade - Web page: https://patentgrep.com/patent/US20190170415A1 ## CPC - F25B 49/02: for compression type machines, plants or systems - F25B 41/34: with the valve member being actuated by electric means, e.g. by piezoelectric actuators - F25B 49/005: {of safety devices (F25B49/02 and F25B49/04 take precedence)} - F25B 2300/00: Special arrangements or features for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems - F25B 2400/19: Pumping down refrigerant from one part of the cycle to another part of the cycle, e.g. when the cycle is changed from cooling to heating, or before a defrost cycle is started - F25B 2500/222: Detecting refrigerant leaks - F25B 2600/01: Timing - F25B 2600/0251: with on-off operation - F25B 2600/2513: Expansion valves - F25B 2700/19: Pressures - F25B 2700/1931: Discharge pressures - F25B 2700/195: of the condenser - F25B 2700/197: of the evaporator - F25B 2700/2104: of an indoor room or compartment - F25B 2700/2106: of fresh outdoor air - F25B 2700/21171: of the fluid cooled by the evaporator - F25B: REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS ## Abstract The present disclosure relates to a refrigeration circuit that includes a controller communicatively coupled to a compressor, an expansion valve, and a sensor of the refrigeration circuit. The controller may activate the compressor and actuate the expansion valve such that the compressor is active while the expansion valve is closed. The controller may also measure a pressure of a refrigerant in the refrigeration circuit using the sensor while the compressor is active and the expansion valve is closed. Additionally, the controller may determine whether a refrigerant leak exists based on a maximum measurement time being reached or a time difference between a first time associated with the compressor being active while the expansion valve is closed and a second time associated with the measured pressure falling below a threshold value. ## Claims ### Claim 1 A refrigeration circuit, comprising: a controller communicatively coupled to a compressor, an expansion valve, and a sensor of the refrigeration circuit, wherein the controller is configured to: activate the compressor and actuate the expansion valve such that the compressor is active while the expansion valve is closed; measure a pressure of a refrigerant in the refrigeration circuit using the sensor at least while the compressor is active and the expansion valve is closed; determine whether a refrigerant leak exists based on a time difference between a first time associated with the compressor being active while the expansion valve is closed and a second time associated with the measured pressure falling below a threshold value. ### Claim 2 (depends on 1) The refrigeration circuit of claim 1, wherein the controller is configured to close the expansion valve before activating the compressor. ### Claim 3 (depends on 1) The refrigeration circuit of claim 1, wherein the controller is configured to determine whether the refrigerant leak exists by comparing the time difference to an expected pump-down time or the maximum measurement time. ### Claim 4 (depends on 3) The refrigeration circuit of claim 3, wherein the controller is configured to determine that the refrigerant leak exists when the time difference is substantially shorter than the expected pump-down time due to a loss of refrigerant in the refrigeration circuit. ### Claim 5 (depends on 3) The refrigeration circuit of claim 3, wherein the controller is configured to determine that the refrigerant leak exists when the time difference is substantially longer than the expected pump-down time due to air leaking into the refrigeration circuit. ### Claim 6 (depends on 3) The refrigeration circuit of claim 3, wherein the controller is configured to determine that the refrigerant leak exists when the time difference equals or exceeds the maximum measurement time due to air leaking into the refrigeration circuit. ### Claim 7 (depends on 3) The refrigeration circuit of claim 3, wherein the controller is configured to determine the expected pump-down time based at least partially on previous pump-down times stored in a memory of the controller. ### Claim 8 (depends on 7) The refrigeration circuit of claim 7, comprising a temperature sensor communicatively coupled to the controller and configured to measure an air temperature associated with the HVAC unit, wherein the controller is configured to measure the air temperature using the temperature sensor and to determine the expected pump-down time at least partially based on the measured air temperature. ### Claim 9 (depends on 8) The refrigeration circuit of claim 8, wherein the air temperature corresponds to an environmental air temperature. ### Claim 10 (depends on 8) The refrigeration circuit of claim 8, wherein the air temperature corresponds to a return air temperature. ### Claim 11 (depends on 1) The refrigeration circuit of claim 1, wherein the threshold value is substantially lower than a refrigerant pressure associated with normal operation of the refrigeration circuit. ### Claim 12 (depends on 1) The refrigeration circuit of claim 1, comprising a second sensor disposed upstream of the expansion valve, wherein the sensor is disposed downstream of the expansion valve, and wherein the controller is configured to: measure a second pressure of the refrigerant in the refrigeration circuit using the second sensor; determine that the expansion valve is faulty when the pressure measured by the sensor and the second pressure measured by the second sensor are changing by a corresponding amount when the maximum measurement time is reached. ### Claim 13 (depends on 1) The refrigeration circuit of claim 1, wherein the controller is configured to determine whether the refrigerant leak exists based on a maximum measurement time being reached. ### Claim 14 A heating, ventilating, and air conditioning (HVAC) unit, comprising: a refrigeration circuit comprising a compressor and an expansion valve; a sensor configured to measure a pressure of a refrigerant within the refrigeration circuit; and a controller configured to: activate the compressor with the expansion valve closed; obtain a measure of the pressure of the refrigerant from the sensor; and determine whether a refrigerant leak exists based on a time difference between a time associated with activation of the compressor and a subsequent time associated with the pressure falling below a threshold value. ### Claim 15 (depends on 14) The HVAC unit of claim 14, wherein the sensor is positioned downstream of the expansion valve and upstream of an evaporator of the refrigeration circuit. ### Claim 16 (depends on 14) The HVAC unit of claim 14, wherein, the controller is configured to stop the compressor when measure of the pressure of the refrigerant does not fall below the threshold value within set timeframe. ### Claim 17 (depends on 14) The HVAC unit of claim 14, wherein the controller is configured to determine an expected pump-down time, and wherein the controller is configured to determine that the refrigerant leak exists when the time difference is substantially more or substantially less than the expected pump-down time. ### Claim 18 (depends on 14) The HVAC unit of claim 14, comprising an environmental air sensor and a return air sensor communicatively coupled to the controller, wherein the controller is configured to: measure an environmental air temperature associated with the HVAC unit using the environmental air sensor; measure a return air temperature associated with the HVAC unit using the return air sensor; determine an expected pump-down time based, at least in part, on the measured environmental air temperature and the return air temperature; and determine that the refrigerant leak exists when the time difference is substantially above or below the expected pump-down time. ### Claim 19 (depends on 18) The HVAC unit of claim 18, wherein the controller is configured to determine the expected pump-down time based at least partially based on previous pump-down times. ### Claim 20 (depends on 14) The HVAC unit of claim 14, comprising a second sensor communicatively coupled to the controller and configured to measure a second pressure of the refrigerant within the refrigeration circuit, wherein the sensor and the second sensor are disposed on opposite sides of the expansion valve in the refrigeration circuit, and wherein the controller is configured to obtain a second measure of the pressure of the refrigerant from the second sensor. ### Claim 21 (depends on 20) The HVAC unit of claim 20, wherein, when a maximum measurement time is reached, the controller is configured to: determine whether the refrigerant leak exists or the expansion valve is faulty based, at least in part, on the first and the second measure of the pressure of the refrigerant obtained by the sensor and the second sensor. ### Claim 22 (depends on 14) The HVAC unit of claim 14, wherein the controller is configured to send a signal to notify an electronic device of the refrigerant leak when the refrigerant leak is determined to exist. ### Claim 23 (depends on 14) The HVAC unit of claim 14, wherein the controller is configured to block the expansion valve from reopening when the refrigerant leak is determined to exist. ### Claim 24 (depends on 14) The HVAC unit of claim 14, wherein the controller is configured to: determine whether the HVAC unit is operating in an on-cycle based on initiating a diagnostic mode, and when it is operating in the on-cycle, switch the HVAC unit into an off-cycle and close the expansion valve before activating the compressor in the diagnostic mode. ### Claim 25 A diagnostic mode method of operation of a heating, ventilating, and air conditioning (HVAC) unit having a refrigeration circuit, the method comprising: activating a compressor and closing an expansion valve of the refrigeration circuit such that the compressor is active and the expansion valve is closed during a timeframe; measuring a pressure of a refrigerant in the refrigeration circuit using a sensor of the refrigeration circuit positioned downstream of the expansion valve and upstream of an evaporator of the refrigeration circuit during the timeframe; determining a pump-down time as a difference between a beginning of the timeframe and a time associated with reaching a threshold value for the pressure; and determining whether a refrigerant leak exists based on a comparison between the determined pump-down time and an expected pump-down time. ### Claim 26 (depends on 25) The diagnostic mode method of operation of claim 25, comprising blocking the expansion valve from reopening to prevent on-cycle operation of the HVAC unit when the refrigerant leak is determined to exist. ### Claim 27 (depends on 25) The diagnostic mode method of operation of claim 25, wherein the threshold value corresponds to substantially all of the refrigerant of the refrigeration circuit being disposed in an outdoor portion of the refrigeration circuit. ### Claim 28 (depends on 25) The diagnostic mode method of operation of claim 25, comprising: measuring an environmental air temperature associated with the HVAC unit using a second sensor; measuring a return air temperature associated with the HVAC unit using a third sensor; and determining the expected pump-down time based on the measured environmental air temperature, the return air temperature, and a previous pump-down time. ### Claim 29 (depends on 25) The diagnostic mode method of operation of claim 25, wherein the expected pump-down time is determined based on an amount of the refrigerant in the refrigeration circuit.