# US 11,898,764 B2 · HVAC system leak detection

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 11,898,764 B2
- Document ID: US11898764B2
- Status: Granted
- Kind: B2
- Application number: 18/153,237
- Filed: 2023-01-11
- Published: 2023-05-25
- Granted: 2024-02-13
- Earliest claimed: 2021-06-18
- Assignees: Lennox Industries Inc.
- Applicants: Lennox Industries Inc.
- Inventors: Payam Delgoshaei; Eric Berg
- Web page: https://patentgrep.com/patent/US11898764B2

## CPC

- F24F 11/36: to leakage of heat-exchange fluid
- F25B 49/005: {of safety devices (F25B49/02 and F25B49/04 take precedence)}
- F24F 11/84: using valves
- F24F 11/86: by controlling compressors within refrigeration or heat pump circuits
- F25B 1/00: Compression machines, plants or systems with non-reversible cycle (F25B3/00, F25B5/00, F25B6/00, F25B7/00, F25B9/00 take precedence)
- G01M 3/26: by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors
- F24F 2140/12: Heat-exchange fluid pressure
- F24F 2140/20: Heat-exchange fluid temperature
- F25B 2500/222: Detecting refrigerant leaks
- F24F: AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING (removing dirt or fumes from areas where they are produced B08B15/00; vertical ducts for carrying away waste gases from buildings E04F17/02; tops for chimneys or ventilating shafts, terminals for flues F23L17/02)
- F25B: REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR

## Abstract

An HVAC system includes a high-pressure subsystem and a low-pressure subsystem. After determining that refrigerant leak diagnostics should be performed, a controllable valve is closed between a condenser and compressor of the HVAC system. The compressor then operates until a predetermined input refrigerant pressure is reached. After the predetermined input refrigerant pressure is reached, operation of the compressor is stopped. After stopping operation of the compressor and waiting at least a predetermined wait time, the pressure in the low-pressure subsystem of the HVAC system is monitored. A rate of change of the pressure in the low-pressure subsystem is determined. If the rate of change is negative and a magnitude of the rate of change is greater than a threshold value, a leak location is determined to be in the low-pressure subsystem.

## Claims

### Claim 1

A heating, ventilation, and air conditioning (HVAC) system, the HVAC system comprising:
a high-pressure subsystem comprising:
a condenser operable to receive refrigerant and transfer heat from the refrigerant to a flow of outdoor air, thereby generating a cooled refrigerant; and
a controllable valve positioned in a refrigerant conduit connecting the condenser to an evaporator; and
a low-pressure subsystem comprising:
the evaporator operable to receive the cooled refrigerant and transfer heat from a flow of air to the cooled refrigerant;
a compressor operable to compress the refrigerant; and
a pressure sensor operable to measure a refrigerant pressure in the low-pressure subsystem; and
a controller communicatively coupled to the pressure sensor, and the controllable valve, wherein the controller comprises a processor configured to:
close the controllable valve;
cause the compressor to operate until a particular refrigerant pressure is reached;
after the particular refrigerant pressure is reached, stop operation of the compressor;
after stopping operation of the compressor and waiting at least a particular wait time, monitor the refrigerant pressure in the low-pressure subsystem of the HVAC system for a period of time;
determine a rate of change of the refrigerant pressure in the low-pressure subsystem for the period of time;
if the rate of change is negative and a magnitude of the rate of change is greater than a threshold value, determine that a leak location of the refrigerant is in the low-pressure subsystem of the HVAC system; and
if one or both of the rate of change is not negative and the magnitude of the rate of change is not greater than a threshold value, determine that the leak location of the refrigerant is in the high-pressure subsystem of the HVAC system.

### Claim 2 (depends on 1)

The HVAC system of claim 1, wherein the HVAC system further comprises:
a first sensor positioned and configured to measure a saturation temperature of the refrigerant in the evaporator; and
a second sensor positioned and configured to measure a superheated vapor temperature of the refrigerant in the evaporator; and
the controller is further configured to detect a possible leak of the refrigerant by:
determining a superheat value based on a difference between the saturation temperature and the superheated vapor temperature; and
determining that both the saturation temperature is less than a corresponding threshold value and the superheat value is greater than a corresponding threshold value.

### Claim 3 (depends on 1)

The HVAC system of claim 1, wherein the processor is further configured to:
determine a system diagnosis comprising the leak location; and
cause the system diagnosis to be provided to a service provider associated with the HVAC system.

### Claim 4 (depends on 1)

The HVAC system of claim 1, wherein the processor is further configured to:
determine a system diagnosis comprising the leak location; and
cause the system diagnosis to be displayed on a thermostat associated with the HVAC system.

### Claim 5 (depends on 1)

The HVAC system of claim 1, wherein the processor is further configured to cause display of a mode indication on a thermostat of the HVAC system indicating that the HVAC system is operating in a diagnostic mode.

### Claim 6 (depends on 1)

The HVAC system of claim 1, further comprising:
a blower operable, when functioning as intended, to provide the flow of air across the evaporator;
wherein the controller is further communicatively coupled to the blower and configured to:
determine a blower status indicating whether the blower is operating as intended; and
determine a system diagnosis comprising the leak location and the blower status.

### Claim 7 (depends on 1)

The HVAC system of claim 1, further comprising:
an air filter positioned and configured to filter the flow of air before the flow of air reaches the evaporator;
an air filter sensor operable to measure a change in air pressure across the air filter;
wherein the controller is further communicatively coupled to the filter sensor and configured to:
detect a blockage of the air filter based on the change in air pressure across the air filter; and
determine a system diagnosis comprising the leak location and an indication of the detected blockage of the air filter.

### Claim 8 (depends on 1)

The HVAC system of claim 1, wherein the HVAC system further comprises a check valve positioned proximate an output of the compressor and configured to prevent the refrigerant from flowing into the outlet of the compressor after operation of the compressor is stopped.

### Claim 9

A method of operating a heating, ventilation, and air conditioning (HVAC) system, the method comprising:
closing a controllable valve of the HVAC system, wherein the controllable valve is positioned in a refrigerant conduit connecting a condenser to an evaporator;
causing a compressor of the HVAC system to operate until a particular refrigerant pressure is reached;
after the predetermined refrigerant pressure is reached, causing the compressor to stop operating;
after stopping operation of the compressor and waiting at least a particular wait time, monitoring a refrigerant pressure in a low-pressure subsystem of the HVAC system for a period of time;
determining a rate of change of the refrigerant pressure in the low-pressure subsystem for the period of time;
if the rate of change is negative and a magnitude of the rate of change is greater than a threshold value, determining that a leak location of the refrigerant is in the low-pressure subsystem of the HVAC system; and
if one or both of the rate of change is not negative and the magnitude of the rate of change is not greater than a threshold value, determining that the leak location of the refrigerant is in a high-pressure subsystem of the HVAC system.

### Claim 10 (depends on 9)

The method of claim 9, further comprising detecting a possible leak of refrigerant from the HVAC system by:
receiving a saturation temperature determined by a first sensor positioned and configured to measure the saturation temperature of the refrigerant in the evaporator;
receiving a superheated vapor temperature determined by a second sensor positioned and configured to measure the superheated vapor temperature of the refrigerant in the evaporator;
determining a superheat value based on a difference between the saturation temperature and the superheated vapor temperature; and
determining that both the saturation temperature is less than a corresponding threshold value and the superheat value is greater than a corresponding threshold value.

### Claim 11 (depends on 9)

The method of claim 9, further comprising:
determining a system diagnosis comprising the leak location; and
causing the system diagnosis to be provided to a service provider associated with the HVAC system.

### Claim 12 (depends on 9)

The method of claim 9, further comprising:
determining a system diagnosis comprising the leak location; and
causing the system diagnosis to be displayed on a thermostat associated with the HVAC system.

### Claim 13 (depends on 9)

The method of claim 9, further comprising causing display of a mode indication on a thermostat of the HVAC system indicating that the HVAC system is operating in a diagnostic mode.

### Claim 14 (depends on 9)

The method of claim 9, further comprising:
determining a blower status indicating whether a blower of the HVAC system is operating as intended; and
determining a system diagnosis comprising the leak location and the blower status.

### Claim 15 (depends on 9)

The method of claim 9, further comprising:
detecting a blockage of an air filter of the HVAC system based on a change in air pressure across the air filter; and
determining a system diagnosis comprising the leak location and an indication of the detected blockage of the air filter.

### Claim 16

A controller of a heating, ventilation, and air conditioning (HVAC) system, the controller comprising:
an input/output interface configured to communicate with:
a compressor of the HVAC system;
a controllable valve positioned in a refrigerant conduit connecting a condenser of the HVAC system to an evaporator of the HVAC system; and
a pressure sensor operable to measure a refrigerant pressure in a low-pressure subsystem of the HVAC system; and
a processor communicatively coupled to the input/output interface and configured to:
close the controllable valve;
cause the compressor to operate until a particular refrigerant pressure is reached;
after the particular refrigerant pressure is reached, stop operation of the compressor;
after stopping operation of the compressor and waiting at least a particular wait time, monitor the refrigerant pressure in the low-pressure subsystem of the HVAC system for a period of time;
determine a rate of change of the refrigerant pressure in the low-pressure subsystem for the period of time;
if the rate of change is negative and a magnitude of the rate of change is greater than a threshold value, determine that a leak location of the refrigerant is in the low-pressure subsystem of the HVAC system; and
if one or both of the rate of change is not negative and the magnitude of the rate of change is not greater than a threshold value, determine that the leak location of the refrigerant is in a high-pressure subsystem of the HVAC system.

### Claim 17 (depends on 16)

The controller of claim 16, wherein:
the processor is further configured to detect a possible leak of the refrigerant by:
determining a superheat value based on a difference between a saturation temperature of refrigerant in the evaporator and a superheated vapor temperature of refrigerant in the evaporator; and
determining that both the saturation temperature is less than a corresponding threshold value and the superheat value is greater than a corresponding threshold value.

### Claim 18 (depends on 16)

The controller of claim 16, wherein the processor is further configured to:
determine a system diagnosis comprising the leak location; and
cause the system diagnosis to be provided to a service provider associated with the HVAC system.

### Claim 19 (depends on 16)

The controller of claim 16, wherein the processor is further configured to cause display of a mode indication on a thermostat of the HVAC system indicating that the HVAC system is operating in a diagnostic mode.

### Claim 20 (depends on 16)

The controller of claim 16, wherein:
the input/output interface is further configured to communicate with an air filter sensor operable to measure a change in air pressure across an air filter positioned and configured to filter a flow of air before the flow of air reaches the evaporator; and
the processor is further configured to:
detect a blockage of the air filter based on the change in air pressure across the air filter; and
determine a system diagnosis comprising the leak location and an indication of the detected blockage of the air filter.