# US 7,610,765 B2 · Refrigerant charge status indication method and device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,610,765 B2 - Document ID: US7610765B2 - Status: Granted - Kind: B2 - Application number: 11/025,836 - Filed: 2004-12-27 - Published: 2006-06-29 - Granted: 2009-11-03 - Earliest claimed: 2004-12-27 - Assignees: Carrier Corporation - Inventors: Pengju Kang; Alan M. Finn; Sivakumar Gopalnarayanan; Dong Luo; Timothy P. Galante - Web page: https://patentgrep.com/patent/US7610765B2 ## CPC - F25B 45/00: Arrangements for charging or discharging refrigerant - F25B 49/005: {of safety devices (F25B49/02 and F25B49/04 take precedence)} - F25B 2345/001: Charging refrigerant to a cycle - F25B 2700/04: Refrigerant level - F25B 2700/2106: of fresh outdoor air - F25B 2700/21163: of the refrigerant at the outlet of the condenser - F25B: REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS ## Abstract A method and apparatus for determining the sufficiency of the refrigerant charge in an air conditioning system by use of temperature measurements. The temperature of the liquid refrigerant leaving the condenser coil and the outdoor temperature are sensed and representative electrical signals are generated. The electrical signals are converted to digital values that are than compared to predetermined optimal values to determine whether the system is properly charged with refrigerant. An appropriate LED is lighted to indicate that the system is undercharged, overcharged or properly charged. For non-TXV/EXV systems a third parameter i.e. the return air wet bulb temperature is also sensed and a representative digital value thereof is included in the comparison with the predetermined known values to determine if the charge is proper. ## Claims ### Claim 1 A method of determining the sufficiency of refrigerant charge in an air conditioning system having a compressor, a condenser coil, an expansion device and an evaporator coil connected in serial refrigerant flow relationship, comprising the steps of: sensing the temperature of the refrigerant leaving the condenser coil and generating a first electrical signal representative thereof; sensing the outdoor temperature and generating a second electrical signal representative thereof; converting said first and second electrical signals to first and second digital values; and comparing said first and second digital values to obtain an approach temperature difference; and comparing said approach temperature difference with predetermined optimal values to determine whether a proper refrigerant charge condition exists. ### Claim 2 (depends on 1) A method as set forth in claim 1 wherein said outdoor temperature is sensed by a standalone temperature sensor and said second electrical signal is generated by a variable device which is selectively adjustable as a function of the sensed outdoor temperature. ### Claim 3 (depends on 1) A method as set forth in claim 1 wherein said step of comparing said first and second digital values is accomplished by way of a computer. ### Claim 4 (depends on 1) A method as set forth in claim 1 wherein said predetermined optimal values are empirically determined for a particular air conditioning system. ### Claim 5 (depends on 1) A method as set forth in claim 1 wherein said predetermined optimal values are stored in a ROM. ### Claim 6 (depends on 1) A method as set forth in claim 1 and including the further steps of: sensing an indoor air wet bulb temperature and generating a third electrical signal representative thereof; and converting said third electrical signal to a third digital value and including said third digital value with said approach temperature difference to be compared with said predetermined optimal values. ### Claim 7 (depends on 6) A method as set forth in claim 6 wherein said indoor air wet bulb temperature is sensed by a standalone sensor and said third electrical signal is generated by way of selective adjustment of a variable device. ### Claim 8 (depends on 1) A method as set forth in claim 1 and including the further step of providing a visual indication of said refrigerant charge condition. ### Claim 9 (depends on 8) A method as set forth in claim 8 wherein said visual indication is by way of selectively lighting one of a plurality of LEDs. ### Claim 10 Apparatus for determining the sufficiency of refrigerant charge in an air conditioning system having a compressor, condenser coil, an expansion device and an evaporator coil interconnected in serial refrigerant flow relationship comprising: a temperature sensor for sensing the temperature of the liquid refrigerant leaving the condenser; a first signal generator for generating an electrical signal representative of said sensed liquid refrigerant temperature; a second signal generator for generating a second electrical signal representative of a sensed outdoor temperature; an analog-to-digital converter for converting said first and second electrical signals to first and second digital values, respectively; a first comparator for comparing said first and second digital values to obtain an approach temperature difference; and a second comparator for comparing said approach temperature difference with predetermined optimal values to determine whether a proper refrigerant charge condition exists. ### Claim 11 (depends on 10) Apparatus as set forth in claim 10 wherein said second signal generator comprises a variable resistance device which is selectively adjusted to generate an electrical signal that is representative of a sensed outdoor temperature. ### Claim 12 (depends on 10) Apparatus as set forth in claim 10 wherein said comparing means is a computer. ### Claim 13 (depends on 10) Apparatus as set forth in claim 10 wherein said predetermined optimal values are empirically determined for a particular air conditioning system. ### Claim 14 (depends on 10) Apparatus as set forth in claim 10 wherein said predetermined optimal values are stored in a ROM. ### Claim 15 (depends on 10) Apparatus as set forth in claim 10 and including a third signal generator for generating a third electrical signal representative of indoor wet bulb temperature. ### Claim 16 (depends on 15) Apparatus as set forth in claim 15 wherein said third electrical signal is converted to a third digital value by said analog-to-digital converter. ### Claim 17 (depends on 16) Apparatus as set forth in claim 16 wherein said comparing means includes said third digital value with said first and second digital values to be compared with said optimal values.