# US 10,309,679 B2 · Method of and system for minimization of condenser-fan cycling for low ambient temperature > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,309,679 B2 - Document ID: US10309679B2 - Status: Granted - Kind: B2 - Application number: 15/909,159 - Filed: 2018-03-01 - Published: 2018-07-05 - Granted: 2019-06-04 - Earliest claimed: 2016-02-04 - Assignees: Lennox Industries Inc. - Applicants: Lennox Industries LLC - Inventors: Siddarth Rajan; John Tran, N.; Rakesh Goel; Clay Toombs - Web page: https://patentgrep.com/patent/US10309679B2 ## CPC - F24F 11/83: by controlling the supply of heat-exchange fluids to heat-exchangers - F24F 1/38: Fan details of outdoor units, e.g. bell-mouth shaped inlets or fan mountings - F24F 11/30: for purposes related to the operation of the system, e.g. for safety or monitoring - F25B 49/022: {Compressor control arrangements} - F25B 49/027: {Condenser control arrangements} - F24F 11/85: using variable-flow pumps - F24F 2110/00: Control inputs relating to air properties - F24F 2110/12: of the outside air - F25B 2500/19: Calculation of parameters - F25B 2500/31: Low ambient temperatures - F25B 2600/0253: with variable speed - F25B 2600/111: of condenser fans - F25B 2700/195: of the condenser - F25B 2700/2106: of fresh outdoor air - Y02B 30/70: Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating - 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 - Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS ## Abstract A method of controlling a heating, ventilation and air-conditioning (HVAC) system includes measuring an ambient temperature and determining whether the ambient temperature is below a threshold temperature value. Responsive to a determination that the ambient temperature is below the threshold temperature value, measuring a condenser-fan cycle time of the HVAC system and setting a speed of the compressor based on the measured condenser-fan cycle time. ## Claims ### Claim 1 A method of controlling a heating, ventilation and air-conditioning (HVAC) system, the method comprising: measuring an ambient temperature; determining whether the ambient temperature is below a threshold temperature value; responsive to a determination that the ambient temperature is below the threshold temperature value, determining whether a condenser-fan cycle time is greater than a first threshold time; and responsive to a determination that the condenser-fan cycle time is greater than the first threshold time, setting a speed of a compressor to operate at a demand speed. ### Claim 2 (depends on 1) The method of claim 1, wherein the condenser-fan cycle time is an average of at least two measured condenser-fan cycle times. ### Claim 3 (depends on 1) The method of claim 1, further comprising: responsive to a determination that the condenser-fan cycle time is below the first threshold time, determining whether the condenser-fan cycle time is below a second threshold time; and responsive to a determination that the condenser-fan cycle time is below the second threshold time, setting the compressor to operate at a low operating speed for a desired runtime. ### Claim 4 (depends on 3) The method of claim 3, wherein the low operating speed comprises operating the compressor at an operating speed between about 22 Hz and about 30 Hz. ### Claim 5 (depends on 4) The method of claim 4, wherein the desired runtime is a multiple of the condenser-fan cycle time. ### Claim 6 (depends on 3) The method of claim 3, further comprising: responsive to a determination that the condenser-fan cycle time is below the first threshold time and above the second threshold time, setting the compressor to operate at a speed between a high operating speed and the low operating speed for the desired runtime. ### Claim 7 (depends on 6) The method of claim 6, wherein the high operating speed comprises operating the compressor at an operating speed between about 50 Hz and about 64 Hz. ### Claim 8 (depends on 1) The method of claim 1, wherein the measuring is performed via a temperature sensor. ### Claim 9 (depends on 1) The method of claim 1, wherein the determining and setting steps are performed by a controller associated with the HVAC system. ### Claim 10 (depends on 1) The method of claim 1, wherein the condenser-fan cycle time comprises time elapsed between occurrences of a liquid pressure of a refrigerant reaching a maximum acceptable liquid pressure. ### Claim 11 (depends on 10) The method of claim 10, wherein a pressure sensor is tripped responsive to the liquid pressure of the refrigerant reaching the maximum acceptable liquid pressure. ### Claim 12 (depends on 1) The method of claim 1, wherein a temperature of a refrigerant of the HVAC system is monitored to calculate a pressure of the refrigerant. ### Claim 13 A heating, ventilation, and air-conditioning (HVAC) system comprising: a controller configured to: receive an ambient temperature of an area surrounding an outdoor unit of the HVAC system; determine whether the ambient temperature is below a threshold temperature value; responsive to a determination that the ambient temperature is below the threshold temperature value, determine whether a condenser-fan cycle time is greater than a first threshold time; and responsive to a determination that the condenser-fan cycle time is greater than the first threshold time, set a speed of a compressor to operate at a demand speed. ### Claim 14 (depends on 13) The system of claim 13, wherein the controller is further configured to: responsive to a determination that the condenser-fan cycle time is below the first threshold time, determine if the condenser-fan cycle time is below a second threshold time; and responsive to a determination that the condenser-fan cycle time is below the second threshold time, set the compressor to operate at a low operating speed for a desired runtime. ### Claim 15 (depends on 13) The system of claim 13, wherein the low operating speed comprises operating the compressor at an operating speed between about 22 Hz and about 30 Hz. ### Claim 16 (depends on 14) The system of claim 14, wherein the controller is further configured to: responsive to a determination that the condenser-fan cycle time is below the first threshold time and above the second threshold time, set the compressor to operate at a speed that is between a high operating speed and the low operating speed for the desired runtime. ### Claim 17 (depends on 16) The system of claim 16, wherein the high operating speed comprises operating the compressor at an operating speed between about 50 Hz and about 64 Hz. ### Claim 18 (depends on 13) The system of claim 13, further comprising an indoor unit, the indoor unit comprising the controller. ### Claim 19 (depends on 18) The system of claim 18, wherein the outdoor unit is in fluid and electronic communication with the indoor unit, the outdoor unit comprising: the compressor, wherein the compressor is fluidly coupled to an evaporator coil of the indoor unit; a condenser coil fluidly coupled to the compressor to receive a compressed refrigerant from the compressor, a condenser fan disposed in proximity to the condenser coil and adapted to direct ambient air around the condenser coil; a pressure sensor disposed downstream from the compressor and adapted to measure a liquid pressure of the compressed refrigerant; and an ambient air temperature sensor for measuring an ambient temperature of an area surrounding the outdoor unit.