US20200355418A1 - Method and system to vary suction temperature to postpone frost formation - Google Patents
Method and system to vary suction temperature to postpone frost formation Download PDFInfo
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- US20200355418A1 US20200355418A1 US16/406,431 US201916406431A US2020355418A1 US 20200355418 A1 US20200355418 A1 US 20200355418A1 US 201916406431 A US201916406431 A US 201916406431A US 2020355418 A1 US2020355418 A1 US 2020355418A1
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- Prior art keywords
- evaporator coil
- hvac
- sensor
- temperature
- compressor
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- A—HUMAN NECESSITIES
- A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
- A47F—SPECIAL FURNITURE, FITTINGS, OR ACCESSORIES FOR SHOPS, STOREHOUSES, BARS, RESTAURANTS OR THE LIKE; PAYING COUNTERS
- A47F3/00—Show cases or show cabinets
- A47F3/04—Show cases or show cabinets air-conditioned, refrigerated
- A47F3/0478—Control or safety arrangements
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- F25B41/043—
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B41/00—Fluid-circulation arrangements
- F25B41/20—Disposition of valves, e.g. of on-off valves or flow control valves
- F25B41/22—Disposition of valves, e.g. of on-off valves or flow control valves between evaporator and compressor
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B47/00—Arrangements for preventing or removing deposits or corrosion, not provided for in another subclass
- F25B47/006—Arrangements for preventing or removing deposits or corrosion, not provided for in another subclass for preventing frost
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B47/00—Arrangements for preventing or removing deposits or corrosion, not provided for in another subclass
- F25B47/02—Defrosting cycles
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2600/00—Control issues
- F25B2600/02—Compressor control
- F25B2600/025—Compressor control by controlling speed
- F25B2600/0251—Compressor control by controlling speed with on-off operation
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2600/00—Control issues
- F25B2600/02—Compressor control
- F25B2600/025—Compressor control by controlling speed
- F25B2600/0253—Compressor control by controlling speed with variable speed
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2600/00—Control issues
- F25B2600/25—Control of valves
- F25B2600/2513—Expansion valves
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2600/00—Control issues
- F25B2600/25—Control of valves
- F25B2600/2525—Pressure relief valves
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2700/00—Sensing or detecting of parameters; Sensors therefor
- F25B2700/21—Temperatures
- F25B2700/2104—Temperatures of an indoor room or compartment
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2700/00—Sensing or detecting of parameters; Sensors therefor
- F25B2700/21—Temperatures
- F25B2700/2117—Temperatures of an evaporator
- F25B2700/21171—Temperatures of an evaporator of the fluid cooled by the evaporator
- F25B2700/21173—Temperatures of an evaporator of the fluid cooled by the evaporator at the outlet
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2700/00—Sensing or detecting of parameters; Sensors therefor
- F25B2700/21—Temperatures
- F25B2700/2117—Temperatures of an evaporator
- F25B2700/21174—Temperatures of an evaporator of the refrigerant at the inlet of the evaporator
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2700/00—Sensing or detecting of parameters; Sensors therefor
- F25B2700/21—Temperatures
- F25B2700/2117—Temperatures of an evaporator
- F25B2700/21175—Temperatures of an evaporator of the refrigerant at the outlet of the evaporator
Definitions
- the present disclosure relates generally to refrigerated display cases and more particularly, but not by way of limitation to refrigerated display cases that vary saturated suction temperature in order to delay frost formation.
- Refrigerated display cases that are capable of refrigerating contents are common features in many retail outlets.
- Refrigerated display cases often include a fan that circulates refrigerated air over contents of the refrigerated display case.
- Such display cases require periodic defrosting.
- Frost formation will often occur quickly after completion of a defrost cycle. Frost formation leads to diminished efficiency of an evaporator coil. Additionally, frost formation interferes with an air curtain on the display cases allowing increased infiltration of warmer ambient air and leading to elevated product temperatures.
- the cooling system includes an evaporator coil and a compressor fluidly coupled to the evaporator coil.
- a circulation fan is arranged to direct air through the evaporator coil and through a discharge air duct into a conditioned space.
- At least one sensor is disposed in at least one of the discharge air duct, the conditioned space, and the evaporator coil.
- An HVAC controller is electrically coupled to the at least one sensor and electrically coupled to the compressor.
- the HVAC controller is configured to receive a measurement of an HVAC parameter from the at least one sensor, determine if the HVAC parameter indicates frost formation on the evaporator coil, and, responsive to a determination that the HVAC parameter indicates frost formation on the evaporator coil, raise a saturated suction temperature of the evaporator coil.
- Various aspects of the disclosure relate to a method for operating a refrigerated display case.
- the method includes measuring, by at least one sensor, an HVAC parameter.
- An HVAC controller electrically coupled to the at least one sensor, determines if the HVAC parameter indicates frost formation on an evaporator coil. Responsive to a determination that the HVAC parameter indicates frost formation on the evaporator coil, by the HVAC controller signals an evaporator pressure regulator (“EPR”) to reduce a flow of refrigerant from an evaporator coil to a compressor thereby raising a saturated suction temperature of the evaporator coil.
- EPR evaporator pressure regulator
- Various aspects of the disclosure relate to a method for operating a refrigerated display case.
- the method includes measuring, by at least one sensor, an HVAC parameter.
- An HVAC controller electrically coupled to the at least one sensor, determines if the HVAC parameter indicates frost formation on an evaporator coil. Responsive to a determination that the HVAC parameter indicates frost formation on the evaporator coil, signaling, by the HVAC controller, a compressor to modulate a speed of the compressor thereby raising a saturated suction temperature of the evaporator coil.
- FIG. 1 is a schematic diagram of a cooling system according to aspects of the disclosure
- FIG. 2 is a flow diagram illustrating a process for operating a refrigerated display case utilizing the cooling system of FIG. 1 ;
- FIG. 3 is a flow diagram illustrating an alternative process for operating a refrigerated display case utilizing the cooling system of FIG. 1
- FIG. 4 is a graph of time versus discharge air temperature utilizing existing display cases
- FIG. 5 is a graph of time versus discharge air temperature utilizing the cooling system of FIG. 1 ;
- FIG. 6 is a diagram of product temperature utilizing existing cooling systems
- FIG. 7 is a diagram of product temperature utilizing the cooling system of FIG. 1 ;
- FIG. 8 is a graph of discharge air temperature versus time comparing existing cooling systems to the cooling system of FIG. 1 .
- FIG. 1 is a schematic diagram of a cooling system 100 .
- the cooling system 100 includes an evaporator coil 102 , a condenser coil 104 , a compressor 106 , and a metering device 108 .
- a circulation fan 110 circulates air around the evaporator coil 102 .
- the compressor 106 is, for example, a single-stage compressor, a multi-stage compressor, a single-speed compressor, or a multi-speed compressor.
- the circulation fan 110 may, in various embodiments, be configured to operate at different capacities (i.e., variable motor speeds) to circulate air through the cooling system 100 , whereby the circulated air is conditioned and supplied to a conditioned space 112 .
- the metering device 108 is, for example, a thermostatic expansion valve or a throttling valve.
- the evaporator coil 102 is fluidly coupled to the compressor 106 via a suction line 114 .
- the compressor 106 is fluidly coupled to the condenser coil 104 via a discharge line 116 .
- the condenser coil 104 is fluidly coupled to the metering device 108 via a liquid line 118 .
- low-temperature refrigerant is circulated through the evaporator coil 102 .
- the refrigerant is initially in a liquid/vapor state.
- the refrigerant is, for example, R-22, R-134a, R-410A, R-744, or any other suitable type of refrigerant as dictated by design requirements.
- Air from within the conditioned space 112 which is typically warmer than the refrigerant, is circulated around the evaporator coil 102 by the circulation fan 110 .
- the refrigerant begins to boil after absorbing heat from the air and changes state to a low-pressure, low-temperature, super-heated vapor refrigerant.
- Saturated vapor, saturated liquid, and saturated fluid refer to a thermodynamic state where a liquid and its vapor exist in approximate equilibrium with each other.
- Super-heated ,fluid and super-heated vapor refer to a thermodynamic state where a vapor is heated above a saturation temperature of the vapor.
- Sub-cooled fluid and sub-cooled liquid refers to a thermodynamic state where a liquid is cooled below the saturation temperature of the liquid.
- the low-pressure, low-temperature, super-heated vapor refrigerant is introduced into the compressor 106 via the suction line 114 .
- the compressor 106 increases the pressure of the low-pressure, low-temperature, super-heated vapor refrigerant and, by operation of the ideal gas law, also increases the temperature of the low-pressure, low-temperature, super-heated vapor refrigerant to form a high-pressure, high-temperature, superheated vapor refrigerant.
- the high-pressure, high-temperature, superheated vapor refrigerant leaves the compressor 106 via the discharge line 116 and enters the condenser coil 104 .
- outside air is circulated around the condenser coil 104 by a condenser fan 120 .
- the outside air is typically cooler than the high-pressure, high-temperature, superheated vapor refrigerant present in the condenser coil 104 .
- heat is transferred from the high-pressure, high-temperature, superheated vapor refrigerant to the outside air.
- Removal of heat from the high-pressure, high-temperature, superheated vapor refrigerant causes the high-pressure, high-temperature, superheated vapor refrigerant to condense and change from a vapor state to a high-pressure, high-temperature, sub-cooled liquid state.
- the high-pressure, high-temperature, sub-cooled liquid refrigerant leaves the condenser coil 104 via the liquid line 118 and enters the metering device 108 .
- the pressure of the high-pressure, high-temperature, sub-cooled liquid refrigerant is abruptly reduced.
- the metering device 108 is, for example, a thermostatic expansion valve
- the metering device 108 reduces the pressure of the high-pressure, high-temperature, sub-cooled liquid refrigerant by regulating an amount of refrigerant that travels to the evaporator coil 102 .
- an evaporator pressure regulator (“EPR”) 122 is disposed in the suction line 114 between the evaporator coil 102 and the compressor 106 .
- the EPR 122 is an electronically-actuated valve such as, for example, a solenoid valve; however, in other embodiments, other valve types could be utilized.
- the EPR 122 is electrically coupled to an HVAC controller 130 , via a wired or wireless connection, such that, during operation, the HVAC controller 130 signals the ERR 122 to actuate between an open position and a closed position responsive to a measured HVAC parameter.
- actuation of the EPR 122 is not limited to a fully-opened state and a fully-closed state.
- the EPR 122 may be actuated to an intermediate position that is between the fully-opened state and the fully-closed state. Closure of the EPR 122 reduces a flow of refrigerant between the evaporator coil 102 and the compressor 106 thereby causing refrigerant pressure within the evaporator coil 102 to rise while causing refrigerant pressure at a suction side 132 of the compressor 106 to fall.
- a first temperature sensor 124 is disposed within the evaporator coil 102 .
- the first temperature sensor 124 may be, for example, a thermocouple, a thermometer, a thermostat, or any other appropriate temperature sensor.
- the first temperature sensor 124 is electrically coupled to the HVAC controller 130 and measures a refrigerant temperature within the evaporator coil 102 (also known as the “saturated suction temperature”).
- the first temperature sensor 124 may be disposed on an exterior surface of the evaporator coil 102 thereby using an evaporator coil 102 surface temperature as a proxy measurement for the saturated suction temperature.
- a second temperature sensor 126 is disposed within the conditioned space 112 and is electrically coupled to the HVAC controller 130 .
- the second temperature sensor 126 may be, for example, a thermocouple, a thermometer, a thermostat, or any other appropriate temperature sensor.
- the second temperature sensor 126 is positioned near a discharge air duct 134 so as to measure discharge air temperature; however, in other embodiments, the second temperature sensor 126 may be positioned at any location within the conditioned space 112 so as to accurately measure discharge air temperature.
- a flow meter 128 is positioned in the discharge air duct 134 and electrically coupled to the EIVAC controller 130 .
- the flow meter 128 measures a velocity of air discharged from the discharge air duct 134 .
- the flow meter 128 could be, for example, a rotor-type flow meter or any other type of flow meter.
- only one of the first temperature sensor 124 , the second temperature sensor 126 , and the flow meter 128 may be utilized in operation.
- any two of the first temperature sensor 124 , the second temperature sensor 126 , and the flow meter 128 could be omitted.
- the first temperature sensor 124 , the second temperature sensor 126 , and the flow meter 128 are electrically coupled to the HVAC controller 130 via, for example, a wired or a wireless connection.
- the HVAC controller 130 receives measurements of the HVAC parameter.
- the HVAC parameter could be at least one of, for example, a saturated suction temperature, measured by the first temperature sensor 124 , a discharge air temperature, measured by the second temperature sensor 126 , or a discharge air velocity, measured by the flow meter 128 . If the HVAC controller 130 detects a change in the HVAC parameter that is indicative of frost formation, the HVAC controller 130 signals the EPR 122 to restrict flow of refrigerant from the evaporator coil 102 to the compressor 106 . That is, the HVAC controller 130 signals the EPR 122 to move closer to the fully-closed position.
- conditions of the HVAC parameter that could be indicative of frost formation include, for example, a saturated suction temperature measured by the first temperature sensor 124 to be below a pre-determined minimum threshold, an increase in discharge air temperature measured by the second temperature sensor 126 , or a decrease in discharge air velocity measured by the flow meter 128 .
- a saturated suction temperature measured by the first temperature sensor 124 to be below a pre-determined minimum threshold
- an increase in discharge air temperature measured by the second temperature sensor 126 or a decrease in discharge air velocity measured by the flow meter 128 .
- the ERR 122 could be omitted.
- the HVAC controller 130 receives measurements of the HVAC parameter. If the HVAC controller 130 detects a change in the HVAC parameter that is indicative of frost formation, the HVAC controller 130 modulates a speed of the compressor 106 .
- the modulation may include adjusting the speed of the compressor 106 to a value between a maximum-rated speed and a minimum-rated speed.
- the modulation may include cycling the compressor 106 between an activated state and a deactivated state. Modulation of the speed of the compressor 106 impacts the saturated suction temperature such that the saturated suction temperature can be lowered by either deactivating the compressor 106 or reducing a speed of the compressor 106 .
- FIG. 2 is a flow diagram illustrating a process 200 for operating a refrigerated display case utilizing the cooling system 100 .
- the process 200 begins at step 201 .
- a defrost cycle is completed.
- the HVAC controller 130 receives a measurement of the HVAC parameter.
- the HVAC parameter could he at least one of, for example, a saturated suction temperature, measured by the first temperature sensor 124 , a discharge air temperature, measured by the second temperature sensor 126 , or a discharge air velocity, measured by the flow meter 128 .
- the HVAC controller 130 determines if the HVAC parameter indicates frost formation.
- conditions of the HVAC parameter that could be indicative of frost formation include, for example, a saturated suction temperature measured by the first temperature sensor 124 to be below a pre-determined minimum threshold, an increase in discharge air temperature measured by the second temperature sensor 126 , or a decrease in discharge air velocity measured by the flow meter 128 . If, at step 206 , the HVAC controller 130 determines that the HVAC parameter indicates frost formation, the process 200 proceeds to step 208 . If, at step 206 , the HVAC controller 130 determines that the HVAC parameter does not indicate frost formation, the process 200 returns to step 204 .
- the HVAC controller 130 signals the EPR 122 to restrict flow of refrigerant from the evaporator coil 102 to the compressor 106 . That is, the HVAC controller 130 signals the EPR 122 to move closer to the fully-closed position. Following step 208 , the process 200 returns to step 204 .
- FIG. 3 is a flow diagram illustrating an alternative process 300 for operating a refrigerated display case utilizing the cooling system 100 .
- the process 300 begins at step 301 .
- a defrost cycle is completed.
- the HVAC controller 130 receives a measurement of the HVAC parameter.
- the HVAC controller 130 determines if the HVAC parameter indicates frost formation.
- conditions of the HVAC parameter that could be indicative of frost formation include, for example, a saturated suction temperature measured by the first temperature sensor 124 to he below a pre-determined minimum threshold, an increase in discharge air temperature measured by the second temperature sensor 126 , or a decrease in discharge air velocity measured by the flow meter 128 .
- the process 300 proceeds to step 308 . If, at step 306 , the HVAC controller 130 determines that the HVAC parameter indicates frost formation, the process 300 proceeds to step 308 . If, at step 306 , the HVAC controller 130 determines that the HVAC parameter does not indicate frost formation, the process 300 returns to step 304 . At step 308 , responsive to a determination that the HVAC parameter indicates frost formation, the FIVAC controller 130 modulates a speed of the compressor 106 . In embodiments, where the compressor 106 is a variable-speed compressor, the modulation may include adjusting the speed of the compressor 106 to a value between a maximum-rated speed and a minimum-rated speed.
- the modulation may include cycling the compressor 106 between an activated state and a deactivated state. Modulation of the speed of the compressor 106 impacts the saturated suction temperature such that the saturated suction temperature can be lowered by either deactivating the compressor 106 or reducing a speed of the compressor 106 . Following step 308 , the process 300 returns to step 304 .
- FIG. 4 is a graph of time versus discharge air temperature utilizing existing display cases.
- FIG. 5 is a graph of time versus discharge air temperature utilizing the cooling system 100 .
- existing display cases exhibit an average saturated suction temperature of 22° F.
- display cases utilizing the cooling system 100 exhibit a saturated suction temperature of 23° F.
- FIG. 5 illustrates that the display case utilizing the cooling system 100 also exhibits a lower product temperature.
- FIG. 6 is a diagram of product temperature utilizing existing cooling systems.
- FIG. 7 is a diagram of product temperature utilizing the cooling system 100 .
- display case certification determined by, for example, NSF International, requires that an average product temperature not exceed 41° F. and a maximum product temperature not exceed 43° F.
- FIG. 6 illustrates that existing display cases could exceed NSF standards at many locations within the existing display case.
- FIG. 7 illustrates that display cases utilizing the cooling system 100 exhibit lower product temperatures that are compliant with NSF standards at all locations within the display case.
- FIG. 8 is a graph of discharge air temperature versus time comparing existing cooling systems to the cooling system 100 .
- Line 802 illustrates discharge air temperature of an existing cooling system.
- the existing cooling system is defrosted.
- Line 802 illustrates that, approximately two hours following completion of a defrost cycle, the discharge air temperature begins to rise, which is indicative of frost formation.
- line 806 illustrates discharge air temperature of the cooling system 100 .
- the cooling system 100 is defrosted. Following completion of the defrost cycle, the line 806 illustrates that the discharge air temperature continues to fall, which indicates that frost formation has been delayed.
- substantially is defined as largely but not necessarily wholly what is specified (and includes what is specified; e.g., substantially 90 degrees includes 90 degrees and substantially parallel includes parallel), as understood by a person of ordinary skill in the art.
- the terms “substantially,” “approximately,” “generally,” and “about” may be substituted with “within a percentage of” what is specified.
Abstract
Description
- The present disclosure relates generally to refrigerated display cases and more particularly, but not by way of limitation to refrigerated display cases that vary saturated suction temperature in order to delay frost formation.
- This section provides background information to facilitate a better understanding of the various aspects of the disclosure. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art.
- Display cases that are capable of refrigerating contents are common features in many retail outlets. Refrigerated display cases often include a fan that circulates refrigerated air over contents of the refrigerated display case. Such display cases require periodic defrosting. Frost formation will often occur quickly after completion of a defrost cycle. Frost formation leads to diminished efficiency of an evaporator coil. Additionally, frost formation interferes with an air curtain on the display cases allowing increased infiltration of warmer ambient air and leading to elevated product temperatures.
- Various aspects of the disclosure relate to a cooling system. The cooling system includes an evaporator coil and a compressor fluidly coupled to the evaporator coil. A circulation fan is arranged to direct air through the evaporator coil and through a discharge air duct into a conditioned space. At least one sensor is disposed in at least one of the discharge air duct, the conditioned space, and the evaporator coil. An HVAC controller is electrically coupled to the at least one sensor and electrically coupled to the compressor. The HVAC controller is configured to receive a measurement of an HVAC parameter from the at least one sensor, determine if the HVAC parameter indicates frost formation on the evaporator coil, and, responsive to a determination that the HVAC parameter indicates frost formation on the evaporator coil, raise a saturated suction temperature of the evaporator coil.
- Various aspects of the disclosure relate to a method for operating a refrigerated display case. The method includes measuring, by at least one sensor, an HVAC parameter. An HVAC controller, electrically coupled to the at least one sensor, determines if the HVAC parameter indicates frost formation on an evaporator coil. Responsive to a determination that the HVAC parameter indicates frost formation on the evaporator coil, by the HVAC controller signals an evaporator pressure regulator (“EPR”) to reduce a flow of refrigerant from an evaporator coil to a compressor thereby raising a saturated suction temperature of the evaporator coil.
- Various aspects of the disclosure relate to a method for operating a refrigerated display case. The method includes measuring, by at least one sensor, an HVAC parameter. An HVAC controller, electrically coupled to the at least one sensor, determines if the HVAC parameter indicates frost formation on an evaporator coil. Responsive to a determination that the HVAC parameter indicates frost formation on the evaporator coil, signaling, by the HVAC controller, a compressor to modulate a speed of the compressor thereby raising a saturated suction temperature of the evaporator coil.
- This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of claimed subject matter.
- The disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or reduced for clarity of discussion.
-
FIG. 1 is a schematic diagram of a cooling system according to aspects of the disclosure; -
FIG. 2 is a flow diagram illustrating a process for operating a refrigerated display case utilizing the cooling system ofFIG. 1 ; -
FIG. 3 is a flow diagram illustrating an alternative process for operating a refrigerated display case utilizing the cooling system ofFIG. 1 -
FIG. 4 is a graph of time versus discharge air temperature utilizing existing display cases; -
FIG. 5 is a graph of time versus discharge air temperature utilizing the cooling system ofFIG. 1 ; -
FIG. 6 is a diagram of product temperature utilizing existing cooling systems; -
FIG. 7 is a diagram of product temperature utilizing the cooling system ofFIG. 1 ; and -
FIG. 8 is a graph of discharge air temperature versus time comparing existing cooling systems to the cooling system ofFIG. 1 . - Various embodiments will now be described more fully with reference to the accompanying drawings. The disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.
-
FIG. 1 is a schematic diagram of acooling system 100. Thecooling system 100 includes anevaporator coil 102, acondenser coil 104, acompressor 106, and ametering device 108. During operation, acirculation fan 110 circulates air around theevaporator coil 102. In various embodiments, thecompressor 106 is, for example, a single-stage compressor, a multi-stage compressor, a single-speed compressor, or a multi-speed compressor. Thecirculation fan 110, sometimes referred to as a blower, may, in various embodiments, be configured to operate at different capacities (i.e., variable motor speeds) to circulate air through thecooling system 100, whereby the circulated air is conditioned and supplied to a conditionedspace 112. In a typical embodiment, themetering device 108 is, for example, a thermostatic expansion valve or a throttling valve. Theevaporator coil 102 is fluidly coupled to thecompressor 106 via asuction line 114. Thecompressor 106 is fluidly coupled to thecondenser coil 104 via adischarge line 116. Thecondenser coil 104 is fluidly coupled to themetering device 108 via aliquid line 118. - Still referring to
FIG. 1 , during operation, to pressure, low-temperature refrigerant is circulated through theevaporator coil 102. The refrigerant is initially in a liquid/vapor state. In a typical embodiment, the refrigerant is, for example, R-22, R-134a, R-410A, R-744, or any other suitable type of refrigerant as dictated by design requirements. Air from within the conditionedspace 112, which is typically warmer than the refrigerant, is circulated around theevaporator coil 102 by thecirculation fan 110. In a typical embodiment, the refrigerant begins to boil after absorbing heat from the air and changes state to a low-pressure, low-temperature, super-heated vapor refrigerant. Saturated vapor, saturated liquid, and saturated fluid refer to a thermodynamic state where a liquid and its vapor exist in approximate equilibrium with each other. Super-heated ,fluid and super-heated vapor refer to a thermodynamic state where a vapor is heated above a saturation temperature of the vapor. Sub-cooled fluid and sub-cooled liquid refers to a thermodynamic state where a liquid is cooled below the saturation temperature of the liquid. - The low-pressure, low-temperature, super-heated vapor refrigerant is introduced into the
compressor 106 via thesuction line 114. in a typical embodiment, thecompressor 106 increases the pressure of the low-pressure, low-temperature, super-heated vapor refrigerant and, by operation of the ideal gas law, also increases the temperature of the low-pressure, low-temperature, super-heated vapor refrigerant to form a high-pressure, high-temperature, superheated vapor refrigerant. The high-pressure, high-temperature, superheated vapor refrigerant leaves thecompressor 106 via thedischarge line 116 and enters thecondenser coil 104. - Still referring to
FIG. 1 , outside air is circulated around thecondenser coil 104 by acondenser fan 120. The outside air is typically cooler than the high-pressure, high-temperature, superheated vapor refrigerant present in thecondenser coil 104. Thus, heat is transferred from the high-pressure, high-temperature, superheated vapor refrigerant to the outside air. Removal of heat from the high-pressure, high-temperature, superheated vapor refrigerant causes the high-pressure, high-temperature, superheated vapor refrigerant to condense and change from a vapor state to a high-pressure, high-temperature, sub-cooled liquid state. The high-pressure, high-temperature, sub-cooled liquid refrigerant leaves thecondenser coil 104 via theliquid line 118 and enters themetering device 108. - In the
metering device 108, the pressure of the high-pressure, high-temperature, sub-cooled liquid refrigerant is abruptly reduced. In various embodiments where themetering device 108 is, for example, a thermostatic expansion valve, themetering device 108 reduces the pressure of the high-pressure, high-temperature, sub-cooled liquid refrigerant by regulating an amount of refrigerant that travels to theevaporator coil 102. Abrupt reduction of the pressure of the high-pressure, high-temperature, sub-cooled liquid refrigerant causes sudden, rapid, evaporation of a portion of the high-pressure, high-temperature, sub-cooled liquid refrigerant, commonly known as “flash evaporation.” The flash evaporation lowers the temperature of the resulting liquid/vapor refrigerant mixture to a temperature lower than a temperature of the air in the conditionedspace 112. The liquid/vapor refrigerant mixture leaves themetering device 108 and returns to theevaporator coil 102. - Still referring to
FIG. 1 , an evaporator pressure regulator (“EPR”) 122 is disposed in thesuction line 114 between theevaporator coil 102 and thecompressor 106. In various embodiments, theEPR 122 is an electronically-actuated valve such as, for example, a solenoid valve; however, in other embodiments, other valve types could be utilized. TheEPR 122 is electrically coupled to anHVAC controller 130, via a wired or wireless connection, such that, during operation, theHVAC controller 130 signals theERR 122 to actuate between an open position and a closed position responsive to a measured HVAC parameter. In various embodiments, actuation of theEPR 122 is not limited to a fully-opened state and a fully-closed state. That is, in various embodiments, theEPR 122 may be actuated to an intermediate position that is between the fully-opened state and the fully-closed state. Closure of theEPR 122 reduces a flow of refrigerant between theevaporator coil 102 and thecompressor 106 thereby causing refrigerant pressure within theevaporator coil 102 to rise while causing refrigerant pressure at asuction side 132 of thecompressor 106 to fall. - Still referring to
FIG. 1 , afirst temperature sensor 124 is disposed within theevaporator coil 102. In various embodiments, thefirst temperature sensor 124 may be, for example, a thermocouple, a thermometer, a thermostat, or any other appropriate temperature sensor. Thefirst temperature sensor 124 is electrically coupled to theHVAC controller 130 and measures a refrigerant temperature within the evaporator coil 102 (also known as the “saturated suction temperature”). In other embodiments, however, thefirst temperature sensor 124 may be disposed on an exterior surface of theevaporator coil 102 thereby using anevaporator coil 102 surface temperature as a proxy measurement for the saturated suction temperature. Asecond temperature sensor 126 is disposed within the conditionedspace 112 and is electrically coupled to theHVAC controller 130. In various embodiments, thesecond temperature sensor 126 may be, for example, a thermocouple, a thermometer, a thermostat, or any other appropriate temperature sensor. In various embodiments, thesecond temperature sensor 126 is positioned near adischarge air duct 134 so as to measure discharge air temperature; however, in other embodiments, thesecond temperature sensor 126 may be positioned at any location within the conditionedspace 112 so as to accurately measure discharge air temperature. Aflow meter 128 is positioned in thedischarge air duct 134 and electrically coupled to theEIVAC controller 130. In various embodiments, theflow meter 128 measures a velocity of air discharged from thedischarge air duct 134. In various embodiments, theflow meter 128 could be, for example, a rotor-type flow meter or any other type of flow meter. In various embodiments, only one of thefirst temperature sensor 124, thesecond temperature sensor 126, and theflow meter 128 may be utilized in operation. Thus, in various embodiments, any two of thefirst temperature sensor 124, thesecond temperature sensor 126, and theflow meter 128 could be omitted. In various embodiments, thefirst temperature sensor 124, thesecond temperature sensor 126, and theflow meter 128 are electrically coupled to theHVAC controller 130 via, for example, a wired or a wireless connection. - Still referring to
FIG. 1 , during operation, theHVAC controller 130 receives measurements of the HVAC parameter. In various embodiments, the HVAC parameter could be at least one of, for example, a saturated suction temperature, measured by thefirst temperature sensor 124, a discharge air temperature, measured by thesecond temperature sensor 126, or a discharge air velocity, measured by theflow meter 128. If theHVAC controller 130 detects a change in the HVAC parameter that is indicative of frost formation, theHVAC controller 130 signals theEPR 122 to restrict flow of refrigerant from theevaporator coil 102 to thecompressor 106. That is, theHVAC controller 130 signals theEPR 122 to move closer to the fully-closed position. In various embodiments, conditions of the HVAC parameter that could be indicative of frost formation include, for example, a saturated suction temperature measured by thefirst temperature sensor 124 to be below a pre-determined minimum threshold, an increase in discharge air temperature measured by thesecond temperature sensor 126, or a decrease in discharge air velocity measured by theflow meter 128. Restriction, by theEPR 122, of refrigerant flow between theevaporator coil 102 and thecompressor 106 results in the saturated suction temperature rising and frost formation being delayed. - Still referring to
FIG. 1 , in other embodiments, theERR 122 could be omitted. In such an embodiment, theHVAC controller 130 receives measurements of the HVAC parameter. If theHVAC controller 130 detects a change in the HVAC parameter that is indicative of frost formation, theHVAC controller 130 modulates a speed of thecompressor 106. In embodiments, where thecompressor 106 is a variable-speed compressor, the modulation may include adjusting the speed of thecompressor 106 to a value between a maximum-rated speed and a minimum-rated speed. In embodiments where thecompressor 106 is a fixed-speed compressor, the modulation may include cycling thecompressor 106 between an activated state and a deactivated state. Modulation of the speed of thecompressor 106 impacts the saturated suction temperature such that the saturated suction temperature can be lowered by either deactivating thecompressor 106 or reducing a speed of thecompressor 106. -
FIG. 2 is a flow diagram illustrating aprocess 200 for operating a refrigerated display case utilizing thecooling system 100. Theprocess 200 begins atstep 201. Atstep 202, a defrost cycle is completed. Atstep 204, theHVAC controller 130 receives a measurement of the HVAC parameter. In various embodiments, the HVAC parameter could he at least one of, for example, a saturated suction temperature, measured by thefirst temperature sensor 124, a discharge air temperature, measured by thesecond temperature sensor 126, or a discharge air velocity, measured by theflow meter 128. Atstep 206, theHVAC controller 130 determines if the HVAC parameter indicates frost formation. In various embodiments, conditions of the HVAC parameter that could be indicative of frost formation include, for example, a saturated suction temperature measured by thefirst temperature sensor 124 to be below a pre-determined minimum threshold, an increase in discharge air temperature measured by thesecond temperature sensor 126, or a decrease in discharge air velocity measured by theflow meter 128. If, atstep 206, theHVAC controller 130 determines that the HVAC parameter indicates frost formation, theprocess 200 proceeds to step 208. If, atstep 206, theHVAC controller 130 determines that the HVAC parameter does not indicate frost formation, theprocess 200 returns to step 204. Atstep 208, responsive to a determination that the HVAC parameter indicates frost formation, theHVAC controller 130 signals theEPR 122 to restrict flow of refrigerant from theevaporator coil 102 to thecompressor 106. That is, theHVAC controller 130 signals theEPR 122 to move closer to the fully-closed position. Followingstep 208, theprocess 200 returns to step 204. -
FIG. 3 is a flow diagram illustrating analternative process 300 for operating a refrigerated display case utilizing thecooling system 100. Theprocess 300 begins atstep 301. Atstep 302, a defrost cycle is completed. Atstep 304, theHVAC controller 130 receives a measurement of the HVAC parameter. Atstep 306, theHVAC controller 130 determines if the HVAC parameter indicates frost formation. In various embodiments, conditions of the HVAC parameter that could be indicative of frost formation include, for example, a saturated suction temperature measured by thefirst temperature sensor 124 to he below a pre-determined minimum threshold, an increase in discharge air temperature measured by thesecond temperature sensor 126, or a decrease in discharge air velocity measured by theflow meter 128. If, atstep 306, theHVAC controller 130 determines that the HVAC parameter indicates frost formation, theprocess 300 proceeds to step 308. If, atstep 306, theHVAC controller 130 determines that the HVAC parameter does not indicate frost formation, theprocess 300 returns to step 304. Atstep 308, responsive to a determination that the HVAC parameter indicates frost formation, theFIVAC controller 130 modulates a speed of thecompressor 106. In embodiments, where thecompressor 106 is a variable-speed compressor, the modulation may include adjusting the speed of thecompressor 106 to a value between a maximum-rated speed and a minimum-rated speed. In embodiments where thecompressor 106 is a fixed-speed compressor, the modulation may include cycling thecompressor 106 between an activated state and a deactivated state. Modulation of the speed of thecompressor 106 impacts the saturated suction temperature such that the saturated suction temperature can be lowered by either deactivating thecompressor 106 or reducing a speed of thecompressor 106. Followingstep 308, theprocess 300 returns to step 304. -
FIG. 4 is a graph of time versus discharge air temperature utilizing existing display cases.FIG. 5 is a graph of time versus discharge air temperature utilizing thecooling system 100. As illustrated inFIG. 4 , existing display cases exhibit an average saturated suction temperature of 22° F. while, as illustrated inFIG. 5 , display cases utilizing thecooling system 100 exhibit a saturated suction temperature of 23° F. While the display case utilizing thecooling system 100 exhibits a higher saturated suction temperature,FIG. 5 illustrates that the display case utilizing thecooling system 100 also exhibits a lower product temperature. -
FIG. 6 is a diagram of product temperature utilizing existing cooling systems.FIG. 7 is a diagram of product temperature utilizing thecooling system 100. Referring toFIGS. 6-7 collectively, display case certification determined by, for example, NSF International, requires that an average product temperature not exceed 41° F. and a maximum product temperature not exceed 43° F.FIG. 6 illustrates that existing display cases could exceed NSF standards at many locations within the existing display case. In contrast,FIG. 7 illustrates that display cases utilizing thecooling system 100 exhibit lower product temperatures that are compliant with NSF standards at all locations within the display case. -
FIG. 8 is a graph of discharge air temperature versus time comparing existing cooling systems to thecooling system 100.Line 802 illustrates discharge air temperature of an existing cooling system. In region 804, the existing cooling system is defrosted.Line 802 illustrates that, approximately two hours following completion of a defrost cycle, the discharge air temperature begins to rise, which is indicative of frost formation. In comparison,line 806 illustrates discharge air temperature of thecooling system 100. In the region 804, thecooling system 100 is defrosted. Following completion of the defrost cycle, theline 806 illustrates that the discharge air temperature continues to fall, which indicates that frost formation has been delayed. - The term “substantially” is defined as largely but not necessarily wholly what is specified (and includes what is specified; e.g., substantially 90 degrees includes 90 degrees and substantially parallel includes parallel), as understood by a person of ordinary skill in the art. In any disclosed embodiment, the terms “substantially,” “approximately,” “generally,” and “about” may be substituted with “within a percentage of” what is specified.
- Conditional language used herein, such as, among others, “can,” “might,” “may,” “e.g.,” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or states are included or are to be performed in any particular embodiment.
- While the above detailed description has shown, described, and pointed out novel features as applied to various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the devices or algorithms illustrated can be made without departing from the spirit of the disclosure. As will be recognized, the processes described herein can be embodied within a form that does not provide all of the features and benefits set forth herein, as some features can be used or practiced separately from others. The scope of protection is defined by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.
Claims (20)
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
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US16/406,431 US20200355418A1 (en) | 2019-05-08 | 2019-05-08 | Method and system to vary suction temperature to postpone frost formation |
CA3048557A CA3048557A1 (en) | 2019-05-08 | 2019-07-04 | Method and system to vary suction temperature to postpone frost formation |
US17/699,298 US20220202208A1 (en) | 2019-05-08 | 2022-03-21 | Method and system to vary suction temperature to postpone frost formation |
Applications Claiming Priority (1)
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US16/406,431 US20200355418A1 (en) | 2019-05-08 | 2019-05-08 | Method and system to vary suction temperature to postpone frost formation |
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US17/699,298 Division US20220202208A1 (en) | 2019-05-08 | 2022-03-21 | Method and system to vary suction temperature to postpone frost formation |
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US20200355418A1 true US20200355418A1 (en) | 2020-11-12 |
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US16/406,431 Abandoned US20200355418A1 (en) | 2019-05-08 | 2019-05-08 | Method and system to vary suction temperature to postpone frost formation |
US17/699,298 Pending US20220202208A1 (en) | 2019-05-08 | 2022-03-21 | Method and system to vary suction temperature to postpone frost formation |
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US17/699,298 Pending US20220202208A1 (en) | 2019-05-08 | 2022-03-21 | Method and system to vary suction temperature to postpone frost formation |
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Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20220186997A1 (en) * | 2020-12-16 | 2022-06-16 | Lennox Industries Inc. | Method and a system for preventing a freeze event using refrigerant temperature |
US20220268456A1 (en) * | 2021-02-22 | 2022-08-25 | Lennox Industries Inc. | Preventing evaporator coil freeze during re-heat dehumidification |
US11781793B2 (en) | 2020-12-16 | 2023-10-10 | Lennox Industries Inc. | Control systems and methods for preventing evaporator coil freeze |
Family Cites Families (7)
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JPH08494B2 (en) * | 1991-04-26 | 1996-01-10 | 株式会社ゼクセル | Compressor capacity control device for vehicle air conditioner |
US5970726A (en) * | 1997-04-08 | 1999-10-26 | Heatcraft Inc. | Defrost control for space cooling system |
US7080521B2 (en) * | 2004-08-31 | 2006-07-25 | Thermo King Corporation | Mobile refrigeration system and control |
EP2122274B1 (en) * | 2007-02-15 | 2017-10-11 | Carrier Corporation | Pulse width modulation with reduced suction pressure to improve efficiency |
US9528745B2 (en) * | 2011-07-12 | 2016-12-27 | Maersk Line A/S | Reducing or avoiding ice formation in an intermittently operated cooling unit |
CA2948193A1 (en) * | 2014-05-15 | 2015-11-19 | Emerson Electric Co. | Hvac system air filter diagnostics and monitoring |
WO2018078809A1 (en) * | 2016-10-28 | 2018-05-03 | 三菱電機株式会社 | Refrigeration cycle device |
-
2019
- 2019-05-08 US US16/406,431 patent/US20200355418A1/en not_active Abandoned
- 2019-07-04 CA CA3048557A patent/CA3048557A1/en active Pending
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2022
- 2022-03-21 US US17/699,298 patent/US20220202208A1/en active Pending
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20220186997A1 (en) * | 2020-12-16 | 2022-06-16 | Lennox Industries Inc. | Method and a system for preventing a freeze event using refrigerant temperature |
US11709004B2 (en) * | 2020-12-16 | 2023-07-25 | Lennox Industries Inc. | Method and a system for preventing a freeze event using refrigerant temperature |
US11781793B2 (en) | 2020-12-16 | 2023-10-10 | Lennox Industries Inc. | Control systems and methods for preventing evaporator coil freeze |
US20220268456A1 (en) * | 2021-02-22 | 2022-08-25 | Lennox Industries Inc. | Preventing evaporator coil freeze during re-heat dehumidification |
US11561015B2 (en) * | 2021-02-22 | 2023-01-24 | Lennox Industries Inc. | Preventing evaporator coil freeze during re-heat dehumidification |
US11927362B2 (en) | 2021-02-22 | 2024-03-12 | Lennox Industries Inc. | Preventing evaporator coil freeze during re-heat dehumidification |
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US20220202208A1 (en) | 2022-06-30 |
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