Refrigerants, heat transfer compositions, and heat transfer systems and methods

Abstract

New non-flammable refrigerants having a GWP of less than 750, including R-32, R-125, R-134a, and R-1234yf, and new air conditioning systems (including heat pumps) using such refrigerants, and methods for retrofitting standard single-refrigerant vapor compression air conditioning systems using such refrigerants, particularly residential heat pumps and residential split direct expansion air conditioning systems.

Description

[Technical Field]

[0001] (cross reference) This application claims the benefit of priority to and incorporates by reference U.S. Provisional Application Nos. 63 / 421,136, filed October 31, 2022, and 63 / 412,193, filed September 30, 2022, respectively.

[0002] FIELD OF THE INVENTION The present invention relates to highly efficient, low global warming potential ("low GWP"), non-flammable refrigerants, and air conditioning and / or refrigeration systems and methods for providing safe and effective cooling or heating, including refrigerants and refrigeration / air conditioning systems and methods that have exceptional performance as replacements and retrofits for R-410A in air conditioning, particularly R-410A in split direct expansion systems. [Background technology]

[0003] The refrigeration industry is increasingly under pressure, through regulatory changes and otherwise, to replace high global warming potential (GWP) refrigerants, such as R410A, with low-GWP refrigerants. Under many current and future proposed regulations, refrigerants must have a GWP of less than 750. The use of refrigerants with GWP values ​​less than 750 is particularly important in residential air conditioning systems, where the potential negative environmental impacts are significant if refrigerants with substantially higher GWPs are used. The high-GWP refrigerant R-410A, with a GWP of 2088, is frequently used in residential air conditioning systems.

[0004] One approach is to use low-GWP refrigerants, such as carbon dioxide (R744) and hydrocarbon refrigerants, in typical vapor compression systems. However, such approaches, as used to date, can suffer from significant safety and financial drawbacks, including increased operating costs due to low system energy efficiency, high initial system costs due to system complexity, high maintenance costs due to low system availability and reliability, and high system flammability. Systems with highly flammable refrigerants, as configured in conventional designs, are particularly disadvantageous because they can reduce safety levels, violate regulatory code constraints, and increase liability for refrigeration system operators and manufacturers. Safety is a particular concern when residential air conditioning applications operate in occupied spaces. Thus, while refrigerant R410A is non-flammable and therefore safe for use in homes (because the evaporator is located inside the home), it has the significant drawback of being a high-GWP refrigerant, i.e., having a GWP well above 750. However, many low-GWP refrigerants that have been proposed to replace R410A in such systems suffer from the same unfavorable characteristic of being flammable. Therefore, residential air conditioning systems using such proposed flammable fluids create the risk of a flammable atmosphere within the home in the event of a leak in the evaporator area.

[0005] EP 2367601 discloses a number of potential refrigerants as replacements for various existing refrigerants, including R-410A. Among the proposed refrigerants is a blend containing 50 wt% HFO-1234yf, 40 wt% HFC-32, 5 wt% HFC-125, and 5 wt% HFC-134a, which is disclosed to have a GWP of 519. While such a blend has a substantially lower GWP than R-410A, it has the significant drawback of not being non-flammable, i.e., not being a Class A1 refrigerant. EP 2367601 also discloses a possible refrigerant generally comprising 50 wt% HFO-1234yf, 5 wt% HFC-32, 7 wt% HFC-125%, and 38 wt% HFC-134a, but this blend has a GWP substantially greater than 750 and is therefore not a possible low GWP replacement for R-410A as described herein. Furthermore, this blend is not disclosed for use in any particular application.

[0006] Applicants have come to recognize that the residential air conditioning industry continues to need safe, robust, and sustainable solutions to reduce the use of high GWP refrigerants, particularly Class A1 refrigerants having a GWP of less than 750, and Applicants have addressed this need by developing novel refrigerants and novel air conditioning systems (including heat pumps) that use such refrigerants to provide a close capacity match to the use of R-410 in standard single refrigerant vapor compression air conditioning systems, including, particularly, residential heat pumps and residential split direct expansion air conditioning systems that can operate as heat pumps.

[0007] Applicants have discovered that certain refrigerant blends, including carefully selected combinations of components in specific concentrations, as described in detail below, can possess advantageous yet unexpected combinations of non-flammability, while simultaneously possessing, among other things, excellent heat transfer properties, low GWP (e.g., GWP less than about 750), low or no toxicity, and chemical stability. Additionally, Applicants have discovered that the refrigerant compositions of the present invention are particularly advantageous in split residential air conditioning systems (including residential heat pumps) and in connection with methods for retrofitting existing split direct expansion residential air conditioning systems (including, particularly, those having reversing valves that allow operation in heating mode) to create secondary loop air conditioning systems therefrom that achieve advantageous results using such new refrigerants.

[0008] These and other unmet needs in the prior art are met by the present invention, as described in detail herein. Summary of the Invention

[0009] Applicants have discovered refrigerant compositions, heat transfer compositions including refrigerants, heat transfer methods and systems, including residential air conditioning methods and systems, and methods for retrofitting existing residential heat pump systems.

[0010] Refrigerants of the present invention include refrigerants having a GWP of less than about 750, classified by ASHRAE as A1 (non-flammable and low toxicity), and preferably having an evaporator glide of less than about 0°C to 5°C.

[0011] The present invention comprises at least about 95% by weight of the following four components, based on all refrigerant components: (a) about 50.5 wt. % to about 52.5 wt. % HFO-1234yf; (b) about 35.5% to 41% by weight of HFC-134a; (c) 2.2% to 5.5% by weight of HFC-125, and (d) A refrigerant comprising 3.8% to about 8% by weight of HFC-32, said percentages being based on the sum of (a) through (d). The refrigerant according to this paragraph may be referred to herein for convenience as Refrigerant 1.

[0012] The present invention also provides about 50.5 wt.% to about 52.5 wt.% HFO-1234yf, about 35.5% to 41% by weight of HFC-134a; 2.2% to 5.5% by weight of HFC-125, and The refrigerant comprises from 3.8% to about 8% by weight of HFC-32. The refrigerant according to this paragraph may be referred to herein for convenience as Refrigerant 2.

[0013] The present invention also provides 51% to 52.5% by weight of HFO-1234yf, 35.8% by weight to 37.8% by weight of HFC-134a, 4.5% to 5.5% by weight of HFC-125, and The refrigerant consists essentially of 6% to 8% by weight of HFC-32. The refrigerant according to this paragraph may be referred to herein for convenience as Refrigerant 3A.

[0014] The present invention also provides 51% to 52.5% by weight of HFO-1234yf, 35.8% by weight to 37.8% by weight of HFC-134a, 4.5% to 5.5% by weight of HFC-125, and It contains a refrigerant consisting of 6% to 8% by weight of HFC-32.

[0015] The refrigerant according to this paragraph may be referred to herein for convenience as Refrigerant 3B. The present invention also provides 52 wt% +0.5 / -0.5 wt% HFO-1234yf, 39% by weight +0.5 / -0.5% by weight HFC-134a, 3% by weight + 0.3 / - 0.5% by weight HFC-125, and It contains a refrigerant consisting essentially of 6% + 0.5 / - 0.3% by weight HFC-32. The refrigerant according to this paragraph may be referred to herein for convenience as Refrigerant 3B.

[0016] The present invention also provides 52 wt% +0.5 / -0.5 wt% HFO-1234yf, 39% by weight + 0.5 / 0.5% by weight HFC-134a, 3% by weight + 0.3 / 0.5% by weight HFC-125, and It contains a refrigerant consisting of 6% by weight + 0.5 / - 0.3% by weight HFC-32. Refrigerants according to this paragraph may be referred to herein for convenience as Refrigerant 3C.

[0017] The present invention also provides 51.4 wt% +0.5 / -0.5 wt% HFO-1234yf, 40.4 wt% +0.5 / -0.5 wt% HFC-134a; 4.1 wt% +0.3 / -0.5 wt% HFC-125, and 4.1% by weight +0.5 / -0.3% by weight of a refrigerant consisting essentially of HFC-32. The refrigerant according to this paragraph may be referred to herein for convenience as Refrigerant 3D.

[0018] The present invention also provides 51.4 wt% +0.5 / -0.5 wt% HFO-1234yf, 40.4 wt% +0.5 / -0.5 wt% HFC-134a, 4.1 wt% +0.3 / -0.5 wt% HFC-125, and It contains a refrigerant consisting of 4.1% by weight + 0.5 / - 0.3% by weight HFC-32. The refrigerant according to this paragraph may be referred to herein for convenience as Refrigerant 3E.

[0019] The present invention also provides 51.3 wt% +0.5 / -0.5 wt% HFO-1234yf, 36% by weight +0.5 / -0.5% by weight HFC-134a, 5.2 wt% +0.3 / -0.5 wt% HFC-125, and It contains a refrigerant consisting essentially of 7.5% by weight +0.5 / -0.3% by weight HFC-32. Refrigerants according to this paragraph may be referred to herein for convenience as Refrigerant 3F.

[0020] The present invention also provides 51.3 wt% +0.5 / -0.5 wt% HFO-1234yf, 36% by weight +0.5 / -0.5% by weight HFC-134a, 5.2 wt% +0.3 / -0.5 wt% HFC-125, and It contains a refrigerant consisting of 7.5% by weight + 0.5 / - 0.3% by weight HFC-32. The refrigerant according to this paragraph may be referred to herein for convenience as Refrigerant 3G.

[0021] The present invention also provides 45% to 47% by weight of HFO-1234yf, 36% to 37% by weight of HFC-134a, 4.5% to 5.5% by weight of HFC-125, 7% to 8% by weight of HFC-32, and The refrigerant consists essentially of about 5% by weight HFO-1234ze(E). The refrigerant according to this paragraph may be referred to herein for convenience as Refrigerant 4A.

[0022] The present invention also provides approximately 46% by weight of HFO-1234yf; about 36.5% by weight of HFC-134a; about 5% by weight of HFC-125; about 7.5% by weight of HFC-32, and The refrigerant consists essentially of about 5% by weight HFO-1234ze(E). The refrigerant according to this paragraph may be referred to herein for convenience as Refrigerant 4B.

[0023] The present invention also provides 46 wt% +0.5 / -0.5 wt% HFO-1234yf, 36.5 wt% +0.5 / -0.5 wt% HFC-134a, 5% by weight + 0.3 / - 0.5% by weight HFC-125, 7.5% by weight + 0.5 / - 0.3% by weight HFC-32, and Contains a refrigerant consisting essentially of 5% by weight + 0.5 / - 0.5% by weight HFO-1234ze(E). Refrigerants according to this paragraph may be referred to herein for convenience as Refrigerant 4C.

[0024] The present invention also provides 46 wt% +0.5 / -0.5 wt% HFO-1234yf, 36.5 wt% +0.5 / -0.5 wt% HFC-134a, 5% by weight + 0.3 / - 0.5% by weight HFC-125, 7.5% by weight + 0.5 / - 0.3% by weight HFC-32, and It contains a refrigerant consisting of 5% by weight + 0.5 / - 0.5% by weight of HFO-1234ze(E). The refrigerant according to this paragraph may be referred to herein for convenience as refrigerant 4D.

[0025] The present invention also provides a refrigerant comprising at least about 95% by weight of all refrigerant components of the following four components: (a) about 50.5 wt. % to about 52.5 wt. % HFO-1234yf; (b) about 35.5% to 41% by weight of HFC-134a; (c) 2.2% to 5.5% by weight of HFC-125, and (d) providing a refrigerant comprising 3.8% to about 8% by weight of HFC-32, said percentage being based on the sum of (a) through (d), provided that the refrigerant has a GWP of less than 750 and is a Class A1 non-flammable refrigerant. The refrigerant according to this paragraph may be referred to herein for convenience as Refrigerant 5A.

[0026] The present invention also provides a refrigerant comprising at least about 95% by weight of all refrigerant components of the following four components: (a) about 50.5 wt. % to about 52.5 wt. % HFO-1234yf; (b) about 35.5% to 41% by weight of HFC-134a; (c) 2.2% to 5.5% by weight of HFC-125, and (d) providing a refrigerant comprising 3.8% to about 8% by weight of HFC-32, said percentage being based on the sum of (a) through (d), provided that the refrigerant has a GWP of less than 750, is a Class A1 non-flammable refrigerant, and has an evaporator glide of 0°C to about 5°C. The refrigerant according to this paragraph may be referred to herein for convenience as Refrigerant 5B.

[0027] The present invention provides a secondary loop air conditioning system for heating and / or cooling indoor air within a residence, comprising: (a) Indoor refrigerants with Class A1 flammability and a GWP of approximately 750 or less; an indoor heat exchanger for exchanging heat with the air inside the house; and a pumping chamber heat transfer circuit including a liquid pump for moving the indoor refrigerant in a liquid phase in the indoor circuit; (b) Outdoor refrigerant, a compressor for compressing the outdoor refrigerant in a gas phase; an expansion valve for reducing the pressure of the outdoor refrigerant in a liquid phase; and a vapor compression outdoor heat transfer circuit including an outdoor heat exchanger for exchanging heat with outdoor air; (c) an inter-circuit heat exchanger in which the indoor refrigerant exchanges heat with the outdoor refrigerant. The system according to this paragraph may be referred to herein as heat transfer system 1 for convenience.

[0028] The present invention provides a secondary loop air conditioning system for heating and / or cooling indoor air, comprising: (a) a heat transfer circuit within a pump pumping chamber, a. At least about 95% by weight based on all refrigerant components 1. about 50 wt% to about 52.5 wt% HFO-1234yf; 2. about 35.5% to about 41% by weight of HFC-134a; 3.2.2% to 5.5% by weight of HFC-125, and 4.3.8% to about 8% by weight of HFC-32 (the percentages are based on the sum of (1.) through (4.)); b. an indoor heat exchanger for absorbing heat from the indoor air in a cooling mode and for adding heat to the indoor air in a heating mode; c. a pumping chamber heat transfer circuit including a liquid pump for moving the indoor refrigerant in a liquid phase to the indoor heat exchanger; (b) A vapor compression chamber exterior heat transfer circuit, a. Outdoor refrigerant, b. A compressor for compressing the outdoor refrigerant in gas phase; c. an expansion valve for reducing the pressure of the outdoor refrigerant in the liquid phase; d. an outdoor heat exchanger for exchanging heat with outdoor air; and e. a vapor compression outdoor heat transfer circuit including a reversing valve connected to the outlet of the compressor and to the outdoor heat exchanger; (c) an inter-circuit heat exchanger in which the indoor refrigerant exchanges heat with the outdoor refrigerant, and the reversing valve directs the outdoor refrigerant vapor from the compressor to the inter-circuit heat exchanger or the outdoor heat exchanger. The system according to this paragraph may be referred to herein for convenience as heat transfer system 2.

[0029] The present invention provides a secondary loop air conditioning system for heating and / or cooling indoor air, comprising: (a) A pump chamber heat transfer circuit, a. A refrigerant 1. about 49% by weight of difluoromethane (HFC-32); 2. about 11.5% by weight of pentafluoroethane (HFC-125), and 3. A refrigerant consisting essentially of about 39.5% by weight trifluoroiodomethane (CF3I); b. an indoor heat exchanger for absorbing heat from the indoor air in a cooling mode and for adding heat to the indoor air in a heating mode; c. a pumping chamber heat transfer circuit including a liquid pump for moving the indoor refrigerant in a liquid phase to the indoor heat exchanger; (b) A vapor compression chamber exterior heat transfer circuit, a. Outdoor refrigerant, b. A compressor for compressing the outdoor refrigerant in gas phase; c. an expansion valve for reducing the pressure of the outdoor refrigerant in the liquid phase; d. an outdoor heat exchanger for exchanging heat with outdoor air; and e. a vapor compression outdoor heat transfer circuit including a reversing valve connected to the outlet of the compressor and to the outdoor heat exchanger; (c) an inter-circuit heat exchanger in which the indoor refrigerant exchanges heat with the outdoor refrigerant, and the reversing valve directs the outdoor refrigerant vapor from the compressor to the inter-circuit heat exchanger or the outdoor heat exchanger. The system according to this paragraph may be referred to herein for convenience as heat transfer system 3.

[0030] The present invention provides a method for providing heating and / or cooling to indoor air in a residence, comprising: (a) at least about 95% by weight, based on all refrigerant components, of the following components: a. about 50.5% by weight to about 52.5% by weight of HFO-1234yf; b. about 35.5% to 41% by weight of HFC-134a; c.2.2% to 5.5% by weight of HFC-125, and d. providing an indoor refrigerant comprising 3.8% to about 8% by weight of HFC-32, said percentage being based on the sum of a. through d.; (b) heating or cooling the indoor air by heat exchange with the indoor refrigerant. The method according to this paragraph may be referred to herein for convenience as Heat Transfer Method 1.

[0031] The present invention also provides a method of providing indoor air heating and / or cooling in a residence, comprising: (a) a. Indoor refrigerants with Class A1 flammability and a GWP of approximately 750 or less; b. An indoor heat exchanger for exchanging heat with the air inside the house; and c. providing an intra-pumping chamber heat transfer circuit including a liquid pump for moving the indoor refrigerant in liquid phase in the indoor circuit; (b) a. Outdoor refrigerant, b. A compressor for compressing the outdoor refrigerant in gas phase; c. an expansion valve for reducing the pressure of the outdoor refrigerant in the liquid phase; and d. providing a vapor compression outdoor heat transfer circuit including an outdoor heat exchanger for exchanging heat with outdoor air; (c) exchanging heat between the indoor refrigerant and the outdoor refrigerant. The method according to this paragraph may be referred to herein for convenience as Heat Transfer Method 2.

[0032] The present invention provides a method for providing heating and / or cooling to indoor air in a residence, comprising: (a) a. A refrigerant, 1. about 49% by weight of difluoromethane (HFC-32); 2. about 11.5% by weight of pentafluoroethane (HFC-125), and 3. A refrigerant consisting essentially of about 39.5% by weight trifluoroiodomethane (CF3I); b. an indoor heat exchanger for absorbing heat from the indoor air in a cooling mode and for adding heat to the indoor air in a heating mode; c. providing an internal pumping chamber heat transfer circuit including a liquid pump for moving the internal refrigerant in a liquid phase to the internal heat exchanger; (b) heating or cooling the indoor air by heat exchange with the indoor refrigerant. A system according to this paragraph may be referred to herein for convenience as Heat Transfer Method 3.

[0033] The present invention provides a method for retrofitting an existing residential heat pump air conditioning system that uses a vapor compression cycle having R410a as a refrigerant and a reversing valve to provide heating or cooling to indoor air within a residence, comprising: (a) a. Compressor, b. An outdoor heat exchanger for exchanging heat between outdoor air and the R410A refrigerant; c. An indoor heat exchanger for exchanging heat between indoor air and the R410A refrigerant; d. Reversing valves connected to the inlet and outlet of the compressor and to each of the outdoor heat exchanger and the indoor heat exchanger; e. providing an existing heat pump system comprising an expansion valve connected between the outdoor heat exchanger and the indoor heat exchanger; (b) isolating the indoor heat exchanger from the expansion valve and the reversing valve; (c) providing an intercircuit heat exchanger, connecting the intercircuit heat exchanger to the expansion valve and the reversing valve to provide a flow path for R410A refrigerant therethrough; (d) connecting the pump to each of the inter-circuit heat exchanger and the indoor coil to create a pumped secondary refrigerant loop comprising the indoor heat exchanger, the liquid pump, and the inter-circuit heat exchanger; (e) in said pumped secondary circuit an indoor refrigerant having at least about 95% by weight, based on all refrigerant components, of the following components: a. about 50.5% by weight to about 52.5% by weight of HFO-1234yf; b. about 35.5% to 41% by weight of HFC-134a; c.2.2% to 5.5% by weight of HFC-125, and and d. providing an indoor refrigerant comprising 3.8% to about 8% by weight of HFC-32, said percentages being based on the sum of a. through d. The method according to this paragraph may be referred to herein for convenience as Retrofit Method 1A.

[0034] The present invention provides a method for retrofitting an existing residential heat pump air conditioning system that uses a vapor compression cycle having R410a as a refrigerant and a reversing valve to provide heating or cooling to indoor air within a residence, comprising: (a) a. Compressor, b. An outdoor heat exchanger for exchanging heat between outdoor air and the R410A refrigerant; c. An indoor heat exchanger for exchanging heat between indoor air and the R410A refrigerant; d. Reversing valves connected to the inlet and outlet of the compressor and to each of the outdoor heat exchanger and the indoor heat exchanger; e. providing an existing heat pump system including fluid flow lines connecting said expansion valve to said indoor heat exchanger and connecting said indoor heat exchanger to said reversing valve; (b) disconnecting the indoor heat exchanger from the expansion valve and from the reversing valve; (c) providing an intercircuit heat exchanger and connecting the intercircuit heat exchanger to the expansion valve and the reversing valve using a substantial portion of the fluid flow line to provide a flow path for R410A refrigerant therethrough; (d) connecting the pump to each of the inter-circuit heat exchanger and the indoor coil to create a pumped secondary refrigerant loop comprising the indoor heat exchanger, the liquid pump, and the inter-circuit heat exchanger; (e) in said pumped secondary circuit an indoor refrigerant having at least about 95% by weight, based on all refrigerant components, of the following components: a. about 50.5% by weight to about 52.5% by weight of HFO-1234yf; b. about 35.5% to 41% by weight of HFC-134a; c. 2.2% to about 5.5% by weight of HFC-125, and and d. providing an indoor refrigerant comprising 3.8% to about 8% by weight of HFC-32, said percentages being based on the sum of a. through d. The method according to this paragraph may be referred to herein for convenience as Retrofit Method 1B.

[0035] The present invention provides a method for retrofitting an existing residential heat pump air conditioning system that uses a vapor compression cycle having R410a as a refrigerant and a reversing valve to provide heating or cooling to indoor air within a residence, comprising: (f) a. Compressor, b. An outdoor heat exchanger for exchanging heat between outdoor air and the R410A refrigerant; c. An indoor heat exchanger for exchanging heat between indoor air and the R410A refrigerant; d. Reversing valves connected to the inlet and outlet of the compressor and to each of the outdoor heat exchanger and the indoor heat exchanger; e. providing an existing heat pump system comprising an expansion valve connected between the outdoor heat exchanger and the indoor heat exchanger; (g) disconnecting the indoor heat exchanger from the expansion valve and from the reversing valve; (h) providing an intercircuit heat exchanger, connecting said intercircuit heat exchanger to said expansion valve and said reversing valve to provide a flow path for R410A refrigerant therethrough; (i) connecting the pump to each of the inter-circuit heat exchanger and the indoor coil to create a pumped secondary refrigerant loop comprising the indoor heat exchanger, a liquid pump, and the inter-circuit heat exchanger; (j) in said pumped secondary circuit at least about 95% by weight, based on all refrigerant components, of the following components: a. about 49% by weight HFC-32; b. about 11.5% by weight of HFC-125, and c. providing an indoor refrigerant comprising about 39.5% by weight of CF3I. The method according to this paragraph may be referred to herein as Retrofit Method 2 for convenience.

[0036] The present invention provides a method for retrofitting an existing residential heat pump air conditioning system that uses a vapor compression cycle having R410a as a refrigerant and a reversing valve to provide heating or cooling to indoor air within a residence, comprising: (a) a. Compressor, b. An outdoor heat exchanger for exchanging heat between outdoor air and the R410A refrigerant; c. An indoor heat exchanger for exchanging heat between indoor air and the R410A refrigerant; d. Reversing valves connected to the inlet and outlet of the compressor and to each of the outdoor heat exchanger and the indoor heat exchanger; e. providing an existing heat pump system comprising an expansion valve connected between the outdoor heat exchanger and the indoor heat exchanger; (b) isolating the indoor heat exchanger from the expansion valve and the reversing valve; (c) providing an intercircuit heat exchanger, connecting the intercircuit heat exchanger to the expansion valve and the reversing valve to provide a flow path for R410A refrigerant therethrough; (d) connecting the pump to each of the inter-circuit heat exchanger and the indoor coil to create a pumped secondary refrigerant loop comprising the indoor heat exchanger, the liquid pump, and the inter-circuit heat exchanger; (e) providing to the pumped secondary circuit an indoor refrigerant having Class A1 flammability and a GWP of about 750 or less. The method according to this paragraph may be referred to herein for convenience as Retrofit Method 2A.

[0037] The present invention provides a method for retrofitting an existing residential heat pump air conditioning system that uses a vapor compression cycle having R410a as a refrigerant and a reversing valve to provide heating or cooling to indoor air within a residence, comprising: (a) a. Compressor, b. An outdoor heat exchanger for exchanging heat between outdoor air and the R410A refrigerant; c. An indoor heat exchanger for exchanging heat between indoor air and the R410A refrigerant; d. Reversing valves connected to the inlet and outlet of the compressor and to each of the outdoor heat exchanger and the indoor heat exchanger; e. an expansion valve connected between the outdoor heat exchanger and the indoor heat exchanger; f. providing an existing heat pump system including fluid flow lines connecting said expansion valve to said indoor heat exchanger and connecting said indoor heat exchanger to said reversing valve; (b) isolating the indoor heat exchanger from the expansion valve and the reversing valve; (c) providing an intercircuit heat exchanger and connecting the intercircuit heat exchanger to the expansion valve and the reversing valve using a substantial portion of the fluid flow line to provide a flow path for R410A refrigerant therethrough; (d) connecting the pump to each of the inter-circuit heat exchanger and the indoor coil to create a pumped secondary refrigerant loop comprising the indoor heat exchanger, the liquid pump, and the inter-circuit heat exchanger; (e) providing to the pumped secondary circuit an indoor refrigerant having Class A1 flammability and a GWP of about 750 or less. The method according to this paragraph may be referred to herein for convenience as Retrofit Method 2B. [Brief explanation of the drawings]

[0038] [Figure 1A] 1 is a schematic diagram of an exemplary residential air conditioning system of the present invention in a cooling mode. [Figure 1B] 1 is a schematic diagram of an exemplary residential air conditioning system of the present invention in a heating mode. [Figure 2A] 1 is a schematic diagram of a typical residential heat pump system operating in cooling mode that is the subject of the retrofit method of the present invention. [Figure 2B] 1 is a schematic diagram of a typical residential heat pump system operating in heating mode that is the subject of the retrofit method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0039] Definition: The phrase "coefficient of performance" (hereinafter "COP") is a widely accepted measure of refrigerant performance that is particularly useful for expressing the relative thermodynamic efficiency of a refrigerant system in a specific heating or cooling cycle involving evaporation or condensation of the refrigerant. In refrigeration engineering, this term refers to the ratio of useful refrigeration or cooling capacity to the energy applied by the compressor during vapor compression, and thus to the ability of a given compressor to pump a quantity of heat for a given volumetric flow rate of a heat-transfer fluid, such as a refrigerant. In other words, given a specific compressor, a refrigerant with a higher COP will provide more cooling or heating power. One means for estimating the COP of a refrigerant at specific operating conditions is from the thermodynamic properties of the refrigerant using standard refrigeration cycle analysis techniques (see, for example, R.C. Downing, FLUOROCARBON REFRIGERANTS HANDBOOK, Chapter 3, Prentice-Hall, 1988, incorporated herein by reference in its entirety). The term "capacity" refers to the amount of cooling (BTU / hr) provided by the refrigerant in a refrigeration system. This is determined experimentally by multiplying the change in enthalpy in BTU / lb of the refrigerant as it passes through the evaporator by the mass flow rate of the refrigerant. Enthalpy can be determined from measurements of the refrigerant's pressure and temperature. The capacity of a refrigeration system relates to its ability to maintain a particular temperature in a cooled area. Refrigerant capacity represents the amount of cooling or heating the refrigerant provides and provides a measure of the compressor's ability to pump that amount of heat for a given volumetric flow rate of refrigerant. In other words, given a particular compressor, a refrigerant with a higher capacity will provide more cooling or heating power.

[0040] The phrase "global warming potential" (hereinafter "GWP") was developed to allow for comparison of the global warming impact of various gases. It compares the amount of heat trapped by a particular mass of gas with the amount of heat trapped by a similar mass of carbon dioxide over a particular period of time. Carbon dioxide was chosen by the Intergovernmental Panel on Climate Change (IPCC) as the standard gas, giving it a GWP of 1. The higher the GWP, the more a given gas will warm the Earth over that period of time compared to CO2. As used herein, the term GWP refers to the GWP value measured in accordance with the IPCC Fourth Assessment Report, 2014 (Note 1), referred to and abbreviated herein as AR4. Note 1: Myhre, G., D. Shindell, F.-M. Breon, W. Collins, J. Fuglestvedt, J. Huang, D. Koch, J.-F. Lamarque, D. Lee, B. Mendoza, T. Nakajima, A. Robock, G. Stephens, T. Takemura and H. Zhang, 2013: Anthropogenic and Natural Radiative Forcing. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. https: / / www.ipcc.ch / pdf / assessmentreport / ar4 / wg1 / WG1AR4_Chapter08_FINAL.pdf (p.73-79)

[0041] The term "non-flammable" refers to a compound or composition that is determined to be non-flammable in accordance with ASTM Standard E-681-2009 Standard Test Method for Concentration Limits of Flammability of Chemicals (Vapors and Gases), as determined under the conditions set forth in ASHRAE Standard 34-2016 Designation and Safety Classification of Refrigerants, and Appendix B1 to ASHRAE Standard 34-2016, each as in existence as of the filing date of this application, which are incorporated herein by reference in their entireties (the "Non-flammability Test"). Flammability is defined as the ability of a composition to ignite and / or spread a flame. Under this test, flammability is determined by measuring the flame angle. Non-combustible materials would be classified as Class "1" per ASHRAE Standard 34-2016 Designation and Safety Classification of Refrigerants test protocol defining conditions and equipment, using current method ASTM E681-09 annex A1 (as each standard exists as of the filing date of this application).

[0042] As used herein, the term "evaporator glide" means the difference between the saturation temperature of the refrigerant at the evaporator inlet and the dew point of the refrigerant at the evaporator outlet, assuming the pressure at the evaporator outlet is the same as the pressure at the inlet. As used herein, the phrase "saturation temperature" means the temperature at which liquid refrigerant boils to a vapor at a given pressure.

[0043] As used herein, the phrase "non-toxic or low-toxicity" means that the composition is classified as Class "A" by ASHRAE Standard 34-2016 Designation and Safety Classification of Refrigerants and is described in Appendix B1 of ASHRAE Standard 34-2016, as each standard exists as of the filing date of this application. A material that is non-flammable and low-toxicity is classified as "A1" by ASHRAE Standard 34-2016 Designation and Safety Classification of Refrigerants and is described in Appendix B1 of ASHRAE Standard 34-2016, as each standard exists as of the filing date of this application.

[0044] The term "superheat" or simply "superheat" refers to the temperature rise of the refrigerant at the outlet of the evaporator above the saturated vapor temperature (or dew point temperature) of the refrigerant.

[0045] As used herein, the term "E-1,3,3,3-tetrafluoropropene" means the trans isomer of HFO-1234ze and is abbreviated as HFO-1234ze(E).

[0046] As used herein, the term "2,3,3,3-tetrafluoropropene" is abbreviated as HFO-1234yf.

[0047] As used herein, the term "1,1,1,2-tetrafluoroethane" is known in the industry by the abbreviation HFC-134a and is abbreviated herein as HFC-134a. As used herein, the term "pentafluoroethane" is known in the industry by the abbreviation HFC-125 and is abbreviated herein as HFC-125.

[0048] As used herein, the term "difluoromethane" is known in the industry by the abbreviation HFC-32, and is abbreviated herein as HFC-32.

[0049] As used herein, the term "chlorodifluoromethane" is known in the industry by the abbreviation R-22 and is abbreviated herein as R-22.

[0050] As used herein, the term "trifluoroiodomethane" means CF3I and is abbreviated as CF3I.

[0051] As used herein, the term "residential air conditioning" refers to a refrigeration system that operates with a heat exchanger to absorb heat from or add heat to the indoor air within a structure inhabited by humans.

[0052] As used herein, the term "split direct expansion air conditioning system" refers to an air conditioning system that operates with an indoor unit located within a residence and including a heat exchanger that absorbs heat from or adds heat to the indoor air within the human-occupied structure, and an outdoor unit located outside the residence and including a heat exchanger that rejects heat to or absorbs heat from the outdoor air.

[0053] As used herein, the term "secondary loop air conditioning system" refers to an air conditioning system having an internal refrigeration circuit that uses an indoor (or secondary) refrigerant to heat and / or cool the internal air, and an external refrigeration circuit that uses an outdoor (or primary) refrigerant that, unlike the indoor refrigerant, rejects heat to or absorbs heat from the external air.

[0054] As used herein, the term "suction line" when used in connection with a secondary loop air conditioning system refers to the refrigerant flow path from the outlet of the intermediate heat exchanger to the inlet of the compressor.

[0055] As used herein, the term "liquid line" when used in connection with a secondary loop air conditioning system refers to the refrigerant flow path from the outlet of the condenser to the inlet of the intermediate heat exchanger.

[0056] As used herein, the term "R410A" means the refrigerant designated 410A by ASHRAE and consisting of 50% + 2 / - 2% R-32 and 50% + 2 / - 2% HFC-125.

[0057] As used herein, the term "R454B" means the refrigerant designated 454B by ASHRAE and consisting of 69.9% +2 / -2% R-32 and 31.1% +2 / -2% HFC-1234yf.

[0058] As used herein, the term "R466A" means the refrigerant designated as 466A by ASHRAE and consisting of 49% + 0.5 / - 2.0% R-32, 11.5% + 2.0 / - 0.5% HFC-125, and 39.5% + 2.0 / - 0.5% CF3I.

[0059] As used herein, the term "about" in reference to amounts expressed as weight percent means that the amount of the ingredient can vary in an amount of + / - 2% by weight.

[0060] Refrigerant and Heat Transfer Compositions Applicants have discovered that the refrigerants of the present invention, including each of Refrigerants 1-5 described herein, are unexpectedly capable of providing a range of highly advantageous properties, including excellent heat transfer characteristics, acceptable toxicity and non-flammability (i.e., Class 1A), zero or near-zero ozone depletion potential (ODP), and preferably relatively low evaporator glide, i.e., from 0°C to less than 5°C.

[0061] As used herein, reference to a numbered refrigerant, system, or method, or to a group of such numbered refrigerants, systems, and methods, as defined herein, means each such numbered system, including each system having a number within the group, including any suffix numbered systems. For example, reference to refrigerant 4 includes reference to each of refrigerants 4A, 4B, 4C, and 4D.

[0062] A particular advantage of the refrigerants of the present invention, particularly including each of Refrigerants 1-5, is that they are non-flammable and have acceptable toxicity, i.e., each is a Class A1 refrigerant. Those skilled in the art will appreciate that refrigerant flammability can be a consideration in certain critical heat transfer applications, and that refrigerants classified as Class A1 can often be advantageous over non-Class A1 refrigerants. Accordingly, it is desirable in the art to provide refrigerant compositions that can be used as replacements for conventional non-flammable refrigerants, including R410A and R-22, that have excellent heat transfer properties, acceptable toxicity, and zero or near-zero ODP. This combination of desirable advantages is achieved by the refrigerants of the present invention, particularly including each of Refrigerants 1-5, and further in conjunction with the use of such refrigerants in the systems of the present invention, including Systems 1 and 2, and the methods of the present invention, including Methods 1 and 2.

[0063] Applicants have discovered that inventive refrigerant compositions containing each of Refrigerants 1-5 achieve a difficult to achieve combination of properties, including, inter alia, a GWP of 750 or less and a Life A1 flammability.

[0064] Additionally, the refrigerant compositions of the invention containing each of Refrigerants 1-5 have an ODP of zero or near zero. Thus, the compositions of the present invention have an ODP of 0.02 or less, and more preferably zero.

[0065] Additionally, the refrigerant compositions of the invention, including each of Refrigerants 1-5, have acceptable toxicity and preferably have an OEL greater than about 400. As those skilled in the art will recognize, non-flammable refrigerants with an OEL greater than about 400 are advantageous because they provide refrigerants that meet the desirable "Class A" classification of ASHRAE Standard 34.

[0066] Preferred refrigerant compositions of the invention comprising each of Refrigerants 1-5 have both acceptable toxicity and non-flammability under ASHRAE Standard 34, and are therefore Class A1 refrigerants. Applicants have discovered that the heat transfer compositions of the invention, including those comprising each of Refrigerants 1-5 described herein, can provide a highly advantageous and unexpected combination of properties including good heat transfer characteristics, acceptable toxicity, non-flammability, and zero or near-zero ozone depletion potential ("ODP"), as well as chemical stability under conditions of use, including over the operating temperature range used in air conditioning, particularly residential air conditioning.

[0067] Methods, Uses, and Systems system The present invention includes all types of heat transfer systems that include a refrigerant of the present invention, including each of Refrigerants 1 through 5. The heat transfer system described in this paragraph may be referred to as Heat Transfer System 3 for convenience.

[0068] The present invention also includes, and provides certain advantages in connection with, secondary loop air conditioning systems that include, within the indoor loop of such systems, a refrigerant of the present invention, including each of Refrigerants 1 through 5. The heat transfer system described in this paragraph may be conveniently referred to as heat transfer system 4.

[0069] The present invention also includes, and provides certain advantages associated with, secondary loop residential air conditioning systems that include, within the indoor loop of such systems, a refrigerant of the present invention, including each of Refrigerants 1 through 5. The heat transfer system described in this paragraph may be conveniently referred to as heat transfer system 5.

[0070] Methods - Heat Transfer Methods The present invention includes all types of heat transfer systems that include a refrigerant of the present invention, including each of Refrigerants 1 through 5. The heat transfer method described in this paragraph may be referred to as Heat Transfer Method 3 for convenience.

[0071] The present invention also includes, and provides certain advantages associated with, a heat transfer method implemented in a secondary loop air conditioning system, wherein the system includes, in the indoor loop of such system, a refrigerant of the present invention, including each of Refrigerants 1 through 5. The heat transfer method described in this paragraph may be conveniently referred to as Heat Transfer Method 4.

[0072] The present invention also provides certain advantages in connection with a heat transfer method implemented in a secondary loop residential air conditioning system, the system including, within the indoor loop of such a system, a refrigerant of the present invention, including each of Refrigerants 1 through 5. The heat transfer system described in this paragraph may be conveniently referred to as Heat Transfer Method 5.

[0073] Method - Renovation method The present invention includes a retrofit method based on an existing split direct expansion vapor compression air conditioning system. The existing system uses the same existing high GWP refrigerant, including R410A or R-22, in both the indoor and outdoor units prior to being subject to the present invention. According to this retrofit method, the existing system is modified so that the secondary loop (indoor) system uses a refrigerant of the present invention, including each of Refrigerants 1 through 5, in place of the previously used existing refrigerant. For convenience, the retrofit method described in this paragraph may be referred to as Retrofit Method 3.

[0074] The present invention includes a retrofit method based on an existing split direct expansion vapor compression air conditioning system that includes a reversing valve that allows the system to operate in heating and cooling modes. The existing system, prior to being subject to the present invention, uses existing high-GWP refrigerants, including R410A or R-22, to create a secondary loop air conditioning system capable of operating in either heating or cooling mode. According to this retrofit method, the existing system is modified so that the refrigerant in the indoor (secondary) loop is a refrigerant of the present invention, including each of Refrigerants 1 through 5. For convenience, the retrofit method described in this paragraph may be referred to as Retrofit Method 4.

[0075] The present invention includes a retrofit method based on an existing split direct expansion vapor compression air conditioning system that includes inter-unit refrigerant piping between the indoor and outdoor units, a reversing valve that enables operation of the system in heating mode, and an existing high-GWP refrigerant, including R410A or R-22, in the indoor and outdoor units. According to this retrofit method, the existing system is modified to create a secondary loop system in which the refrigerant in the indoor (secondary) loop is a refrigerant of the present invention, including each of Refrigerants 1 through 5, without replacing much of the inter-unit piping. For convenience, the retrofit method described in this paragraph may be referred to as Retrofit Method 5.

[0076] The present invention includes a retrofit method based on an existing split direct expansion vapor compression air conditioning system containing inter-unit refrigerant piping between indoor and outdoor units, a reversing valve that allows the system to operate in heating and cooling modes, and an existing high-GWP refrigerant, including R410A or R-22, in the indoor and outdoor units. According to this retrofit method, the existing system is modified to create a secondary loop system in which the refrigerant in the secondary loop is a refrigerant of the present invention, including each of Refrigerants 1 through 5, without replacing much of the inter-unit piping. For convenience, the retrofit method described in this paragraph may be referred to as Retrofit Method 6.

[0077] The present invention includes a retrofit method based on an existing split-direct-expansion vapor-compression air conditioning system containing inter-unit refrigerant piping between the indoor and outdoor units, a reversing valve that allows the system to operate in heating or cooling mode, and an existing high-GWP refrigerant, including R410A or R-22, in the indoor and outdoor units. According to this retrofit method, the existing system is modified, without replacing much of the inter-unit piping, to create a secondary loop system in which (i) the refrigerant in the secondary loop is a refrigerant of the present invention, including each of Refrigerants 1 through 5, (ii) the saturation temperature drop in the suction line is 2°F or less, and (iii) the saturation temperature drop in the liquid line is 1°F or less. For convenience, the retrofit method described in this paragraph may be referred to as Retrofit Method 7A.

[0078] The present invention includes a retrofit method based on an existing split direct expansion vapor compression air conditioning system containing a reversing valve that allows the system to operate in heating or cooling mode, and an existing high-GWP refrigerant, including R410A or R-22, in the indoor and outdoor units. According to this retrofit method, the existing system is modified to produce a secondary loop system (i) where the refrigerant in the secondary loop is a refrigerant of the present invention, including each of Refrigerants 1-5, (ii) where the capacity is at least about 90% of the capacity of the existing split direct expansion vapor compression air conditioning system, and (iii) where the COP is at least about 90% of the COP of the existing split direct expansion vapor compression air conditioning system. For convenience, the retrofit method described in this paragraph may be referred to as Retrofit Method 7B.

[0079] The present invention includes a retrofit method based on an existing split direct expansion vapor compression air conditioning system containing inter-unit refrigerant piping between the indoor and outdoor units, a reversing valve that allows the system to operate in heating or cooling mode, and an existing high-GWP refrigerant, including R410A or R-22, in the indoor and outdoor units. According to this retrofit method, the existing system is modified, without replacing a significant portion of the inter-unit piping, to create a secondary loop system in which: (i) the refrigerant in the secondary loop is a refrigerant of the present invention, including each of Refrigerants 1 through 5; (ii) the capacity is at least about 90% of the capacity of the existing split direct expansion vapor compression air conditioning system; (iii) the COP is at least about 90% of the COP of the existing split direct expansion vapor compression air conditioning system; (iv) the saturation temperature drop in the suction line is 2°F or less; and (v) the saturation temperature drop in the liquid line is 1°F or less. For convenience, the retrofit method described in this paragraph may be referred to as Retrofit Method 7C.

[0080] The present invention includes a retrofit method based on an existing split direct expansion vapor compression air conditioning system that includes (i) a reversing valve that enables operation of the system in heating or cooling mode, (ii) an existing high-GWP refrigerant, including R410A or R-22, in the indoor and outdoor units, (iii) an existing compressor, and (iv) an existing outdoor heat exchanger. According to this retrofit method, the existing system is modified so that (i) the refrigerant in the secondary loop is a refrigerant of the present invention, including each of Refrigerants 1 through 5, (ii) the compressor in the outdoor unit has a displacement that is about 4% to about 96% greater than the compressor displacement in the existing system, and (iii) the outdoor heat exchanger has a heat transfer surface that is about 16% to about 68% greater than the area of ​​the outdoor heat exchanger in the existing system. For convenience, the retrofit method described in this paragraph may be referred to as Retrofit Method 7D.

[0081] The present invention includes a retrofit method based on an existing split direct expansion vapor compression air conditioning system, including (i) inter-unit refrigerant piping between the indoor unit and the outdoor unit, (ii) a reversing valve that enables operation of the system in heating mode, (iii) an existing high-GWP refrigerant, including R410A or R-22, in the indoor and outdoor units, (iv) an existing compressor, and (v) an existing outdoor heat exchanger. According to this retrofit method, the existing system is modified, without replacing most of the inter-unit piping, to create a secondary loop system in which: (i) the refrigerant in the secondary loop is a refrigerant of the present invention, including each of Refrigerants 1 through 5; (ii) the compressor in the outdoor unit has a displacement that is about 4% to about 96% greater than the compressor displacement in the existing system; (iii) the outdoor heat exchanger has a heat transfer surface that is about 16% to about 68% greater than the area of ​​the outdoor heat exchanger in the existing system; (iv) the saturation temperature drop in the suction line is 2°F or less; and (v) the saturation temperature drop in the liquid line is 1°F or less. The retrofit method described in this paragraph may be referred to as Retrofit Method 7E for convenience.

[0082] The present invention includes a retrofit method based on an existing split direct expansion vapor compression air conditioning system containing inter-unit refrigerant piping between the indoor and outdoor units, a reversing valve that allows the system to operate in heating or cooling mode, an expansion valve in the outdoor unit, and an existing high-GWP refrigerant, including R410A or R-22, in the indoor and outdoor units. According to this retrofit method, the existing system is modified, without replacing much of the inter-unit piping, to create a secondary loop system in which (i) the refrigerant in the secondary loop is a refrigerant of the present invention, including each of Refrigerants 1 through 5; (ii) a replacement expansion valve is introduced into the system and operates in the outdoor loop; (iii) the saturation temperature drop in the suction line is 2°F or less; and (iv) the saturation temperature drop in the liquid line is 1°F or less. For convenience, the retrofit method described in this paragraph may be referred to as Retrofit Method 7A.

[0083] The present invention includes a retrofit method based on an existing split direct expansion vapor compression air conditioning system containing a reversing valve that enables operation of the system in heating or cooling mode, an expansion valve in the outdoor unit, and an existing high-GWP refrigerant, including R410A or R-22, in the indoor and outdoor units. According to this retrofit method, the existing system is modified so that (i) the refrigerant in the secondary loop is a refrigerant of the present invention, including each of Refrigerants 1-5, (ii) a replacement expansion valve is introduced into the system and operates in the outdoor loop, (iii) a capacity is at least about 90% of the capacity of the existing split direct expansion vapor compression air conditioning system, and (iv) a COP is at least about 90% of the COP of the existing split direct expansion vapor compression air conditioning system. For convenience, the retrofit method described in this paragraph may be referred to as Retrofit Method 7B.

[0084] The present invention includes a retrofit method based on an existing split direct expansion vapor compression air conditioning system containing inter-unit refrigerant piping between the indoor unit and the outdoor unit, a reversing valve that enables operation of the system in heating or cooling mode, an expansion valve in the outdoor unit, and an existing high-GWP refrigerant, including R410A or R-22, in the indoor and outdoor units. According to this retrofit method, the existing system is modified, without replacing a significant portion of the inter-unit piping, to create a secondary loop system having: (i) a refrigerant in the secondary loop that is a refrigerant of the present invention, including each of Refrigerants 1 through 5; (ii) a replacement expansion valve is introduced into the system to operate in the outdoor loop; (iii) a capacity that is at least about 90% of the capacity of the existing split direct expansion vapor compression air conditioning system; (iv) a COP that is at least about 90% of the COP of the existing split direct expansion vapor compression air conditioning system; (v) a saturation temperature drop in the suction line of 2°F or less; and (vi) a saturation temperature drop in the liquid line of 1°F or less. For convenience, the retrofit method described in this paragraph may be referred to as Retrofit Method 7C.

[0085] The present invention includes a retrofit method based on an existing split direct expansion vapor compression air conditioning system that includes (i) a reversing valve that enables operation of the system in heating or cooling mode, (ii) an expansion valve in the outdoor unit, (iii) an existing high-GWP refrigerant, including R410A or R-22, in the indoor and outdoor units, (iv) an existing compressor, and (v) an existing outdoor heat exchanger. According to this retrofit method, the existing system is modified so that (i) the refrigerant in the secondary loop is a refrigerant of the present invention, including each of Refrigerants 1 through 5; (ii) a replacement expansion valve is introduced into the system and operates in the outdoor loop; (iii) the compressor in the outdoor unit has a displacement that is about 4% to about 96% greater than the compressor displacement in the existing system; and (iv) the outdoor heat exchanger has a heat transfer surface that is about 16% to about 68% greater than the area of ​​the outdoor heat exchanger in the existing system. For convenience, the retrofit method described in this paragraph may be referred to as Retrofit Method 7D.

[0086] The present invention includes a retrofit method based on an existing split direct expansion vapor compression air conditioning system that includes (i) inter-unit refrigerant piping between the indoor unit and the outdoor unit, (ii) a reversing valve that enables operation of the system in heating mode, (iii) an existing high GWP refrigerant including R410A or R-22 in the indoor and outdoor units, (iv) an existing compressor, (v) an expansion valve in the outdoor unit, and (vi) an existing outdoor heat exchanger. According to this retrofit method, an existing system is modified, without replacing most of the inter-unit piping, to create a secondary loop system in which: (i) the refrigerant in the secondary loop is a refrigerant of the present invention, including each of Refrigerants 1-5; (ii) the compressor in the outdoor unit has a displacement that is about 4% to about 96% greater than the compressor displacement in the existing system; (iii) the outdoor heat exchanger has a heat transfer surface that is about 16% to about 68% greater than the area of ​​the outdoor heat exchanger in the existing system; (iv) a replacement expansion valve is introduced into the system and operates in the outdoor loop; (v) the saturation temperature drop in the suction line is 2°F or less; and (vi) the saturation temperature drop in the liquid line is 1°F or less. For convenience, the retrofit method described in this paragraph may be referred to as Retrofit Method 7E.

[0087] use The present invention includes the use of the refrigerants of the present invention, including each of Refrigerants 1-5, to provide heating and / or cooling to a fluid or body. The use described in this paragraph may be conveniently referred to as Heat Transfer Use 1.

[0088] The present invention also includes the use of the refrigerants of the present invention, including each of Refrigerants 1-5, in the indoor loop of a secondary loop air conditioning system to provide heating and / or cooling in such a system, and provides certain advantages associated therewith. The use described in this paragraph may be conveniently referred to as Heat Transfer Use 2.

[0089] The present invention also includes the use of the refrigerants of the present invention, including each of Refrigerants 1-5, in the indoor loop of a secondary loop residential air conditioning system to provide heating and / or cooling in such a system, and provides certain advantages associated therewith. The use described in this paragraph may be conveniently referred to as Heat Transfer Use 3.

[0090] The present invention includes the use of a refrigerant of the present invention, including each of Refrigerants 1 through 5, to retrofit an existing single-refrigerant vapor compression heat pump that uses an existing refrigerant, including R410A or R-22, to create a pumped secondary loop system in which the refrigerant in the pumped secondary loop is a refrigerant of the present invention, including each of Refrigerants 1 through 5. The use described in this paragraph may be referred to as Retrofit Use 1 for convenience.

[0091] The present invention includes the use of a refrigerant of the present invention, including each of Refrigerants 1 through 5, to retrofit an existing single-refrigerant vapor compression heat pump air conditioning system that uses an existing refrigerant, including R410A or R-22, to produce a pumped secondary loop system in which the refrigerant in the pumped secondary loop is a refrigerant of the present invention, including each of Refrigerants 1 through 5. The use described in this paragraph may be referred to as Retrofit Use 2 for convenience.

[0092] The present invention includes the use of a refrigerant of the present invention, including each of Refrigerants 1 through 5, to retrofit an existing single-refrigerant residential vapor compression heat pump air conditioning system that uses an existing refrigerant, including R410A or R-22, to produce a pumped secondary loop system in which the refrigerant in the pumped secondary loop is a refrigerant of the present invention, including each of Refrigerants 1 through 5. The use described in this paragraph may be referred to as Retrofit Use 3 for convenience.

[0093] Exemplary Heat Transfer Systems, Methods, and Uses As described in detail below, preferred methods, uses, and systems of the present invention include or utilize a secondary loop air conditioning configuration. In such a configuration, the outdoor loop includes a compressor, condenser, expansion device, and evaporator, all in fluid communication using piping, valves, and control systems, so that the outdoor refrigerant and related components of the heat transfer composition can flow through the system in a well-known manner to complete a vapor-compression refrigeration cycle. The indoor loop includes a pumped liquid refrigerant system including a liquid refrigerant of the present invention, including each of Refrigerants 1-5, a pump for moving the liquid refrigerant within the loop, and a heat exchanger for exchanging heat between the indoor refrigerant and indoor air.

[0094] Exemplary schematic diagrams of the heat transfer system of the present invention are illustrated in Figure 1A, showing operation in a cooling mode, and Figure 1B, showing operation in a heating mode. For convenience, operation in the cooling mode will be first described with reference to Figure 1A, which shows compressor 14 providing compressed outdoor refrigerant vapor through reversing valve 10 and line 8 to outdoor heat exchanger 11, which, in the cooling mode, acts as a condenser to reject heat to the outdoor ambient air. The compressed refrigerant vapor is condensed in heat exchanger 11 to produce liquid outdoor refrigerant, which is directed via line 9 to an expansion device, such as expansion valve 12, which produces a liquid outdoor refrigerant of reduced temperature and pressure that is then provided to intercircuit heat exchanger 13 via line 5. In a preferred embodiment, expansion valve 12 is a replacement expansion valve, i.e., an expansion valve from an existing system is not used during operation, either by locking the existing valve in an open position, bypassing the existing valve, or removing the existing valve. In this regard, with particular reference to FIGS. 2A and 2b, it should be noted that in a typical existing R410A system, the expansion valve is upstream of the indoor evaporator coil and physically located indoors near the indoor coil / evaporator. Because the preferred retrofit method of the present invention involves creating an indoor loop that is a pumped loop, an indoor expansion valve is generally not present. On the other hand, the outdoor loop according to the present retrofit method is a vapor compression loop, in which case an expansion valve is required. Therefore, installation of an outdoor-located replacement expansion valve is a preferred step according to the present retrofit method. Furthermore, those skilled in the art will understand from the teachings contained herein that because the outdoor refrigerant formed according to the present invention is not R410A, the specific design characteristics of the replacement expansion valve in such cases are preferably selected for the desired operation of the outdoor loop with the replacement refrigerant used in the outdoor loop according to the present invention.

[0095] 1A and 1B, while intercircuit heat exchanger 13 is shown in its preferred location in FIGS. 1A and 1B as being located outside the home, it will be understood that in other embodiments, the intercircuit heat exchanger may be located within the home. In the cooling mode, intercircuit heat exchanger 13 acts as an evaporator for the outdoor refrigerant, absorbing heat from the secondary (indoor) refrigerant of the present invention, which includes refrigerants 1-10, preferably via a pumped secondary circuit including at least a portion of lines 1-4 as shown in FIG. 1A. This absorption of heat by the outdoor refrigerant from the indoor refrigerant in intercircuit heat exchanger 13 thus produces outdoor refrigerant vapor, which is passed through line 6 to reversing valve 10 and then to suction line 7 of compressor 14.

[0096] An indoor refrigerant of the present invention, including refrigerants 1-10, circulates through a pumped secondary loop including receiver 15, pump 16, and indoor heat exchanger 17. In the cooling mode, indoor heat exchanger 17 acts as an evaporator producing indoor refrigerant vapor via line 2, which is delivered to inter-circuit heat exchanger 13 via line 3. In the cooling mode, inter-circuit heat exchanger 13 condenses the indoor refrigerant vapor to produce indoor refrigerant liquid via line 4, which is then directed to receiver 15. Receiver 15 directs the indoor refrigerant liquid to pump 16, which provides energy to circulate the refrigerant through the circuit, particularly to the indoor heat exchanger via line 1. Preferably, the indoor loop includes a flow valve, preferably control valve 1A operated by a suitable control circuit (not shown), which opens in the cooling mode to allow indoor refrigerant to flow from pump 16 to evaporator 17. Meanwhile, valves 1B and 1C in lines 20 and 21, which are also preferably control valves operated by a suitable control circuit (not shown), are closed during operation in the cooling mode but open in the heating mode, as disclosed in detail below.

[0097] Referring now to FIG. 1B, operation in heating mode will be described. Compressor 14 provides compressed outdoor refrigerant vapor through reversing valve 10 and line 5 to inter-circuit heat exchanger 13, which, in heating mode, acts as a condenser to reject heat to a secondary (indoor) refrigerant of the present invention, including refrigerants 1-10, preferably via a pumped secondary circuit as shown in FIG. 1B. The liquid outdoor refrigerant condensed in inter-circuit heat exchanger 13 is sent via line 6 to an expansion device, such as expansion valve 12, which produces a liquid outdoor refrigerant of reduced temperature and pressure, which is then provided to outdoor heat exchanger 11 via line 7. In a preferred embodiment, expansion valve 12 is a replacement expansion valve, i.e., the expansion valve from the existing system is not used during operation, either by fixing the existing valve in an open position, by bypassing the existing valve, or by removing the existing valve. In outdoor heat exchanger 11, liquid outdoor refrigerant absorbs heat from the outdoor ambient air to produce outdoor refrigerant vapor, which is directed via line 8 to reversing valve 10, which then directs the vapor flow via line 9 to the inlet of compressor 14. The compressed outdoor refrigerant vapor passes through reversing valve 10 and line 5 to inter-circuit heat exchanger 13, which acts as a condenser to reject heat to a secondary refrigerant in a heating mode. The compressed refrigerant vapor is condensed in inter-circuit heat exchanger 13 to reject heat to an indoor refrigerant in the indoor circuit to produce liquid outdoor refrigerant, as described in more detail below.

[0098] In heating mode, the indoor refrigerant of the present invention, including refrigerants 1-5, circulates through the same pumped secondary loop used in cooling mode, i.e., receiver 15, pump 16, and indoor heat exchanger 17, except for the modified flow path as illustrated in FIG. 1B and described herein. In heating mode, the pumped circuit operates with valve 1A in a closed position and valves 1B and 1C open. In this configuration, indoor liquid refrigerant flow is directed from receiver 15 to pump 16, but via line 21 and valve 1C to line 3 leading to intercircuit heat exchanger 13, where it absorbs heat from the outdoor refrigerant. Thus, in heating mode, the intercircuit heat exchanger acts as an evaporator for the indoor refrigerant of the present invention, including each of refrigerants 1-5, to generate indoor refrigerant vapor. The indoor refrigerant vapor is routed from intercircuit heat exchanger 13 via line 4 to indoor heat exchanger 17, where it rejects heat to the indoor air, thereby providing heating to the home. Thus, in the heating mode, the indoor coil acts as a condenser for the indoor refrigerant of the present invention. The condensed liquid from indoor heat exchanger 17 is then directed to receiver 15 via line 2 and valve 1B. [Example]

[0099] In the following examples, refrigerant compositions according to the present invention are identified in Table E below as compositions L1-L4, with composition L5, which is R466A, also being used in accordance with the heat transfer system and method. Each of the L1-L5 refrigerants was tested and evaluated by the applicant and found to be non-flammable, i.e., a Class A1 refrigerant. However, each of the L1-L5 refrigerants was also subjected to thermodynamic analysis to determine its ability to match the performance of R-410A when used in a single-refrigerant vapor-compression heat pump air-conditioning system. The analysis was performed using experimental data collected on the properties of various binary and ternary pairs of components used in the refrigerants. In the experimental evaluation, the composition of each pair was varied over a range of relative percentages, and the mixture parameters for each pair were regressed to the experimentally obtained data. The examples used known vapor / liquid equilibrium behavior data available in the National Institute of Science and Technology (NIST) Reference Fluid Thermodynamic and Transport Properties Database software (Refprop 9.1 NIST Standard Database 23 (from April 2016)). Each blend was also evaluated to determine its classification for flammability as described above.

[0100] [Table 1]

[0101] As can be seen from Table E above, each of the refrigerants L1 to L4 according to the present invention achieves a GWP value (AR4) of less than 750 while at the same time achieving Class A1 flammability. The same is true for R466A.

[0102] Comparative Example 1 - Single Refrigerant Residential Heat Pump Using R410A - Cooling Mode A residential heat pump air conditioning system known as a ductless mini-split system, which uses R410A as the sole refrigerant and generally corresponds to the basic structure shown in Figure 2A, operates in cooling mode (as shown in Figure 2A). The system includes a compressor, an outdoor condenser, an expansion valve, an indoor evaporator, and a reversing valve. As is typical for operation of this type of system in cooling mode, the reversing valve is set to direct high-temperature vapor from the compressor to the inlet of the outdoor condenser, where the vapor rejects heat to the outdoor ambient air. The liquid refrigerant exiting the condenser is then directed to the expansion valve, which reduces the pressure, creating a low-pressure refrigerant liquid with a temperature below the setpoint temperature of the ambient air inside the home. The low-temperature liquid refrigerant exiting the expansion device is directed to the indoor evaporator. In the evaporator, heat is absorbed by the low-temperature refrigerant as it evaporates, thereby cooling the indoor air inside the home. The vapor flow from the evaporator is directed through a reversing valve, which is set to direct the refrigerant vapor flow back to the suction side of the compressor. In a typical configuration, both the compressor and condenser are located outside the home, while the evaporator is located inside the home. The basic operating conditions for this comparative system are as follows: 1. Refrigerant condensation temperature = 45℃, corresponding outdoor ambient temperature = 35℃ 2. Expansion device subcooling = 5.0℃ 3. Refrigerant evaporation temperature = 10℃, corresponding indoor temperature = 27℃ 4. Evaporator superheat degree = 5.0℃ 5.Volumetric efficiency = 100% 6. Isentropic efficiency = 74% For purposes of relative comparison, performance results for capacity and efficiency are considered to be 100%, compressor displacement and heat exchanger heat transfer surface area are considered to be 100%, and compressor horsepower is considered to be 100%.

[0103] Example 1A - Secondary Loop Residential Heat Pump Using Various Low GWP Refrigerants in the Outdoor Loop and Refrigerants L1-L5 in the Indoor Loop, and Increased Compressor Displacement to Match Capacity A compact secondary residential air conditioning system of the present invention, generally corresponding to the basic configuration shown in Figure 1A, operates in cooling mode as described herein. The system has been tested using 15 different refrigerant pairs, namely, three different outdoor refrigerants (propane, R454B, and R32) paired with four indoor refrigerants of the present invention, namely, L1, L2, L3, and L4, each identified in Table E above, and L5. The system is configured to use essentially the same equipment in the outdoor loop as used in Comparative Example 1, except that the compressor size is increased by an amount sufficient to provide 100% capacity relative to Comparative Example 1, and the expansion valve is a replacement expansion valve as described herein, as identified in Table E1A below. Operating conditions are as follows: 1. Condensation temperature = 45°C, corresponding outdoor ambient temperature = 35°C 2. Expansion device subcooling = 5.0℃ 3. Evaporation temperature = 5.0℃, corresponding indoor temperature = 27℃ 4. Evaporator superheat degree = 0.0℃ (flooded) 5. Intermediate heat exchanger superheat = 5.0℃ 6.Volumetric efficiency = 100% 7. Difference in saturation temperature of inter-circuit heat exchanger = 5°C Therefore, the same operating conditions are used as in Comparative Example 1, except that the evaporation temperature of the refrigerant in the pump chamber loop is 5° C., 5° C. lower than the temperature used in Comparative Example 1. The reported results compared to the results from the Comparative Example are reported in Table E1 below.

[0104] [Table 2]

[0105] Example 1B - Secondary Loop Residential Heat Pump Using Various Low GWP Refrigerants in the Outdoor Loop and Refrigerants L1-L4 in the Indoor Loop and Increased Condenser Heat Transfer Surface to Improve Efficiency The small secondary residential air conditioning system of the present invention described in Example 1A is operated in cooling mode as described in Example 1A, except that (1) the heat transfer area of ​​the outdoor heat exchanger is increased relative to the condenser of Comparative Example 1 and the expansion valve is replaced as described in Example 1An, and (2) the condenser temperature is reduced relative to Comparative Example 1. The system has been tested using 15 different refrigerant pairs, namely, three different outdoor refrigerants (propane, R454B, and R32) paired with four indoor refrigerants of the present invention, namely, L1, L2, L3, and L4, each identified in Table E above, and L5. The reported results compared to the results from Comparative Example 1 are reported in Table E1B below.

[0106] [Table 3]

[0107] As illustrated by the results of Example 1B, in each case, the secondary loop system of the present invention can achieve efficiencies that are at least about 93%, and when using propane as the outdoor refrigerant, can achieve efficiencies of over 95%, an unexpected and highly desirable result given the dramatic reduction in GWP of the refrigerants used in the inventive system of the present invention.

[0108] Example 1C - Secondary Loop Residential Heat Pump with High Efficiency Compressor Using Various Low GWP Refrigerants in the Outdoor Loop and Refrigerants L1-L5 in the Indoor Loop The compact secondary residential air conditioning system of the present invention described in Example 1B is operated in cooling mode as described in Example 1B, except that a compressor having the same displacement but higher efficiency is used. In particular, the compressor used in this example has an efficiency that is about 2% higher than the compressor of Example 1B. The reported results compared to the results from Comparative Example 1 are reported in Table E1C below.

[0109] [Table 4]

[0110] Comparative Example 2 - Single Refrigerant Residential Heat Pump Using R410A - Heating Mode A residential heat pump air conditioning system known as a ductless mini-split system, which uses R410A as the sole refrigerant and generally corresponds to the basic structure shown in Figure 2B, operates in heating mode (as shown in Figure 2B). The system includes a compressor, an outdoor condenser, an expansion valve, an indoor evaporator, and a reversing valve. As is typical for this type of system operating in heating mode, the reversing valve is set to direct high-temperature vapor from the compressor to the inlet of the indoor condenser, where the high-temperature vapor heats the indoor ambient air as it condenses in the refrigerant liquid. The liquid refrigerant exiting the condenser is then directed to the expansion valve, which reduces the pressure and creates a low-pressure refrigerant liquid with a temperature below that of the outdoor ambient air. The low-temperature liquid refrigerant exiting the expansion device is directed to the outdoor evaporator; in heating mode, the low-temperature refrigerant liquid absorbs heat to produce refrigerant vapor, which is directed by the reversing valve to the suction side of the compressor. In a typical configuration, both the compressor and evaporator are located outside the home, while the condenser is located inside the home. The basic operating conditions for this comparative example system are as follows: 1. Evaporation temperature = 0.5℃, corresponding outdoor ambient temperature = 8.3℃ 2. Evaporator superheat degree = 5.0℃ 3. Condensation temperature = 40.0°C, corresponding indoor temperature = 21.1°C 4. Expansion device subcooling = 5.0℃ 5.Volumetric efficiency = 100% For purposes of relative comparison, performance results for capacity and efficiency are considered to be 100%, and compressor displacement and heat exchanger heat transfer surface area are considered to be 100%.

[0111] Example 2A - Secondary Loop Residential Heat Pump Using Various Low GWP Refrigerants in the Outdoor Loop and Refrigerants L1-L5 in the Indoor Loop and Increased Compressor Displacement to Match Capacity - Heating Mode A small secondary residential air conditioning system of the present invention generally corresponding to the basic configuration shown in FIG. 1B (same as the system of FIG. 1A but operated in heating mode as described herein. The system has been tested using nine different refrigerant pairs, namely, five indoor refrigerants of the present invention, namely, L1, L2, L3, and L4, each identified in Table E above, and three different outdoor refrigerants (propane, R454B, and R32) paired with L4, as identified in Table E2A below. The system is configured to use essentially the same equipment in the outdoor loop as used in Comparative Example 2, except that the compressor size is increased by an amount sufficient to provide 100% capacity relative to Comparative Example 2, and the expansion valve is a replacement valve as described herein. The operating conditions are as shown below: 1. Evaporation temperature = 0.5℃, corresponding outdoor ambient temperature = 8.3℃ 2. Ambient temperature - evaporation temperature = 7.8°C 3. Evaporator superheat = 5.0℃ 4. Evaporation temperature = 5.0℃, corresponding indoor temperature = 27℃ 5. Condensation temperature = 45.0°C, corresponding indoor temperature = 21.1°C 6. Expansion device subcooling = 5.0℃ 7.Volumetric efficiency = 100% 8. Difference in saturation temperature of intermediate heat exchanger = 5℃ Therefore, the same operating conditions are used as in Comparative Example 2, except that the condensation temperature of the refrigerant in the pump chamber loop is 45° C., 5° C. higher than the condensation temperature used in Comparative Example 2. The reported results compared to the results from Comparative Example 2 are reported in Table E2A below.

[0112] [Table 5]

[0113] Example 2B - Secondary Loop Residential Heat Pump Using Various Low GWP Refrigerants in the Outdoor Loop and Refrigerants L1-L5 in the Indoor Loop and Increased Evaporator Heat Transfer Surface to Improve Efficiency - Heating Mode The small secondary residential air conditioning system of the present invention described in Example 1A is operated in the heating mode described in Example 2A, except that (1) the heat transfer area of ​​the outdoor heat exchanger is increased relative to the evaporator of Comparative Example 2, and (2) the evaporator temperature is decreased relative to Example 2A. The system is tested using nine different refrigerant pairs, namely, three different outdoor refrigerants (propane, R454B, and R32) paired with five indoor refrigerants of the present invention, namely, L1, L2, L3, and L4, each identified in Table E above, and L5. The reported results compared to the results from Comparative Example 2 are reported in Table E2B below.

[0114] [Table 6]

[0115] As illustrated by the results of Example 2B, in each case, the secondary loop system of the present invention can achieve efficiencies that are at least about 89%, and when using propane as the outdoor refrigerant, can achieve efficiencies of over 93%. This is an unexpected and highly desirable result in view of the dramatic reduction in GWP of the refrigerant used in the system of the present invention, and in view of the exceptional performance achieved when the same system operates in cooling mode.

[0116] Example 2C - Secondary Loop Residential Heat Pump with High Efficiency Compressor Using Various Low GWP Refrigerants in the Outdoor Loop and Refrigerants L1-L5 in the Indoor Loop - Heating Mode The compact secondary residential air conditioning system of the present invention described in Example 1B is operated in cooling mode as described in Example 1B, except that a compressor having the same displacement but higher efficiency is used. In particular, the compressor used in this example has an efficiency that is approximately 2-5% higher than the compressor of Example 2B. The results are reported in Table E2C below, in comparison with the results from Comparative Example 2.

[0117] [Table 7]

[0118] Example 3 - Retrofit of an existing single refrigerant R-410A heat pump with a secondary loop residential heat pump using various low GWP refrigerants in the outdoor loop and refrigerants L1-L5 in the indoor loop An existing residential air conditioning / heat pump system is provided that uses R410A and has the configuration illustrated in Figures 2A and 2B. In the existing system, the following components are located in a unit located outdoors: a compressor, a reversing valve, an outdoor heat exchanger (condenser), and an expansion valve. Refrigerant flow lines to and from the outdoor unit circulate the refrigerant to an indoor unit that contains an indoor heat exchanger. The existing system has a capacity of 10.5 KW and has the following nominal operating parameters: 1. Evaporation temperature = 10°C, corresponding indoor ambient temperature = 27°C 2. Evaporator superheat degree = 5℃ 3. Condensation temperature = 45℃, corresponding outdoor temperature = 35℃ 4. Expansion device subcooling = 5.0℃ 5. Compressor isentropic efficiency = 74% 6.Volumetric efficiency = 100% 7. Change in enthalpy = 164 kJ / kg 8.Mass flow rate=0.064kg / s 9.Volume flow rate=0.0016m 3 / sec

[0119] The system is retrofitted by removing substantially all of the R-410A refrigerant from the system using standard industry techniques. The system is modified to have the configuration illustrated in Figures 1A and 1B by disconnecting the refrigerant flow lines at or adjacent to the outdoor unit but not replacing the refrigerant flow lines to or from the indoor unit. The intermediate heat exchanger, receiver, and liquid pump disclosed herein are added to the system and located within the indoor unit. The existing refrigerant flow lines to and from the indoor unit are used to allow refrigerant flow to / from the pump and the intercircuit heat exchanger, and to transport indoor refrigerant between the pump and the indoor heat exchanger, and between the intercircuit heat exchanger and the indoor heat exchanger. The outdoor compressor displacement is increased, the outdoor heat exchanger surface area is increased, and additional indoor refrigerant flow lines and valves are added to allow operation in heating mode, as illustrated in Figures 1A and 1B. The expansion valve is replaced as described herein. The retrofitted system operates at mass flow rates of indoor refrigerants L1-L5 based on a system capacity of 10.5 KW, an evaporating temperature of 10°C, an inlet quality of zero, and an outlet quality of 0.86. The performance of the retrofitted system in terms of delta enthalpy and mass and volumetric flow rates of the indoor refrigerant through the existing lines for each of the inventive refrigerants L1-L4 and refrigerant L5 is reported in Table E3 below, and operation in the original R-410A system is included in Table E3A for comparison.

[0120] [Table 8]

[0121] Based on the operation reported in Table E3A, the operation of the existing refrigerant flow lines between the outdoor unit and the indoor unit in the retrofitted system is determined and reported in Table E3B below.

[0122] [Table 9]

[0123] As will be appreciated by those skilled in the art, a retrofit system of the present invention using existing refrigerant flow lines will provide acceptable performance with respect to indoor refrigerant pressure drop in the existing connecting lines. Based on industry standards, the maximum drop in saturation temperature in the suction line is considered to be 2°F (1.1°C) and in the liquid line is 1°F (0.56°C). As reported in Table E3B above, these standards are met in accordance with the retrofit method of the present invention.

Claims

1. At least about 95% by weight of the following four components, based on all refrigerant components: (a) about 50.5 wt. % to about 52.5 wt. % HFO-1234yf; (b) about 35.5% to 41% by weight of HFC-134a; (c) 2.2 wt % to 5.5 wt % HFC-125, and (d) 3.8% to about 8% by weight of HFC-32, said percentages being based on the sum of (a) through (d).

2. about 50.5 wt. % to about 52.5 wt. % HFO-1234yf; about 35.5% to 41% by weight of HFC-134a; 2.2% to 5.5% by weight of HFC-125, and 10. The refrigerant of claim 1 consisting essentially of from 3.8% to about 8% by weight of HFC-32.

3. 51 wt% to 52.5 wt% HFO-1234yf, 35.8% by weight to 37.8% by weight of HFC-134a, 4.5% to 5.5% by weight of HFC-125, and 10. The refrigerant of claim 1 consisting essentially of 6 to 8 weight percent HFC-32.

4. 10. A secondary loop residential refrigeration system comprising the indoor refrigerant of claim 1 and an outdoor refrigerant comprising propane, R454B, or R32.

5. 1. A method of retrofitting an existing residential heat pump air conditioning system that uses a vapor compression cycle having R410a as a refrigerant and a reversing valve to provide heating or cooling to indoor air within a residence, comprising: (a) a. a compressor; b. An outdoor heat exchanger for exchanging heat between outdoor air and the R410A refrigerant; c. an indoor heat exchanger for exchanging heat between indoor air and the R410A refrigerant; d. Reversing valves connected to the inlet and outlet of the compressor and to each of the outdoor heat exchanger and the indoor heat exchanger; e. providing an existing heat pump system comprising an expansion valve connected between the outdoor heat exchanger and the indoor heat exchanger; (b) isolating the indoor heat exchanger from the expansion valve and the reversing valve; (c) providing an inter-circuit heat exchanger, connecting said inter-circuit heat exchanger to said expansion valve and said reversing valve to provide a flow path for R410A refrigerant through said inter-circuit heat exchanger; (d) creating a secondary loop circuit including the indoor heat exchanger and the inter-circuit heat exchanger; (e) in said secondary loop circuit, an indoor refrigerant comprising at least about 95% by weight of the following components, based on all refrigerant components: a. about 50.5% to about 52.5% by weight of HFO-1234yf; b. about 35.5% to 41% by weight of HFC-134a; c. 2.2% to 5.5% by weight of HFC-125, and and (d) providing an indoor refrigerant comprising 3.8% to about 8% by weight of HFC-32, said percentage being based on the sum of (a) through (d).

6. The method of claim 5 , wherein the step of creating the secondary loop circuit further comprises including a liquid pump connected between the indoor heat exchanger and the inter-circuit heat exchanger.

7. 7. The method of claim 6, wherein the step of creating the secondary loop circuit further comprises including a liquid receiver upstream of the pump and including piping and valves connectable alternately to the indoor heat exchanger or to the inter-circuit heat exchanger.

8. 1. A method for retrofitting an existing split direct expansion vapor compression air conditioning system having an indoor unit with an indoor heat exchanger, an outdoor unit with a compressor and an outdoor heat exchanger, refrigerant flow lines connected between the indoor unit and the outdoor unit, and R410A in the indoor unit and the outdoor unit, comprising: (a) disconnecting the refrigerant flow lines at or adjacent to the outdoor unit; (b) removing the R410A refrigerant from the indoor unit and the outdoor unit; (c) forming an outdoor refrigeration circuit comprising the compressor and the outdoor heat exchanger and a refrigerant having a GWP of less than 750; (d) the indoor heat exchanger; and a refrigerant comprising at least about 95% by weight of the following components, based on all refrigerant components: a. about 50.5% to about 52.5% by weight of HFO-1234yf; b. about 35.5% to 41% by weight of HFC-134a; c. 2.2% to 5.5% by weight of HFC-125, and and (d) a refrigerant comprising 3.8% to about 8% by weight of HFC-32, said percentage being based on the sum of (a) through (d); (e) providing an inter-circuit heat exchanger thermally connecting the indoor and outdoor loops.

9. The retrofit method of claim 8 , wherein the indoor loop is connected to the outdoor loop using existing refrigerant flow lines.

10. 10. The retrofit method of claim 9, wherein the inter-circuit heat exchanger is located within the outdoor unit, and the outdoor circuit is connected to the inter-circuit heat exchanger using the existing refrigerant flow lines.

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