TECHNICAL FIELD

The present disclosure relates to an air-conditioning unit.

BACKGROUND ART

Hitherto, in heat cycle systems, such as air conditioners, R410A is often used as a refrigerant. R410A is a two-component mixed refrigerant of difluoromethane (CH2F2; HFC-32, or R32) and pentafluoroethane (C2HF5; HFC-125, or R125) and is a pseudo-azeotropic composition.

However, the global warming potential (GWP) of R410A is 2088, and, in recent years, because of growing concern about global warming, R32 that has a further lower GWP of 675 is used more often.

For this reason, for example, PTL 1 (International Publication No. 2015/141678) suggests various types of low-GWP refrigerant mixtures as alternatives to R410A.

SUMMARY OF THE INVENTION

Technical Problem

However, such low-GWP refrigerants include flammable refrigerants. In air-conditioning units, an electric heatier having a high electric power consumption can be used for various purposes. In this way, in air-conditioning units in which an electric heater having a high electric power consumption is used, it is desired to suppress ignition at the electric heater even when leakage of flammable refrigerant occurs.

The contents of the present disclosure are described in view of the above-described points, and it is an object to provide an air-conditioning unit that is able to suppress ignition at an electric heater even when leakage of refrigerant occurs while a low-GWP refrigerant is used.

Solution to Problem

An air-conditioning unit according to a first aspect includes a casing, a device, and an electric heater. The device is provided inside the casing. The electric heater is provided inside the casing. The device is a compressor configured to compress refrigerant containing 1,2-difluoroethylene and/or a heat exchanger configured to exchange heat between outside air and refrigerant containing 1,2-difluoroethylene. An electric power consumption of the electric heater is lower than or equal to 300 W.

The air-conditioning unit is not limited and may be, for example, a heat source unit or a service unit in a refrigeration cycle apparatus, such as an air conditioner in which the heat source unit, such as an outdoor unit, and the service unit, such as an indoor unit, are connected via a connection pipe. The heat source unit may include only the heat exchanger, and the compressor may be provided in a different unit.

In this air-conditioning unit, the compressor configured to compress refrigerant containing 1,2-difluoroethylene and/or the heat exchanger configured to exchange heat between outside air and refrigerant containing 1,2-difluoroethylene is accommodated together with the electric heater in the casing; however, the electric power consumption of the electric heater is lower than or equal to 300 W. Therefore, if the above-described refrigerant leaks, ignition at the electric heater is suppressed.

An air-conditioning unit according to a second aspect is the air-conditioning unit of the first aspect, and the casing has an air outlet for discharging air having passed through the heat exchanger at a side in an installation state. The electric power consumption of the electric heater is higher than or equal to 75 W.

Since the electric power consumption of the electric heater is higher than or equal to 75 W in this air-conditioning unit, the function of the electric heater is easily exercised.

An air-conditioning unit according to a third aspect is the air-conditioning unit of the second aspect and has a single fan configured to form air flow passing through the heat exchanger. The electric power consumption of the electric heater is higher than or equal to 75 W and lower than or equal to 100 W.

Preferably, an internal volume (the volume of fluid that can be filled inside) of the heat exchanger of the air-conditioning unit including only a single fan is greater than or equal to 0.4 L and less than 3.5 L. Specifically, for the one in which no refrigerant container (which is a low-pressure receiver, a high-pressure receiver, or the like, except an accumulator attached to the compressor) in a refrigerant circuit in which the air-conditioning unit is used, the internal volume is preferably greater than or equal to 0.4 L and less than or equal to 2.5 L; for the one in which a refrigerant container is provided in a refrigerant circuit (preferably, the number of service units, such as indoor units, is one), the internal volume is preferably greater than or equal to 1.4 L and less than 3.5 L.

Since this air-conditioning unit has a capacity to such a degree that only a single fan is provided, even when the electric power consumption of the electric heater is lower than or equal to 100 W, the function of the electric heater is sufficiently exercised.

An air-conditioning unit according to a fourth aspect is the air-conditioning unit of the second aspect and has two fans configured to form air flow passing through the heat exchanger. The electric power consumption of the electric heater is higher than or equal to 100 W.

Preferably, an internal volume (the volume of fluid that can be filled inside) of the heat exchanger of the air-conditioning unit including two fans is greater than or equal to 3.5 L and less than or equal to 7.0 L. Specifically, for the one in which one or multiple service units, such as indoor units including no expansion valve are provided in a refrigerant circuit in which an air-conditioning unit is used, the internal volume is preferably greater than or equal to 3.5 L and less than 5.0 L; for the one in which multiple service units, such as indoor units including an expansion valve are provided in a refrigerant circuit, the internal volume is preferably greater than or equal to 5.0 L and less than or equal to 7.0 L.

Since this air-conditioning unit includes two fans, the capacity of the air-conditioning unit is large, and a large-capacity electric heater tends to be required. Here, the electric power consumption of the electric heater is higher than or equal to 100 W, so the function of the electric heater can be sufficiently exercised appropriately for the capacity of the air-conditioning unit.

An air-conditioning unit according to a fifth aspect is the air-conditioning unit of the first aspect, and the casing has an air outlet for upwardly discharging air having passed through the heat exchanger. The electric power consumption of the electric heater is higher than or equal to 200 W.

Preferably, an internal volume (the volume of fluid that can be filled inside) of the heat exchanger of the air-conditioning unit that upwardly discharges air having passed through the heat exchanger is greater than or equal to 5.5 Landless than or equal to 38 L. Preferably, the one in which the internal volume of the heat exchanger is greater than or equal to 5.5 L and less than or equal to 38 L in this way is employed in the one in which multiple service units, such as indoor units including an expansion valve, are provided in a refrigerant circuit.

Since this air-conditioning unit upwardly sends air having passed through the heat exchanger, the capacity of the air-conditioning unit is large, and a large-capacity electric heater tends to be required. Here, the electric power consumption of the electric heater is higher than or equal to 200 W, so the function of the electric heater can be sufficiently exercised appropriately for the capacity of the air-conditioning unit.

An air-conditioning unit according to a sixth aspect is the air-conditioning unit of any one of the first aspect to the fifth aspect, and the electric heater is at least any one of a drain pan heater, a crankcase heater, and a refrigerant heater.

When this air-conditioning unit includes a drain pan heater, freezing of dew condensation water on a drain pan can be suppressed in the air-conditioning unit including the drain pan. When the air-conditioning unit includes a crankcase heater, generation of bubbles of refrigerating machine oil (oil foaming) at the startup of the compressor can be suppressed in the air-conditioning unit including the compressor. When the air-conditioning unit includes a refrigerant heater, refrigerant in the refrigerant circuit can be heated.

An air-conditioning unit according to a seventh aspect is the air-conditioning unit according to any of the first through sixth aspects, whereinthe refrigerant comprises trans-1,2-difluoroethylene (HFO-1132(E)), trifluoroethylene (HFO-1123), and 2,3,3,3-tetrafluoro-1-propene (R1234yf).

With this air-conditioning unit, a refrigerant having such performance that the refrigerant has a sufficiently low GWP and a refrigeration capacity (which may be referred to as cooling capacity or capacity) and a coefficient of performance (COP) equivalent to those of R410A is used, and ignition at the electric heater can be suppressed even when leakage of the refrigerant occurs.

An air-conditioning unit according to an eighth aspect is the air-conditioning unit according to the seventh aspect, wherein when the mass % of HFO-1132(E), HFO-1123, and R1234yf based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of FO-1132(E), HFO-1123, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments AA′, A′B, BD, DC′, C′C, CO, and OA that connect the following 7 points:

point A (68.6, 0.0, 31.4),

point A′ (30.6, 30.0, 39.4),

point B (0.0, 58.7, 41.3),

point D (0.0, 80.4, 19.6),

point C′ (19.5, 70.5, 10.0),

point C (32.9, 67.1, 0.0), and

point O (100.0, 0.0, 0.0),

or on the above line segments (excluding the points on the line segments BD, CO, and OA);

the line segment AA′ is represented by coordinates (x, 0.0016x2−0.9473x+57.497, −0.0016x2−0.0527x+42.503),

the line segment A′B is represented by coordinates (x, 0.0029x2−1.0268x+58.7, −0.0029x2+0.0268x+41.3),

the line segment DC′ is represented by coordinates (x, 0.0082x2−0.6671x+80.4, −0.0082x2−0.3329x+19.6),

the line segment C′C is represented by coordinates (x, 0.0067x2−0.6034x+79.729, −0.0067x2−0.3966x+20.271), and

the line segments BD, CO, and OA are straight lines.

An air-conditioning unit according to a ninth aspect is the air-conditioning unit according to the seventh aspect, wherein

when the mass % of HFO-1132(E), HFO-1123, and R1234yf based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments GI, IA, AA′, A′B, BD, DC′, C′C, and CG that connect the following 8 points:

point G (72.0, 28.0, 0.0),

point I (72.0, 0.0, 28.0),

point A (68.6, 0.0, 31.4),

point A′ (30.6, 30.0, 39.4),

point B (0.0, 58.7, 41.3),

point D (0.0, 80.4, 19.6),

point C′(19.5, 70.5, 10.0), and

point C (32.9, 67.1, 0.0),

or on the above line segments (excluding the points on the line segments IA, BD, and CG);

the line segment AA′ is represented by coordinates (x, 0.0016x2−0.9473x+57.497, −0.0016x2−0.0527x+42.503),

the line segment A′B is represented by coordinates (x, 0.0029x2−1.0268x+58.7, −0.0029x2+0.0268x+41.3),

the line segment DC′ is represented by coordinates (x, 0.0082x2−0.6671x+80.4, −0.0082x2−0.3329x+19.6),

the line segment C′C is represented by coordinates (x, 0.0067x2−0.6034x+79.729, −0.0067x2−0.3966x+20.271), and

the line segments GI, IA, BD, and CG are straight lines.

An air-conditioning unit according to a tenth aspect is the air-conditioning unit according to the seventh aspect, wherein

when the mass % of HFO-1132(E), HFO-1123, and R1234yf based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments JP, PN, NK, KA′, A′B, BD, DC′, C′C, and CJ that connect the following 9 points:

point J (47.1, 52.9, 0.0),

point P (55.8, 42.0, 2.2),

point N (68.6, 16.3, 15.1),

point K (61.3, 5.4, 33.3),

point A′ (30.6, 30.0, 39.4),

point B (0.0, 58.7, 41.3),

point D (0.0, 80.4, 19.6),

point C′(19.5, 70.5, 10.0), and

point C (32.9, 67.1, 0.0),

or on the above line segments (excluding the points on the line segments BD and CJ);

the line segment PN is represented by coordinates (x, −0.1135x2+12.112x−280.43, 0.1135x2−13.112x+380.43),

the line segment NK is represented by coordinates (x, 0.2421x2−29.955x+931.91, −0.2421x2+28.955x−831.91),

the line segment KA′ is represented by coordinates (x, 0.0016x2−0.9473x+57.497, −0.0016x2−0.0527x+42.503), the line segment A′B is represented by coordinates (x, 0.0029x2−1.0268x+58.7, −0.0029x2+0.0268x+41.3),

the line segment DC′ is represented by coordinates (x, 0.0082x2−0.6671x+80.4, −0.0082x2−0.3329x+19.6),

the line segment C′C is represented by coordinates (x, 0.0067x2−0.6034x+79.729, −0.0067x2−0.3966x+20.271), and

the line segments JP, BD, and CG are straight lines.

An air-conditioning unit according to an eleventh aspect is the air-conditioning unit according to the seventh aspect, wherein

when the mass % of HFO-1132(E), HFO-1123, and R1234yf based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments JP, PL, LM, MA′, A′B, BD, DC′, C′C, and CJ that connect the following 9 points:

point J (47.1, 52.9, 0.0),

point P (55.8, 42.0, 2.2),

point L (63.1, 31.9, 5.0),

point M (60.3, 6.2, 33.5),

point A′ (30.6, 30.0, 39.4),

point B (0.0, 58.7, 41.3),

point D (0.0, 80.4, 19.6),

point C′ (19.5, 70.5, 10.0), and

point C (32.9, 67.1, 0.0),

or on the above line segments (excluding the points on the line segments BD and CJ);

the line segment PL is represented by coordinates (x, −0.1135x2+12.112x−280.43, 0.1135x2−13.112x+380.43)

the line segment MA′ is represented by coordinates (x, 0.0016x2−0.9473x+57.497, −0.0016x2−0.0527x+42.503),

the line segment A′B is represented by coordinates (x, 0.0029x2−1.0268x+58.7, −0.0029x2+0.0268x+41.3),

the line segment DC′ is represented by coordinates (x, 0.0082x2−0.6671x+80.4, −0.0082x2−0.3329x+19.6),

the line segment C′C is represented by coordinates (x, 0.0067x2−0.6034x+79.729, −0.0067x2−0.3966x+20.271), and

the line segments JP, LM, BD, and CG are straight lines.

An air-conditioning unit according to a twelfth aspect is the air-conditioning unit according to the seventh aspect, wherein when the mass % of HFO-1132(E), HFO-1123, and R1234yf based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments PL, LM, MA′, A′B, BF, FT, and TP that connect the following 7 points:

point P (55.8, 42.0, 2.2),

point L (63.1, 31.9, 5.0),

point M (60.3, 6.2, 33.5),

point A′ (30.6, 30.0, 39.4),

point B (0.0, 58.7, 41.3),

point F (0.0, 61.8, 38.2), and

point T (35.8, 44.9, 19.3),

or on the above line segments (excluding the points on the line segment BF);

the line segment PL is represented by coordinates (x, −0.1135x2+12.112x−280.43, 0.1135x2−13.112x+380.43),

the line segment MA′ is represented by coordinates (x, 0.0016x2−0.9473x+57.497, −0.0016x2−0.0527x+42.503),

the line segment A′B is represented by coordinates (x, 0.0029x2−1.0268x+58.7, −0.0029x2+0.0268x+41.3),

the line segment FT is represented by coordinates (x, 0.0078x2−0.7501x+61.8, −0.0078x2−0.2499x+38.2),

the line segment TP is represented by coordinates (x, 0.00672x2−0.7607x+63.525, −0.00672x2−0.2393x+36.475), and

the line segments LM and BF are straight lines.

An air-conditioning unit according to a thirteenth aspect is the air-conditioning unit according to the seventh aspect, wherein

when the mass % of HFO-1132(E), HFO-1123, and R1234yf based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments PL, LQ, QR, and RP that connect the following 4 points:

point P (55.8, 42.0, 2.2),

point L (63.1, 31.9, 5.0),

point Q (62.8, 29.6, 7.6), and

point R (49.8, 42.3, 7.9),

or on the above line segments;

the line segment PL is represented by coordinates (x, −0.1135x2+12.112x−280.43, 0.1135x2−13.112x+380.43),

the line segment RP is represented by coordinates (x, 0.00672x2−0.7607x+63.525, −0.00672x2−0.2393x+36.475), and

the line segments LQ and QR are straight lines.

An air-conditioning unit according to a fourteenth aspect is the air-conditioning unit according to the seventh aspect, wherein

when the mass % of HFO-1132(E), HFO-1123, and R1234yf based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments SM, MA′, A′B, BF, FT, and TS that connect the following 6 points:

point S (62.6, 28.3, 9.1),

point M (60.3, 6.2, 33.5),

point A′ (30.6, 30.0, 39.4),

point B (0.0, 58.7, 41.3),

point F (0.0, 61.8, 38.2), and

point T (35.8, 44.9, 19.3),

or on the above line segments,

the line segment MA′ is represented by coordinates (x, 0.0016x2−0.9473x+57.497, −0.0016x2−0.0527x+42.503),

the line segment A′B is represented by coordinates (x, 0.0029x2−1.0268x+58.7, −0.0029x2+0.0268x+41.3),

the line segment FT is represented by coordinates (x, 0.0078x2−0.7501x+61.8, −0.0078x2−0.2499x+38.2),

the line segment TS is represented by coordinates (x, −0.0017x2−0.7869x+70.888, −0.0017x2−0.2131x+29.112), and

the line segments SM and BF are straight lines.

An air-conditioning unit according to a fifteenth aspect is the air-conditioning unit according to any of the first through sixth aspects, wherein

the refrigerant comprises trans-1,2-difluoroethylene (HFO-1132(E)) and trifluoroethylene (HFO-1123) in a total amount of 99.5 mass % or more based on the entire refrigerant, and

the refrigerant comprises 62.0 mass % to 72.0 mass % of HFO-1132(E) based on the entire refrigerant.

With this air-conditioning unit, a refrigerant having such performance that the refrigerant has a sufficiently low GWP and a coefficient of performance (COP) and a refrigeration capacity (which may be referred to as cooling capacity or capacity) equivalent to those of R410A and is classified with lower flammability (class 2L) under the standard of American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE) is used, and ignition at the electric heater can be suppressed even when leakage of the refrigerant occurs.

An air-conditioning unit according to a sixteenth aspect is the air-conditioning unit according to any of the first through sixth aspects, wherein

the refrigerant comprises HFO-1132(E) and HFO-1123 in a total amount of 99.5 mass % or more based on the entire refrigerant, and

the refrigerant comprises 45.1 mass % to 47.1 mass % of HFO-1132(E) based on the entire refrigerant.

With this air-conditioning unit, a refrigerant having such performance that the refrigerant has a sufficiently low GWP and a coefficient of performance (COP) and a refrigeration capacity (which may be referred to as cooling capacity or capacity) equivalent to those of R410A and is classified with lower flammability (class 2L) under the standard of American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE) is used, and ignition at the electric heater can be suppressed even when leakage of the refrigerant occurs.

An air-conditioning unit according to a seventeenth aspect is the air-conditioning unit according to any of the first through sixth aspects, wherein

the refrigerant comprises trans-1,2-difluoroethylene (HFO-1132(E)), trifluoroethylene (HFO-1123), 2,3,3,3-tetrafluoro-1-propene (R1234yf), and difluoromethane (R32),

wherein

when the mass % of HFO-1132(E), HFO-1123, R1234yf, and R32 based on their sum in the refrigerant is respectively represented by x, y, z, and a,

if 0<a≤11.1, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is (100−a) mass % are within the range of a figure surrounded by straight lines GI, IA, AB, BD′, D′C, and CG that connect the following 6 points:

point G (0.026a2−1.7478a+72.0, −0.026a2+0.7478a+28.0, 0.0),

point I (0.026a2−1.7478a+72.0, 0.0, −0.026a2+0.7478a+28.0),

point A (0.0134a2−1.9681a+68.6, 0.0, −0.0134a2+0.9681a+31.4),

point B (0.0, 0.0144a2−1.6377a+58.7, −0.0144a2+0.6377a+41.3),

point D′ (0.0, 0.0224a2+0.968a+75.4, −0.0224a2−1.968a+24.6), and

point C (−0.2304a2−0.4062a+32.9, 0.2304a2−0.5938a+67.1, 0.0),

or on the straight lines GI, AB, and D′C (excluding point G, point I, point A, point B, point D′, and point C);

if 11.1<a≤18.2, coordinates (x,y,z) in the ternary composition diagram are within the range of a figure surrounded by straight lines GI, IA, AB, BW, and WG that connect the following 5 points:

point G (0.02a2−1.6013a+71.105, −0.02a2+0.6013a+28.895, 0.0),

point I (0.02a2−1.6013a+71.105, 0.0, −0.02a2+0.6013a+28.895),

point A (0.0112a2−1.9337a+68.484, 0.0, −0.0112a2+0.9337a+31.516),

point B (0.0, 0.0075a2−1.5156a+58.199, −0.0075a2+0.5156a+41.801), and

point W (0.0, 100.0−a, 0.0),

or on the straight lines GI and AB (excluding point G, point I, point A, point B, and point W);

if 18.2<a≤26.7, coordinates (x,y,z) in the ternary composition diagram are within the range of a figure surrounded by straight lines GI, IA, AB, BW, and WG that connect the following 5 points:

point G (0.0135a2−1.4068a+69.727, −0.0135a2+0.4068a+30.273, 0.0),

point I (0.0135a2−1.4068a+69.727, 0.0, −0.0135a2+0.4068a+30.273),

point A (0.0107a2−1.9142a+68.305, 0.0, −0.0107a2+0.9142a+31.695),

point B (0.0, 0.009a2−1.6045a+59.318, −0.009a2+0.6045a+40.682), and

point W (0.0, 100.0−a, 0.0),

or on the straight lines GI and AB (excluding point G, point I, point A, point B, and point W);

if 26.7<a≤36.7, coordinates (x,y,z) in the ternary composition diagram are within the range of a figure surrounded by straight lines GI, IA, AB, BW, and WG that connect the following 5 points:

point G (0.0111a2−1.3152a+68.986, −0.0111a2+0.3152a+31.014, 0.0),

point I (0.0111a2−1.3152a+68.986, 0.0, −0.0111a2+0.3152a+31.014),

point A (0.0103a2−1.9225a+68.793, 0.0, −0.0103a2+0.9225a+31.207),

point B (0.0, 0.0046a2−1.41a+57.286, −0.0046a2+0.41a+42.714), and

point W (0.0, 100.0−a, 0.0),

or on the straight lines GI and AB (excluding point G, point I, point A, point B, and point W); and

if 36.7<a≤46.7, coordinates (x,y,z) in the ternary composition diagram are within the range of a figure surrounded by straight lines GI, IA, AB, BW, and WG that connect the following 5 points:

point G (0.0061a2−0.9918a+63.902, −0.0061a2−0.0082a+36.098, 0.0),

point I (0.0061a2−0.9918a+63.902, 0.0, −0.0061a2−0.0082a+36.098),

point A (0.0085a2−1.8102a+67.1, 0.0, −0.0085a2+0.8102a+32.9),

point B (0.0, 0.0012a2−1.1659a+52.95, −0.0012a2+0.1659a+47.05), and

point W (0.0, 100.0−a, 0.0),

or on the straight lines GI and AB (excluding point G, point I, point A, point B, and point W).

With this air-conditioning unit, a refrigerant having such performance that the refrigerant has a sufficiently low GWP and a refrigeration capacity (which may be referred to as cooling capacity or capacity) and a coefficient of performance (COP) equivalent to those of R410A is used, and ignition at the electric heater can be suppressed even when leakage of the refrigerant occurs.

An air-conditioning unit according to an eighteenth aspect is the air-conditioning unit according to any of the first through sixth aspects, wherein

the refrigerant comprises trans-1,2-difluoroethylene (HFO-1132(E)), trifluoroethylene (HFO-1123), 2,3,3,3-tetrafluoro-1-propene (R1234yf), and difluoromethane (R32),

wherein

when the mass % of HFO-1132(E), HFO-1123, R1234yf, and R32 based on their sum in the refrigerant is respectively represented by x, y, z, and a,

if 0<a≤11.1, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is (100−a) mass % are within the range of a figure surrounded by straight lines JK′, K′B, BD′, D′C, and CJ that connect the following 5 points:

point J (0.0049a2−0.9645a+47.1, −0.0049a2−0.0355a+52.9, 0.0),

point K′ (0.0514a2−2.4353a+61.7, −0.0323a2+0.4122a+5.9, −0.0191a2+1.0231a+32.4),

point B (0.0, 0.0144a2−1.6377a+58.7, −0.0144a2+0.6377a+41.3),

point D′ (0.0, 0.0224a2+0.968a+75.4, −0.0224a2−1.968a+24.6), and

point C (−0.2304a2−0.4062a+32.9, 0.2304a2−0.5938a+67.1, 0.0),

or on the straight lines JK′, K′B, and D′C (excluding point J, point B, point D′, and point C);

if 11.1<a≤18.2, coordinates (x,y,z) in the ternary composition diagram are within the range of a figure surrounded by straight lines JK′, K′B, BW, and WJ that connect the following 4 points:

point J (0.0243a2−1.4161a+49.725, −0.0243a2+0.4161a+50.275, 0.0),

point K′ (0.0341a2−2.1977a+61.187, −0.0236a2+0.34a+5.636, −0.0105a2+0.8577a+33.177),

point B (0.0, 0.0075a2−1.5156a+58.199, −0.0075a2+0.5156a+41.801), and

point W (0.0, 100.0−a, 0.0),

or on the straight lines JK′ and K′B (excluding point J, point B, and point W);

if 18.2<a≤26.7, coordinates (x,y,z) in the ternary composition diagram are within the range of a figure surrounded by straight lines JK′, K′B, BW, and WJ that connect the following 4 points:

point J (0.0246a2−1.4476a+50.184, −0.0246a2+0.4476a+49.816, 0.0),

point K′ (0.0196a2−1.7863a+58.515, −0.0079a2−0.1136a+8.702, −0.0117a2+0.8999a+32.783),

point B (0.0, 0.009a2−1.6045a+59.318, −0.009a2+0.6045a+40.682), and

point W (0.0, 100.0−a, 0.0),

or on the straight lines JK′ and K′B (excluding point J, point B, and point W);

if 26.7<a≤36.7, coordinates (x,y,z) in the ternary composition diagram are within the range of a figure surrounded by straight lines JK′, K′A, AB, BW, and WJ that connect the following 5 points:

point J (0.0183a2−1.1399a+46.493, −0.0183a2+0.1399a+53.507, 0.0),

point K′ (−0.0051a2+0.0929a+25.95, 0.0, 0.0051a2−1.0929a+74.05),

point A (0.0103a2−1.9225a+68.793, 0.0, −0.0103a2+0.9225a+31.207),

point B (0.0, 0.0046a2−1.41a+57.286, −0.0046a2+0.41a+42.714), and

point W (0.0, 100.0−a, 0.0),

or on the straight lines JK′, K′A, and AB (excluding point J, point B, and point W); and

if 36.7<a≤46.7, coordinates (x,y,z) in the ternary composition diagram are within the range of a figure surrounded by straight lines JK′, K′A, AB, BW, and WJ that connect the following 5 points:

point J (−0.0134a2+1.0956a+7.13, 0.0134a2−2.0956a+92.87, 0.0),

point K′(−1.892a+29.443, 0.0, 0.892a+70.557),

point A (0.0085a2−1.8102a+67.1, 0.0, −0.0085a2+0.8102a+32.9),

point B (0.0, 0.0012a2−1.1659a+52.95, −0.0012a2+0.1659a+47.05), and

point W (0.0, 100.0−a, 0.0),

or on the straight lines JK′, K′A, and AB (excluding point J, point B, and point W).

With this air-conditioning unit, a refrigerant having such performance that the refrigerant has a sufficiently low GWP and a refrigeration capacity (which may be referred to as cooling capacity or capacity) and a coefficient of performance (COP) equivalent to those of R410A is used, and ignition at the electric heater can be suppressed even when leakage of the refrigerant occurs.

An air-conditioning unit according to a nineteenth aspect is the air-conditioning unit according to any of the first through sixth aspects, wherein

the refrigerant comprises trans-1,2-difluoroethylene (HFO-1132(E)), difluoromethane (R32), and 2,3,3,3-tetrafluoro-1-propene (R1234yf),

wherein

when the mass % of HFO-1132(E), R32, and R1234yf based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), R32, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments IJ, JN, NE, and EI that connect the following 4 points:

point I (72.0, 0.0, 28.0),

point J (48.5, 18.3, 33.2),

point N (27.7, 18.2, 54.1), and

point E (58.3, 0.0, 41.7),

or on these line segments (excluding the points on the line segment EI;

the line segment IJ is represented by coordinates (0.0236y2−1.7616y+72.0, y, −0.0236y2+0.7616y+28.0);

the line segment NE is represented by coordinates (0.012y2−1.9003y+58.3, y, −0.012y2+0.9003y+41.7); and

the line segments JN and E are straight lines.

With this air-conditioning unit, a refrigerant having such performance that the refrigerant has a sufficiently low GWP and a refrigeration capacity (which may be referred to as cooling capacity or capacity) equivalent to that of R410A and is classified with lower flammability (class 2L) under the standard of American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE) is used, and ignition at the electric heater can be suppressed even when leakage of the refrigerant occurs.

An air-conditioning unit according to a twentieth aspect is the air-conditioning unit according to any of the first through sixth aspects, wherein

the refrigerant comprises HFO-1132(E), R32, and R1234yf,

wherein

when the mass % of HFO-1132(E), R32, and R1234yf based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), R32, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments MM′, M′N, NV, VG, and GM that connect the following 5 points:

point M (52.6, 0.0, 47.4),

point M′(39.2, 5.0, 55.8),

point N (27.7, 18.2, 54.1),

point V (11.0, 18.1, 70.9), and

point G (39.6, 0.0, 60.4),

or on these line segments (excluding the points on the line segment GM);

the line segment MM′ is represented by coordinates (0.132y2−3.34y+52.6, y, −0.132y2+2.34y+47.4);

the line segment M′N is represented by coordinates (0.0596y2−2.2541y+48.98, y, −0.0596y2+1.2541y+51.02);

the line segment VG is represented by coordinates (0.0123y2−1.8033y+39.6, y, −0.0123y2+0.8033y+60.4); and

the line segments NV and GM are straight lines.

With this air-conditioning unit, a refrigerant having such performance that the refrigerant has a sufficiently low GWP and a refrigeration capacity (which may be referred to as cooling capacity or capacity) equivalent to that of R410A and is classified with lower flammability (class 2L) under the standard of American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE) is used, and ignition at the electric heater can be suppressed even when leakage of the refrigerant occurs.

An air-conditioning unit according to a twenty first aspect is the air-conditioning unit according to any of the first through sixth aspects, wherein

the refrigerant comprises HFO-1132(E), R32, and R1234yf, wherein

when the mass % of HFO-1132(E), R32, and R1234yf based on their sum in the refrigerant is respectively represented by x, y and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), R32, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments ON, NU, and UO that connect the following 3 points:

point O (22.6, 36.8, 40.6),

point N (27.7, 18.2, 54.1), and

point U (3.9, 36.7, 59.4),

or on these line segments;

the line segment ON is represented by coordinates (0.0072y2−0.6701y+37.512, y, −0.0072y2−0.3299y+62.488);

the line segment NU is represented by coordinates (0.0083y2−1.7403y+56.635, y, −0.0083y2+0.7403y+43.365); and

the line segment UO is a straight line.

With this air-conditioning unit, a refrigerant having such performance that the refrigerant has a sufficiently low GWP and a refrigeration capacity (which may be referred to as cooling capacity or capacity) equivalent to that of R410A and is classified with lower flammability (class 2L) under the standard of American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE) is used, and ignition at the electric heater can be suppressed even when leakage of the refrigerant occurs.

An air-conditioning unit according to a twenty second aspect is the air-conditioning unit according to any of the first through sixth aspects, wherein

the refrigerant comprises HFO-1132(E), R32, and R1234yf,

wherein

when the mass % of HFO-1132(E), R32, and R1234yf based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), R32, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments QR, RT, TL, LK, and KQ that connect the following 5 points:

point Q (44.6, 23.0, 32.4),

point R (25.5, 36.8, 37.7),

point T (8.6, 51.6, 39.8),

point L (28.9, 51.7, 19.4), and

point K (35.6, 36.8, 27.6),

or on these line segments;

the line segment QR is represented by coordinates (0.0099y2−1.975y+84.765, y, −0.0099y2+0.975y+15.235);

the line segment RT is represented by coordinates (0.0082y2−1.8683y+83.126, y, −0.0082y2+0.8683y+16.874);

the line segment LK is represented by coordinates (0.0049y2−0.8842y+61.488, y, −0.0049y2−0.1158y+38.512);

the line segment KQ is represented by coordinates (0.0095y2−1.2222y+67.676, y, −0.0095y2+0.2222y+32.324); and

the line segment TL is a straight line.

With this air-conditioning unit, a refrigerant having such performance that the refrigerant has a sufficiently low GWP and a refrigeration capacity (which may be referred to as cooling capacity or capacity) equivalent to that of R410A and is classified with lower flammability (class 2L) under the standard of American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE) is used, and ignition at the electric heater can be suppressed even when leakage of the refrigerant occurs.

An air-conditioning unit according to a twenty third aspect is the air-conditioning unit according to any of the first through sixth aspects, wherein

the refrigerant comprises HFO-1132(E), R32, and R1234yf,

wherein

when the mass % of HFO-1132(E), R32, and R1234yf based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), R32, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments PS, ST, and TP that connect the following 3 points:

point P (20.5, 51.7, 27.8),

point S (21.9, 39.7, 38.4), and

point T (8.6, 51.6, 39.8),

or on these line segments;

the line segment PS is represented by coordinates (0.0064y2−0.7103y+40.1, y, −0.0064y2−0.2897y+59.9);

the line segment ST is represented by coordinates (0.0082y2−1.8683y+83.126, y, −0.0082y2+0.8683y+16.874); and

the line segment TP is a straight line.

With this air-conditioning unit, a refrigerant having such performance that the refrigerant has a sufficiently low GWP and a refrigeration capacity (which may be referred to as cooling capacity or capacity) equivalent to that of R410A and is classified with lower flammability (class 2L) under the standard of American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE) is used, and ignition at the electric heater can be suppressed even when leakage of the refrigerant occurs.

An air-conditioning unit according to a twenty fourth aspect is the air-conditioning unit according to any of the first through sixth aspects, wherein

the refrigerant comprises trans-1,2-difluoroethylene (HFO-1132(E)), trifluoroethylene (HFO-1123), and difluoromethane (R32),

wherein

when the mass % of HFO-1132(E), HFO-1123, and R32 based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R32 is 100 mass % are within the range of a figure surrounded by line segments IK, KB′, B′H, HR, RG, and GI that connect the following 6 points:

point I (72.0, 28.0, 0.0),

point K (48.4, 33.2, 18.4),

point B′ (0.0, 81.6, 18.4),

point H (0.0, 84.2, 15.8),

point R (23.1, 67.4, 9.5), and

point G (38.5, 61.5, 0.0),

or on these line segments (excluding the points on the line segments B′H and GI);

the line segment IK is represented by coordinates (0.025z2−1.7429z+72.00, −0.025z2+0.7429z+28.0, z),

the line segment HR is represented by coordinates (−0.3123z2+4.234z+11.06, 0.3123z2−5.234z+88.94, z),

the line segment RG is represented by coordinates (−0.0491z2−1.1544z+38.5, 0.0491z2+0.1544z+61.5, z), and

the line segments KB′ and GI are straight lines.

With this air-conditioning unit, a refrigerant having such performance that the refrigerant has a sufficiently low GWP and a coefficient of performance (COP) equivalent to that of R410A is used, and ignition at the electric heater can be suppressed even when leakage of the refrigerant occurs.

An air-conditioning unit according to a twenty fifth aspect is the air-conditioning unit according to any of the first through sixth aspects, wherein

the refrigerant comprises HFO-1132(E), HFO-1123, and R32,

wherein

when the mass % of HFO-1132(E), HFO-1123, and R32 based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R32 is 100 mass % are within the range of a figure surrounded by line segments IJ, JR, RG, and GI that connect the following 4 points:

point I (72.0, 28.0, 0.0),

point J (57.7, 32.8, 9.5),

point R (23.1, 67.4, 9.5), and

point G (38.5, 61.5, 0.0),

or on these line segments (excluding the points on the line segment GI);

the line segment IJ is represented by coordinates (0.025z2−1.7429z+72.0, −0.025z2+0.7429z+28.0, z),

the line segment RG is represented by coordinates (−0.0491z2−1.1544z+38.5, 0.0491z2+0.1544z+61.5, z), and

the line segments JR and GI are straight lines.

With this air-conditioning unit, a refrigerant having such performance that the refrigerant has a sufficiently low GWP and a coefficient of performance (COP) equivalent to that of R410A is used, and ignition at the electric heater can be suppressed even when leakage of the refrigerant occurs.

An air-conditioning unit according to a twenty sixth aspect is the air-conditioning unit according to any of the first through sixth aspects, wherein

the refrigerant comprises HFO-1132(E), HFO-1123, and R32,

wherein

when the mass % of HFO-1132(E), HFO-1123, and R32 based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R32 is 100 mass % are within the range of a figure surrounded by line segments MP, PB′, B′H, HR, RG, and GM that connect the following 6 points:

point M (47.1, 52.9, 0.0),

point P (31.8, 49.8, 18.4),

point B′ (0.0, 81.6, 18.4),

point H (0.0, 84.2, 15.8),

point R (23.1, 67.4, 9.5), and

point G (38.5, 61.5, 0.0),

or on these line segments (excluding the points on the line segments B′H and GM);

the line segment MP is represented by coordinates (0.0083z2−0.984z+47.1, −0.0083z2−0.016z+52.9, z),

the line segment HR is represented by coordinates (−0.3123z2+4.234z+11.06, 0.3123z2−5.234z+88.94, z),

the line segment RG is represented by coordinates (−0.0491z2−1.1544z+38.5, 0.0491zz+0.1544z+61.5, z), and

the line segments PB′ and GM are straight lines.

With this air-conditioning unit, a refrigerant having such performance that the refrigerant has a sufficiently low GWP and a coefficient of performance (COP) equivalent to that of R410A is used, and ignition at the electric heater can be suppressed even when leakage of the refrigerant occurs.

An air-conditioning unit according to a twenty seventh aspect is the air-conditioning unit according to any of the first through sixth aspects, wherein

the refrigerant comprises HFO-1132(E), HFO-1123, and R32,

wherein

when the mass % of HFO-1132(E), HFO-1123, and R32 based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R32 is 100 mass % are within the range of a figure surrounded by line segments MN, NR, RG, and GM that connect the following 4 points:

point M (47.1, 52.9, 0.0),

point N (38.5, 52.1, 9.5),

point R (23.1, 67.4, 9.5), and

point G (38.5, 61.5, 0.0),

or on these line segments (excluding the points on the line segment GM);

the line segment MN is represented by coordinates (0.0083z2−0.984z+47.1, −0.0083z2−0.016z+52.9, z),

the line segment RG is represented by coordinates (−0.0491z2−1.1544z+38.5, 0.0491z2+0.1544z+61.5, z), and

the line segments JR and GI are straight lines.

With this air-conditioning unit, a refrigerant having such performance that the refrigerant has a sufficiently low GWP and a coefficient of performance (COP) equivalent to that of R410A is used, and ignition at the electric heater can be suppressed even when leakage of the refrigerant occurs.

An air-conditioning unit according to a twenty eighth aspect is the air-conditioning unit according to any of the first through sixth aspects, wherein

the refrigerant comprises HFO-1132(E), HFO-1123, and R32,

wherein

when the mass % of HFO-1132(E), HFO-1123, and R32 based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R32 is 100 mass % are within the range of a figure surrounded by line segments PS, ST, and TP that connect the following 3 points:

point P (31.8, 49.8, 18.4),

point S (25.4, 56.2, 18.4), and

point T (34.8, 51.0, 14.2),

or on these line segments;

the line segment ST is represented by coordinates (−0.0982z2+0.9622z+40.931, 0.0982z2−1.9622z+59.069, z),

the line segment TP is represented by coordinates (0.0083z2−0.984z+47.1, −0.0083z2−0.016z+52.9, z), and

the line segment PS is a straight line.

With this air-conditioning unit, a refrigerant having such performance that the refrigerant has a sufficiently low GWP and a coefficient of performance (COP) equivalent to that of R410A is used, and ignition at the electric heater can be suppressed even when leakage of the refrigerant occurs.

An air-conditioning unit according to a twenty ninth aspect is the air-conditioning unit according to any of the first through sixth aspects, wherein

the refrigerant comprises HFO-1132(E), HFO-1123, and R32,

wherein

when the mass % of HFO-1132(E), HFO-1123, and R32 based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R32 is 100 mass % are within the range of a figure surrounded by line segments QB″, B″D, DU, and UQ that connect the following 4 points:

point Q (28.6, 34.4, 37.0),

point B″ (0.0, 63.0, 37.0),

point D (0.0, 67.0, 33.0), and

point U (28.7, 41.2, 30.1),

or on these line segments (excluding the points on the line segment B″D);

the line segment DU is represented by coordinates (−3.4962z2+210.71z−3146.1, 3.4962z2−211.71z+3246.1, z),

the line segment UQ is represented by coordinates (0.0135z2−0.9181z+44.133, −0.0135z2−0.0819z+55.867, z), and

the line segments QB″ and B″D are straight lines.

With this air-conditioning unit, a refrigerant having such performance that the refrigerant has a sufficiently low GWP and a coefficient of performance (COP) equivalent to that of R410A is used, and ignition at the electric heater can be suppressed even when leakage of the refrigerant occurs.

