RefrigerantASHRAE R-1234ze(Z)

R1234ze(Z) PT Chart

Q: Why is R-1234ze(Z) different from R-1234ze(E) if it's the same chemical formula?

Geometric isomers — same atoms, different spatial arrangement around the carbon-carbon double bond. In R-1234ze(E) (trans, "entgegen") the two larger substituents on the double bond are on opposite sides; in R-1234ze(Z) (cis, "zusammen") they're on the same side. This changes the molecule's dipole moment, intermolecular packing, and ultimately its boiling point (Z: +9.7°C vs E: −19°C). The boiling-point difference makes them suitable for completely different temperature ranges of HVAC operation.

Q: Can R-1234ze(Z) be used as a replacement for R-1234ze(E)?

No. The 28°C difference in normal boiling point means R-1234ze(Z) operates at much lower pressures across any given temperature range — an R-1234ze(E) chiller compressor would not develop adequate mass flow with R-1234ze(Z). The two refrigerants are application-distinct: R-1234ze(E) for conventional chillers and HVAC, R-1234ze(Z) for high-temperature heat pumps and ORC. They share a chemical name; they are not interchangeable.

Q: What's an organic Rankine cycle?

A power-generation cycle that uses an organic working fluid (refrigerant-class molecule) instead of water in a Rankine cycle. Waste heat (from industrial processes, biomass, geothermal, or solar thermal) vaporizes the working fluid, the vapor expands through a turbine to produce mechanical/electrical power, then condenses for return to the boiler. ORC is used where the heat-source temperature is too low for steam — water Rankine cycles need much higher temperatures. R-1234ze(Z) and R-245fa are ORC working fluids in the medium-temperature range; R-1336mzz(Z) for higher temperatures.

Q: Where are industrial high-temperature heat pumps used?

Process heating applications where waste heat (40-60°C) is upgraded to useful heat (80-150°C) — district heating networks, dairy and food processing pasteurization, paper drying, chemical batch heating.

Q: Is R-1234ze(Z) more or less stable than R-1234ze(E)?

Slightly less stable at the upper end of typical operating temperatures. The cis configuration is the higher-energy isomer; under prolonged high-temperature operation R-1234ze(Z) can isomerize to R-1234ze(E). This is generally not significant within rated operating envelopes (condensing <130°C) and proper lubrication, but does mean compressor discharge temperatures should stay within OEM-rated limits.

Updated October 12, 2026

R-1234ze(Z)

A2L Lower toxicity, lower flammabilityHFO (pure)

Illustration of a refrigerant cylinder painted light green gray (RAL 7044), the color AHRI Guideline N-2017 calls for on all new refrigerant containers from 2020^{[1], section 4.8}. Label: R-1234ze(Z), safety class A2L, GWP <1. Red band on the shoulder: AHRI Guideline N-2017 calls for one on containers of flammable refrigerants^{[1], section 4.7}.

CHF=CHCF3 (Z isomer)

Pure HFO — the cis (Z) isomer of 1,3,3,3-tetrafluoropropene (CHF=CHCF₃). Distinct from the more common E-isomer (R-1234ze(E)) — different physical properties, different applications. Normal boiling point +9.7°C (E-isomer is −19°C). A2L. Used in high-temperature heat pumps and organic Rankine cycle systems.

R-1234ze(Z) saturation pressure is 5.7 in. Hg vacuum at 40°F, 7.8 PSIG at 70°F, and 24.5 PSIG at 100°F. These are the gauge readings on a static, fully-saturated system; a running system's high side sits well above them. The full table below runs from 32°F to 150°F in 1°F steps.

Not yet checked against an independent source.

Saturation @ 70°F

7.8 PSIG

GWP (100-yr)

<1 IPCC AR5

Boiling point

49.5°F

R-1234ze(Z) PT calculator Superheat

R-1234ze(Z) PT chart — printable saturation table

Looking for the R-1234ze(Z) PT chart PDF for shop reference? The complete pressure-temperature saturation table is below: every 1° increment from −40°F to 150°F (or to the refrigerant's critical temperature). Use the Print / Save as PDF button in the table header to download a clean, table-only PDF (the rest of the page is hidden from the print output).

R-1234ze(Z) PT Chart — Pressure-Temperature Saturation Table

Computed with CoolProp 7.2.0 in 1°F steps · hvacptcharts.com

R-1234ze(Z) · 1° increments · °F / PSIG

Tinted rows: NBP atmospheric crossover · 32°F H₂O freeze

R-1234ze(Z) pressure-temperature saturation table in Fahrenheit and PSIG
Temp (°F)	Pressure (PSIG)
32°F H₂O freeze	9.8 in. Hg vac.
33°F	9.3 in. Hg vac.
34°F	8.8 in. Hg vac.
35°F	8.3 in. Hg vac.
36°F	7.8 in. Hg vac.
37°F	7.3 in. Hg vac.
38°F	6.8 in. Hg vac.
39°F	6.2 in. Hg vac.
40°F	5.7 in. Hg vac.
41°F	5.1 in. Hg vac.
42°F	4.6 in. Hg vac.
43°F	4.0 in. Hg vac.
44°F	3.4 in. Hg vac.
45°F	2.8 in. Hg vac.
46°F	2.2 in. Hg vac.
47°F	1.6 in. Hg vac.
48°F	1.0 in. Hg vac.
49°F NBP (atmospheric)	0.3 in. Hg vac.
50°F	0.2
51°F	0.5
52°F	0.8
53°F	1.1
54°F	1.5
55°F	1.8
56°F	2.2
57°F	2.5
58°F	2.9
59°F	3.3
60°F	3.7
61°F	4.0
62°F	4.4
63°F	4.8
64°F	5.2
65°F	5.6
66°F	6.0
67°F	6.5
68°F	6.9
69°F	7.3
70°F	7.8
71°F	8.2
72°F	8.7
73°F	9.1
74°F	9.6
75°F	10.1
76°F	10.6
77°F	11.0
78°F	11.5
79°F	12.0
80°F	12.6
81°F	13.1
82°F	13.6
83°F	14.1
84°F	14.7
85°F	15.2
86°F	15.8
87°F	16.4
88°F	16.9
89°F	17.5
90°F	18.1
91°F	18.7
92°F	19.3
93°F	20.0
94°F	20.6
95°F	21.2
96°F	21.9
97°F	22.5
98°F	23.2
99°F	23.9
100°F	24.5
101°F	25.2
102°F	25.9
103°F	26.6
104°F	27.4
105°F	28.1
106°F	28.8
107°F	29.6
108°F	30.3
109°F	31.1
110°F	31.9
111°F	32.7
112°F	33.4
113°F	34.3
114°F	35.1
115°F	35.9
116°F	36.7
117°F	37.6
118°F	38.5
119°F	39.3
120°F	40.2
121°F	41.1
122°F	42.0
123°F	42.9
124°F	43.8
125°F	44.8
126°F	45.7
127°F	46.7
128°F	47.7
129°F	48.7
130°F	49.6
131°F	50.7
132°F	51.7
133°F	52.7
134°F	53.8
135°F	54.8
136°F	55.9
137°F	57.0
138°F	58.1
139°F	59.2
140°F	60.3
141°F	61.4
142°F	62.6
143°F	63.7
144°F	64.9
145°F	66.1
146°F	67.3
147°F	68.5
148°F	69.7
149°F	70.9
150°F	72.2

R-1234ze(Z) pressure-temperature saturation table in Celsius and kPa
Temp (°C)	Pressure (kPa)
0°C H₂O freeze	−33
1°C	−30
2°C	−27
3°C	−24
4°C	−21
5°C	−17
6°C	−14
7°C	−10
8°C	−7
9°C	−3
10°C NBP (atmospheric)	1
11°C	5
12°C	9
13°C	14
14°C	18
15°C	23
16°C	27
17°C	32
18°C	37
19°C	42
20°C	47
21°C	53
22°C	58
23°C	64
24°C	70
25°C	76
26°C	82
27°C	89
28°C	95
29°C	102
30°C	109
31°C	116
32°C	123
33°C	131
34°C	138
35°C	146
36°C	154
37°C	163
38°C	171
39°C	180
40°C	189
41°C	198
42°C	207
43°C	216
44°C	226
45°C	236
46°C	246
47°C	257
48°C	268
49°C	278
50°C	290
51°C	301
52°C	313
53°C	325
54°C	337
55°C	349
56°C	362
57°C	375
58°C	388
59°C	402
60°C	416
61°C	430
62°C	444
63°C	459
64°C	474
65°C	489
66°C	505

CoolProp 7.2.0 · PSIG/kPa = gauge · PSIA = PSIG + 14.6959 · kPa(abs) = kPa(gauge) + 101.325

Full saturation values at 1° increments. Toggle between °F / PSIG and °C / kPa. Use Print / Save as PDF for laminated shop reference, or download the CSV / JSON below for use in other tools. R-1234ze(Z) PT chart data: CoolProp 7.2.0 (published Helmholtz equations of state / mixture models — see the source citations above).

A2L

Lower toxicity, lower flammability

Lower toxicity. Flame propagates in air at 60°C, but with a low burning velocity (≤ 10 cm/s) and a heat of combustion < 19,000 kJ/kg. ASHRAE safety group A2L: lower toxicity and lower flammability. R-32, R-454B, R-1234yf, R-1234ze(E), R-452B, R-454C, R-455A, R-516A are A2L.

Flammability: Low (burning velocity ≤ 10 cm/s)
Toxicity: Lower (OEL ≥ 400 ppm)

Classification per ANSI/ASHRAE Standard 34-2022. See full reference.

Saturation pressure-temperature curve

Pressure

Temperature

Highlight at°F

Quick lookup — R-1234ze(Z)

Temp:°F

7.8PSIG(54 kPa)

Range: 32 to 150°F Open full PT calculator →

Common service temperatures

32°F

−5PSIG

Freezing

45°F

−1PSIG

Heat-pump heat

70°F

8PSIG

Standard

75°F

10PSIG

Test ref

80°F

13PSIG

Warm

95°F

21PSIG

Summer peak

Saturation values from CoolProp 7.2.0^[2]. Operating pressure on a running system differs — see the operating-pressure references for in-use values.

At a glance

Chemistry

CHF=CHCF3 (Z isomer)

(Z)-1,3,3,3-Tetrafluoropropene

Lubricant compatibility

POEMO

Z-isomer with higher boiling point than R-1234ze(E). Used in high-temperature heat pumps and organic Rankine cycle applications.

Trade names

Solstice zd — Honeywell (related lines)

Common applications

High-temperature heat pumps (industrial)
Organic Rankine cycle working fluid

Properties

Boiling point (1 atm)
49.5°F (9.7°C)
Critical point
302.2°F (150.1°C) at 497 PSIG
Molar mass
114.04 g/mol
ODP
0
GWP (100-yr)
<1 IPCC AR5 IPCC: AR4 not assessed · AR5 <1 · AR6 0.315 Not in 40 CFR 84.64(b) or AR4; headline shows the AR5 value.
New-equipment status (US)
Not an AIM Act regulated substance; 40 CFR 84.54 GWP limits don't apply.

What is R-1234ze(Z)?

R-1234ze(Z) is the cis (Z) isomer of 1,3,3,3-tetrafluoropropene. Same molecular formula and same atoms as R-1234ze(E), but with the carbon-carbon double bond in cis configuration rather than trans. The geometric difference produces substantially different physical properties — the Z-isomer has a normal boiling point of +9.7°C (49.5°F) versus the E-isomer's −19°C (−2.2°F).

The higher boiling point makes R-1234ze(Z) unsuitable for typical air-conditioning or chiller applications — its saturation pressure at ambient temperatures is too low (sub-atmospheric on the evaporator side for cooling work). Where it shines is in high-temperature heat pumps and organic Rankine cycle (ORC) systems where the refrigerant's condensing temperature is well above ambient (60-120°C in some industrial process-heating applications). For those applications, the E-isomer's pressure profile is too low; the Z-isomer's profile is appropriate.

Where R-1234ze(Z) is used

High-temperature industrial heat pumps (process heating 60-130°C condensing)
Organic Rankine cycle (ORC) working fluid for waste-heat recovery
Research applications in academic and pre-commercial settings
Not used in conventional HVAC chiller or AC service

Regulatory & phase-down status

R-1234ze(Z) is not subject to phase-down — its GWP is in the same very-low range as R-1234ze(E), below 1 on the strict IPCC AR5/AR6 basis (dataset value pending peer-reviewed publication). No regulatory pressure exists. The constraints on adoption are commercial availability (specialty manufacturer Honeywell), application narrowness (only high-temperature systems), and equipment scarcity (industrial heat pumps and ORC systems are niche markets).

Service notes

POE oil is standard; PVE oil is approved in some applications. Mineral oil is not used.

A2L safety class applies though with reduced practical concern due to the relatively high boiling point — the refrigerant is liquid at ambient temperatures, reducing the vapor-cloud risk that's the primary A2L concern. Standard A2L service procedures (no open flames, refrigerant detection where the standard requires it, A2L-listed equipment) still apply.

Industrial heat-pump and ORC equipment is OEM-specific; consult equipment service literature for refrigerant handling. Generic HVAC procedures don't fully cover these specialty applications.

Operating cycle

Phase-down timeline

R-1234ze(Z) is not an AIM Act regulated substance (not one of the 18 HFCs in 42 U.S.C. 7675(c), and not a blend containing one). The 40 CFR 84.54 GWP limits don't apply.

Global warming potential, in context

Frequently asked

›Why is R-1234ze(Z) different from R-1234ze(E) if it's the same chemical formula?

Geometric isomers — same atoms, different spatial arrangement around the carbon-carbon double bond. In R-1234ze(E) (trans, "entgegen") the two larger substituents on the double bond are on opposite sides; in R-1234ze(Z) (cis, "zusammen") they're on the same side. This changes the molecule's dipole moment, intermolecular packing, and ultimately its boiling point (Z: +9.7°C vs E: −19°C). The boiling-point difference makes them suitable for completely different temperature ranges of HVAC operation.

›Can R-1234ze(Z) be used as a replacement for R-1234ze(E)?

No. The 28°C difference in normal boiling point means R-1234ze(Z) operates at much lower pressures across any given temperature range — an R-1234ze(E) chiller compressor would not develop adequate mass flow with R-1234ze(Z). The two refrigerants are application-distinct: R-1234ze(E) for conventional chillers and HVAC, R-1234ze(Z) for high-temperature heat pumps and ORC. They share a chemical name; they are not interchangeable.

›What's an organic Rankine cycle?

A power-generation cycle that uses an organic working fluid (refrigerant-class molecule) instead of water in a Rankine cycle. Waste heat (from industrial processes, biomass, geothermal, or solar thermal) vaporizes the working fluid, the vapor expands through a turbine to produce mechanical/electrical power, then condenses for return to the boiler. ORC is used where the heat-source temperature is too low for steam — water Rankine cycles need much higher temperatures. R-1234ze(Z) and R-245fa are ORC working fluids in the medium-temperature range; R-1336mzz(Z) for higher temperatures.

›Where are industrial high-temperature heat pumps used?