R1233zd(E) Refrigeranttrans-1-chloro-3,3,3-trifluoropropene · Low-pressure centrifugal chillers · R123 alternative
R1233zd(E) is a single-component hydrochlorofluoroolefin (HCFO) developed for ultra-low-GWP low-pressure chillers, industrial process cooling and related thermal applications. Its normal boiling point is about 18.3°C, so parts of a chiller circuit often operate below atmospheric pressure. That makes air and moisture ingress, purge-system operation and vacuum-side leak testing unusually important compared with conventional positive-pressure refrigerants.
What is R1233zd(E) refrigerant?
R1233zd(E) is trans-1-chloro-3,3,3-trifluoropropene, an A1 low-pressure refrigerant primarily used as a modern replacement for R123 and in some R245fa-class applications. EPA’s current Technology Transitions GWP is 4. It contains chlorine and has a very small but non-zero ODP—EPA SNAP publishes values below 0.0004—so describing its ODP as exactly zero would be technically imprecise.
R1233zd(E) refrigerant properties
Use these values for research and screening. For equipment design, charging and compliance, use the exact supplier PT data, SDS, OEM documentation and regulation that governs the project.
| Property | Reference | Engineering / source note |
|---|---|---|
| Designation | R1233zd(E) / HCFO-1233zd(E) | ASHRAE designation |
| Chemical name | trans-1-chloro-3,3,3-trifluoroprop-1-ene | Single-component HCFO |
| CAS number | 102687-65-0 | NIST research reference |
| Molecular weight | ≈130.5 g/mol | Honeywell technical data |
| Normal boiling point | ≈18.3°C | Honeywell storage/handling data |
| Critical temperature | ≈165.5–165.6°C | Honeywell / NIST |
| Critical pressure | ≈35.7 bar | Honeywell |
| ODP | 0.00024–0.00034 / <0.0004 | EPA SNAP / published atmospheric analysis |
| 100-year GWP | 4 | Current EPA Technology Transitions reference |
| Safety classification | A1 | EPA SNAP / ASHRAE |
EPA Technology Transitions uses the values shown on this page. Older product literature may use IPCC AR4/AR5 or another assessment, so a different number is not automatically an error.
Where is R1233zd(E) used?
Applications must be evaluated by system type, charge, compressor, heat exchanger, safety class and current regulation. The examples below describe recognized use contexts, not automatic approval for every installation.
Low-pressure centrifugal chillers
The flagship application, particularly large-building and district cooling.
Industrial process refrigeration
EPA SNAP lists HCFO-1233zd(E) as acceptable for new and retrofit IPR applications.
Industrial process air conditioning
EPA SNAP lists the fluid as acceptable.
Non-mechanical heat-transfer systems
EPA has listed R1233zd(E) as acceptable in this specialized end use.
High-temperature heat pumps
Research and commercial development use its high critical temperature for elevated sink temperatures.
Organic Rankine cycle / heat recovery
The fluid is widely studied as a low-GWP working fluid, though ORC use is distinct from refrigerant approval.
Continue through the Refrigerant Replacements and Low-GWP Refrigerants hubs for broader selection context.
Why R1233zd(E) chillers can operate under vacuum
R1233zd(E) boils at roughly 18.3°C at one atmosphere. A chiller evaporator operating well below that temperature therefore requires saturation pressure below atmospheric pressure.
In positive-pressure systems, leaks usually push refrigerant outward. In a low-pressure R1233zd(E) evaporator, a leak can instead pull air and water vapor into the system.
That distinction changes maintenance priorities: vacuum integrity, purge operation and non-condensable control become core efficiency and reliability topics.
Air ingress, purge systems and non-condensables
Air entering a low-pressure chiller does not condense with the refrigerant at normal condenser conditions. Non-condensables can accumulate, raise condenser pressure and reduce heat-transfer performance.
Low-pressure chillers commonly use purge systems to remove air and other non-condensables. Excessive purge operation can be a symptom of air leakage rather than something to ignore.
Moisture ingress also matters because water can interact with lubricant, metals and refrigerant chemistry. Maintaining deep vacuum integrity can therefore protect both efficiency and system life.
R1233zd(E) has chlorine but extremely low ODP
Unlike HFO-1234ze(E), R1233zd(E) contains chlorine. Its short atmospheric lifetime means most molecules break down before reaching the stratosphere, resulting in an ODP several orders of magnitude below R22 or R123.
EPA SNAP lists an ODP range around 0.00024–0.00034, while some marketing literature describes it as non-ozone-depleting. For a technical database, the more precise statement is 'very low / negligible ODP, but not mathematically zero.'
This is also why R1233zd(E) is classified as an HCFO rather than a chlorine-free HFO.
R1233zd(E) vs R123 and R245fa
R1233zd(E) was developed in part to replace HCFC-123 in low-pressure centrifugal chillers. It offers a similar low-pressure design concept without R123’s much larger ozone-depletion impact.
R245fa has zero ODP but EPA GWP 1,030 and a B1 safety classification in refrigerant references, while R1233zd(E) has current EPA GWP 4 and A1 classification.
Even when two fluids share low-pressure or ORC applications, compressor, turbine, seals, lubricant, heat exchangers and pressure-relief design remain refrigerant-specific.
R1233zd(E) vs R1234ze(E)
The table highlights engineering differences rather than implying direct interchangeability.
| Characteristic | R1233zd(E) | R1234ze(E) |
|---|---|---|
| Chemical family | HCFO with chlorine | HFO without chlorine |
| EPA GWP | 4 | 1 |
| ODP | Very low, non-zero (<0.0004) | 0 |
| Safety class | A1 | A2L |
| Normal boiling point | ≈18.3°C | −18.95°C |
| Pressure class | Low-pressure chiller fluid | Higher-pressure chiller fluid |
| Typical chiller issue | Vacuum-side air ingress / purge | A2L safety and compressor optimization |
R1233zd(E) safety: A1 classification with low-pressure system hazards
R1233zd(E) is A1, but low-pressure chillers have hazards that differ from typical DX systems. Vacuum conditions can pull contaminants inward, large liquid inventories can still create cold-exposure and confined-space risks during service, and hot surfaces can decompose fluorinated/chlorinated refrigerant.
Vacuum-side integrity
Air/moisture ingress can degrade efficiency and refrigerant/lubricant condition.
Large chiller inventory
Recovery and ventilation planning remain important despite A1 classification.
Thermal decomposition
Avoid flame/hot-work exposure until the circuit is safely recovered and controlled.
Actual risk depends on charge, release rate, pressure, room volume, ventilation, ignition sources, equipment construction, alarm logic and service condition.
See the Refrigerant Safety Guide for classification context.
R1233zd(E) refrigerant leak detection
Validate detector response to the finished blend
Leak management should include both outward refrigerant leak detection and inward air-leak diagnosis. Portable electronic detectors can locate positive-pressure or charged-component leaks, while purge runtime, vacuum-decay testing, ultrasonic methods and other vacuum-side techniques help identify air ingress. GasNose does not currently publish a dedicated R1233zd(E) page, so the general refrigerant detection library is linked.
Portable service leak detectors, fixed area monitors, A2L mitigation sensors and refrigerant identifiers perform different functions. Define the alarm action and concentration range before selecting the technology.
Regulatory position of R1233zd(E) in 2026
United States
EPA SNAP lists R1233zd(E) as acceptable in centrifugal chillers, industrial process refrigeration, industrial process air conditioning and other specialized uses. The current Technology Transitions reference GWP is 4. EPA SNAP pages also show ODP below 0.0004 and older GWP values/ranges around 3.7–7 depending on listing date and assessment basis.
European Union
R1233zd(E) has ultra-low climate impact and negligible ODP, but it remains subject to applicable EU chemical, ozone/F-gas and equipment rules. Its low GWP makes it far less exposed to numerical GWP limits than R134a- or R404A-class fluids.
Is R1233zd(E) being phased out?
R1233zd(E) is not being phased out as a high-GWP refrigerant. Its practical constraints are low-pressure equipment architecture, material/lubricant compatibility, manufacturer availability and future chemical-policy developments.
U.S. refrigeration limits differ by cold storage, supermarket, remote condensing, stand-alone product, industrial process and chiller category. A refrigerant may fit one pathway and fail another.
Use the Refrigerant Regulations Hub for regional research.
What should be compared with R1233zd(E)?
Compare the real equipment pathway: retrofit vs new system, A1 vs A2L capability, GWP threshold, glide, compressor envelope, energy efficiency and service ecosystem.
Practical misconceptions about R1233zd(E)
“R1233zd(E) has ODP exactly zero.”
EPA SNAP publishes a very small non-zero range below 0.0004.
“A leak always means refrigerant escapes outward.”
Sub-atmospheric portions of a low-pressure chiller can pull air and moisture inward.
“A1 means purge systems are unnecessary.”
Purge is about non-condensables and vacuum-side air ingress, not flammability.
“R1233zd(E) and R1234ze(E) are basically the same.”
They differ in chlorine content, boiling point, pressure level, safety class and typical equipment architecture.
R1233zd(E) refrigerant FAQ
Concise answers to common composition, retrofit, glide, safety and regulation questions.
What is R1233zd(E)?
What is its EPA GWP?
Does R1233zd(E) have zero ODP?
Is R1233zd(E) flammable?
Why do R1233zd(E) chillers operate under vacuum?
Why is a purge system important?
Can R1233zd(E) replace R123?
How does it compare with R245fa?
How are leaks found in a low-pressure chiller?
Is R1233zd(E) a pure refrigerant?
R1233zd(E) sources and further reading
This profile uses current EPA regulatory references plus refrigerant supplier, NIST, scientific and GasNose resources. Re-check the latest edition before design or compliance decisions.
Working with R1233zd(E) or planning a refrigerant transition?
Compare GWP, safety class, temperature glide, equipment compatibility and regulatory lifetime before selecting a refrigerant.
Technical Notice: This page is for refrigerant research and general technical reference. Refrigerant suitability, permitted charge, equipment approval, leak mitigation, servicing procedures and regulatory compliance depend on the exact equipment, installation and jurisdiction. Always verify current manufacturer documentation, SDS, applicable standards and local regulations before selecting, replacing, charging or servicing a refrigerant.