At a glance
| R-134a | R-1234yf | |
|---|---|---|
| Type | HFC, single component | HFO, single component |
| ASHRAE 34 safety class | A1 | A2L |
| GWP (EPA Technology Transitions table) | 1,430 | 1 |
| Boiling point at 1 atm | -14.9°F | -21.0°F |
| Critical temperature | 213.9°F | 202.5°F |
| Service port fittings | R-134a quick-connect | SAE J639 quick-connect, 17 mm high side, 14 mm low side |
| Container thread | 1/2 in-16 Acme, right-hand | 1/2 in-16, left-hand |
| Recovery/recharge equipment | R-134a machines | SAE J2843, R-1234yf only |
Chemours sells R-1234yf as Opteon YF and Solstice Advanced Materials (formerly part of Honeywell) as Solstice yf. GWP figures for R-1234yf vary by source and basis: EPA's MVAC refrigerant page lists 4, Chemours lists 4 on the IPCC AR4 basis and 1 on AR5, and EPA's Technology Transitions reference table lists 1, citing WMO 2022.
Operating pressures
The two PT curves nearly overlap. R-1234yf runs a few psi higher at evaporator temperatures, the curves cross between 100°F and 110°F, and above that R-134a is higher:
- 40°F: R-134a 35.0 psig, R-1234yf 38.4 psig
- 80°F: R-134a 86.7 psig, R-1234yf 89.0 psig
- 100°F: R-134a 124.2 psig, R-1234yf 124.9 psig
- 110°F: R-134a 146.4 psig, R-1234yf 145.9 psig
- 130°F: R-134a 198.7 psig, R-1234yf 195.0 psig
Because the pressures are so close, gauges cannot tell you which refrigerant is in a car. Read the underhood label and check with a refrigerant identifier before recovering. SAE J2912 covers identifiers for both refrigerants, and SAE J2851 covers separate equipment for removing contaminated refrigerant.
Fittings and equipment
EPA requires a unique set of fittings for every refrigerant approved for motor vehicle AC, so that refrigerants are not mixed, and states that "an adapter may not be used to convert a fitting". R-1234yf service ports are SAE J639 quick-connects with a 17 mm high side and 14 mm low side; R-1234yf containers have left-hand threads where R-134a containers are right-hand Acme. Professional service containers must use fittings consistent with SAE J2844.
Recovery, recycling and recharging machines for R-1234yf are built to SAE J2843, which applies to equipment used with R-1234yf only. Chemours also lists SAE J2913 for R-1234yf leak detectors. Because J2843 machines are for R-1234yf only and EPA bars fitting adapters, an R-134a machine is not used on an R-1234yf system.
Flammability
R-1234yf is A2L: lower toxicity, lower flammability. EPA's use conditions require R-1234yf systems to meet the safety requirements of SAE J639, including a flammable refrigerant warning label, a high-pressure compressor cutoff switch, pressure relief devices and unique fittings. EPA describes it as mildly flammable but able to be used safely. See A2L refrigerants.
Not a retrofit
Chemours states that Opteon YF "cannot be used for retrofit applications", and EPA's acceptability listing for R-1234yf covers new vehicles. An R-134a car is serviced with R-134a and an R-1234yf car with R-1234yf. Chemours says Opteon YF is compatible with POE lubricants and PAGs formulated specifically for R-1234yf; use the oil the vehicle maker specifies.
US regulatory status
- New vehicles. EPA's 2023 Technology Transitions rule bars refrigerants with a GWP of 150 or more in model year 2025 and later light-duty passenger cars and trucks, effective no earlier than October 24, 2024. Medium-duty passenger vehicles, heavy-duty pickups and complete heavy-duty vans follow in model year 2028. R-134a is above that limit; R-1234yf is far below it.
- Existing vehicles. EPA says the rule does not affect existing systems, so cars built with R-134a can continue to be serviced with R-134a.
- Who can service. Under Clean Air Act Section 609, anyone who services motor vehicle AC for payment or barter must be trained and certified, regardless of refrigerant. Small cans of two pounds or less with unique fittings and self-sealing valves can be sold to owners for do-it-yourself use on their own vehicles. Intentional venting is prohibited.