R-1336mzz is a hydrofluoroolefin (HFO) refrigerant with the chemical formula CF₃CH=CHCF₃, developed as a low global warming potential (GWP) alternative to legacy refrigerants used in large commercial cooling and heat recovery systems. It exists in two isomeric forms — R-1336mzz(Z) (cis) and R-1336mzz(E) (trans) — with the Z isomer being the most commercially relevant for HVAC applications, particularly in low-pressure centrifugal chillers. Its combination of favorable thermodynamic properties, an A1 safety classification, and near-zero environmental impact has made it a leading candidate for next-generation chiller designs.
Technical Specifications
R-1336mzz(Z) offers a unique set of characteristics that distinguish it from both older high-GWP refrigerants and other HFO alternatives:
- GWP: 2 (AR5, 100-year horizon), dramatically lower than R-134a (GWP of 1,430) and R-123 (GWP of 77).
- Ozone Depletion Potential (ODP): 0.
- ASHRAE 34 Safety Classification: A1 (non-toxic, non-flammable), allowing use without the added safety measures required for A2L or B2L refrigerants.
- Normal Boiling Point: 33.4°C (92.1°F), making it a low-pressure refrigerant similar in operating pressures to R-123.
- Critical Temperature: 176.65°C (349.97°F).
- Critical Pressure: 3.38 MPa (490 psi).
The high critical temperature and relatively high boiling point make R-1336mzz(Z) particularly well suited for heat pump applications and Organic Rankine Cycle (ORC) systems that recover low-grade waste heat.
Common HVAC Applications
R-1336mzz(Z) is primarily used in low-pressure centrifugal chillers serving large commercial and institutional buildings, data centers, and district cooling plants. It functions as a near drop-in replacement for R-123 in new chiller designs, though equipment must be specifically engineered for its thermodynamic profile. Beyond conventional cooling, it is increasingly adopted in high-temperature heat pumps operating at condensing temperatures above 100°C and in ORC power generation systems that convert waste heat into electricity. The E isomer, R-1336mzz(E), has found use as a foam blowing agent and specialty solvent rather than as a primary HVAC refrigerant.
Regulatory Context and Standards
R-1336mzz(Z) aligns with the goals of the Kigali Amendment to the Montreal Protocol, which mandates a global phasedown of high-GWP hydrofluorocarbons (HFCs). In the United States, the EPA’s AIM Act and associated regulations under 40 CFR Part 84 support the transition to low-GWP alternatives like this refrigerant. Its A1 safety classification under ASHRAE Standard 34 simplifies compliance with ASHRAE Standard 15 (Safety Standard for Refrigeration Systems) and local mechanical codes, as it does not trigger the additional ventilation, detection, or charge-limit requirements associated with flammable or toxic refrigerants.
Practical Significance for HVAC Professionals
For engineers and technicians, R-1336mzz(Z) represents a path to meeting increasingly strict environmental regulations without compromising on safety or requiring extensive building-level mitigation measures. Its low operating pressures reduce mechanical stress on system components, and its thermodynamic stability supports long equipment lifespans with minimal refrigerant degradation. However, because it operates at sub-atmospheric pressures on the evaporator side in many configurations, leak prevention and system tightness are critical considerations during installation and maintenance to prevent air and moisture infiltration.