The impact of new refrigerants on centrifugal chillers

R-134a has long been the dominant refrigerant in centrifugal chillers, praised for its stability, non-flammability and favourable thermodynamic properties. However, with a Global Warming Potential (GWP) of approximately 1,430, R-134a is now under regulatory pressure as nations worldwide strive to reduce greenhouse gas emissions. This has led to an industry-wide transition towards next-generation, low-GWP refrigerants that meet both environmental goals and operational performance standards.

This article explores the implications of this transition, the emerging refrigerant alternatives, and how they impact centrifugal chiller design, operation and lifecycle costs.

Why R-134a Is Being Phased Down

R-134a, a hydrofluorocarbon (HFC), has zero ozone-depleting potential (ODP), which made it a suitable replacement for CFCs and HCFCs in the 1990s and early 2000s. However, its high GWP has placed it squarely in the crosshairs of climate-focused regulations, including:

• The Kigali Amendment to the Montreal Protocol, which mandates a global phase-down of HFCs
• The U.S. AIM Act, which aims to phase down HFC production and consumption by 85% by 2036
• The EU F-Gas Regulations, which enforces quotas and bans on high-GWP refrigerants

Emerging low-GWP alternatives to R-134a

Manufacturers and refrigerant developers have introduced several next-generation refrigerants designed to replace R-134a in centrifugal chillers. The most promising candidates are hydro-fluoro-olefins (HFOs) and HFO-HFC blends, which offer low GWP, zero ODP and compatibility with modern equipment:

R-513A

• Type: HFO/HFC blend (50% R-134a / 50% R-1234yf)
• GWP: ~631 (about 55% lower than R-134a)
• Flammability: A1 (non-flammable)
• Compatibility: Retrofit-compatible in many R-134a systems
• Use Case: Ideal for facilities needing a near-term drop-in solution with minimal system modification

R-1234ze(E)

• Type: Pure HFO
• GWP: ~7
• Flammability: A2L (mildly flammable)
• Performance: Lower cooling capacity compared to R-134a; requires system redesign
• Use Case: Suited for new chiller designs prioritising environmental performance

R-515B

• Type: HFO blend (with R-1234ze and small amount of R-227ea)
• GWP: ~293
• Flammability: A1 (non-flammable)
• Performance: Designed for use in new centrifugal chillers; lower pressure than R-134a
• Use Case: Emerging solution for end users seeking safety as well as environmental performance

R-1233zd(E)

• Type: HFO
• GWP: ~1
• Flammability: A1
• Performance: High efficiency, but lower operating pressure than R-134a; more common in large, low-pressure centrifugal chillers
• Use Case: New equipment only, especially for large-scale applications

Technical and operational impacts

System design modifications

Next-generation refrigerants vary in pressure, density and heat transfer properties, which means:

• New compressors and heat exchanger designs may be required
• Expansion devices, controls and oil systems must be recalibrated or replaced

Energy efficiency

• R-1234ze(E) and R-1233zd(E) are highly efficient in chillers specifically designed for them
• R-513A offers similar performance to R-134a, making it an attractive retrofit solution

Safety and handling

• The A2L classification for some alternatives (e.g., R-1234ze) introduces mild flammability, requiring updated safety procedures and potentially new building codes
• A1 alternatives like R-515B and R-513A are preferred in mission-critical or conservative environments

Environmental and regulatory compliance

Switching to low-GWP refrigerants helps:

• Reduce direct greenhouse gas emissions
• Qualify for green building certifications like LEED
• Meet upcoming regulatory bans on high-GWP refrigerants

Retrofit versus replacement: Strategic considerations

Retrofit scenarii

• R-513A is often the most practical option for retrofitting existing R-134a centrifugal chillers
• Retrofitting typically involves minimal component changes but may still require refrigerant charge adjustments and software updates

Replacement scenarii

• For long-term investment and maximum sustainability, new chiller systems designed for R-1234ze, R-515B or R-1233zd(E) are recommended
• Upfront costs are higher, but lifecycle energy savings and regulatory compliance benefits make it a compelling option

Industry adoption

Leading manufacturers such as Carrier, Daikin, Johnson Controls and Trane have released centrifugal chillers compatible with or optimised for next-gen refrigerants. Trane’s CenTraVac line and Carrier’s AquaEdge series, to cite two examples, support R-1233zd(E), R-513A and R-515B, offering customers flexibility based on local codes and sustainability goals.

Conclusion

The transition from R-134a to next-generation refrigerants marks a pivotal shift in the centrifugal chiller market. While R-134a has served the industry well, environmental imperatives and evolving regulations are driving adoption of low-GWP alternatives that offer equivalent performance with a significantly reduced environmental impact.

Facility managers, mechanical contractors and design engineers must stay informed on refrigerant developments to ensure systems remain efficient, compliant and future-ready. Whether through retrofits or full system upgrades, embracing next-generation refrigerants is no longer optional – it’s essential.