As industry faces increasing regulatory pressure to shrink its growing environmental footprint, hydrofluoro-olefin (HFO)-based refrigerants provide design engineers and equipment owners with non-ozone-depleting, low global-warming potential (GWP) alternatives. The energy-efficient solutions are suited for a range of end-use applications and climates without compromising system performance.

Environmental Regulations Driving Change

Refrigeration system owners have only a short time to put into place changes to comply with the U.S. Clean Air Act and the International Montreal Protocol Agreement. These agreements, which phase out the use of ozone-depleting substances, prohibit the manufacture or use of virgin R22 in the refrigeration industry in three years. Starting in 2020, the supply of R22 for servicing refrigeration systems must come from remaining inventory across the value chain or recovered and reclaimed material. To reduce dependence on R22, and based on the life of existing equipment, many end-users have developed plans to retrofit or replace the existing equipment with non-ozone-depleting hydrofluorocarbon (HFC) refrigerants such as R404A, R507, R407A, R407C, R438A and R410A.

More recently, the focus of environmental policy has expanded to include climate-change considerations. With this new attention to the global-warming potential and atmospheric life of gases used in emissive applications, regulations have started to incorporate restrictions on the use of HFC refrigerants. For example, last year the U.S. Environmental Protection Agency announced — via its significant new alternatives policy (SNAP) program — limitations on the use of R404A, R507, R134a and R407A in specific end-uses in the retail food refrigeration industry over the course of 2016 to 2020. In addition, in March 2016, the EPA proposed additional regulations to make the use of R404A, R507, R410A, R407C and R134a unacceptable in new centrifugal and positive-displacement chillers used in air-conditioning systems starting in 2024.

HFO-Based Refrigerants Satisfy Performance and Regulatory Requirements

For engineers and system owners looking to meet the increasing regulatory constraints in a cost-effective manner while ensuring performance and energy efficiency are not sacrificed, several HFO refrigerants and refrigerant blends have been developed.

HFOs contain the same molecular building blocks as HFCs — hydrogen, fluorine and carbon — but HFO refrigerants have a significantly lower global-warming potential because of a double-bond between two of the carbon atoms. This olefinic bond allows the molecule to breakdown quickly in the atmosphere — giving it a short atmospheric life — though it remains stable within refrigeration systems and chillers. In addition, HFOs are compatible with the plastics, elastomers, metals and polyolester (POE) lubricants currently used with HFCs. In many cases, HFO blends can be used to retrofit existing equipment as well as in newly designed systems.

Several HFO blends have been commercialized over the past few years to address the latest climate-change regulations. For instance, HFO blend R449A is an ASHRAE listed A1 (nonflammable) refrigerant that was designed specifically to replace R404A, R507 or R22 in direct-expansion systems. Compared to R404A, R449A provides a 67 percent reduction in global-warming potential while offering comparable capacity and as much as a 12 percent increase in energy efficiency. Compared to R22, R449A offers a 27 percent reduction in global-warming potential without sacrificing capacity or energy efficiency.

For systems designed for R134a, the azeotropic HFO blend R513A offers more than 50 percent reduction in global-warming potential while matching the performance and efficiency and remaining nonflammable. Also, due to its close match to the incumbent R134a, R513A has been selected by several major chiller OEMs as their R134a replacement.

In addition to the HFO blends already in use commercially, several other pre-commercial low global-warming potential alternatives have been evaluated by OEMs and industry associations with positive results. For example, R452B is a R410A replacement in scroll chillers, with a 67 percent reduction in global-warming potential, high efficiency and low 2L flammability. Another refrigerant, R452B, is design compatible with R410A equipment, enabling a smooth transition with minimal redesign.

For systems currently designed for R123, HFO-based blend R514A is an azeotropic low global-warming potential replacement suitable for retrofit or new equipment design. Another refrigerant, R514A, offers a 97 percent reduction in global-warming potential compared to R123 while maintaining comparable capacity and energy efficiency.

When considering a system retrofit of any type of process cooling equipment to prolong the useful life of the equipment, or when evaluating new equipment and refrigerants, it is always prudent to review the manufacturer’s guidelines for any equipment- or application-specific considerations. Though the regulatory landscape and the phase-out or restricted use of familiar refrigerants may at first seem daunting, sustainable and cost-effective solutions are available to meet high performance, efficiency and regulatory requirements.