REFRIGERANTS
low-GWP options (<150) currently undergoing the EPA’s SNAP approval process. However, to achieve extremely low GWP levels, these HFO blends all fall under the A2L (mildly flammable) classification. As such, studies are currently underway by the governing bodies to develop safety use standards for this emerging class of refrigerants. Among the medium-pressure alternatives include R455A, R454C and R457A, while HFO1234yf/ze and ARM42 comprise the low-pressure refrigerant options. As these compounds navigate the EPA approval process, look for future SNAP ruling updates to verify their specific use parameters.
Natural refrigerants
Aside from these synthetic blends, there are also a few high-performance natural refrigerant alternatives that are not only very low-GWP options, but acceptable for use per the EPA’s SNAP ruling. Ammonia (NH3
or refrigerant name R717), propane (refrigerant name R290) and carbon dioxide (CO2 or
refrigerant name R744) are all refrigerants that occur naturally in the environment and have a long history of use in refrigeration applications.
Ammonia has excellent thermodynamic properties and was among the first refrigerants used in refrigeration applications. As a B2L refrigerant, R717 use requires careful adherence to safe application procedures. Ammonia’s suitability in low- temperature applications has made it a mainstay in industrial, process cooling, cold storage and ice rink applications. Today, some environmentally conscious supermarkets are trialing all-natural NH3
/CO2
cascade systems to significantly reduce their carbon footprints.
Propane is a hydrocarbon that was also identified in the early days of refrigeration as a high- capacity, energy-efficient refrigerant with superior performance characteristics. The advent of synthetic A1 refrigerants moved the industry away from R290.
But since the 2000s, R290 has been regaining global popularity as a lower-GWP, effective alternative to HFCs such as R404A and HFC134a. R290 applications typically have a charge limit of 150 grams, making it especially well-suited for a wide range of low- charge, reach-in display cases. Regulatory bodies that govern refrigerant safety standards are currently evaluating expanding its charge limits. CO2
is a non-flammable and non-toxic refrigerant that has proved a very effective alternative in both low- and medium-temperature applications, especially in regions with lower ambient temperatures. Its low critical point and high operating pressure (around 1,500 psig or 103 bar) dictate that CO2
refrigeration strategies must be
cascade, secondary and transcritical booster systems have been successfully deployed in commercial and industrial applications in Europe for nearly two decades. Recent environmental regulations have driven the wider adoption of these systems in North America.
The EPA’s 2015 refrigerant ruling marked the beginning of a major transition for the U.S. commercial refrigeration industry. While several new A1 alternatives have been introduced as viable in some applications, there is still quite a bit of work needed to meet the needs of the wide range of refrigeration applications and achieve desired reductions in GWP. Globally, the industry can expect continued regulatory activity in the coming years, especially with the introduction of new lower-GWP alternatives.
It’s also important to remember that many operators are also stating corporate sustainability objectives, while others wish to put an end to compliance concerns once and for all. To implement truly “future proof” refrigeration systems, many
designed to account for these unique characteristics. CO2
Updates to safety standards underway
To help ensure the safe use of A2L and A3 refrigerants, national and international governing bodies are currently evaluating safety standards and charge limits. These efforts include:
Review A2L safety standards: ■ US: UL 1995, ASHRAE 15; target date is late 2017
■ International: ISO 5149, IEC 60335, EN378; target date is late 2017. Update building codes: ■ Building codes for mildly flammable (A2L) refrigerants are being expedited for adoption in the 2021 code cycle.
Evaluate A3 charge limits: ■ US: raising the A3 charge limit from 150g to 300g–500g. Flammable refrigerant study: ■ $5.2M partnership by AHRI, ASHRAE and DOE to study flammable refrigerant behavior in real-world applications.
operators are trying to limit their carbon footprint with refrigerants that do not exceed the 150 GWP threshold. Today, natural refrigerants are the best way to achieve this goal, even though they present their own unique operating challenges. As A2Ls make their way through environmental regulations and safety standard approvals, operators will have a broader range of options from which to choose. It remains to be seen which refrigerant alternatives will become the go-to options of the future.
www.acr-news.com
August 2017 43
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