USA: Honeywell and Trane are to conduct field tests on Trane rooftop units with R466A – Honeywell’s long-awaited non-flammable alternative refrigerant to R410A.
Trane Technologies is said to be currently testing the refrigerant at the University of California, Davis, Western Cooling Efficiency Center (WCEC), evaluating its performance with a Trane rooftop unit used in light commercial HVAC applications. The US manufacturer will also deploy and test R466A at three customer locations in different parts of the United States as part of a one-year field trial.
The field trials will test compatibility with new equipment installations and retrofit conversions. It is said that Trane will closely monitor power and energy consumption and analyse the refrigerant characteristics “to further assess the refrigerant as a replacement for R410A”.
First announced in June 2018, R466A is branded by Honeywell as Solstice N41. It is a blend of R32 and R125 – the two components of R410A – with the addition of 39.5% of trifluoroiodomethane, better known as CF3I or R13I1. This gives the refrigerant a GWP of 733, just slightly more than R32’s GWP of 675, but with zero flammability.
In 2019, air conditioning manufacturers Toshiba Carrier and Midea both reported “promising” test results with R466A. Toshiba Carrier said it intended to follow up “promising initial performance testing” with reliability testing in VRF systems. Midea described R466A as “a promising option” as a “sustainable and safe offering” for end users. Since then, we have heard nothing from either manufacturer.
Despite the initial market enthusiasm, three years on, R466A is still yet to be adopted by any OEM. This is despite Honeywell’s insistence that R466A has undergone “extensive analysis” by over 15 OEMs and leading compressor manufacturers, clocking up more than 100,000 hours in applications including VRF, rooftops and the unitary ducted equipment used in the US.
Previous tests have indicated that R466A performs similarly to R410A. Any reticence to adopt R466A appears to be centred on concerns involving the use of the CF3I component, the stability of the molecule and/or the material compatibility of the refrigerant. Honeywell has consistently denied these claims, telling the Cooling Post that the stability and shelf-life can be addressed with standard measures practiced in the industry.
However, compressor manufacturer Bitzer, referring to R466A in its highly-respected Refrigerant Report, raises concerns regarding the refrigerant’s “long-term chemical stability and material compatibility under the special requirements of the refrigeration cycle”.
Also, while R466A has a far lower GWP than R410A, some of that advantage is negated by the fact that it requires a comparatively larger system charge. In addition, despite talk of it being a retrofit product, its use in split systems, at least, would require replacement of the condensing unit.
Previous retrofit test
The Cooling Post has found that Trane has carried out at least one other previous trial with R466A in one of its rooftop units at the University of California. A report published in 2019 reveals the results of a comparative test between R466A and R410A carried out by the University’s Western Cooling Efficiency Center on a 4-ton Trane RTU.
The standard unit under test was fitted with an adjustable TXV to accommodate the variation in system pressures for the two different refrigerants. The heat pump equipment was tested in cooling mode at six outdoor air conditions from 75°F-115°F (24ºC-46ºC) using R410A to obtain a baseline and repeated the tests after a drop-in replacement with R466A.
Tests showed a 5% reduction in capacity on average for R466A across all test temperatures and a 2% decrease in efficiency compared to R410A, although it was recognised that the efficiency drop could be minimised through more extensive tuning of the system.
The WCEC test report also raises questions about the durability of the refrigerant: “There has been some concern about the durability of the refrigerant with existing equipment that can result in breaking down of the molecule. These durability issues need to be investigated further before a firm recommendation can be made,” it says.
Commenting on the new trials, Randy Newton, vice president, engineering at Trane Technologies, said: “Our continuous testing, research and development support new technologies that improve the carbon footprint in support of our customers’ needs and contribute to our Gigaton Challenge. As we evaluate refrigerants to replace R-410A, we seek to balance environmental impact, safety, efficiency and affordability. We look forward to working with Honeywell to assess the feasibility of Solstice N41 as a safe option for the industry that could enable ease of transition to meet regulatory deadlines and help our customers meet their overall sustainability goals.”
Ken West, Honeywell Fluorine Products’ vice president and general manager, added: “Honeywell scientists devoted years of research and development to develop a nonflammable product that can safely replace R-410A in homes and small business as a near drop-in replacement within existing infrastructures, while providing a reduced GWP coupled with similar energy efficiency. This next step with Trane solidifies our confidence in moving towards industry adoption of R-466A.”
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