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In the United States, increased restrictions on the use, production, and importation of R-22 have been introduced, which will result in higher prices and reduced availability. So, how do we deal with these issues related to HCFCs such as R-22? The scale of the problem is little short of daunting.
TRANSITIONSBeside its long-standing use in air conditioning, R-22 also found its way into the refrigeration section over the years. During the transition away from CFCs, retrofitting directly from a CFC to a HFC was found in some instances to be both costly and technically unsatisfactory. The oil in the system needed to be replaced by a synthetic lubricant, which in some cases was not practical. And there were many cases of a deleterious effect on the seals. Also, hardware changes were required.
For such reasons, interim HCFC refrigerants were introduced to replace CFCs in refrigeration. These transitional refrigerants, which included many blends, contained at least one HCFC component that facilitated oil return and eliminated the need to make changes to the hardware.
OPTIONSThe first HFCs, such as R-407C, were not soluble in mineral and alkyl benzene (AB) lubricants, and new synthetic oils had to be developed. The new synthetic lubricants pick up moisture rapidly and are more expensive than the traditional oils.
So another option was to figure a way to use HFCs with the existing mineral or AB oil when retrofitting HCFC systems. In one case, Refrigerant Solutions (RSL) took that premise and started work on replacements for R-22. The new replacement refrigerants needed to be compatible with the existing lubricant in the system, provide a similar performance to R-22 and, of course, have zero ozone depletion potential (ODP).
The resulting refrigerants from RSL are R-424A, R-434A, and R-428A (which the company respectively brands as RS-44, RS-45, and RS-52.) Each uses a small amount of an HC refrigerant to help in oil return. They are Significant New Alternatives Program- (SNAP-) approved with an A-1 safety classification from the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE).
R-424A is suitable to replace R-22 in air conditioning applications in systems with a capillary as well as an expansion device. R-424A is a replacement for R-22 in existing equipment. There is no need to change the lubricant since R-424A is compatible with mineral, AB, and POE oils.
A testing program was carried out on R-424A which, compared to R-22, demonstrated a higher coefficient of performance, lower head pressures, lower discharge temperatures and pressures, a similar performance, and good oil return with all types of oils.
Conversions to and trials with R-424A have shown energy savings ranging from 10-20 percent compared to R-22 when R-424A is retrofitted into the same system while achieving similar capacity.
Companies which have converted away from R-22 to R-424A include Cable & Wireless, UK; Loblaws supermarket in Canada; Pratt & Whitney in the United States; Tropicana in the United States; Suncor in Canada; Kraft in the Philippines; Coca-Cola in Thailand; Irichi in Malaysia; and Valeo in China, amongst many others. Carrier Commercial replaced R-22 with R-424A in Carrier equipment at the Pratt & Whitney plant in Connecticut in 2007.
R-434A, with its high-cooling capacity, complements R-424A. R-434A replaces R-22 in both larger refrigeration and air conditioning equipment. With its low glide (less than one-third of R-407C), R-434A can be used in a wide range of applications such as air conditioning, refrigerated transport, bus, train, supermarkets, dairy chillers, cold stores, freezers, beer cellars, water chillers, and others.
R-434A has a coefficient of performance that matches R-22, similar discharge pressure to R-22, identical compression ratio, and a considerably lower discharge temperature than R-22. That makes R-434A a good alternative to replace R-22 in a low-cost retrofit situation, and in new, larger R-22 systems. OEMs can achieve cost savings as opposed to converting or redesigning R-22 systems for other HFC alternatives such as R-407C, R-410A, or R-134a.
For low temperatures, RSL developed R-428, which is similar to CFC-507 in its performance with a high capacity. R-428A has been designed as a replacement for R-502 and the interim HCFC blends (such as R-402A, R-403B, R-408A and R-411B), but also a replacement for R-22 at low temperatures where the system is designed to withstand R-502 pressures and can accommodate the higher capacity of R-428A (as compared to R-22).
R-428A replaced R-402A in Bidgood’s supermarket, Newfoundland, Canada. Provincial Refrigeration Ltd., working with Kerr Controls Ltd., carried out the conversion.
The high capacity of R-428A at low temperatures is a prominent feature of this new refrigerant. R-428A has a low-temperature glide of less than ½°C and is suitable for use in flooded systems.
Contractors and service technicians will do well to explore the new options and share them with their customers.
For more information, visit www.comstarproducts.com.
Publication Date: 07/06/2009