retrofitting with non-cfc substitutes
retrofitting with non-cfc substitutes
retrofitting with non-cfc substitutes
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RETROFITTING WITH NON-CFC SUBSTITUTES<br />
Its use requires higher tip speeds than CFC-12, so impeller and/or gearbox replacementä is<br />
necessary. Typically, oils used for CFC-12 are not miscible <strong>with</strong> HFC-134a. PAG oils<br />
developed for HFC-134a are not compatible <strong>with</strong> CFC-12 residues, thus requiring thorough<br />
flushing of the systems before replacement. Ester oils seem to have overcome this problem.<br />
Some desiccants (e.g. activated alumina) commonly used in CFC-12 systems are not compatible<br />
<strong>with</strong> HFC-134a.<br />
HCFC-124 retrofit for CFC-114<br />
This has been suggested as an alternative to CFC-114 in centrifugal chillers such as those used<br />
in naval applications. It is not readily available for use in either new or retrofit chillers. (1991)<br />
Problems<br />
HCFC-124 requires operation at higher pressure levels, higher compressor speeds, and smaller<br />
impeller diameters than CFC-114. HCFC-124 is not suitable for use in existing systems in most<br />
cases because the pressure levels will exceed design ratings and complete compressors<br />
replacement is necessary.<br />
HFC-152a/HCFC-124/HCFC-22 mixture for CFC-12<br />
Benefits<br />
It is compatible <strong>with</strong> conventional refrigeration oils.<br />
Problems<br />
It is not readily available because HCFC-124 is not in large production. The mixture is likely<br />
to have degraded heat transfer performance in the flooded evaporators and shell side<br />
condensation normally used in centrifugal chillers. Thus there is likely to be a significant<br />
performance penalty when substituted in existing chillers. Servicing such a system brings on<br />
new difficulties because any vapour losses will change composition and performance.<br />
Measuring and changing equipment are not available to mitigate this problem.<br />
HCFC-22/HCFC-142b mixture retrofit for CFC-12<br />
This azeotropic mixture is being used in France to retrofit systems using CFC-12.<br />
Benefits<br />
Both components of the mixture are available commercially. The mixture is not flammable to<br />
the proportions used to emulate CFC-12 (but flammable proportions can be encountered as a<br />
result of spills or losses).<br />
An updated version of this document will be available November 1994.<br />
HCFC-123 retrofit for CFC-11<br />
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