Tom Gardner wrote:



I was thinking of just replacing the refrigerant *IF* an energy savings
would justify it. The 40% they state is mighty attractive! My system
is in good shape and should last a little while yet. I sell to a HVAC
supply outfit and am able to purchase from them. I imagine I'll be
replacing the unit in a number of years so I'll keep abreast of what to
do and what to buy.
40%?? VERRRY unlikely. You can swap to Propane, it will improve
efficiency by MAYBE 5% or so. Not so good if you spring a leak in
the evaporator coil. Next time the A/C starts up, the furnace
blows apart like a grenade.

There may be some other mixtures that are also available as drop-in
replacements, but anybody that claims they can get a 40% efficiency
boost without changing anything else in the system is selling snake
oil!

Also, many home A/C systems, especially older ones, use capillary
tube metering, and any change in heat capacity, saturation curve
or liquid viscosity will end up throwing the metering of liquid
into the evaporator off. Well, of course, cap tube systems don't
really meter the liquid well except at one set of temperatures,
anyway. And, a system with a thermal expansion valve needs to
have the same fluid in the sensing bulb as the refrigerant, so
changing the refrig. in those systems can lead to major malfunctions.
The worst would be "slugging", where a huge load of liquid pools in
the evaporator and is then slugged into the compressor, possibly
destroying it the first time this happens.

Jon