Recycled freon colder???? Now there's some prime malarkey! The gentleman
speak with forked tongue. It never ceases to amaze me what some people come
up with, including some professionals.
First of all, it is the evaporation point of the Freon that matters.
Different freon have different evap points. A btu is the amount of energy
to change the temperature of 1 lb of water by one degree. An evap point is
at what pressure the freon actually boils. This is what's happening in the
evaporator and what's commonly referred to as the suction or low side. As
the freon boils, it leaches the heat from it's environment, as heat always
migrates to colder, in one direction. This is why reverse cycle units (heat
pumps) for homes only do well in certain climates. What actually occurs is
the removal of heat, not the adding of cold. But this is why when a system
loses pressure, the coils actually freeze up because a lower pressure
translates to a lower temp, too low. When even more freon escapes, there is
not enough freon to fill the evaporator and evaporate, and it warms up. Too
much freon and the pressure increases, ergo temp, and the coil warms up
because the freon doesn't boil (evaporate) at the higher pressure.
Secondly, the greatest threat is air in the system. Air is a non-condensable
compound. You can detect this by the movement of a gauge placed on the high
side, preferable one that is silicone damped. The needle will jump like
crazy as the noncondensables make it through the system. Undamped gauges
jiggle a lot especially if it is placed closer to the compressor.
Air in the system will also cause higher condenser pressures, but not better
cooling since it cannot condense. This is why one purges the charging hoses,
both pre- and post-guage low side, with freon before opening the system and
charging. Freon good, air bad, very bad. Generally, a vacuum will remove
all the air, but only a two stage vacuum goes beyond 28 inches of mercury
( a perfect vacuum is approx 30inches and water boils at about 29). This
deep vacuum has to be maintained for some time before all the water
literally boils off and is sucked up as steam. The problem is even with a
two stage vacuum, most auto systems leak, so this is never achieved and you
end up not only failing to evaporate the moisture, you actually bring
moisture into the system through the leaks! Back in the good old days, when
freon was less than a buck a pound and considered safe, we would just blow a
charge through the system to remove all the air and most of the moisture as
the water forms little ice crystals and is carried off by the freon and into
the atmosphere. Moisture in the system can be detected by wider and more
irregular swings of the low side gauge (as opposed to regular swings that
may occur from a bad expansion valve or device). These swings occur as the
ice crystals form and block the orifice of the x-valve or device. This is
especially true of pressure regulated x valves as opposed to
thermostatically controlled x valves.
Finally, if you can find virgin, use it. R12 just had a recent wholesale
price increase, a friend of mine is a regional distributor and there's less
and less virgin available. Recycled is not quite as pure, as not all the
contaminants can be removed, and a great deal depends on the recycling plant
and the source of the material. If the R12 came from an electric
compressor, such as a commercial or earlier model refrigerator, there is
always a risk of some corrosive compounds remaining if the compressor burned
out. Once you smell that (what happens is the burned windings' insulation
reacts with the freon), you never forget it, and it is not an uncommon
occurrence. But I do agree conversion to R134 should not be jumped into
until a major overhaul is necessary. I still would not opt for it based on
the OEM condenser limits.
BTW, if you want to change out the compressor you do NOT need to bring down
the charge or open the system up. The service valves can be turned IN all
the way closing the valve from the system and the you only lose the charge
out of the compressor and a lot less risk of contamination. Just be sure to
crack the fittings slowly when under pressure. After you hook up the
compressor, only crack the low side valve a hair while leaving the high side
connection still closed and a little lose to allow a small amount of freon
and air to escape out of the lose fitting. Then, while it's flowing out,
tighten the lose fitting down. After you've done that, open both service
valves all the way. You can also do this with a charging hose attached to
the high side and letting the air out that way while the valve is fully
turned in. This way, you can tighten all the fittings before purging.
These methods protect against air and some moisture remaining trapped in the
system.
So there you have it, A/C 101, and then some. I really hope this helps
someone out there as this is a lot of typing ;o)
stephan #2821
> I installed recaptured/recycled R12 in my car and the gentleman who
performed the
> work stated that it was actually colder than virgin R12. The price he
mentioned
> was $20-25/ pound, not to bad! He was also recommending to keep it R12
until
> major surgery on the system was needed.
> Jim
> 1191
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