> 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
///
/// bricklin@autox.team.net mailing list
///
|