Oct 09 1998
Subject: R-12, classic cars and the ozone layer

Freon (CFC's) and the Ozone Layer

Owners of air conditioned classic cars designed to use R-12
refrigerant are having a tough time keeping their cool these
days. The price of R-12 is approaching $25 a pound and
converting older A\C systems to use the new R-134a
refrigerant can be prohibitively expensive. So we're left
with a choice of taking a hard hit in the wallet or
sweltering in the heat.  

Are we really in danger of increased ultraviolet radiation
due to ozone layer damage from CFC's? The government mandated
phase-out of CFC refrigerants is based on this theory but
much of the information in circulation on this subject is
quite misleading and some of it is just flat wrong.

First off, what is the ozone layer and how is it supposedly
damaged by CFC's?

Ozone is made of 3 atoms of oxygen that have joined up to
form a molecule. (O3) In the stratosphere, molecules of
ordinary oxygen (O2) absorb photons of ultraviolet light from
the sun and are converted to ozone. Ozone strongly absorbs UV
light and protects living things below on the surface from
damage. The ozone layer is formed and maintained by the sun.

The important thing to grasp is that the sun produces ozone.
If, by some magic, ALL the ozone were to disappear NOW...a
new ozone layer would be formed by the sun's action on
atmospheric O2 in a matter of days.

How do CFC's damage the ozone layer? Let's take a look at how
the damage is done. Chlorine monoxide is the culprit.
A single molecule of chlorine monoxide can split tens of
thousands of ozone molecules. This much is absolutely true.
It's where the chlorine monoxide comes from that is the
subject of controversy.

How do CFC's which are many times heavier than air get high
into the stratosphere in the first place? The plain truth
is...most of it doesn't! When CFC's are released into the
air, they immediately seek the lowest level available and
stay there for the most part. Since CFC's are extremely
stable, they remain in their non-toxic, non-ozone damaging
form for a very long time. The only possible way for such a
heavy molecule to ever reach the stratosphere is to be
carried aloft on a violent updraft such as occurs in
thunderstorms.

The few CFC molecules that actually do reach the ozone layer
account for a very small percentage of all the chlorine
monoxide found in the stratosphere. So where does the rest
come from? There are several sources and we'll look at them
one at a time.

VOLCANOS: Volcanos account for about 30% of atmospheric
chlorine monoxide. The Mt. Pinatubo eruption in the early
90's released vast quantities of chlorine monoxide into the
atmosphere, probably more than that contained in all the
CFC's manufactured to that date.

SEAWATER: The sea covers about 70 percent of Earth's surface.
Seawater contains sodium chloride - common salt. The wave
action from all the world's coastlines produces a very fine
spray. Some of the very tiny spray droplets evaporate leaving
crystals of salt suspended in the air. The really small ones
can float in the atmosphere for decades and, eventually,
reach the upper atmosphere. Here, water vapor condenses on
the salt crystals to form tiny salt water droplets. Exposed
to UV light, they split to become atoms of chlorine and
sodium.  The chlorine atoms pick up oxygen atoms from the
atmosphere and are converted into chlorine monoxide. Each
chlorine monoxide molecule can destroy thousands of ozone
molecules.

Volcanos erupt from time to time but the sea never sleeps.
Chlorine monoxide from seawater probably accounts for about
70 percent of that found in the stratosphere.

SPACE SHUTTLE LAUNCHES: Volcanos and seawater account for the
vast majority of chlorine monoxide found in the stratosphere,
but there are other contributors as well. The space shuttle's
main engines burn liquid hydrogen and liquid oxygen. The
exhaust product is mainly water and has no detrimental effect
on the ozone layer, but the boosters are a different story.
The solid fuel boosters belch out vast quantities of chlorine
compounds and they bore directly through the stratosphere
with every launch and so deliver the nasty stuff right where
it will do the most harm.

The space shuttle program probably does more to damage the
ozone layer than all the leaking air conditioners in the
country but we (the users of CFC refrigerants) are the ones
who get the blame and have to pay the price. It just ain't
fair.

SO WHAT CAN WE DO ABOUT IT? There are several R-12
substitutes available, the most common is a mixture of 60%
iso-butane and 40% propane. It is compatible with all mineral
based compressor oils and can be mixed with R-12 in any
combination. This substitute (commonly known as Hot Shot)
works well in systems designed for R-12 but is quite
flammable and could present a fire hazard in the event of a
head-on collision. Use of a flammable R-12 substitute could
also present a hazard for service personal using R-12
recovery equipment. Also, it may be illegal in some states.

Anyone considering the use of a flammable substitute should
be aware of the danger involved and clearly mark any system
containing a flammable substance to warn A\C service personal
that may need to work on the vehicle in the future.

Personally, I have been using pure propane as an R-12
substitute for over 15 years with excellent results. Pure
propane runs about 20 degrees colder in the evaporator and
about 40 degrees hotter in the condenser. Also pressures on
both the high side and low side run a bit higher. Typically,
the low side pressure will be about 50 psi and high side
pressure will run at about 300 psi depending on outside air
temperature.

I have had some reports of newer rotary compressors failing
in service while using propane. The plastic vanes can't take
the higher temperatures and melt. Running these compressors
about 1\2 to 1 pound low seems to solve the heat problem.
Older piston type compressors use metal reed valves and have
no problem with the additional heat.

Propane (common torch gas) is cheap, convenient, and
available everywhere. A modified propane torch can be used to
charge propane into an A\C system. (An illustration is
available at my website - link is posted below)

Propane can only be used in systems designed for R-12.
Propane cannot be used in systems designed for R-22 or R-134a

No inexperienced person ever should attempt repairs on any
air conditioning system. If in doubt, please seek the help of
a qualified professional.

The bottom line is R-12 substitutes do work and for the
classic car collector experienced in A\C repairs, it could be
a viable option.

Comments invited.

John Young

HTTP://www.prelube.com