Refrigerant and rebuilding AC (In defense of Durocool)

Fri Jun 13 21:50:07 EDT 2003

You make a good point. I wouldn't relish the idea of being the subject of
any highway pyrotechnics.
But I can't think of a likely scenario that would result in rapid release
into the passenger compartment (hell; I've never even seen an evaporator
leak).
W/ regards to George Gobel; I would charecterize him as a man who's spent a
great deal of his life studying refrigeration science & technology. He did
develop R406 which (because it's 4% isobutane) is considered "weakly
flammable" meaning in the worst case, if you try real hard, you might be
able to ignite it, but it won't sustane a flame. (more info at
http://www.vettenet.org/acfaq.txt ).
I'm just trying to make sense of ALL the alternatives. I need to do
something with two vehicles of mine (87 CGT, and 92 dorf). While r134a works
fairly well in my A6, I was not satisfied with it's performance in the
Mitsubishi we owned a couple years ago. And I suspect a conversion can only
be worse. When I lived in th North East, AC wasn't much of a concern, but in
SE Virginia it matters.
Anyway; Here are the choices as I see it.
1) stick w/ R12   Pros; great performance, no equipment change. Cons;
expensive to purchase, and (for someone like me who does give a sh!t) not
eco-freindly.
2) R134 Pros; readily available, cheap, pretty much eco-freindly, can be
topped off. Cons; toxic?, does not perform as well as other options, if
"done right" can be somewhat expensive to convert, uses hydroscopic oil.
3) R406 (autofrost, GHG12, etc.) Pros; pretty much eco freindly, claims
great performance, fairly inexpensive, uses mineral oil. Cons; it's a blend-
as such it will leak at unequal rates resulting in need to evacuate and
start over, barrier hoses are a must due to small molecule size.
4) Hydrocarbon refrigerants (isobutal-propane mix) Pros; eco freindly,
claims great performance, inexpensive, can be mixed from stuff available at
the hardware store, no equipment change out. Cons; it's a blend- as such it
will leak at unequal rates resulting in need to evacuate and start over,
then there's the "Pinto hit from behind" exploding car thing.
I supose if you put together a leak-tight system (always the goal), one of
the drawbacks of blends goes away.
So here I am, closer maybe. But still waffling over a decision. It's getting
hot out though, so I'll need to do something soon...
Steve

-----Original Message-----
From: Robert Myers [mailto:robert at s-cars.org]
Sent: Friday, June 13, 2003 9:14 AM
To: santoli9 at cox.net; quattro at audifans.com
Subject: Re: RE: Refrigerant and rebuilding AC (In defence of Durocool)

IIRC, George Goble (not the comedian so popular in the 60's) is in the
business of selling flammable AC components.  Perhaps that's enough said.

Yes the point that a large volume of exceedingly flammable gasoline is in
the fuel tank of your car and can, under certain circumstances, pose a
significant fire hazard is valid.  Gasoline, however is not normally
connected directly to a clear and open pathway into the interior of your
vehicle.  Perhaps this refrigerant is not a _significant_ hazard as you
suggest.  However, it is a hazard which is easily avoided simply by using a
non-flammable (and also non-toxic) refrigerant.

1.5 pounds (say 750 grams - that's a low estimate) of butane (at 58 grams
per mole) is nearly 13 moles of butane.  One mole of butane will occupy
approximately 22 liters (22.4 liters at STP) of volume at 100% concentration
(depending on temperature and pressure).  13 moles (at 100% concentration)
will occupy approximately 290 liters.  A 9.1% concentration of butane in air
is an explosive mixture.  These 290 liters of pure butane gas are sufficient
to produce approximately 3200 liters of (a 9.1%) explosive mixture when
mixed with air.  (All numbers are only approximate but are reasonably
close.)

Now, let's see...  What do you suppose the volume of the interior of my car
is?  A space measuring 2 meters by 3 meters by 1.5 meters will contain 2100
liters.

I don't want it in my HVAC system - certainly not since there is a readily
available and comparatively safe alternative.

At 08:27 AM 6/13/2003 -0400, santoli9 at cox.net wrote:

You might find George Goble's take on this interesting. The full text is at
http://www.yarchive.net/ac/politics.html
I've extracted a bit here:

There is some flammability risk for running pure hydrocarbons
(propane/butane, etc) in automotive A/C.. but it is pretty small.
OZ-12 (propane/isobutane) was installed in 50,000 cars with no
fire/safety problems reported.. until somebody "rigged" a controlled
demo, where 3 cans of it were released (took several tries) in a sealed
car passenger compartment, and recirulated until the correct fuel/air
mix was obtained.. and BOOM.. it did blow up.  Film at 11.. went to
CNN, etc.. which pretty much got it banned.  Using the fear of fire
in a non scientific manner to fear-monger the public.. Remember the
Hindenburg, the Pinto, The side mounted Pickup truck gas tanks, etc..
(remember the rocket engine ignitors?? on the truck blowing up?)

The A/C only holds 1.5lbs or so of propane/isobutane.  The gas tank
holds over 100lbs of gasoline.  Oil, brake fluid, transmission fluid,
power steering fluid, are all EXTREMELY FLAMMABLE/EXPLOSIVE when they
drip on hot enging/exhaust components. Hydrocarbons have to be at a fuel/air
ratio of roughly between 2% - 8% by volume in air in order to ignite.

In a hose break/leak, propane/butane dissipate rapidly, gasoline
hangs around, fuming, waiting for an ignition source.
R-12 systems contain approx 10-15% by volume of mineral oil, which
is dissolved in the refrigerant.  A line rupture creates in "oil fog"
which can be quite explosive.  A jet of R-12/oil mist leaking can be
ignited (I have a pix) and does sustain fire (looked like a flame-thrower).
That is why "those in charge" are VERY CAREFUL to specify flammability
specs WITHOUT the oil present, rather that what is really found in
a car A/C.  When you include the compressor oil, all the refrigerants burn.

Also, many common "tire inflator/sealer kits" use propane
and butane, and it is mixed with AIR UNDER PRESSURE in a TIRE.. and
this IS A BOMB by definition.  How come nobody raises much ruckus over
tire inflators, R-12 and oil burning, etc.  Those things do not have
the power to prevent the sale of millions of "extra" new cars like the
alternative refrigerants do (when the R-12 is gone). R-134a does become
flammable at just above atmospheric pressure (5 PSI).  There have been
reports of R-134a explosions in refrigerant lines/compressors.. Workers
unsoldering lines (had air/R-134a in them), after letting out the
refrigerant, built up a small positive pressure, or the burning of
the oil at the joint raised the local pressure above 5 PSI, and blam.
Go figure for yourself.

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