NetNews Usenet Archive 1992 #16/NN_1992_16.iso/spool/rec/autos/tech/10137

Text File | 1992-07-25 | 10.7 KB | 212 lines

Newsgroups: rec.autos.tech
Path: sparky!uunet!cis.ohio-state.edu!pacific.mps.ohio-state.edu!linac!att!news.cs.indiana.edu!noose.ecn.purdue.edu!en.ecn.purdue.edu!ghg
From: [e-mail] (George Goble)
Subject: Re: Charging A/C with Freon
Message-ID: <[e-mail]>
Organization: Purdue University Engineering Computer Network
References: <[e-mail]> <[e-mail]> <[e-mail]>
Distribution: na
Date: Sat, 25 Jul 92 15:42:35 GMT
Lines: 200

In article <[e-mail]> [e-mail] (Bruce G. Bostwick) writes:
>In article <[e-mail]> Peon w/o Email priv (Eric Youngblood) writes:
>
>>P.S. "In December of 1991 Northern Telecom became the first global
>>      telecommunications company in the world to eliminate chlorfluorcarbon
>>      (CFC-113) solvents from its manufacturing operation."
>
>Speaking of which, are ALL CFC's ozone-killers or just the ones with
>chlorine in them?  I would imagine the pure flourocarbons (like CFC-14
>which is pure perflouromethane) could be called into service as
>refrigerants with very little industry hassle or cost, and a BIG
>source of upper-atmosphere chlorine monoxide would be removed..  any
>thoughts, y'all?

Chlorine (and Bromine [from halons]) eat the ozone.
R-14 (really FC-14, no chlorine) has much too low a boiling point
(i.e. much too high pressures).  It  may not even liquify at ambient
temps (I am too lazy to look it up).  You are on the right idea though.
The molecule HFC-134a (R-134a), tetrafluoroethane has been designated
the replacement for CFC-12 for new equipment manufacture. It has pressures
and temps similar to CFC-12.  It has around a 30% lower capacity, so
systems need to be a little larger.  R-134a will not run in an R-12
system since it is not miscible (i.e. dissolves in) the mineral based
compressor oil used in R-12 systems.

The real problem is what to do with the 225 million R-12 based auto
A/C systems (and lots of fixed equipment) when then need recharges
in a couple of years when the R-12 is almost gone (1995 ban).

The auto industry (i.e. MACS - the Mobile A/C society) is pushing
for only conversion to R-134a systems, at a cost of $1000-$1500
per car.  Currently the compressor oils used for auto A/C R-134a
systems is PAG (polyalkaneglycol) and it is sensitive to the
slightest contamination from "chlorides" (R-12, "flush", etc).
Systems which have run R-12, have a "chloride film" inside them,
which is enough to cause the PAG oil to self destruct, and fail
the compressor.  Using hoses/gauges on R-12, then on R-134a, even
when a vacuum is pulled, still results in PAG oil failure from
R-12 contaimination.  If scientists can't clean up a R-12 system
good enough for a R-134a conversion, how will a garage mechanic
do it?  This currently means, for a system to be converted to R-134a,
all parts which touch the refrigerant have to be replaced, even
the evaporator, which means mucho labor.

The Purdue Compressor conference last week, revealed that NEW SYSTEMS
for R-134a are holding up pretty well, if they are manufactured
"cleanly".  "Retrofits", where all refrigerant containing parts
were not replaced, were having problmes with R-134a, even with
"ester" based oils, which are more tolerant than PAG oils to chloride
contamination.

There are several refrigerant "blends" in existance, which can be
used in R-12 equipment to avoid early replacement when the R-12
is expensive or gone.

R-176:  Blend of approx 15% R-12  60% R-142b  25% R-22

        Will probably "work", but has a working pressure too low
        (around 50-55 PSIG @ 70F, R-12 is 71 PSIG @ 70F), so
        you may only see around 1/2 your cooling capacity.
    It also has 15% CFC-12, which will be gone soon.

DuPont SUVA MP-series  (MP33, MP39, MP52, etc)
       Blend of R-124 / R-152a / R-22

       This requires the oil to be flushed out of the system, and
       replaced with alkyl-benzene (synthetic) oil.  It is not
       miscible in the standard mineral used in auto-A/C systems.
       Also a new kind of drier desiccant (XH9 instead of XH5)
       molecular sieve is needed due to reported action of the
       R-152a on causing breakdown of the XH5 material.  The R-124
       is a new molecule, currently undergoing "PAFT" (program for
       alternate fluorocarbon toxicity) testing.  It will not be
       finished until 1995 or so.  Another refrigerant, R-123
       (replacement for R-11), is two years farther in the PAFT,
       and it was discovered to cause testicle tumors in rats
       at 300 ppm exposure.  Human exposure limits for R-123
       are now at 10ppm.  R-124 is only 1 atom different from
       R-123, but in a year or so we will know more about R-124
       as it will be at the same place in testing as the R-123 was when
       its problems were discovered.

    DanFoss (European compressor mfgr) reported breakdown of
    the R-152a happening above temps of 150C.  This is probably
    not going to cause any problems for auto A/C, but much
    be watched for long running stationary equipment, such as
    freezers, which may produce valve temps of this.

    The DuPont SUVA MP blends (Think MP52 is currently for auto A/C)
    will be much less expensive and painful then retrofitting
    to a R-134a system.

Hydrocarbons:  Blend of 21% isobutane, 79% propane (by weight)
    These are flammable, so be careful. I assume no liability
    if you do this and blow up or burn yourself or others.

    I ran this blend for no problems for 3 months in a Datsun 810
    and it worked fine.  The auto companies and the public
    blow the flammability issue way out of proportion.  You have
    only 1.5 lbs or so of material in your A/C system (hydrocarbons
    weigh less than Freon).  You have 20 gal gasoline on board, hot
    engine oil, brake fluid, auto transmission fluid, etc, which
    all can burn.  If bought in bulk, hydrocarbons only cost
    about $.50 to recharge your A/C system.  There is no money to
    be made (mfgr would like to sell  you an $1500 R-134a
        retrofit instead or a new car).

    Hydrocarbons are much less sensitive to moisture than is
    Freon.  Hydrocarbons do not break down into acids and cause
    corrosion like Freons do when moisture is present.  Lots if
    moisture in a hydrocarbon system will still freeze in the
    expansion device though.

    For those wanting to roll their own, make sure you pull a
    29 in or better vac on the system before charging.  Air/
    hydrocarbon mixtures are explosive.  Don't use straight
    propane, as the pressures will be too high. Always add
    the isobutane first.

    Go get a 6oz can of "isobutane" camping fuel.  Charge that
    into the evacuated system first.  Next follow up with 16 oz
    of propane (you will have to crock up a fitting to mate with
    a 16 oz torch tank).  That should be close to correct blend
    and amount of charge to run a typical car A/C.  It will
    be slightly lower in capacity then R-12.  This mix will be
    37.5% isobutane, 62.5% and will cause lower pressures than
    R-12, but should be close enough to work. Isobutane is lower
    pressure than propane.  Adding another oz or two of propane
    may help a bit.  When it is time to recharge again, vent
    the remaining charge, and start over with a new fresh charge
    as the isobutane and propane may leak at different rates.
    You can skip the vacuum if you still had pressure in the system.
    If it went clear flat, you need a vac to get the air out.

    If you switch back to R-12 or other blend, then you should
    change the drier at that time, since the propane/isobutane
    probably has some moisture in it, unless you used "instrument"
    grade

GHG refrigerant-12 substitute:
    blend of 8% isobutane, 37% R-142b, 55% R-22.

    I invented this one two years ago.  It is running in approx
    500 vehicles now, and several stationary units.  It requires
    no system changes, and works with existing (mineral) compressor
    oils, and driers. Also a "self-sealing" version available
    which has a "gaseous" epoxy, which circulates with the refrigerant
    and upon leaking,  is actived (polymerizes) when it hits moisture
    and oxygen on the outside of the system.  The sealant stays in
    the system and seals new leaks as they form.  Will not seal
    compressor shaft seals (moving parts), but these are rare in
    cars. Cryo-Chem makes the sealant.  They also make R-12 and
    R-22 "self-sealing" kits (800-237-4001 for Cryo Chem).

    GHG refrigerant (and INFO) is available to airshops and qualified
    service personal from Monroe Air Tech, [phone].


The Mobile Air Conditioning Society (MACS) has filed a petition with
the EPA (Mar 30, 1992) asking the EPA to ban the use off all substitutes
and/or blends for CFC-12 auto systems, unless MACS and SAE "approve"
them first.  MACS claims that the blends will destroy the national
recycling program, ruin hoses, seals, compressors, etc.  We haven't
seen that any of this to be true.  In fact most R-12 recyclers are already
water contaminated now.  Visiting about a dozen air shops last year,
all had "WET" moisture indicators.  They are putting WET R-12 back in
cars they service, which could cause corrosion and acid eat outs
a few months down the road.  Moisture is a far more serious problem
then mixing small amounts of blends with each other and CFC-12.
One has to keep R-12, and all the blends OUT OF A R-134a system, or
the PAG oil will self-destruct.  Small amounts of R-134a or mixed blends
in an R-12 system (or recycler) will not cause problems.  R-134a
systems alrealy use different fittings (ACME "square" threads) to
prevent this problem.

The president of MACS, Art Hobbs, works for a company, "Four Seasons"
which makes replacement A/C systems and parts, and recyclers.  Ward
Atkinson, MACS technical advisor, has told the press that "there is
nothing which will replace CFCs" [for auto A/C], and they must be
retrofitted to "harmless " R-134a at $800 to $1000 each.  There are 140
million A/C cars in the US (225 million worldwide) with A/C.  This amounts
to around $100 Billion in retrofit business in the US alone.

Last week I gave a seminar to a group from the North American Council
of Automotive Teachers (NACAT), and nobody in one group of 40 or so
HAD EVER SEEN A GREEN MOISTURE SIGHT GLASS. They were always "wet"
(yellow). I passed around a green (dry) one in the talk.  I am hearing
that mechanics almost never change their driers in the recycling
equipment.  I, personally, would always insist, that new virgin R-12
(aka Freon) be used during A/C service, along with a new drier
(if the system has to be "opened up").  It may cost $50 more or so,
but it may save your system from total failure in the next year or so
from moisture.  If moisture/corrosion eats your evaporator full of
holes, one is talking about $600-$1200 to replace it.  One may be
able to use Cryo-Chem self-sealant (kits) on evaporator leaks
of 1lb/day leaks or use GHG self-sealing on (30 day or longer leaks)
instead of changing an evaporator.

--ghg