From: ghg@shay.ecn.purdue.edu (George Goble)
Newsgroups: sci.engr.heat-vent-ac
Message-ID: <6o3i6i$oec@mozo.cc.purdue.edu>
Subject: Re: R-134a question
Date: 9 Jul 1998 23:02:42 GMT

In article <6o0rlj$5tf@bgtnsc03.worldnet.att.net>,
JSmart <SmartSys@worldnet.att.net> wrote:
>OK,
>
>Let me elaborate.  A large number of new cars, previously un-worked on
>outside of the factory (these cars are 18 to 30 months! old).  are showing
>8 to22% "non compressible gases.  The chemistry of the r134a gas itself is
>not conducive to from water, or liberating O2 molecule is it?  Can it be
>the type of oil that the GM. ford Chrysler charges their products with?
>Marc

Compared to R-12 mineral oils, PAG (new OEM), and POE (retrofits) oils are
quite unstable.. Also extremely sensitive to moisture..

You meant to say "non condensible" gasses?  If refrigerant is
breaking down, it would probably be H2.. The HF "acids" would
eat away at the aluminum (and the oil) and form aluminum chloride
(sludge), that would either clog the system or the evap/condenser
would "eat through".. Many 134a cars  come into service right
after 3yr warranty is up, with 7 or 8 holes in evap or condenser..
PAG oil turned bright orange.  Automakers seldom do a vacuum
over 1 min during the initial charge.. Moisture varies from
run to run.. Chrysler is near the worst on moisture.
Back in the R-12 days we gave a Chrysler dealer a "dry-eye"
on a quick connect.. so he could weed out all the new "wet" cars
(most of them), and recover the charge, change dryer, recharge
before the water reacted into acids and failed the system
6mo later and for sure warranty work (eaten out evap, etc).

--ghg

From: ghg@pier.ecn.purdue.edu (George Goble)
Newsgroups: sci.engr.heat-vent-ac
Message-ID: <86fkv0$mvq$1@mozo.cc.purdue.edu>
Subject: Re: Helical Oil Separator Experience with R508B
Date: 23 Jan 2000 19:31:44 GMT

In article <388A6EF5.6AE341CC@smartlink.net>,
Kesselman  <pkay@smartlink.net> wrote:
>George Goble wrote:
>>
>> In article <38894712.83A9D293@smartlink.net>,
>> Kesselman  <pkay@smartlink.net> wrote:
>> >I was using AC&R's Helical Oil Separator in the low-stage (R508B) of a
>> >small cascade system (environmental chamber) and found it to be
>> >completely ineffective under low mass flow conditions. Replacing it with
>>
>> ULT companies have told me that there is no equal to the Temprite
>> 900 series oil seps for ultra low temp systems.  However, this is
>> back in the mineral oil days and CFCs.  I have used 3 or 4 (medium temp)
>> and they worked fine.. Bleeding some liquid refrigerant (after the sep)
>> into a piece of typing paper, showed NO OIL.
>>
>> Reclaimers tell me that POE oil is much harder to sep out of
>> refrigerant than was the mineral oil.
>>
>> --ghg
>
>R508B is extremely miscible with POE. That's good when things are
>flowing. In my failure mode, things are barely flowing. A liquid-line
>solenoid controls the flow to the evaporator TXV. The solenoid is
>controlled by a time-proportioned signal from a PID controller which
>senses the workspace temp (there is also a resistance heater which is
>controlled by the heat output). This method is capable of achieving 0.1C
>control tolerance throughout an extremely wide range of temperature/load
>conditions. The application is an environmental chamber which has a
>range of -75 to +175C. But to maintain relatively high temperatures of 0
>to +55C (cooling is required even at +55C due to air movement of the
>conditioner fan), the system requires occasional tiny pulses, <1%
>on-time. Almost no mass flow, yet parts of the system under these
>conditions still measure as low as -81degC! Interesingly enough, the
>system worked flawlessly when trying to maintain low temperatures for
>extended periods.
>
>I'll look into the Temprite oil seps. Someone else told me that's all he
>uses.
>
>Peter

Also, the ULT companies used to heat oil (over a flat plate) in
a vacuum at 300F for a week to try to drive out out any moisture
before charging it into compressors. Even a few ppm moisture
can freeze/plug the expansion device on a ULT and cause problems,
even below the amounts that cause corrosion, acids, etc.


There is an interesting product, call "DRY-PAK" made by Cryo-Chem,
Dry-Pak chemically reacts with the moisture and converts it to
some kind of "silicone oil", that at least in high/med temp systems
is "harmless".  Dunno what this silicone oil would do in a ULT
though. See http://www.cryochem.com for more info.

After realizing that automotive dryers don't "suck" or "blow"
when popping off the caps (are probably already water logged
from breathing as atm pressure changes), and GM shipping PAG
oil (for R-134a A/C for cars), with 4200ppm moisture, I use
plenty of dry-pak in those systems.

--ghg