[Gmecm] OT - alternative refrigerant test... HFC152A

[David Allen]

Good morning! Thanks for the interest in this. My replies are below, all messages combined into one.

----- Original Message ----- 
From: "Jay Vessels" <jay at vessels-clan.com>
To: <gmecm at diy-efi.org>
Sent: Sunday, May 12, 2013 8:30 PM
Subject: Re: [Gmecm] OT - alternative refrigerant test... HFC152A


> Hi there!
> 
> One other thing -- I was always told that on CCOT A/C systems (almost 
> all GM in the 1980s) to put the gas in with the can inverted.  I don't 
> know if that's specific to the R12 cans or not, but I noticed you didn't 
> seem to bother with that.
> 
> Given that the industry is moving to HFC152a, assuming there's no really 
> goofy issues with a conversion that we don't yet know about, I suspect 
> we'll start seeing kits to do this.
> 
----
> Did you add any oil to the system, and if you did, what kind?


Hi Jay - yes it's good to charge LIQUID into the CCOT system. The charge should go into the accumulator and fill it with liquid.

Insise the accumulator there is an oil-metering orifice. This orifice is supposed to meter a "mist" of oil and liquid refrigerant to the compressor return.

The level of liquid in the accumulator needs to be high enough so that oil metering orifice can work. If you start with an empty system (only oil in the accumulator and compressor), the compressor is running dry during gas charging. It won't get any oil return until the system is almost completely charged and the refrigerant is making it all the way 'round back to the compressor.

As for the oil - the system was previously converted to R134A.  The R152A is compatible with the same oils as R134A. The system has an HR6 compressor. This one needs 8 fluid ounces of 100 or 150 viscosity oil. Mostly I use PAG oils.

----- Original Message ----- 
From: "HotRod" <HotRods442 at live.com>
To: <gmecm at diy-efi.org>
Sent: Monday, May 13, 2013 1:42 AM
Subject: Re: [Gmecm] OT - alternative refrigerant test... HFC152A


> I've often wondered why no one has come up with a viable replacement for 
> R-12. Yes, R-134a works but with major changes to the system, (new seals and 
> hoses)...Why no formulation to easily replace R-12 without having to rebuild 
> system?

Basic chemistry. The chemical properties of R12 are "gentle" on rubber parts, therefore inexpensive rubber components were used on these systems. Also, R12 mixes freely with mineral oils, so that was used to lube the compressor.

The chemical properties of R134A will damage rubber and require synthetic seals. R134A will not mix with oil, it's like mixing oil and vinegar. Shake it up and it stays mized for a mintue then separates. So the oil needs to be replaced with an oil that's mixable.

There are blends of hydrocarbons that will give similar pressure and temperatures of R12, but they have a flammability issue (which may or may not actually be dangerous - but it is prohibited so nobody will SELL a blend like that). Secondly, because they are BLENDED GASES they will leak at different rates. So if there is any leakage, the ratio of the blend changes as the lighter gas leaks out first. That leads to a change in the performance and oil carrying capacity.

----- Original Message ----- 
From: Robert Saar 
To: gmecm at diy-efi.org 
Sent: Sunday, May 12, 2013 8:27 PM
Subject: Re: [Gmecm] OT - alternative refrigerant test... HFC152A

>you know David, that's an interesting way of going about it... i have a 95 monte >carlo(R-134a) with a dead a/c system due to the V5 compressor blowing out at l>east one of it's center seals, which seems to be how most of them go. i'm >interested to see how far you get with this. considering the relatively low cost of >entry, this certainly has my attention.
>
>i do have a few questions at the moment though:
>
>what kind of oil did you give the system and was it an equivalent amount as >what was originally specified?
>
>were you shooting for a specific pressure or volume or just going by whatever >would give the coldest air?
>
>i think that's it as far as important/unspecified questions go.

Robert, yes the oil was the factory-specified volume (8 fl oz) of R134A compatible oil. I am assuming this because the previous owner did a conversion. That is what SHOULD have been put in the system.

As for the refrigerant charge amount, because this is a CCOT system, I tried to get similar VOLUME of liquid as the original R12 charge would have been. Because the HFC-152A ia much less dense, it takes less weight to get this volume. For that car, three 12-oz cans of R12 was an OK charge. I put in two 12-oz cans of the 152A, and it cooled well, but I was concerned the compressor didn't sound good. So I installed a little more. These systems can't be tested by pressures very well due to the nature of the orifice tube / accumulator system.

----- Original Message ----- 
From: Robert Saar 
To: gmecm at diy-efi.org 
Sent: Sunday, May 12, 2013 9:09 PM
Subject: Re: [Gmecm] OT - alternative refrigerant test... HFC152A


> i have 4 V5 compressors and all of them died that way... they hold a charge for about 3 days, but you can see it slowly bubble out of the case halves... luckily, someone on the 60V6 boards did a nice 
> writeup on how to take apart, inspect and reseal them. i think parts came out to between 20 and 30, which is a lot better than the 100+ core that local stores want or risking a junkyard unit.

That was my write-up! I'm glad you find it encouraging. The compressor on my Olds Ciera XC Turbo (from the write-up) has required no additional refrigerant gas since that charge.

Sincerely,
David
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