Quote:
Originally Posted by Shern
Thanks for this.
From what you've written, I realize that I do not understand the differences between what I referred to in the initial post as "alt refrigerants." Is envirosafe considered 12a? Which are considered CFC blends to be avoided?
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You’ll have to go back and read the various discussions and interpretation of the law (clean air act) to get it all straight. But my 85% understanding is this:
- R-12 got phased out
- The EPA set regulations about allowable alternate refrigerants. A variety of things were considered, including blends that got to a reasonable pressure-temperature profile. Some were traditional refrigerants, but the obvious choice for a suitable retrofit was r-134a, which when done well, works ok in many applications. Our Mercedes cars are a tough one as it uses a fairly weak compressor on a low power engine, and had an underwhelming ac to begin with.
- hydrocarbons are a viable replacement for r-134a; officially not for r-12 based upon how the laws are written.
- the most common hydrocarbon blends that match an r12 type pressure temperature curve are called r-12a.
-some folks claim that these propane butane blends aren’t as miscible with oils as refrigerants. While this isn’t a big deal with industrial systems, it is for motor vehicle ac. They claim proof is in the fact that compressor manufacturers don’t warranty compressors used with hydrocarbons. But that isn’t necessarily really proof… there could be a wide range of reasons why they won’t.
- one thing that is known regarding blends, regardless of if they’re hydrocarbon, mixed refrigerant, etc. is that they will leak at different rates, so the blend will change in time. This can result in a mix
That has different pressure properties than originally used. Apparently this can be a concern with propane in the 12a mixtures, because the isobutane will leak faster and then the propane pressures can go too high (IIRC). My angle on this is that it really means one should run slightly undercharged and then replace the mix every so often if you have concerns about leakage. However I’m primarily a believer in using the stuff to identify leak points to fix, then getting real proper refrigerant into a leak free system.
Overall I’m not terribly opposed to the 12a HC blends. But I look at them as a means to have a useful ac in a driving diy repair. Not the actual long term solution. If I had an unfixable leaking vehicle my opinion might differ a bit.