Dawn of a new A/C system era

Tips to prepare for the switch from R-134a to HFO-1234yf refrigerants.


Q: What if the HFO-1234yf system I’m working on doesn’t pass a purity test according to a refrigerant identifier?

A: If you encounter a system with questionable refrigerant, it must be evacuated with recovery-only equipment and disposed of properly. Recovery-only equipment for HFO-1234yf must meet SAE standard J2851.

Q: Will we be able to retrofit R-134a systems to the new HFO-1234yf refrigerant?

A: No, it’s illegal to retrofit R-134a systems to HFO-1234yf, so this is not like the change from R-12 to R-134a. Now, here’s an interesting twist: There’s currently no regulation on the books that makes it illegal to put R-134a into systems originally filled with HFO-1234yf. So, to be clear, the feds say it’s illegal to put HFO-1234yf in R-134a systems, but there’s nothing on the books to prevent you from putting R-134a into an HFO-1234yf system. Go figure.

Remember, though, that laws change, and states and localities have the right to supersede the federal laws if they choose. Also, under no circumstances, should the two refrigerants ever be mixed and as with all refrigerants, HFO-1234yf uses different service fittings. These will be compliant with the October 2011 revision of SAE standard J2844. A system charged with HFO-1234yf will also display a unique label representing the original refrigerant fill and any cautions and warnings.

Q: When compared to R-134a systems, how different are systems that come charged with HFO-1234yf?

A: For the most part, systems filled with HFO-1234yf are substantially identical to R-134a systems. Both systems work at very similar pressures, which became an attractive trait in helping the industry choose HFO-1234yf over carbon dioxide (CO2), which requires higher pressures. Of course, HFO-1234yf must have its own fittings and service label, as is typical for each different refrigerant.

Q: Other than refrigerant, are there any other important engineering or design distinctions found in HFO-1234yf systems?

A: Yes, we’re beginning to see a large migration away from orifice tubes and cycling compressor clutches. In their place, we’re seeing an evolution towards thermostatic expansion valves (TXVs) and variable-displacement compressors.

Fuel economy is the driving force behind these changes, with manufacturers seeking optimum A/C system performance with the lowest possible engine load. There’s one key difference when it comes to servicing HFO-1234yf systems: If you need to replace the system’s evaporator, make sure that the new one bears a label stating that it meets SAE J2842, the standard addressing evaporator design criteria.

Q: Our tool dealer mentioned something to one of our techs about counterfeit and contaminated R-134a. Should we be concerned?

A: There have been confirmed reports of counterfeit/contaminated R134a cylinders appearing in some parts of the middle-east and the Mediterranean. Problem cylinders were first found in Greece. The problem has spread quickly in that part of the world, demonstrated by the fact that some U.S. military vehicles in Afghanistan have this rogue refrigerant in their A/C systems.

The affected cylinders most often contain R40, which is toxic, flammable and highly reactive when exposed to aluminum. When R40 reacts with aluminum, it forms a third, highly unstable compound that can react violently with air. Even worse, when R40 is combined and cross-contaminated with R134a, it assumes the same troubling properties as R40. The presence of R40 cannot be detected using standard pressure/temperature measurements for non-condensable gases (NCGs). To make matters worse, counterfeiting of the associated cylinder packaging is so well done that even the smallest details from legitimate packaging have been replicated. The only way to tell for sure that a cylinder is legit is to use a refrigerant identifier.

So, yes, you should be concerned and wary of anything suspicious when purchasing R-134a. A deal that’s too good to pass up may be one hint that you’re being solicited with bogus R-134a. As of this writing, none of the problem refrigerant had yet been found in the U.S., but the likelihood of it showing up will certainly increase by the time summer rolls around this year.

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