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What about R-152a?

Good question. What about R-152a? Well, if you’ve read anything in the recent past in any A/C publication or web bulletin board, you have probably heard something about a refrigerant known as R-152a. According to industry talk, R-152a is being tossed around as a possible substitute for R-134a. Although it’s still too early to tell what the ‘powers that be’ will do, it’s not too early to get involved and find out what R-152a is all about.

All of the recent discussion about R-152a inspired ChevyBob to leap into action. (http://chevybob.autoACsystems.com) He put his ‘stable’ of Cadillacs to the ultimate hands on test. Why do we refer to it as the ultimate test? Well, in order to do a test that would provide meaningful information when comparing refrigerants, you would have to start with controlled conditions that provide a ‘level’ field. Not having quick access to lab test facilities, the next best thing would be to take 3 identical vehicles and use them. Well, enter ChevyBob’s test Cadillacs.

ChevyBob has three Cadillac Broughams that are virtually identical to each other. In fact, most of the A/C components are interchangeable with each other. Those three vehicles form the basis for a test to compare different refrigerants. Understanding that, ChevyBob waited patiently for a good day over 80ºF in order to do the ultimate hands on test. We’re proud and thankful that he shared his information and photos with us.

For an up close look at some of the test photos, feel free to view them right here. We also took the liberty of creating some simple graphs that help illustrate the data and make it a little easier to compare. You can view those detailed graphs right here.

Before anybody critiques the test, understand that we know this wasn’t done in ‘controlled conditions’ and there were no high end ‘data loggers’ or teams of scientists on hand to record every last detail. What this test does have is this; three vehicles that are as close to each other as you can get; one charged with R-12, one with R-134a and the last one charged with R-152a. The test (conducted on Saturday May , 2005) ran these vehicles at the same time (of day) allowing for the best hands on comparison available at this time. The ambient temperature was 81º F with a relative humidity of 30%. Almost ideal conditions! Does this test provide definitive answers? No, because there isn’t any one test that can provide definitive answers. Does the test provide a real good comparison of these three refrigerants and a close up look at their respective performance? It sure does! So using the data available from this test, let’s consider the possibilities of R-152a as a replacement for R-134a.

First of all, as posted by ChevyBob on the A/C Help and Discussion board at the COOL ZONE, here are some of the details and specifics about R-152a.

CHEMICAL NAME: 1,1-DIFLUOROETHANE (HFC 152a) (Note this is in the same refrigerant ‘family’ as R-134a; they are both HFC’s)
CAS Number: 75-37-6
Percentage: 100%
(As a comparison, R-134a is tetrafluoroethane while R-152a is difluoroethane)

One issue that is not mentioned in the above information is that R-152a is considered a flammable. Now, before you through your arms in the air and run, consider what the term ‘flammable’ really means in the chemical world. It doesn’t mean that it’s explosive. It also doesn’t meant hat it’s going to injure you when you ‘look’ at it. What it does mean is that according the standards set forth, R-152a is a flammable substance. So what’s that mean to you as a technician or DIY’er using R-152a? It means that like any other flammable substance (like gasoline) you have to understand how to handle and use it. Respect the fact that it can do damage... and treat it accordingly. Like any other flammable liquid, when used properly there should be no cause for concern.

Now consider what the test results are actually telling us. When you review the details and charts of pressures and vent temperatures, for the most part there is nothing that you probably didn’t already know. The R-12 system performed the best with excellent high and low side pressures and a vent temperature of about 40ºF. Of course (and as you probably expected) the R-134a system didn’t cool as well. Although the high side pressures were identical and the low side pressures were actually lower (at 25 p.s.i.), but the vent temperatures were considerably higher at only 47ºF. Sill acceptable... but not as efficient as R-12.

Now for a closer look at the R-152a system. What an interesting surprise to see the high pressures at 165 p.s.i. were actually lower than both R-12 and R-134a. The low pressures were also the lowest at only 22 p.s.i. and the system delivered outlet vent temperatures of 45ºF. That’s better than R-134a and with lower high side pressures! That’s interesting.

Conclusions? Well, like we said, it’s a little too early to state any definitive claims. Remember, this is only one test and there are a lot of other considerations that have to be weighed. But for the time being, in short, we can certainly state that R-152a did very well in this test.

Without trying to take the ‘wind’ out of ChevyBob’s ‘sails’, there are several other issues that this test does not address. Some of these issues include long term compatibility; component design; safety; charge weights or conversions and quite possibly several more.

Starting with long term compatibility, we don’t know if the R-134a components are compatible (over the long haul) with R-152a. If you remember when R-12 systems were being retrofitted to R-134a, desiccants (receiver driers and accumulators) had to be changed as only XH-7 and XH-9 desiccants were compatible with R-134a. Additionally, A/C hose construction changed with the use of R-134a and we also saw several changes in condenser designs for improved cooling efficiency.

The change to R-134a also brought up issues of refrigerant oils. R-12 systems used mineral oil while factory R-134a systems used PAG oils. When retrofitting a system from R-12 to R-134a, the industry standard was to use ester oil. To add to the mix, the need for countless oils caused development of other products like Polymax2 refrigerant oil which can be used to top off or replace either mineral, PAG or Ester. One real nice feature is that Polymax2 is non-hygroscopic so it will not absorb moisture (see our oil test details for complete information and photos). So what refrigerant oil (or flavor) will it be with R-152a? That’s not been determined with our test either, however ChevyBob does state that his R-152a system ran with Ester.

What about the hose construction? As we found out with the R-12 conversions, a hose is not a hose. R-134a systems utilize barrier hose which includes a nylon inner core to prevent refrigerant molecules from leaking right through the hose. Will barrier hose be adequate over the long term with R-152a? That hasn’t been established here either.

Condenser design also plays a major roll in how well any particular refrigerant works. Over recent years, we saw that older design ‘tube and fin’ condensers did not perform as well with R-134a refrigerant as they were not as efficient. That led to improvements in serpentine condenser design and development of other configurations including ‘piccolo tube’ and ‘parallel flow’ designs.

Other factors to consider is safety, handling and reclaiming of this refrigerant. Of course, it will require different equipment for recovery, or at the very least, a different container. There are also issues of flammability that need to be addressed. Although we shouldn’t be afraid of it, because R-152a is flammable, it should most certainly be respected. So that means there will have to be some serious education about the use and handling of this refrigerant (and based on issues of training and education of the industry over the last 20 years... that may not be an easy issue... we covered that in last month’s Keepin’Cool).

With respect to component design (evaporators and condensers), that’s something that would best be determined with the help of computer designs in order to best ‘fit’ the design and efficiency of these two heat exchangers to the system and the refrigerant. Technically it’s really not a big undertaking, but it’s likely that design changes would be made in order to deliver maximum cooling performance.

So is R-152a the next drop in retrofit? Not yet. There are several matters that have to be addressed and we’re sure that we haven’t covered all of them here. But is R-152a a good candidate? It certainly looks like it is. After all, with a straight ‘drop in’ charge the refrigerant delivered respectable results and cooled very well. That can only be a sign of more good to come.

We thank ChevyBob for his time, efforts, details and photos of the test. We’re sure there will be more to follow and we look forward to it.

Be sure to check in (and register) at the A/C Help and Discussion board at the COOL ZONE! ChevyBob’s been busy posting updates and he’s doing a great job on the front line! (Thanks for all your efforts Bob!)

Copyright 2005 - autoACsystems.com - eZine - Keepin'Cool
Comments and details supplied by ChevyBob

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