Wheeler on HVACR: Carrier's Puron - the inside story
As everyone who reads this column knows, I think the federal law that requires the phase-out of R-22 starting in the year 2015 is an uncalled-for overreaction. The real problems have been created by unrestrained dumping of the more hazardous CFCs R-11 and R-12 into the atmosphere.
I also believe that the HFC substitutes with their artificial lubricants (PEGs and POEs) are a poor alternative to HCFCs and mineral oils. Standard service and installation techniques with the new systems will ultimately result in more compressor failures and service problems. Therefore, when someone from Carrier Corp.'s public relations department contacted me about doing an article on the company's three-year-old line of air conditioners/heat pumps that don't use HCFC-22, I initially suggested that she find someone else to review the product line.
But wait a minute! How else are we going to find out if there are any problems with the new refrigerant/lubricant combinations, and how else will we know if some of the stories we've heard are true, unless we ask someone who has experience with them? So, with the understanding that I was going to ask some hard questions and expect some straight answers, the folks from Carrier entered the lion's den.
Here's what I found out.
The refrigerant Carrier is using has a fancy name, Puron. However, that's just a trademarked Carrier name for a generic 50-50 mix of HFC-32 and HFC-125, which is manufactured and blended by most refrigerant manufacturers. Its designation is R-410a.
I like that. I thought Carrier might be using HFC-134a, which is a very inefficient (30% less) refrigerant. But R-410a is actually 3% to 5% more efficient than R-22. The blend is a "near azeotrope," which means there isn't much problem with separation or "glide characteristics." It is virtually nontoxic, as long as you don't burn it, and nonflammable. It is also less dense in the liquid phase than R-22, which accounts for its being sold in 25-lb. quantities rather than in the standard 30-lb. quantities you get with R-22.
The main drawback with using R-410a is that it works at a much higher pressure than R-22. The high side runs about 400 psig, and the low side is in the 135-psig range, which means that the coils and the compressor shell have to be beefed up. But the new units aren't much heavier than equivalent R-22 systems, Carrier says, because Puron's higher efficiency allows the manufacturer to use smaller coils. Carrier adds that there isn't much difference in price between its standard refrigerants and its Puron product lines.
The second problem is that R-410a is "significantly more hygroscopic than R-22." That means it holds a lot more moisture when contaminated, which becomes more of a problem when we look at the lubricants.
On the positive side, Carrier's extensive life testing shows that the new refrigerant/lubricant combination works very well and doesn't break down in clean systems. The combination of refrigerant and lubricant mix very well, so there isn't any special problem with suction-line-riser sizing. In fact, there is little variation from standard line sizing anywhere in the system.
Not a leisure suitThe lubricant Carrier is using has a chemical name that puts me in mind of an old pair of bell-bottom pants I had back in the '60s. They call it a polyol ester (POE). And while its name may sound funny, its lubricating qualities are quite impressive. Carrier says POEs have been used in jet and turbine engines since the 1950s, and they are often found in top-grade synthetic motor oils.
What don't I like about POEs? Well, there's nothing wrong with the lubricant - as long as you keep it dry. However, POEs are typically 15 times more hygroscopic than mineral oils. In fact, they can absorb water right through plastic, so it can't be stored in plastic bottles.
Does that mean it doesn't work well in HVAC or refrigeration systems? No, it's just that good dehydration techniques are essential when installing and servicing the new systems and much of our industry just isn't that good or conscientious today.
Carrier isn't sparing the horses when it comes to its Puron line of air conditioners and heat pumps. Not only is the company beefing up the coil thickness, it also is using Copeland scroll compressors with the model designation ZP. These, according to Copeland, are the most reliable compressors in its line, although they are slightly smaller due to the greater vapor density of Puron.
Carrier is dealing with the problem of keeping moisture out of Puron systems by insisting on a program of training and certification of dealers that want to carry the line. Systems must be evacuated to 500 microns, and the 100% molecular sieve filter-drier that comes with each unit must be installed.
According to Carrier, the program is working, and Puron systems are currently its most reliable lines of equipment, with the lowest rates of compressor failures.
An interesting note: While Carrier recommends replacing the evaporator whenever a Puron condensing/outdoor unit is installed on an existing system, the manufacturer does not absolutely require it. Contrary to stories we've heard about the terrible things that happen when the new lubricants are mixed with mineral oil, Carrier says there isn't much of a problem when using POEs, as long as any mineral oil trapped in line dips is removed. Of course, a change in metering devices is also required.
Is it the future?I guess that's the question we all want the answer to. If the laws stay the same - regardless of the fact that HCFCs don't significantly affect the earth's protective ozone layer - HFC refrigerants with POE lubricants are surely the future, so we'd better get used to them.
How is Carrier doing in the sales of their Puron systems? In some markets, as many as 70% of retrofit customers are opting for the alternate refrigerant, according to the manufacturer, and sales are quickly rising toward the 100,000-per-year mark.
The fact is, we're just a little more than 15 years away from the start of the R-22 phaseout, and that's within the expected life of the equipment we're selling today. So there's a story to tell.
On the negative side, if HFCs and POEs are the future, our industry is going to have to get much more professional in the way we do service and installation. Of course, I've been for that all along, but is it a realistic goal?
Finally, I'd like to apologize for the fact that I have told just one manufacturer's story here. I tried to be as unbiased as possible in telling it. However, I want to thank the folks at Carrier for their candid answers and willing response to my questionnaire.
At this time Carrier is the only company I know of that has a line of non-HCFC HVAC units with any experience in the field. As time goes by and more companies try other methods and refrigerants, I hope that they will allow me to tell their stories too.