HCFC refrigerants, oils etc.

I have had extremely good luck with R409a and R408a when doing retrofits. I am wondering if anybody has tried any interim refrigerants and would share their experiences. I know I would be interested in anything helpful, tips to watch for etc.

I used to do tech support and listened to alot of guys complain about POE oils clogging systems etc. I too have worked with the POE oil systems and so-far so-good. I always draw a deep extended vacuum at least down to 100 microns preferably deeper. Sometimes it is tempting to just hit 500 blow a charge in it and run but so-far I have kept myself from doing it.

I know alot of you guys only work on big stuff, but you might find this interesting. Most of your large equipment has replaceable filters, not so with your smaller tonnages.

On smaller equipment it is standard practice to change the entire drier. Well on very small equipment, until recently the manufacturer's were installing "the pencil drier" or also called by some a strainer or sieve. These driers were typically filled with dessicant beads. These beads are rated for crush strength and most manufacturer's are trying to save a buck so typically the crush strength is low if you see it on a new system today.

Most "concerned" manufacturers have gone to solid core driers now. They standup better to the higher head pressures and the POE oils.

On a captube system that the dessicant becomes crushed, the powder like residue coats the wall of the capillary. When this happens your suction drops, starves your compressor and as a result (believe this) your head pressure drops slightly below normal as well... due to the drop in mass flow rate. Symptom of a captube being sized wrong.

Many techs in the field think the system is undercharged, not a restriction. With smaller systems, it is difficult to feel or observe a cold or frosted line such as the captube when seeking a restriction(god knows what they are going to cover it with and where or how they will run it sometimes!) Usually in this case you will find the frost forming on the captube just before the evaporator. On a freezer, you may normally see the captube frosted back say 2 inches... then in this case expect it to be frosted back 4 to 6 inches, perhaps more.

If you suspect this, you can find evidence of it by viewing the ends of the captube, a light colored material buildup will be present. If you open the drier, your remaining beads will be of odd shapes and small if any are left remaining. All you may have left is a small metal screen.

I haven't seen any more moisture related events with POE oils, despite its highly touted hygroscopicity. Nonetheless we have seen Parker Hannifan, Spolan, etc improve the dessicant to alumina gel ratio in their products to do a better job of removing and retaining moisture.

Regarding Marc's observation, I think of it this way. Drying the vapor and liquid refrigerant is not so different than dehumidifying the air in your home. Vapor pressures will exist to lower the moisture in the oil to levels I think below acceptable ARI standards.

Where POE oil can be quite troublesome is when it is added to a system with waxes and oxides on the interior of the piping and components. It is a darn good solvent!

A last note. Perhaps why I do not see moisture related problems any more with POE oils compared to mineral oil is because the oil acts as a pretty good drier in the first place.:)

How would water absorbed by an oil be more likely to produce acid than water absorbed in a dessicant?

I am still seeing the highest acidities with R22 and mineral oil. Especially with "Demand Cooling." Not seeing much with 404A and POE oils. Anybody seeing POE-related acid problems? For me, moisture and acid have have not surfaced with the equipment we service to anywhere near the extent I was warned about. Is it possible that the water dissolved in the oil is not "free" moisture, and thus les likely to form acid throughout the compression cycle?

Dan

More information than I know what to do with. What is volumetric heating capacity? Regardless, it appears you are indicating the relationship between flow rate, compression ratio, and resultant discharge temperatures, perhaps? If the other statistics are relevant, please share.

So the hotter the discharge temperature, the more likely acid formation? And by implication, this explains why I might see more acid formation in low temperature R22 applications than I see with the POE/404A combination?

If if I am understanding your data, does it address the relative effect, for example, that 100 ppm of water in POE has as compared to having 100 ppm in mineral oil? Let's say both systems are R22. Would acid form more readily from the moisture-laden mineral oil as compared to the moisture-laden polyesther oil?

And if acid formation is a result dependent only upon the moisture in the oil, and not so much the chemistry of the oil, would it be logical to assume that systems using POE oils will develop acid more readily than mineral oil-based systems... simply because they will always have more moisture in them?

You said my name twice. I made a similar typo once, myself. I had almost forgotten about it:)