Wednesday, April 24, 2013

R-22 Conversion - What to Avoid

After reading a lot of technical literature, attending several talks and seminars on R-22 conversion I have developed the following cautions on R-22 conversion.

First and foremost – if you convert a system from R-22 to ANY replacement refrigerant, you are conducting a field experiment on the customer’s equipment using their money. Make sure the customer understands that they are paying for an experiment which may or may not end successfully. I think I would get that in writing.

Since all the replacement refrigerants are zeotropes, they should not be used in flooded systems because they will fractionate in the evaporator.

Since all the replacement refrigerants are immiscible with mineral oil, they should not be used in systems with large receivers (without changing the oil to POE) because the mineral oil will separate and float on top of the refrigerant in the receiver.

Some of the replacement refrigerants have trace amounts of hydrocarbons or POE to help prevent oil logging in the coils and lines. This works well in many systems, but it does not help in the receiver where there is not much refrigerant movement.

DuPont says that the churning in accumulators discourages separation in the accumulator. However, they also say that you may need to add 10% POE if you have oil return problems. 

I am nervous about heat pump accumulators – especially in cold weather when a large amount of the charge is just sitting in the accumulator.

You should NOT weigh in the same amount of replacement refrigerant as R-22 because all the replacement refrigerants are less dense than R-22. A general rule is somewhere around 75-80%.

You should NOT just try to match the pressures you are used to seeing with R-22. A better indicator would be to measure the system subcooling and superheat and shoot for “reasonable” numbers.

You should replace all O-rings and Schrader valve cores before putting in the new refrigerant. O-rings can shrink when exposed to the new refrigerant creating a leak where none previously existed.

You should NOT just add the new refrigerant on top of the R-22. If you do that, you are creating your own special blend which is not EPA SNAP approved.

Just because a refrigerant matches the pressures of R-22 does not mean it will match the mass flow rate. If the mass flow rate is too different from R-22 the metering device won’t work correctly.

Make sure any refrigerant you use is EPA SNAP approved for the application. Any reputable refrigerant will have an ASHRAE refrigerant number and safety rating – not just a trade name or number.

One way to be sure what you are using is safe is to only buy refrigerant from recognizable manufacturers at normal supply houses, not online.

Under NO CIRCUMSTANCES should you use any of the “Organic” replacement refrigerants available on the internet. The “organic” components are propane and butane. They don’t have trace amounts of hydrocarbons, they are ALL hydrocarbon. These refrigerants are NOT EPA approved and they are NOT safe to use in a system which was not designed for flammable refrigerant.

If the customer has already purchased some “organic” refrigerant and tried charging their system, I would not work on the system. It is an accident waiting to happen.

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