Basic Conversion Considerations
April 1, 2012 | By Dave Demma
What are the important issues after the decision has been made to move forward with a refrigerant conversion?
There is no question that the life of a refrigeration technician was simpler when it was viewed in three colours: white, green and purple. White and purple are long gone. Green…watch out…your days are numbered. As allocation regulations continue to shrink, there has been increased interest in planning for the future – converting from R-22 to an alternative that will provide similar performance while allowing the equipment owner the assurance of using a relatively inexpensive and ample supply of refrigerant for the remaining life of their equipment.
WHERE TO START
There are so many current refrigerant choices available to replace what were once viewed as great refrigerants that it is truly mind numbing. Not only are there too many choices, but it is sometimes difficult to discern between the marketing campaign designed to sway one to use a particular replacement refrigerant and the technical merits of each refrigerant.
A refrigerant conversion is not a job to be undertaken without first putting a good deal of thought into the merits of it. While the allocations for the manufacturing of new R-22 are continuing to drop, and 2020 will see the end of any new R-22 manufacturing, the estimates are that there will be a decent supply of reclaimed R-22 around for some time. So, does a small package air-conditioning unit whose total refrigerant charge is less than 10 lbs. warrant consideration for a refrigerant conversion at this time? Probably not. The cost of converting the system will far outweigh the increased cost of refrigerant should the equipment experience a leak.
Larger equipment packages such as chillers, multi-compressor supermarket racks, large industrial plants, etc. are good candidates for refrigerant conversions, particularly if they are applications where there have been repetitive refrigerant leak issues.
I spoke with a contractor earlier this week who maintains an ice skating rink. The system’s refrigerant charge is approximately 5000 lbs. of R-22, and as they stated, “you can count on at least one large leak per year.” This is an ideal candidate for a refrigerant conversion. With the price of R-22 nearly double that of some of the more common alternatives to R-22, it is easy to justify recommending a conversion to the customer.
Supermarket chains which have a number of R-22 stores in their organization are another ideal candidate. The average leak rate in a supermarket is in the 15 to 20 per cent range of the total charge per year. Again, it does not take too many leaks to justify converting to an R-22 alternative. In addition, the R-22 that has been removed from the stores that were converted can then provide an ample supply of refrigerant to cover losses in any remaining R-22 stores. It is recommended that the used R-22 be brought to a certified reclamation facility and be brought back to AHRI 700 specification before being added to another system.
PLANNING IS PARAMOUNT
Once the decision has been made to proceed with the conversion there is quite a bit of planning required to insure the job goes smoothly. I recall an experience many years ago at a wholesaler’s where a technician was gathering up a few parts and pieces, notably a few R-22 TEV power assemblies and a crankcase pressure regulator. I asked the technician what kind of problem he had encountered which required him to purchase those parts, and he told me “I’m getting ready to convert a system from R-502 to R-22.” I was dumfounded that those few parts were the extent of his conversion. As an industry, we have learned a lot since those days.
The first decision involved in a conversion is to select one of the refrigeran options in Table 1. There are several criteria that ought to be used to make this choice:
• Is the refrigerant approved by the compressor manufacturer?
• Capacity of new refrigerant versus R-22.
• Will refrigerant flow controls need replacing?
• Will liquid or suction lines need upsizing?
• Price and availability of new refrigerant.
• Will low temperature applications with new refrigerant require demand cooling?
• Oil requirements.
After the refrigerant is selected, but prior to the actual conversion, it is important to check TEV and distributor nozzle capacities with the new refrigerant. Depending on the thermodynamic properties of the new refrigerant, these components may need to be replaced with a larger tonnage model.
Again, depending on the thermodynamic properties of the new refrigerant, some pipe sizes may also need to be upsized.
Elastomer seals (solenoid valves, Schrader valves, seal caps, etc.) will swell in the presence of R-22 and mineral oil. This swelling will aid in the elastomer providing a leak-free seal. Over the course of time these seals will take a set against the surface they are in contact with due to this swell and the refrigerant pressure that is exerted on the seal. When the elastomer comes into contact with the new refrigerant/oil the amount of swelling will generally be reduced. This results in a new shrinkage of the seal.
Additionally, elastomer seals that have likely hardened over time would now be subject to a different pressure than with R-22. All of these factors will combine to make the seal a high-potential leak. As such, they should all be replaced.
After replacing the R-22 with the new refrigerant, TEVs should be checked and reset if necessary. All pressure controls will need to be reset to the appropriate pressures for the new refrigerant. If any pressure regulating valves are utilized, these will also need to be reset.
The lure of some R-22 alternative refrigerants is that they are touted as being compatible with mineral oil. A conversion that does not require an oil change might be attractive, however caution must be exercised. The fine print will normally advise that “if” there are oil return problems after the conversion, some percentage of the total system oil charge should consist of POE oil. <>
Dave Demma holds a degree in refrigeration engineering and worked as a journeyman refrigeration technician before moving into the manufacturing sector where he regularly trains contractor and engineering groups. He can be reached at firstname.lastname@example.org.