Manual for Refrigeration Servicing Technicians - UNEP - Division of ...

5
Retrofitting
Although, in general, car manufacturers do not condone this option
on safety grounds, there have been many hundreds of thousands
of retrofits for ten or more years without any incidents. However,
if such a retrofit is to be carried out, it must be acknowledged and
accepted by the vehicle owner.
The possibility of cross contamination of refrigerants and improper
system evacuation is generally noticed in MVAC servicing in many
developing countries which leads to poor performance of the
system. In some cases, such bad practices are attributed as a result
of improper retrofitting processes.
Retrofitting of R22 supermarket refrigeration system
The following steps should be followed when retrofitting a supermarket
refrigeration system from R502 or R22 to an HFC refrigerant that is not a
drop-in blend:
1 - Pump-down the R502 or R22 refrigerant charge to the liquid receiver.
2 - Drain as much of the old lubricant from the system as possible,
including from the compressor sump, oil reservoir, and oil separator.
If large amounts of mineral oil remain, it may clog the system and
cause the efficiency of the heat exchangers to decline.
3 - Replace oil filters and filter driers when performing oil changes.
4 - Measure the amount of oil removed, add back an identical quantity
of new oil. Ensure that the new oil chosen is approved by the
compressor manufacturer.
5 - Run the system with the existing refrigerant for at least 24 hours.
Systems running for an extended period may require fewer oil
changes.
6 - Check the system for leaks.
7 - Repeat steps 1 through 4 until the residual oil is less than 5%,
testing using lab analysis or a refractometer.
8 - Evaluate expansion devices using the process described.
9 - Recover the R502 or R22 from the system.
10 - Evacuate the system.
11 - Evaluate the pressure controls, including high pressure cut-outs,
fan cycling controls, and pressure relief devices.
12 - Recharge the system with the new HFC refrigerant.
13 - Check the system for leaks.
Valve rebuilds (for systems built before 1995)
Systems built before 1995 will most likely require new gaskets and O-rings
(elastomers):
1 - Rebuild all Evaporator Pressure Regulators (EPRs).
2 - Rebuild all solenoid valves.
3 - Rebuild hold back valves.
4 - Rebuild heat reclaim valves.
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