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When installing a new R410A air-conditioning system to replace an existing R22 system, it
may be possible to use the existing line set. Consult the OEM’s installation manual and
determine if the line sizing is correct and proceed as follows:
1. Before starting any work put on approved safety goggles and nitrile gloves and remember
to work only in a properly ventilated area.
2. Recover the existing R22 charge; it is illegal to vent any refrigerant.
3. Disconnect any electrical power feeds to the system including any solenoids or
reversing valves.
4. Using a tubing cutter cut the liquid and suction line at both the condensing unit and
the evaporator.
5. Temporarily connect the liquid and suction lines at the evaporator using clear plastic tubing,
suitable adapters and hose clamps.
6. Using an injection tool or a compression fitting and adapters, connect a refrigeration service
hose to the suction line at the condensing unit location.
7. Position a clean container at the liquid line to catch solvent and contaminants as they are
purged from the system. Purged material may include acids, oil and particulate debris
which must be disposed of properly.
8. Connect the flush can valve as shown in Figure 1 and 2 or use a valve capable of
connecting to 7/16” 28 thread.These valves are currently offered for sale at most
refrigeration and air-conditioning wholesalers.
9. Connect the refrigeration service hose or refrigeration manifold set to the can valve and the
suction line, invert the ST-20 can, open the valve and give a 15–20 second blast of ST-20
Flush. Inspect the clear tubing at the evaporator and look for liquid. If no liquid is present
continue 15 second purges until it appears. Follow ST-20 with a regulated supply of dry
nitrogen and push the solvent into the receiving container while observing the condition of
the purged material. When the solvent runs clear with no oil or contaminants present the
flushing operation is complete, follow with a dry nitrogen purge. Never pressurize the
Genetron ST-20 container. Dispose of the waste material properly.
10. Connect the line set to the new evaporator and condensing unit and evacuate and leak
check as per current guidelines.
Line Set Cleaning for Retrofitting Procedure
Figure 1 Figure 2