Honeywell Genetron® ST-20™ Flush
AC & Refrigeration Flush
Line Set Cleaning for Retrofitting Procedure
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.
Figure 1
Figure 2
System Repair and Cleanup Procedure
1. After a mechanical failure or hermetic motor burnout, use Genetron ST-20 Flush to
remove contaminants by flushing interconnecting piping as per the directions for Line
Set Cleaning.
2. Remember to disconnect all electrical connections to the system and obtain and use
safety goggles and nitrile gloves.
4. Do not attempt to push ST-20 Flush through compressor bodies.
3. It will be necessary to cut the refrigeration or air conditioning system at several points
to isolate large components such as receivers and condensers which must be cleaned
separately. It may be impractical to clean large components with ST-20 Flush. Inspect
these components and consider mechanical cleaning if large deposits are discovered.
Remove any solenoid or reversing valves from the piping. It may become necessary to
modify procedures for line set cleaning to completely flush these components, use dry
nitrogen to completely purge the component.
5. After cleaning and purging, assemble the refrigeration or AC system. Remember to
purge the system with low pressure nitrogen during brazing operations.
6. Replace the liquid line filter drier and consider installing a suction filter.
7. If the original compressor is being re-installed, change the lubricant. Use only lubricants
specified by the compressor manufacturer.
8. Pressurize the system with nitrogen and leak check as per AHRI and EPA guidelines.
9. Evacuate the system and charge the proper refrigerant as per the system
manufacturer’s recommendations.
10. If a retrofit was accomplished during this repair, label the system indicating the
refrigerant and lubricant used.
11. Properly dispose of contaminated Genetron ST-20 Flush.
Disclaimer
All statements, information and data given herein are believed to be
accurate and reliable but are presented without guaranty, warranty
or responsibility of any kind, expressed or implied. Statements or
suggestions concerning possible use of our products are made
without representation or warranty that any such use is free of
patent infringement and are not recommendations to infringe any
patent. The user should not assume that all safety measures are
Honeywell Genetron Refrigerants
indicated, or that other measures may not be required.
101 Columbia Road
Morristown, NJ 07962-1053
Phone:1-800-631-8138
Genetron is a registered trademark of Honeywell International Inc.
ST-20 is a trademark of Honeywell International Inc.
RX11-Flush is a trademark of Nu-Calgon.
Printed in U.S.A.
© 2009 Honeywell International Inc. All rights reserved.
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