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5
Section 2: Sealed System
2.1 Introduction
The following should always be practiced with any sealed system that has been opened. Only
open the sealed system after proper diagnosis has verified a system issue. Eliminate any
possible non system related problems such as wiring, control system, airflow, etc. before
attempting a sealed system repair. Many times these possibilities can resemble sealed system
problems. Checking the evaporator frost pattern is a great way to determine if a possible
charge related problem is evident.
1. Use a leak detection system that will detect R-134a refrigerant. Check both the high and
low sides slowly for minuscule leaks.
2. The drier must be replaced anytime the sealed system is opened. Always use an
unopened and approved drier. Failure to do so may cause repeated system failure in the
future.
3. Limit time the system is opened. DO NOT EXPOSE THE OPEN SYSTEM FOR MORE THAN
15 MINUTES. This could result in a sealed system failure. Leave replacement parts
sealed and unexposed to the surrounding atmosphere until they are ready to install.
4. Replacing the compressor for a low side leak is not always mandatory. If the system has
not been purged dry of refrigerant and oil as a result of a low side leak, the sealed
system should not be compromised. However, if the system has been purged
completely of refrigerant, a compressor replacement should be completed. Moisture
has been drawn into the system if the unit has been running dry for an extended period
of time. Be sure to flush the system with dry nitrogen gas and evacuate to 50 microns
before re-charging.
5. A new evaporator assembly must be ordered if the capillary tube is found to be plugged
or severely restricted. Restrictions cannot be flushed out.
6. Be sure to purge the system after final brazing. This will flush out any air or moisture
that may have entered the system before being absorbed into the ester oil.
7. A sealed system that has been contaminated by moisture is a very costly repair for the
customer. If the appliance is still under warranty, it would be best to contact the
manufacture for recommendations for either a sealed system replacement or appliance
replacement.
2.2 Low Side Leaks
Low side leaks consist of a break in the system at the evaporator, suction line, or compressor. If
a leak is found in any of these areas, there is a possibility that moisture has been introduced
into the sealed system. The compressor and drier will have to be replaced and the system will
need to be flushed thoroughly with nitrogen gas and evacuated to 50 microns before re-
charging.
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