Leak Testing - EdgeStar CWB8420DZ Service Manual

accumulation of frost. Where possible, check the capillary tube and straighten any kinks to relieve
the restrictions. Check the unit's performance. If the condition persists, replace the defective
part. If the freeze-up condition does not exist and there is not a kink, you can assume that a
foreign particle is causing the restriction. The only remedy in this case is to replace the restricted
part.
Partial Restriction In Low Side Tubing
Bent tubing, foreign matter, or moisture in the system may cause a partial restriction in the low
side tubing. This is usually indicated by frost-free tubing between the restriction and the capillary
tube and by frost-covered tubing between the restriction and the suction line. The restriction acts
like a second capillary tube, increasing the pressure ahead of it (warming) and decreasing the
pressure beyond it (cooling). To confirm the existence of a restriction in the low side tubing,
perform operational pressure checks.
Slow Leak In System
On compressor systems, long run time will be noticed during the early stages of a leak. As the
refrigerant continues to escape, the compartment will gradually warm up and the compressor will
run continuously.
Incorrect Refrigerant Charge
The sealed unit may have too much refrigerant (overcharged system) or too little refrigerant
(undercharged system). The troubleshooting guide will inform you on how to recognize a system
with these defects.
An overcharged system may have a frost back condition appearing on the suction line. When the
compressor stops, the frost melts and drips on the floor. A heat exchanger separation will also
cause this symptom.
An undercharged system, depending on the degree of undercharge, will operate with
temperatures above normal and the compressor run time will be increased. The more
undercharged, the higher the temperature will be and the longer the run time. An undercharged
system must be purged, evacuated, and recharged with the proper amount of refrigerant.
Before recharging, test for refrigerant leaks.

2.6 Leak Testing

Once it has been determined through proper diagnosis that a leak is present in the sealed system,
attempt to find the leak before opening the system if possible. To check the high side for leaks, be
sure that the compressor is running. During run time the high side pressure is greater. To increase
the pressure slightly, stop the condenser fan blade or block the air flow through the condenser. To
check the low side for leaks, stop the compressor. During off times, the low side pressure will
increase to equalize with the high side. By warming the evaporator, this pressure will increase. If
too much refrigerant has leaked out to create enough pressure to locate the leak, add 2 ounces of
the proper refrigerant to the system and proceed with the test procedure.
The presence of oil around a tubing joint usually indicates a leak. Care must still be taken to
pinpoint the exact location. Remember to use a leak detector compatible with R600a. A sealed
system component, such as the evaporator or hot pipe, should not be condemned unless a non-
repairable leak is confirmed. This should be determined by either locating the actual leak or by
isolating the component from the rest of the system and determining if it holds pressure or a
vacuum.