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Note: Portions of the capillary tube and the
suction line are solder together to form the
heat exchanger.
Refrigerant Cycle
The refrigerant cycle is a continuous cycle that occurs
whenever the compressor is in operation. Liquid refrig-
erant is evaporated in the evaporator by the heat that
enters the cabinet through the insulated walls and the
heat introduced by the product load and door openings.
The refrigerant vapor is then drawn from the evaporator,
though the suction line, to the compressor. The pres-
sure and temperature of the vapor is raised in the com-
pressor by compression, and the vapor is then forced
through the discharge valve into the discharge line and
into the condenser. Air passing over the condenser sur-
face removes heat from the high pressure vapor, which
then condenses to a liquid. The liquid refrigerant flows
from the condenser to the evaporator, through the small
diameter liquid line (capillary tube). Before it enters the
evaporator, it is sub-cooled in the heat exchanger by the
low temperature suction vapor in the suction line.
SYSTEM SCHEMATIC
Condenser
Drier
Capillary
Condenser Bottom Loop
Low or High Side Leak or Undercharge
A loss of refrigerant results in excessive or continuous
compressor operation; above normal freezer compart-
ment temperature; a partially frosted evaporator (depend-
ing on the amount of refrigerant loss); above normal
freezer compartment temperature; low suction pressure
(vacuum) and low wattage. The condenser will be "warm
to cool," again, depending on the amount of refrigerant
lost.
When refrigerant is added, the frost pattern will improve;
the suction and discharge pressures will rise; the con-
denser will become hot; and the wattage will increase.
In the case of a low side refrigerant leak, resulting in a
complete loss of refrigerant, the compressor will run, but
Evaporator
Compressor
Suction Tube
Discharge
with no refrigeration. Suction pressure will drop below
atmospheric pressure, and air and moisture will be drawn
into the system, saturating the filter-drier.
If a slight undercharge of refrigerant is indicated, and no
leak could be found after a thorough leak test, the charge
can be corrected without changing the compressor.
If there is reason to believe the system has operated for
a considerable length of time with no refrigerant, and the
leak occurred in the evaporator, excessive amounts of
moisture may have entered the system. In such cases
the compressor may need to be replaced to prevent re-
petitive service.
If a high side leak is located and some refrigerant re-
mains in the system, it is not necessary to change the
compressor.
Test for Refrigerant Leaks
If the system is diagnosed as short of refrigerant and the
system has not been recently opened, there is probably
a leak in the system. Adding refrigerant without first
locating and repairing the leak, or replacing the compo-
nent would not permanently correct the difficulty. THE
LEAK MUST BE FOUND. Sufficient refrigerant may have
escaped to make it impossible to leak test effectively.
In such cases, add a 1/4" line piercing valve to the com-
pressor process tube. Add sufficient refrigerant to in-
crease the pressure to 75 lb. per sq. inch. Through this
procedure, slow leaks are more easily detected before
discharging the system.
Note:
The line piercing valve (clamp on type)
should be used for adding refrigerant and
test purposes only. It must be removed from
the system after it has served its purpose.
Procedure for Checking Condenser Leaks
Before checking for leaks in the condenser, check all
accessible system components and joints for leaks.
If a condenser leak is suspected:
1. Discharge the system by using refrigerant recovery
equipment.
2. Disconnect the condenser tube from the drier and
pinch off and solder both the drier and condenser
tube closed.
3. Remove the discharge tube from the compressor
and seal the opening to the compressor.
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