System Diagnosis
©2007 Viking Preferred Service
33
Symptoms of Refrigeration Shortage
Rise in food product temperature in both compartments.
(See Note below.)
Long or continuous run time.
Look for obvious traces of oil that would occur due to a
leak or cracked refrigerant line.
Lower than normal wattage.
Compressor will be hot to touch because of the heat
generated by the motor windings from long continuous
running. It will not be as hot as it would be with a full
charge and long run times for some other reason such
as a dirty condenser.
Depending on the amount of the shortage, the
condenser will not be hot, but closer to room
temperature. The capillary tube will be warmer than
normal from a slight shortage.
If the leak is on the high side of the system, both gauges
will show lower than normal readings and will show
progressively lower readings as this charge becomes
less. The suction pressure gauge will probably indicate a
vacuum.
If the leak is on the low side of the system the suction
pressure gauge will be lower than normal, probably in a
vacuum, and the head pressure gauge will be higher
than normal. It will probably continue to become higher
because air drawn in through the leak is compressed by
the compressor and accumulates in the high side
(condenser) of the system.
Only partial frosting of evaporator instead of even
frosting of entire coil.
NOTE:
Usually the first thing that is noticed by the user
is a rise in temperature foods. Although
temperatures will rise in both the freezer section
and the food compartment, the frozen meats
and vegetables will not thaw immediately. The
customer doesn't associate the problem with the
freezer section and will first notice that milk and
other food beverages are not cold enough.
Under some circumstances, such as in the case of
forced air meatkeeper model with a slight shortage of
refrigerant, freezing in the food compartment may be
experienced due to the additional running time. With a
refrigerant leak, however, it always gets worse and as
the refrigerant charge decreases the temperature will
continue to rise.
With a shortage of refrigerant the capillary line will not
have a full column of liquid. As a result, there is a
noticeable hissing sound in the evaporator. This should
not be mistaken for the regular refrigerant boiling sounds
that would be considered normal.
Symptoms of Low or High Ambient
Temperature Installation
Lower ambient air temperature reduces the condensing
temperature and therefore reduces the temperature of
the liquid entering the evaporator. The increase in
refrigeration effect due to operation in a lower ambient
results in a decrease in power consumption and run
time. At lower ambients there is a reduction in cabinet
heat leak which is partially responsible for lower power
consumption and run time.
An increase in refrigeration effect cannot be expected
below a certain minimum ambient temperature. This
temperature varies with the type and design of the
product.
Generally speaking, ambient temperatures cannot be
lower than 60° F. without affecting operating efficiency.
Conversely, the higher the ambient temperature the
higher the head pressure must be to raise the high side
refrigerant temperature above that of the condensing
medium. Therefore, head pressure will be higher as the
ambient temperature raises. Refrigerators installed in
ambient temperatures lower than 60° F. will not perform
as well because the pressures within the system are
generally reduced and unbalanced. This means that the
lower head pressure forces less liquid refrigerant
through the capillary line. The result is the symptoms of
a refrigerant shortage. The lower the ambient
temperature the more pronounced this condition
becomes.
When a point where the ambient temperature is below
the cut-in of the Temperature Control is reached, the
compressor won't run.
The drain traps will freeze in ambient temperatures of
32° F.
Heat Load
A greater heat load can result from the addition of more
than normal supply of foods, such as after doing the
weekly shopping. Other items contributing to an
additional heat load would be excessive door openings,
poor door sealing, interior light remaining on, etc.
An increase in heat being absorbed by the refrigerant in
the evaporator will affect the temperature and pressure
of the gas returning to the compressor. Compartment
temperatures, power consumption, discharge, and
suction pressures are all affected by heat load.
Pressures will be higher than normal under heavy heat
load.
