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True Food Service Equipment, Inc.
MAINTENANCE, CARE & CLEANING
4. If all operating conditions are normal,
the voltage supply at the compressor
terminals balanced and within limits, the
compressor crankcase temperature within
normal limits, and the amperage drawn
within the specified range, the motor
protector may be defective, and should
be replaced.
If the operating conditions are normal
and the compressor is running excessively
hot for no observable reason, or if the
amperage drawn is above the normal
range and sufficient to repeatedly trip the
protector, the compressor has internal
damage and should be replaced.
IF THE COMPRESSOR RUNS BUT WILL
NOT REFRIGERATE
1. Check the refrigerant charge. Check
the evaporator surface to determine
if it is evenly cold throughout, or if
partially starved. A lack of charge may
be indicated by light, fluffy frost at
the evaporator inlet. Add refrigerant if
necessary.
2. Check the compressor suction
pressure. An abnormally low pressure
may indicate a loss of refrigerant charge,
a malfunctioning capillary tube, a lack of
evaporator capacity possibly due to icing
or low air flow, or a restriction in the
system.
Often a restriction in a drier or strainer
can be identified by frost or a decrease
in temperature across the restriction due
to the pressure drop in the line. This
will be true only if liquid refrigerant is in
the line at the restricted point, since any
temperature change due to restriction
would be caused by the flashing of liquid
into vapor as the pressure changes.
Any abnormal restriction in the system
must be corrected.
3. Check the compressor discharge
pressure. An abnormally high discharge
pressure can cause a loss of capacity, and
can be caused by a dirty condenser, a
malfunctioning condenser fan, or air in
the system.
4. If the suction pressure is high, and the
evaporator and condenser are functioning
normally, check the compressor
amperage draw. An amperage draw near
or above the nameplate rating indicates
normal compressor or unit may have
damaged valves.
An amperage draw considerably below
the nameplate rating may indicate a
broken suction reed or broken
connecting rod in the compressor.
DIAGNOSIS AND REPLACEMENT OF
FREEZER CABINET COMPONENTS
1. Defrost Time Clock
A. Check timer motor to be sure
it runs.
B. Check contacts on the defrost
timer.
C. Check solenoid windings for
continuity to ensure contact
switching.
D. Check to be sure defrost
actuator pins are in proper
position.
E. Check all wires in the timer for
tightness to terminals and
broken wires.
2. Defrost Control On The
Evaporator Drain Pan
A. If the defrost time is always
35 minutes (or whatever duration the
elapsed time adjustment is set at) and
the fan motors do not delay after a
defrost cycle and it has been determined
that the solenoid in the defrost clock is
functioning, change the defrost control
in the evaporator compartment in
the top of the freezer. This control is
attached to the evaporator drain pan.
3. Coil Defrost Heater
A. Lower the evaporator cover.
Disconnect the coil heater by removing
the wire nuts at the point where the
heater joins the electrical circuit of the
freezer in the evaporator compartment.
Check heater for continuity with an
ohmmeter. If the heater is defective, cut
the bale wires holding the heater to the
coil and remove the heater. Replace with
a new heater using bale wires provided.
4. Drain Tube Heater
A. Lower the evaporator cover.
Disconnect the drain tube heater by
removing the wire nuts at the point
where the heater joins the electrical
circuit of the freezer in the evaporator
compartment. Check the drain tube
heater with an ohmmeter.
B. If the drain tube heater is
defective, disconnect the drain tube from
the rigid plastic drain, bend the tabs that
hold the evaporator drain pan to the
evaporator cover and raise the drain pan
so that the flexible heater is visible, pull
heater out of the plastic drain tube and
replace. Connect heater to the electrical
circuit in the evaporator compartment.
5. Cabinet Temperature
Control
A. Remove the two screws on the
right side of the evaporator housing that
holds the control mounting plate. Reach
behind the evaporator housing on the
control side of the cabinet and pull the
control bulb out of the receptacle in
the roof of the cabinet. Disconnect the
wires from the control. Check control for
continuity, replace if defective.
