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TK 56171-2-OP-EN
Defrost
Frost gradually builds-up on evaporator coils as a result of normal operation.
The unit uses hot refrigerant to defrost the evaporator coil. Hot refrigerant
gas passes through the evaporator coil and melts the frost. The water flows
through collection drain tubes onto the ground. The methods of defrost
initiation are Automatic and Manual.
A
Au
utto
om
ma
attiicc D
De
effrro
osstt:: The SR-4 automatically initiates timed or demand
defrost cycles. The SR-4 microprocessor can be programmed to initiate
timed defrost cycles at intervals of 2, 4, 6, 8, or 12 hours. Demand defrost
cycles occur if the differences between the return air temperature, discharge
air temperature, and coil temperature exceed certain limits. The unit can
enter defrost cycles as often as every 30 minutes if required.
M
Ma
an
nu
ua
all D
De
effrro
osstt:: In Manual Defrost mode, the operator initiates a defrost
cycle. Refer to “Initiating a Manual Defrost Cycle.”
N
No
otte
e:: The unit will not perform a Manual Defrost Cycle unless the unit has
been turned on with the ON key, the unit is running in Continuous or
CYCLE-SENTRY Mode (or shut down in CYCLE-SENTRY Null Mode),
and the coil temperature is below 45°F (7°C).
Precision Temperature Control (PTC)
When activated, PTC pulses the Liquid Line Solenoid (LSS) in the selected
Zone as necessary to control the cooling capacity for more precise
temperature control. PTC is only allowed in one remote zone and only for
fresh setpoints. Contact your Thermo King dealer for information about
programming PTC. PTC is not available on DE units.
Opening the Front Doors
To open the doors and access the engine compartment, pull the right door
latch handle out at a 45 degree angle and turn it down (clockwise) 90 degrees
(
). To close the door, push the door closed while holding the
door latch handle open and then turn it up (counterclockwise) 90 degrees.
