Thermo King SB-III 30 SR+, Manual

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Unit Description (Rev. 04/02)
10
CYCLE-SENTRY Mode, Setpoint Below
Fresh-Frozen Range
Operating mode is controlled by the microprocessor. When
the temperature is within a few degrees of setpoint, the tem-
perature is considered to be in range and the in-range icon
will turn on. The microprocessor will select the operating
mode from the list of possible modes below:
• High Speed Cool
• Low Speed Cool
• Null (if engine temperature and battery are satisfied)
• Low Speed Heat (if engine temperature or battery are
not satisfied)
• Defrost
Defrost
Defrost is initiated manually through the defrost prompt
screen using the microprocessor Select and Enter keys.
Defrost is initiated automatically on demand, by the defrost
timer, or by the air switch.
The evaporator coil temperature must be below 45 F (7 C)
to allow defrost. When the Defrost Icon appears, the damper
door is closed by the damper solenoid.
A demand defrost cycle will occur if the difference between
the return air temperature, discharge air temperature and
coil temperature becomes excessive.
Two defrost timers are used. When the unit is In-Range
(within a few degrees of setpoint), defrost intervals are con-
trolled by the Defrost Interval In-range timer (DEFI). This
timer can be set for 4, 6, 8 or 12 hours. When the unit is not
in range, defrost intervals are determined by the Defrost
Interval Not In-Range timer (DEFN). This timer can be set
for 2, 4, 6, 8 or 12 hours. This feature allows a shorter
defrost timer to be used when the unit is out of range during
a pulldown and more frequent defrost cycles may be benefi-
cial.
If the unit is in CYCLE-SENTRY Null mode, the engine
will start when defrost is initiated. The In-Range Icon will
remain on if it was on when defrost was initiated.
The unit will stay in defrost until the evaporator coil tem-
perature rises to 57 F (13 C). If the evaporator coil tempera-
ture does not rise above 57 F (13 C) within the Defrost
Duration (DDUR) time limit, the microprocessor will termi-
nate defrost. The Defrost Duration can be set for either 30 or
45 minutes.