Unit Description
37
CYCLE-SENTRY Operation
Units that are equipped with the
CYCLE-SENTRY option will shut down when
both evaporators are in Null. The unit starts when
either thermostat calls for high speed or when
Defrost is initiated in either evaporator.
Features of the CYCLE-SENTRY system are:
• Offers either CYCLE-SENTRY (Auto
Start/Stop) or Continuous Run (Cont Run)
operation.
• Thermostat controlled all season temperature
control.
• Maintains minimum engine temperature in
low ambient conditions.
• Battery Sentry keeps batteries fully charged
during unit operation.
• Variable glow plug preheat time.
• Preheat indicator buzzer.
If your unit is equipped with the
CYCLE-SENTRY Start/Stop fuel saving system,
it will provide optimum operating economy. The
CYCLE-SENTRY system automatically starts the
unit when heating or cooling is required and shuts
Off the unit when the compartment temperature
reaches the controller setpoint. Once started, a
unit not using CYCLE-SENTRY runs
continuously.
In addition, the CYCLE-SENTRY system
automatically maintains engine temperature in
cold weather conditions by restarting the unit if
the engine block temperature drops below 30 F
(-1 C). Once the unit is started, it will run until the
demand of the controller is satisfied and the
engine block temperature reaches 90 F (32 C).
NOTE: A buzzer sounds when the unit is
automatically preheating.
WARNING: This unit is equipped with
Auto Start/Stop as standard equipment.
Set all unit On/Off switches to Off before
opening doors or inspecting any part of
the unit. With the On/Off switch in the On
position the unit may start at any time
without warning.
0. Setpoint 4. Cool
1. Temperature Drop 5. Null (Cool if Condensing
Unit is Running)
2. Temperature Rise 6. Null
3. Cool—Force
Condensing Unit
to High Speed
7. Heat—Force
Condensing Unit to High
Speed (Null if Setpoint is
Below 15 F [-9.4 C])
Figure 9: Zone 1 Evaporator CYCLE-SENTRY
Control Algorithm
0. Setpoint 4. Null (Cool if Condensing
Unit is Running)
1. Temperature Drop 5. Null
2. Temperature Rise 6. Heat—Force
Condensing Unit to High
Speed (Null if Setpoint is
Below 15 F [-9.4 C])
3. Cool—Force
Condensing Unit to
High Speed
Figure 10: Zone 2 Evaporator CYCLE-SENTRY
Control Algorithm
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