30
OM
AGSD-1
Ice Mode Start Delay
An adjustable start-to-start ice delay timer will limit the frequency with which the chiller
may start in Ice mode. The timer starts when the first compressor starts while the unit is in
ice mode. While this timer is active, the chiller cannot restart in Ice mode. The time delay
is user adjustable.
The ice delay timer may be manually cleared to force a restart in ice mode. A setpoint
specifically for clearing the ice mode delay is available. In addition, cycling the power to
the controller will clear the ice delay timer.
Evaporator Pump Control
The state-transition diagram shown below controls operation of the evaporator pump.
Figure 7, Evaporator Pump States
Power ON
OFF
RUN
START
T1
T4
T2
T3
Evaporator Pump
States
T5
Transitions:
T1
– Transition from Off to Start requires
any
of the following
•
Unit state = Auto AND If Low OAT Lockout is active then LWT <= 40 °F
•
LWT < Freeze setpoint - 1 °F
T2
– Transition from Start to Run
•
Flow ok for time > evaporator recirculate time
T3
– Transition from Run to Off requires
any
of the following
•
Unit state = Off AND LWT > Freeze setpoint
•
Low OAT Lockout is active AND No compressors running AND LWT > 70°F
T4
– Transition from Start to Off requires
any
of the following
•
Unit state = Off AND LWT > Freeze setpoint
•
Low OAT Lockout is active AND No compressors running AND LWT > 70°F
T5
– Transition from Run to Start
•
Evaporator flow switch is open AND Evaporator state = Run for time greater than Flow
Proof setpoint
Summary of Contents for AGS 225D
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