Daikin AGZ045E - Page 62

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seqUenCe of operaTIon
Figure 53: Circuit Sequence of Operation
Yes
Is circuit commanded to
start?
Unit power up
No
Circuit is in O state
Yes
No
Is circuit is enabled to
start?
When the circuit is in the O state the EXV is in the closed position, compressors are
o, solenoid valves are closed, and all condenser fans are o.
Circuit is ready to start
No
Yes
Are all compressor cycle
timers active?
If the circuit is ready to start when needed, the circuit status will be
O:Ready.
Yes
The circuit must be enabled before it can run. It might be disabled for several
reasons. When the circuit switch is o, the status will be O:Circuit Switch.
If the circuit has an active stop alarm then the status will be O:Alarm. If the circuit
has been disabled via the circuit mode set point, the status will be O:Keypad
Disable. If all compressors are disabled via the settings, the circuit status will be
O:All Comp Disable.
A minimum time must pass between the previous start and stop of a compressor
and the next start. If this time has not passed, a cycle timer will be active. If all
compressors on the circuit have active cycle timers the circuit status will be
O:Cycle Timers.
Capacity control logic at the unit level will determine when a circuit needs to start
and issue a start command to the next circuit to start based on sequencing rules.
Yes
No
Is last compressor
commanded to
Pumpdown circuit
Run circuit
Is pumpdown
complete?
No
The rst compressor will be started and the fans, solenoid valves, and other
devices will be controlled as needed. The normal circuit status at this time will be
Run:Normal. Additional compressors will be started as needed per the unit level
capacity control.
When the circuit needs to shut down, a pumpdown of the circuit will be performed
if the condenser coil is tube and n type. The circuit status during this time will be
Run:Pumpdown.
Pumpdown is complete when the evaporator pressure drops to a certain point or
the circuit has been pumping down for longer than the pumpdown time limit.
Preopen EXV
No
Capacity control logic at the unit level will determine when a compressor needs to
shut down and issue a stop command to the next compressor to stop based on
sequencing rules. If this compressor is the last one on the circuit, the circuit will
need to shut down.
Before the rst compressor on a circuit can start, the EXV performs a brief preopen.
The circuit status during this time will be Preopen.
Yes
Is condenser type
tube and n?
shut down?
When the circuit needs to shut down, a pumpdown of the circuit will NOT be
performed if the condenser coil is Microchannel type. When the circuit needs to
shut down and the condenser is Microchannel type, everything will turn o on the
circuit at approximately the same time.