CIrCuIT funCTIons
www.DaikinApplied.com 59 IOM 1242-2 • PATHFINDER
®
MODEL AWV CHILLERS
Circuit Availability
A circuit is available to start if the following conditions are true:
• Circuit switch input is on
• No manual reset circuit fault alarms are active
• Circuit Mode set point is set to Enable
• BAS Circuit Mode set point is set to Auto
• No cycle timers are active
• Oil Sump Check = Ready
Oil Sump Check
Oil sump check is to make sure that oil in the sump is of
sufcient quality prior to starting the compressor.
Oil sump check is set to Ready when
Discharge Temperature > Saturated Oil Temperature + 5°C
Oil sump check is set to Not Ready when
Discharge Temperature < Saturated Oil Temperature + 4.5°C
Circuit States
There are ve distinct states of control for the circuit as shown.
Figure 62: Circuit State Transitions
T1 – Off to Preopen - All of the following are required:
• Circuit is available to start per the previous section
• Adequate pressure in the evaporator and condenser (see
No Pressure At Start Alarm)
• Unit capacity control logic requires the circuit to start
T2 – Preopen to Start
Evaporator EXV completes preopen operation.
T3 – Start to Run
Compressor speed ≥ 19Hz for at least 30 seconds
T4 – Run to Pumpdown - Any of the following are required:
• Unit capacity control logic requires this circuit to stop
• Unit state is pumpdown
• A pumpdown alarm occurs on the circuit
• Circuit switch input is off
• Control Source = Network and BAS Circuit Mode = Off
T5 – Pumpdown to Off - Any of the following are required:
• Evaporator Pressure drops below Pumpdown Target
Value
• Circuit state has been pump down for longer than the
Pumpdown Time Limit set point
• Unit state is Off
• Rapid stop alarm occurs on the circuit
T6 – Run to Off - Any of the following are required:
• Unit state is Off
• Rapid stop alarm occurs on the circuit
T7 – Start to Off - Any of the following are required:
• Unit state is Off
• Rapid stop alarm occurs on the circuit
T8 – Start to Pumpdown - Any of the following are required:
• Unit capacity control logic requires this circuit to stop
• Unit state is pumpdown
• A pumpdown alarm occurs on the circuit
• Circuit switch is open
• Control Source = Network and BAS Circuit Mode = Off
T9 – Preopen to Off - Any of the following are required:
• Unit state is Off
• A rapid stop alarm occurs on the circuit
• A pumpdown alarm occurs on the circuit
• Circuit switch input is off
• Control Source = Network and BAS Circuit Mode = Offf
OFF PREOPEN
RUN
POWER
ON
START
PUMPDOWN
T2
T3
T4
T5
T6
T7
T1
T8
T9
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