Daikin Navigator WWV - Circuit Level Functions; Approach Value Calculations; Circuit State Transitions Overview

37
IOM 1264-4
WWW.DAIKINAPPLIED.COM
OPERATION
Circuit Functions
Components controlled at the circuit level include:
• Compressor VFD
• Compressor VR Solenoid Valves
• Oil Return Solenoid Valve
• Jet Pump Solenoid Valve
• Evaporator EXV
Approach Values
Evaporator Approach = LWT – Evap Saturated Temp
Condenser Approach = Cond Saturated Temp - LWT
Superheat Values
Suction superheat = Suction Temp – Evap Saturated Temp
Discharge superheat = MAX{0, Discharge Temp – Cond
Saturated Temp}
Subcooling = Cond Saturated Temp – Liquid Line Temp
Di󰀨erential Pressure Values
Oil Pressure Drop = Cond Pressure - Oil Pressure
Pressure Ratio
Pressure Ratio = (Cond Press +101.3) ÷ (Evap Press + 101.3)
Actual Capacity
Actual capacity is a representation of capacity as a percentage of
full capacity based on feedback regarding the actual speed of the
compressor.
Compressors vary capacity via changes to the speed. The actual
compressor speed is read from the VFD. Feedback capacity for a
compressor with a VFD is:
Actual Compressor Speed x 100 ÷ Maximum Speed
Circuit Availability
A circuit is available to start if the following conditions are true:
• 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 if Control Source
= Network
• No cycle timers are active (including the max starts per hour
limit)
Circuit States
There are four distinct states of control for the circuit as shown.
Figure 23: Circuit State Transitions
T1 – O󰀨 to Start - All of the following must be true:
• 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
• BAS Circuit Mode set point is set to Auto if Control Source
= Network
• No cycle timers are active (including max starts per hour)
• Evaporator State = Run
• Condenser State = Run
• Circuit state has been O󰀨 for at least 15 seconds
T2 – Start to Run - All of the following are required:
• Circuit has been in the Start state for 20 seconds
• Evap Pressure ≥ Low Pressure Unload set point
T3 – Run to Shutdown - Any of the following are required:
• Unit capacity control logic requires this circuit to stop
• Unit state is Shutdown
• A normal shutdown alarm occurs on the circuit
• Control Source = Network and BAS Circuit Mode = O󰀨
T4 – Shutdown to O󰀨 - Any of the following are required:
• Unit state is O󰀨
• Rapid stop alarm occurs on the circuit
• Evaporator State is not Run
• Condenser State is not Run
• Compressor speed ≤ 20 Hz
• Circuit State = Shutdown for more than 30 seconds
T5 – Run to O󰀨 - Any of the following are required: