Unit Functions - Daikin Comfort Flex CLIV Series Installation, Operation And Maintenance Manual

The calculations in this section are used in unit-level control logic
or all-circuit control logic.
EVAPORATOR DELTA T
The Delta T of the evaporator water is calculated as the
temperature of the water entering minus that leaving through all
circuits.
PENDING LWT
The slope of LWT is calculated such that the slope represents the
estimated change in LWT is immediately.
RATE OF DECLINE
The slope value calculated above will be a negative value as the
water temperature is dropping. The rate of descent is calculated
by pouring the slope value and imitating it at a minimum value of
4°C/sec.
LWT ERROR
The LWT error is calculated as LWT - target LWT.
UNIT CAPACITY
Unit capacity is the Delta T of the unit operating for GPM of water.
CONTROLLER CALCULATIONS
Refrigerant saturation temperature
The saturated coolant temperature will be calculated from the
pressure sensor readings for each circuit.
Evaporator approach
The evaporator approximation will be calculated for each circuit.
The equation is as follows
Evaporator approximation = LWT - Evaporator saturated
temperature.
Condenser approach
The capacitor approximation will be calculated for each circuit.
The equation is as follows
Capacitor approximation = Capacitor saturated temperature-
OAT.
Suction reheating
The suction superheat shall be calculated for each circuit using
the following equation:
Suction superheat = Suction temperature - Evaporator saturated
temperature.
Pumping pressure
The pressure at which a circuit will pump down is based on the low
pressure set point of the evaporator. The equation is as follows
Pump down pressure = Evaporator low pressure set point -
103KPA (15 PSI)
iom-cliv-eng
CIRCUIT LOGIC CONTROL
Circuit enablement
A circuit must be enabled to start if the following conditions are
met:
• Circuit breaker is closed
• No circuit alarms are active
• Circuit mode setpoint is set to enable
• At least one compressor is enabled to start (according to
enable set points)
COMPRESSOR AVAILABILITY
A compressor is considered to be available to start if all of the
following are met:
• The corresponding circuit is enabled.
• The corresponding circuit is not in pumping stop.
• No cycle timers are active for the compressor.
• The corresponding circuit is not in pump-down stop state
• Compressor is enabled through the enable set points.
• Compressor is not running.
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Unit Functions

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