30
compressor (according to the model).
Heat pump units are provided with a control that automatically actuates defrost procedure, if needed.
The defrosting cycle has a minimum duration, during which time the end defrosting signal is disregarded to allow
the build-up of a minimum thermal fly-wheel to grant the defrost process.
The request for the start-up of a defrosting cycle is given by the low value of suction pressure due to decreased
heat exchange between evaporator and air of at least one compressor, that remains within a time interval that is
inferior to the pressure at the beginning of the cycle.
During a defrosting cycle, the heat pump mode switches over to chiller operation, and fan outputs are disabled.
Before the beginning of a defrosting cycle (in the case of two separate defrosting of refrigerant circuits), the
capacity of the compressor must be forced to 100%; in the case of total defrosting of the entire unit, all compressors
present (that are not excluded due to fault or by the operating cycle) will be forced to 100% capacity.
When refrigerant circuits are defrosted separately, the beginning of the defrosting cycle is timed to a set interval.
Once operation has been switched from heat pump to chiller and the fans have been deactivated, condensation
pressure will rise to reach the end defrosting pressure value. If simultaneous defrosting is possible, the first circuit
to reach this pressure value will give the signal for the end of the defrosting cycle for the whole unit.
Once the minimum defrosting time has elapsed and the controller has received the end defrosting signal, all fans
will be forced to operate at maximum speed before the unit switches back from chiller to heat pump operation.
In the event that the condensation pressure does not reach the end defrosting value by a certain time, the cycle
will end when the maximum defrosting time has elapsedas if the defrosting would be completed.
The control starts the fans and when the pressure decreases below the set value, inverts the cycle.
In this case, the event will be recorded in the alarms and displayed, though the controller will not intervene in any
way.
The maximum time defrosting alarm will automatically disappear from the alarm list display when another
defrosting cycle is completed due to the end defrosting pressure value being reached. All defrosting cycles
completed due to maximum time will in any case be recorded in the alarm history.
In the case of defrosting of separate cooling circuits, each one will have its own maximum time end defrosting
alarm, which will be recorded in the alarm history, and will only be removed from the alarms list when a
defrosting cycle has been correctly completed.
Defrost procedure however will be actuated only if a minimum delay-time (set in the control: 30 minutes) is
passed since last defrost operation. If the maximum time defrosting alarm persist, inform the assistance.
5.2.17 Heat recovery (option)
5.2.17 Heat recovery (option)
5.2.17 Heat recovery (option)
5.2.17 Heat recovery (option)
5.2.17 Heat recovery (option)
This function recovers part or all of the energy on the condenser to be disposed of by means of a special heat
exchanger connected in serie with the condenser. The heat recovery process is controlled by the microprocessor.
The heat recovery process the fans are disabled, the condensing coil is by-passed and discharged through solenoid
valves connected downstream the thermostatic valve. The refrigerant circuit has a liquid reciver. The function is
enabled when the relative digital input is closed.
Heat can only be recovered when the temperature of the water entering the exchanger is lower than the recovery
set point; recovery will end when the temperature has increased by the recovery differential.
The installer must install a pressure switch valve for each water cooling circuit or a 3 way valve, to avoid dangerous
condensation temperatures of the unit.
5.2.18 Dual set point (option)
5.2.18 Dual set point (option)
5.2.18 Dual set point (option)
5.2.18 Dual set point (option)
5.2.18 Dual set point (option)
Operation with dual set point is only possible when the unit is operating in chiller mode.
The refrigerant circuit has two the solenoid valves which enable two thermostatic valves according to the expansion
temperature needed.
The microprocessor control enables the selection of two operating set points and can be made either by keyboard
or digital input. The changeover of the thermosattic valves is automatic and is controlled by the water tempera-
ture. The thermostatic valves are sized according to the temperature range specified at the order.
The working limits of units are unchanged and are as per catalogue; if the unit operates with enough antifreeze
mixture to avoid ice formation, the lower operating limit on leaving water is extended till a minimum temperature
of -5 °C.
Summary of Contents for KAPPA V 2001
Page 69: ......
