Daikin UATYA-B, Руководство по эксплуатации

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Service manual Daikin R32 Rooftops UATYA-B
ESIE21-02 – 2021.03
3.17.4 Refrigeration cycle reversal and defrost
With reversal of the refrigeration cycle and the stopping of ventilation, defrosting of the coil starts.
The parameters involved are shown in the table.
The values of the parameters are representative. In specific cases, different values can be set.
Parameter Value UM Description
DF49 48.0 °C Condensing temperature threshold for end of defrost
DF50 10 s Minimum defrost duration time
DF51 300 s Maximum defrost duration time
In these conditions, the heat produced by the delivery gas warms the coil and melts the frost present. The checks and
actions carried out by the controller during this stage are as follows:
- checking that defrosting has not been stopped accidentally and that it continues for at least the minimum time;
- management of gradual increase in condensing pressure until the end-of-defrost pressure is achieved;
- checking that the defrost time does not exceed the maximum duration. If this happens, the defrost cycle is stopped;
- indifferently of the conditions that lead to the end of the defrost (due to reaching the end-of-defrost threshold or due to
reaching the time limit), the next action is preparation for return of operation in heating mode.
3.17.5 Forcing of a defrost cycle
The starting of a defrost can take place normally or through manual or automatic forcing.
The parameters involved are shown in the table.
The values of the parameters are representative. In specific cases, different values can be set.
Parameter Value UM Description
DF20 1 - Yes - Enables manual defrost from the keypad
DF21 -20.0 °C Evaporating temperature threshold for activating a forced defrost
DF22 10 s Delay to starting forced defrost
When parameter “DF20” is enabled, a defrost cycle can be overridden from the keypad.
If operating conditions make it necessary, the operator can force the controller, from the keypad, to carry out defrost cycles
without needing to comply with the set delays.
So that a defrost can take place, sufficient thermal inertia must in any case be present in the system.
Failing this, the protective devices may trip, and if this happens repeatedly, the compressors can be dama
-
ged.
The controller activates a “forced” defrost cycle, ignoring the set delays, when the evaporating temperature reaches the
threshold setpoint in parameter “DF21” and maintains it for the time set in parameter “DF22”.
3 Software functions