75
ENG
µchiller +0300053EN rel. 2.2 - 14.12.2021
Functions
The control phases are described below.
Synchronisation (1)
Once the defrost start condition is true, there is a fi xed delay of 10 s to check whether the other circuit requires defrosting, so as
to carry out a simultaneous defrost if needed.
User Code Description Def Min Max UOM
S S053 Defrost synchronisation: 0=Independent 1=Separate 2=Simultaneous 40.0 0.0 999.9 rps
Decrease capacity to start defrosting (2)
Capacity at start defrost can be managed in two ways:
• stopping the compressors
• compressors running at minimum power. For circuits with on-off compressors, a single compressor is kept on, while the com-
pressor is kept at minimum capacity for circuits with BLDC compressor.
User Code Description Def Min Max UOM
M S073 Compressor status at start defrost 0/1=On/Off 001-
S S052 BLDC compressor speed for cycle reversing in defrost 40.0 0.0 999.9 rps
Waiting time before reversing the cycle (3)
The 4-way valve is positioned in chiller mode to run the defrost, the fans are stopped and the compressor remains at the cycle-
reversal speed for 5 seconds. Normally during this phase the electronic expansion valve tends to close, due to low superheat. As
a result it is forced to the maximum opening so as to guarantee a constant fl ow of refrigerant and maximum defrost capacity.
User Code Description Def Min Max UOM
S S044 Operation time at min capacity before cycle reversing 20 0 999 s
Cycle reversal and waiting time after reversal (4)
La valvola 4 vie si posiziona in modalità chiller per eseguire lo sbrinamento, i ventilatori si spengono e il compressore rimane alla
velocità di inversione di ciclo per 5 secondi. Normalmente durante questa fase la valvola di espansione elettronica tende a chiu-
dersi per basso surriscaldamento. Per questo essa è forzata alla massima apertura per garantire il fl usso costante di refrigerante
e la potenza massima di sbrinamento.
Defrosting (5)
The actual defrosting procedure starts: the compressor delivers full capacity so as to defrost the outdoor coil. In this phase, the
BLDC compressor goes to the speed set by the corresponding parameter, the electronic expansion valve remains at the maxi-
mum opening and the fans remain off . The minimum/maximum defrost time and minimum time between two consecutive
defrosts start counting in this phase.
User Code Description Def Min Max UOM
S S046 Defrost: min duration 1 0 99 min
S S047 Defrost: max duration 5 0 99 min
S S050 Minimum delay between consecutive defrosts 20 0 999 min
S S051 BDLC compressor speed in defrost 80.0 0.0 999.9 rps
The minimum defrost time protects compressors and circuit components from transients with high dynamics that are too
close together. The maximum defrost time is a safety feature that avoids any abnormal conditions (end defrost threshold not
reached - e.g. due to strong winds) that would stop the production of hot water required by the user terminals. The minimum
time between consecutive defrosts is needed to prevent the unit from defrosting too frequently and thus only partly meeting
demand. The actual defrosting procedure therefore ends after a maximum time or when the set condensing temperature is
reached. If the compressor stops during this phase, the counters are reset.
Dripping (case with compressor on) (6)
In this phase, the compressor remains on at the defrost speed, the electronic valve is opened to the maximum and the fans are
started at maximum speed, and remain at this speed for the entire dripping phase. The duration of the dripping phase can be set.
User Code Description Def Min Max UOM
S S048 Dripping: duration 90 0 999 s
Decreased compressor capacity to end defrost (7)
Circuit capacity is reduced to the minimum and the cycle is reversed. In this phase, the fans are stopped (they are only activated
if necessary for high pressure prevention) and the cycle reversing valve is moved to the heat pump position, controlled based
on the diff erence between condensation and evaporation pressure: as soon as this pressure diff erence falls below the minimum
diff erential for valve activation + 1 bar, the cycle is reversed (return to heat pump mode). If the reversing threshold is not rea-
ched, the cycle is reversed after a fi xed time (60 s). The electronic expansion valve is opened to the maximum position.
User Code Description Def Min Max UOM
M S054 4-way valve: pressure diff erential for reversing 3.0 0.0 999.9 bar
To Next Page
Loading...
