78
ENG
µchiller +0300053EN rel. 2.2 - 14.12.2021
Functions
Separate
When the fi rst circuit requires defrosting:
• it starts the defrost procedure;
• the other continues to work in heat pump mode.
When the fi rst circuit has fi nished defrosting, the other is free to start.
Simultaneous
This procedure is used if the air fl ow cooling the condenser coils on one circuit aff ects the other: during the defrost phase
this would mean a considerable waste of energy to recover the heat lost in the air fl ow on the other circuit. The fi rst circuit that
requires defrosting thus puts the entire unit into defrost mode. If only one circuit starts defrosting, it completes all the defrost
phases while the other remains off . If the other circuit one requires defrosting but is waiting until the defrost start delay elap-
ses, the delay is ignored and the circuit also starts defrosting. When one of the circuits reaches the end defrost condition, it
remains in the dripping phase until the other circuit ends the procedure. In this way, the dripping phase is performed by both
circuits, preventing the air fl ow to the condenser coils from aff ecting the defrost procedure. During this phase, the compressor
is stopped instead of operating at end defrost capacity, to prevent the waiting phase of the other compressor from bringing the
user terminals to excessively low temperatures.
Note: if there is a common air circuit for the condensers, simultaneous defrosting is enabled automatically.
5.18 4-way valve management
A special function has been included to ensure correct control of the 4- way valve that reverses the refrigerating cycle. When
there is a request to reverse the valve, the controller checks whether the pressure diff erence is higher than a threshold before
activating the valve: if the diff erence is lower, the application waits until the compressor starts and then activates the valve when
the pressure diff erence is reached.
User Code Description Def Min Max UOM
M S054 4-way valve: pressure diff erential for reversing 3.0 0.0 999.9 bar
In the event of a power failure, the controller realigns the 4-way valve with the physical position of the valve at next start-up,
considering the status of the circuit at the time of the power failure.
5.19 Manual device management
In the menu relating to the individual devices, operation of the individual actuators fi tted on the unit can be switched from
automatic to manual. For digital outputs, the options are ON or OFF, while analogue outputs can be set from 0 to 100%; the
default values are all Auto.
User Code Description Def Min Max UOM
S E000 ExV circuit 1: manual mode 0/1=No/Yes 001-
S E001 ExV circuit 1: steps in manual mode 0 0 65535 steps
S E002 ExV circuit 2: manual mode 0/1=No/Yes 001-
S E003 ExV circuit 2: steps in manual mode 0 0 65535 steps
S U002 User pump 1: operating mode 0=AUTO; 1=OFF; 2=ON 002-
S U005 User pump 2: operating mode 0=AUTO; 1=OFF; 2=ON 002-
S C002 Comp. 1 circuit 1: operating mode 0=AUTO; 1=OFF; 2=ON 002-
S C005 Comp. 2 circuit 1: operating mode 0=AUTO; 1=OFF; 2=ON 002-
S C008 Comp. 1 circuit 2: operating mode 0=AUTO; 1=OFF; 2=ON 002-
S C011 Comp. 2 circuit 2: operating mode 0=AUTO; 1=OFF; 2=ON 002-
S S002 Source pump 1: operating mode 0=AUTO; 1=OFF; 2=ON 002-
S S011 Source modulating fan circuit 1: operating mode
0=AUTO; 1=0%; 2=1%, .. ; 101=100%
0 0 101 -
S S014 Source ON/OFF fan 1 circuit 2: operating mode
0=AUTO; 1=OFF; 2=ON
002-
S S015 Source modulating fan circuit 2: operating mode
0=AUTO; 1=0%; 2=1%, .. ; 101=100%
0 0 101 -
These operations bypass temperature control, but not the alarm thresholds set to protect unit safety; in general, these opera-
tions are used to test the individual actuators during installation.
Manual operation of the devices is described below:
Device Notes
Compressors Safety times taken into account
All compressor alarms are enabled
User pumps Pump overload and fl ow alarm active
Source pump -
Defrost -
Source fans Speed-up disabled
ExV All alarms disabled
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