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6.5 Summer to Winter mode switching
The unit is switched from summer (cooling) to winter (heating) operating mode in three different ways,
depending on the setting in screen C6 of the Manufacturer menu. Switching may be commanded using the
keyboard, a digital input and/or automatically.
6.5.1 Summer to Winter mode switching using the keyboard
The keyboard can be used for switching on condition that the unit is turned to OFF. Press the Prg button and
select “Win/Sum” in the menu using the arrows. Finally, press the Enter button to confirm. Screen R0 appears
if mode switching using the keyboard is enabled.
A click on the Enter button changes the unit status on exclusive condition that the unit is turned to OFF and
automatic mode switching is not enabled in screen C6 of the Manufacturer menu.
6.5.2 Summer to Winter mode switching using a digital input
Mode switching using a digital input takes place by opening and closing of a dedicated digital input in the
controller.
If the input is open, summer mode is enabled; if it is closed, winter mode is enabled.
If mode is switched with the unit ON, the controller stops any active device (compressors, heaters, etc.), except
for the fans in the delivery and return lines (where fitted), and it restarts them automatically as soon as switching
is completed, based on the load requirements.
Access to the “Win/Sum” menu is not possible when mode switching is enabled using the digital input.
6.5.3 Automatic Summer to Winter mode switching
Automatic switching from winter to summer mode takes place when the ambient air temperature is above the
summer setpoint; automatic switching from summer to winter mode takes place when the ambient air
temperature drops below the winter setpoint.
As the operating mode is switched with the unit ON, the controller stops any active device (compressors,
heaters, etc.), except for the fans, and it restarts them automatically as soon as switching is completed, based
on the load requirements.
Automatic mode switching is successful if the winter setpoint is smaller than the
summer setpoint. If this is not the case, the controller shows a warning message on
screen.
6.6 Compressor and refrigerant circuit operation
The controller is designed to control the operation of the refrigerant circuit fitted in the unit, to prevent potential
hazardous conditions due to an increase of the condensing pressure or a reduction of the evaporation
pressure, to protect its components and to report malfunctioning, if any.
6.6.1 Compressor switch-on and switch-off
The controller enables and disables the compressors based on the request coming from the temperature
regulation system, as illustrated in the relevant section.
Compressors actually get started when ventilation is active, in other words after a settable delay after start-up
of the fan installed in the delivery line. The controller enables the compressors one at a time so as to reduce
inrush currents in the unit.
Once the request from the temperature regulation system is fulfilled, each compressor is switched off after its
min. operating time has elapsed. This min. operating time requirement is not met in cases where a serious
alarm triggers with the compressor or the refrigerant circuit. Similarly, a compressor can be restarted after a
preset time has elapsed so as to limit the number of compressor start-ups per hour.
The controller constantly monitors compressor operation by means of digital and analogue inputs. The main
safety devices fitted in the compressors are those to monitor high and low pressures and the thermal overload
protectors.
Serious alarms leading to a compressor stop - even before the min. operating time has elapsed - are the high
pressure alarm, the low pressure alarm, and the thermal overload switch alarm.
After stopping, each compressor can be started up again on condition that the min. stop time has elapsed and,
in any case, after the min. time between two consecutive start-ups has elapsed.