25 © STULZ SpA . – all rights reserved EN/39B/06.2018
SAL
Operating methods
Cooling
The internal air is taken in by the radial fan, filtered and then cooled as it crosses the evaporator. The
treated air is then returned to the shelter through the supply air opening. The compressor operates
in order to cool the air.
Free cooling (optional)
To enable free cooling, the free cooling module has to be installed behind the internal unit. The
module is equipped with a damper with servomotor, which directs internal and external air flows.
The free cooling damper is proportionally controlled by a modulating signal from the C2020
controller. Its position can be adjusted from 0 to 100% of fresh air, to regulate free cooling capacity.
External fresh air is taken in through an opening on the rear side and, after filtration, blown directly
into the shelter.
Mixed mode (optional)
When the temperature of external air is low enough to enable the free cooling mode, but the
effect of this operating mode is not sufficient to keep the internal temperature within the required
range, the compressor is switched on while the free cooling damper remains open. In this way, the
evaporator cools external air rather than internal re-circulating air, combining the benefits of the free
cooling and the cooling modes. Mixed mode is available only when free cooling module is present.
Emergency ventilation (optional)
When there is a power failure, part of the unit (evaporator fans, control components and the free
cooling damper motor) is powered by an emergency 48 VDC power supply. In this way, continuous
circulation of air inside the shelter is always assured. This circulation of air is combined with free
cooling when the conditions required to enable this mode are satisfied. The emergency ventilation is
possible only when free cooling module is present.
INFORMATION
Units with direct current emergency ventilation always require an external direct current power
line even when mains power is present.
Heating (optional)
When the temperature is low, the heating element turns on (compressor off) and the unit is in
complete re-circulation position, in order to heat internal air. This mode is controlled by the C2020
controller.
Dehumidification (with accessory ACTRHC1)
According to the signal of humidity inside the room, supplied by the optional humidity probe
ACTRHC1, air conditioner C2020 controller reduces evaporator fan speed. Consequent air flow
reduction causes a higher temperature difference between inlet and outlet air, helping condensation
of humidity in it.
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