WDE
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EN/36B/08.2018 © STULZ SpA – all rights reserved
4. Components and operating
principle
4.1. Component layout
The internal air return is located in the upper part of rear panel of the unit. Air is taken in by the radial
fan located at the bottom of the unit immediately over the supply air opening. Then, after crossing
the treatment filter in the centre of the unit, air is blown onto the evaporator and leaves from the
opening in the lower front panel. The compressor is fixed on the unit base in front of the evaporator.
The conditioner is controlled by the electronic board in the electric box, located behind the middle
front panel and closed by a protective cover.
The through holes for the power cables and the electronic board input / output signal cables are
located on the rear panel of the unit, between return and supply openings of internal air.
The condensate drainage pipe exits from a hole on the unit base,
see its position at paragraph 3.3.
4.2. Operating method
Cooling
The shelter air is taken in by the radial fan, filtered and then cooled as it crosses the evaporator.
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)
A damper equipped with servomotor, which directs internal and external air flows, is located in the
central part of the conditioner. External air is taken in through an opening near the damper while
the internal air is discharged by overpressure through an opening located above. This 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.
Mixed mode (optional)
When the temperature of the 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 the external air rather than the internal re-circulating air, combining the benefits of
the free cooling and the cooling modes.
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 48VDC 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.
INFORMATION
Units with direct current emergency ventilation always require an external direct current power
line even when mains power is present.
