System information

C0240111-06-07-GB
64
6.1 Freecooling
The “freecooling” function is applied to the efficient production of cold water by using external air.
The operating principle is illustrated in the following figure
FREECOOLING
COIL
"3-way" valve
EVAPORATOR
Inlet water
External air
Tin
Tfcool
Text
Tout
Outlet water
Figure 6.1: block diagram of the freecooling activation circuit
If the external water is cold, the valve closes and the water passes through the coil which cool the water
by the water-air heat exchange achieved thanks to the internal fans. If, instead, the air is hot, there is no
point in it passing through the coil and all the water is cooled with the evaporator compressors.
Further details of the valve and fan adjustment system are shown in figures 6.2.
1 0 0 %
%
a p e r t u r a
v a l v o l a
T e x t .
T f c o o l .
D e l t a ( P 1 9 . 0 1 )
- V a l v o la O n / O f f
- V a l v o la m o d u la n t e
Figure 6.2a: operation of the valve (On/Off or modulating) depending on the difference between the unit inlet
temperature (Tfcool) and that of the external air (Text)
T . in
O ffs et (P 1 9 .0 2)
S etp o in t
C h ille r
%
a p ertu ra
va lvo la
D iff.
(P 1 9 .0 3 )
1 0 0%
- V alvo la O n /O ff
- V alvo la m o d u la n te
Figure 6.2b: control in low freecooling temperature: to prevent the risk of the coil freezing, the valve is closed
below a suitable offset
Valve
aperture
On/Off valve
Modulatine valve
On/Off valve
Modulatine valve
Valve
aperture
Chiller
setpoint