AIR-COOLED LIQUID CHILLERS 30XA 252-1702
Operating principle
When the chilled water-air temperature difference exceeds
a threshold value, the Touch Pilot control carries out a
comparison between the instantaneous chiller cooling
capacity and the available free cooling capacity. If the
operating conditions allow free cooling operation, the
compressors are stopped, a set of valves on the suction
piping connects the evaporator with the condenser, allowing
the migration of the refrigerant vapours to the condenser.
The refrigeran t condenses in the condenser coils, and the
cooling micro-pump transports the liquid to the evaporator.
The cooling capacity in free cooling mode is controlled by the
opening of the electronic expansion valve (EXV).
Cooling capacities
30XA 252-1002 in free-cooling mode (option
118A)
Condenser entering air temperature, °C
30XA
Operation in combined FC (free-cooling) and MC (mechanical cooling) mode is possible in the two independent
refrigerant circuits. This can optimise the free-cooling
operations and at the same time ensures that the cooling
requirements of the system are met.
°C
252
302
352
402
452
502
602
702
752
802
852
902
1002
EER
FC mode
Circuit 1: FC
Circuit 2: FC
Mixed mode
Circuit 1: MC
Circuit 2: FC
MC mode
Circuit 1: MC
Circuit 2: MC
Freecooling
mode
Evaporator water temperature, °C
Minimum leaving water
3.3
temperature
Maximum leaving water
25
temperature
Condenser air temperature, °C
Minimum leaving air
-20
temperature
Maximum leaving air
20
temperature
*
I
E
R
183.2
182.7
182.6
255.1
255.0
284.2
373.1
407.5
400.1
405.0
476.8
483.4
542.3
EER
kW/
kW
27.7
28.3
27.9
27.9
27.7
27.7
28.7
29.5
29.1
28.8
29.1
29.8
30.2
-10
Qc
kW
186.4
185.9
185.8
274.8
274.6
306.9
415.5
453.8
445.6
451.1
531.0
538.4
603.9
EER
kW/
kW
28.0
28.5
28.1
29.8
29.6
29.6
31.7
32.6
32.2
31.8
32.2
32.9
33.3
Operating limits
■■ Operation without glycol
Unlike traditional hydronic free-cooling systems that require the
use of a glycol solution, the AquaForce DX free cooling chiller
works with pure water. The evaporator is protected against
frost down to -20 °C by an electric resistance heater (option).
R
-5
Qc
kW
Legend
LWT Leaving water temperature, °C
Qc Cooling capacity, kW
EER Energy efficiency ratio, kW/kW
Advantages of the DX free cooling
system
R
143.4
143.0
142.9
182.8
182.6
202.5
253.1
276.6
271.5
274.9
323.6
328.1
368.1
EER
kW/
kW
21.9
22.3
22.0
20.2
20.0
19.9
19.7
20.2
19.9
19.7
19.9
20.4
20.6
2
0
1
6
/
2
0
1
7
Mechanical
cooling mode
(compressors)
3.3
15
CONTROLS
Legend
MC Mechanical cooling (compressors)
FC Free cooling
Delta T Difference between the leaving water temperature and the entering air
temperature, K
A
10
0
Qc
kW
Note: Calculations according to the standard performances (in accordance with EN145113:2011) and Eurovent-certified. Evaporator fouling factor 0 m2 K/W.
Delta T (K)
C
LWT
HEATING HEATING
Important: In order to optimise chiller performances, it
is recommended to use the leaving water set point reset
function.
■■ Low water pressure losses
The AquaForce DX free cooling chiller does not include a
three-way valve nor free cooling coils connected in series
with the evaporator. The AquaForce free cooling chiller has
the same water pressure losses as a standard chiller.
■■ Weight and dimensions gain
-- The DX free cooling option has practically no impact
on the weight of the liquid chiller.
-- The AquaForce free cooling chiller has the same
dimen-sions as a standard chiller.
■■ Increased energy efficiency
-- In free cooling mode only the fans and the cooling
micro-pump run. At an air-water temperature
difference of 10 K for example the average chiller
energy efficiency (EER) is 23 (kW/kW).
-- In the mechanical cooling mode chiller thermal and
energy performances are not reduced by the use of a
water-glycol solution.
-- As the pressure losses of the water circuit are low, the
water pumps use less energy.
AIR TREATMENT
The DX free cooling option permits significant energy savings
for all applications that require cooling in winter. In the free
cooling mode the compressors are stopped and only the
fan and cooling micro-pump are running. The changeover
from compressor cooling mode to free cooling mode is
automatically controlled by the Touch Pilot control, based on
the chiller heat load and the temperature difference between
chilled water and ambient air.
COOLING
DX free cooling system (option 118A)
-20*
55
For operation at an air temperature below -10 °C option 28 (winter operation) is
required.
183