AIR-COOLED LIQUID CHILLERS 30XA 252-1702
DX free cooling system (option 118A)
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. 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.
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 refrigerant 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). 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.
30XA 252-1002 in free-cooling mode (option 118A)
0 Qc kW 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
Note: Calculations according to the standard performances (in accordance with EN145113:2011) and Eurovent-certiﬁed. Evaporator fouling factor 0 m2 K/W. Legend LWT Leaving water temperature, °C Qc Cooling capacity, kW EER Energy efﬁciency ratio, kW/kW Legend MC Mechanical cooling (compressors) FC Free cooling Delta T Difference between the leaving water temperature and the entering air temperature, K
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
Advantages of the DX free cooling system
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).
Mechanical cooling mode (compressors)
For operation at an air temperature below -10 °C option 28 (winter operation) is required.
252 302 352 402 452 502 602 702 752 802 852 902 1002
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
-5 Qc kW 183.2 182.7 182.6 255.1 255.0 284.2 373.1 407.5 400.1 405.0 476.