Free-Cooling - Lennox NEOSYS NAC 200 Application Manual

FREE COOLING
Compared with the basic confi guration this option features one or two additional V free cooling coils at the back of the unit. The free
cooling includes two motorised valves, allowing the chilled water to run through the free-cooling coils, which uses less power and
utilises the lower ambient air to cool the water. The cooling capacity of one V free cooling coil at 0°C ambient is approximately 100 kW.
NEOSYS free cooling system is using the same fans and speed inverters as for the standard unit in order to keep the same acoustic
capabilities. The hydraulic module options are compatible with the Free Cooling option but glycol is of course required.
Typical free cooling applications can be facilities with cooling demand all along the year, such as offi ces with high internal loads like
computer rooms, data centers, etc. In the North and North-East part of Europe, the ambient temperature is below 5°C between 20
and 45% of the year that makes this option very attractive.
Control principle
The control principle is the following: if ambient Temperature < return Temperature – 3°C, motorised valves open to by-pass return
water fl ow through the Free Cooling coils. The Free Cooling fans are driven by the CLIMATIC 60 via a specifi c PID algorithm. The Free
cooling operation is considered as a cooling stage that has a priority on the compressor stages: only if the free cooling fan speed has
reached the maximum fan speed then the compressors are allowed to run with their own PID.
Advantages of the NEOSYS free cooling system
• Simultaneous compressor cooling capability to reach building needs in any conditions (vs. DX free cooling that can not operate
simultaneous compressor and free cooling).
• Design with additional V free cooling coils to eliminate unnecessary air pressure drop when running 100% in compressor cooling
mode thus reducing all along the year energy fan consumption (vs. traditional free cooling system with free cooling coils located in
series with the condensing coil.)
• Free cooling as soon as the air outside is cold enough (3°C below return water temperature).
• Reduce the running use of the compressors.
• Extend the life expectancy of the compressors.
• EER up to 63 (Water 15/10°C, Air -15°C).
• Reduce power costs.
• Payback could be as little as 12 months
Compressor
• 30 •
Air condensers
Evaporator
Free cooling coils
Water in
Water pump (option)
Water out
Application Guide / NEOSYS-AGU-1801-E
15°C
10°C