The MCAE/FC free-cooling units are particularly suitable where chilled water all year long is required, so also by low ambient air temperature. The free-cooling system utilises the low outside temperature for chilling water in the coil starting from 15 °C ambient air temperature.
THE FREE-COOLING PRINCIPLE
The units series MCAEY/FC are designed to cool down water/glycol fluid. This units are equipped, further to the chiller components such as compressors, condensers, evaporator, thermostatic valves, with a water free-cooling coil. The control system consists of a modulating three-way valve and of a certain number of probes allowing the water coil functioning and therefore the “free-cooling” operation. In the standard chiller the return water/glycol fluid is cooled down through the shell and tube evaporator. In the MCAEY/FC units working in free-cooling mode, the water/glycol fluid runs through the free-cooling coil which is cooled by means of the external air, thus reducing the load on the compressors or even completely substituting them. The control system
consists of a microprocessor, an inlet water temperature probe, an external air temperature probe, a working probe and a no-freezing probe.
OPERATION IN SUMMER
When the ambient air temperature is higher than the return water/glycol temperature the cooling capacity is guaranteed by the compressors; the 3-way valve allows the water/glycol to go into the evaporator ; the free-cooling coil is not working. The absorbed power is the same as a traditional electric air cooled chiller.
OPERATION IN WINTER
When the ambient air temperature is lower than 3-0°C, the chiller operates in free cooling mode: the 3-way valve allows the water/glycol mix to go into the free-cooling coil, the probe switch off the compressor. The fans keep working to guarantee the air flow through the freecooling coil. By the external air decreasing, the microprocessor activates the 3 way valve. By reaching the set
point the fans decreas the speed.
OPERATION IN MID-SEASON
It’s a combination of free-cooling and traditional chiller. The free-cooling operation starts when the external air temperature is at least 2 °C lower than the return liquid temperature; so, normally at 15-10 °C. The liquid is pre-cooled in the free-cooling coil. The performance is completed by the compressors. The water temperature probe controls the compressor capacity steps.
• Your overheads would reduce in the mid season
• Your free cooling system could run automatically when required
• There would be less wear and tear due to the reduced hours of operation
• Your maintenance costs would reduce