The SCAE/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 SCAE/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 freecooling
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 SCAE/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 (10); the 3-way valve (9) allows the water/glycol to go into the evaporator (12); the free-cooling coil (11) 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 3-0 °C, the chiller operates in free cooling mode: the 3-way valve (9) allows the water/glycol to go into the free-cooling coil (11), the probe (5) switch off the compressors (10). The fans (13) keep working to guarantee the air flow through the free-cooling coil (11). By the external air decreasing, the microprocessor (15) activates the 3- way valve (9) to mix the free-cooling water with the return water from the plant. By reaching the set point the fans switch off.
Operation in mid season
It’s a combination of free-cooling and traditional electric chiller. The free-cooling operation starts when the external air temperature is at least 1,5 °C lower than the return liquid temperature; so, normally at 15-10 °C. The
liquid is pre-cooled in the free-cooling coil (11). The performance is completed by the compressors. The water temperature probe (5) controls the compressor (10) 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.