The abovementioned types of operation are automatically managed by a microprocessor control system designed to optimise energy consumption keeping to the pre-set working conditions.
The microprocessor receives four temperature inputs from sensors reading the following parameters:
- ambient temperature TAE
- returning water temperature from user’s plant TFC
- evaporator entering water temperature RWT
- evaporator leaving water temperature LWT
When the ambient air is at least 2 °C (5 °F) lower than the returning water temperature, the microprocessor allows the free cooling system to operate. Thanks to the three-way valve opening, water flows into the water coils before crossing the evaporator.
Through the sensor monitoring the evaporator entering water temperature, the microprocessor accordingly reduces the compressor action (multistep capacity control) until they are completely excluded if total free cooling operation is reached.
If the free cooling efficiency is too high (as the ambient or required cooling load is very low) to keep a constant leaving water temperature, the microprocessor proportionally reduces the air flow through the coils and if this is not sufficient, it controls the water flow in the coils by means of the three-way valve opening.