Control principles

Experience and research from schools shows that the average airflow required is normally only about 50–60% of the dimensioned airflow.

A typical room is used for only 60% of the time, and when it is being used, the load is only around 75%.

This clearly highlights the need for ventilation control in order to minimise wasted energy.

Control principles

On-demand control is a way to reduce the energy consumption of ventilation units.

By reducing airflow when there is no-one in a room or building, or regulating airflow to the required load, energy is saved (less outdoor air to warm up) and at the same time, the electrical consumption of the ventilator unit is reduced.

Three different control principles are employed, either individually or in combination, in a ventilation system:

- CAV - Constant air volume
- VAV - Variable air volume
- DCV - Demand controlled air volume

The following graph shows the energy consumption for each control principle (power and heat).


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