Approaches to Temperature Control

Temperature control in an air conditioning system is achieved by passing the air through the cooling or heating coil, which may use any of the following approaches:

1. Vary the temperature of air supplied to the space while keeping the airflow rate constant. This is the basic constant volume, variable temperature approach.

2. Vary the airflow rate while keeping the temperature constant for air supplied to the space. This is the variable volume, constant temperature approach.

3. Vary the airflow rate and change the temperature for air supplied to the space. This is the variable volume and temperature approach.

4. Vary both the supply air temperature and flow rate where the airflow rate is varied down to a minimum value, then energy input to reheat the coil is controlled to vary the supply air temperature. This is the variable volume reheat approach.