Energy Saving in Airconditioning Plants

An evaluation is made of the saving in airconditioning plant power in digital exchanges effected by ventilating with the cool outside air during night hours and possibly some day hours. The effect of the building insulation is also considered. This is done with the aid of a computerised programme taking into account the heat capacity of the building (total thermal time constant method). It is shown that a saving in ventilation power through the use of a special outside air unit for the conventional airconditioning cycle can be achieved. The method of analysis allows us to establish a daily or seasonal heat flow balance for a given inside temperature. The heat capacity tends to flatten the inside air temperature fluctuations. An exact knowledge of this effect makes the choice of a smaller capacity airconditioning plant possible. An additional important decrease in the size of this plant is achieved through cooling the building by nightly ventilation, making use of the heat capacity of the building.