MODULE III - Air-conditioning & cooling technology Page 14

MODULE III Air-conditioning and Cooling technology Page 14

Fig. 13 Ventilation system for room air renewal

1	=	Outside air
2	=	Air damper with actuator
3	=	Air filter
4	=	Air heater
5	=	Supply air fan
6	=	Supply air
7	=	Room
8	=	Radiator
9	=	Extract air
10	=	Extract air fan
11	=	Exhaust air
12	=	Supply air temperature detector
13	=	Temperature controller

Warming of outside air takes place with the help of an air heater. Such units are manufactured for all the common heating media, such as electricity, hot water or steam. In order for the air to be injected into the space with a constant temperature, the ventilation system must be set to the appropriate supply air temperature. In other words, the ventilation plant temperature detector must be mounted in the supply air duct. The supply air controller then compares the temperature measured by the detector with the selected set value.

Heating room air

The heat loss which takes place in a room, the so-called heating load, is caused by the transmission of heat through walls, windows, etc. While a constant room temperature, excluding temporary disturbances, is achieved where there is a ventilation system for room air renewal, through the fact that the heating load is covered by, for example, a radiator set independently of the room temperature, this heating load can be split up for a ventilation system for room air warming between the radiator and the ventilation system (see Fig. 14). The heating capacity of the radiators, also known as basic load heating, can thereby be reduced to the extent that only a warm air veil in front of the windows is achieved. This thereby hinders cold falling air near the windows, which can lead to draughts.
The establishing of basic load heating is dependent upon weather factors. This is because the ventilation system is set dependent upon room temperature (2 room temperature settings influence one another, which leads to instability).