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2
Ventilation theory and air handling units
2.1
Purpose of air-conditioning
The purpose of air-conditioning is to provide comfortable indoor air conditions for the room occu-
pants and to provide energy saving potentials for the owner.
Comfort
If room occupants feel "comfortable" in a given room, depends mainly on the following two factors:
● air temperature
● relative air humidity
However, optimum working or living conditions do not only exist at a specific setpoint of room tem-
perature and room humidity, but also within a certain band width of the setpoint.
A temperature setpoint of 22 °C and a relative humidity setpoint of 45 % with variations of ±2 °C
and ±15 %rh respectively are typical levels used for office spaces. Also, at high temperatures,
maximum limitation of absolute humidity should be provided to avoid "muggy" conditions. Typically,
this limit value lies at about 10 g/kg (H
Cooling and
humdifying
Humdifying only
Energy savings
Besides the advantages in terms of indoor air quality, air conditioning offers also an energy saving
potential. For example, while uncontrolled ventilation through open windows leads to large amounts
of heat being lost to the outside during the heating season or gained from the outside during the
cooling season, air conditioning systems provide possibilities to utilise the extra "free" energy in
heat recovery modules so that overall operating costs will be reduced.
The larger the area of the comfort range, the better the energy saving opportunities.
AHU Kit – Installation Instructions – 07/2023
Heating and
humdifying
Ventilation theory and air handling units
O).
2
Absolute humidity
Cooling only
24 °C
Comfort range
35 %rh
65 %rh
20 °C
Heating only
Humdifying and
reheating, if required
rh = relative humidity
2
19
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