scope:

The calculation procedure is applicable to rooms for which temperature requirements must be complied with in the case of thermal loads, and humidity re¬ quirements in the case of humidity loads.

An important initial design calculation applies here for the case of constant room air temperature (22 °C) and quasi steady State condition under periodic daily load variations. The term used in relation to this is reference cooling load Q_KF (basic cooling load), and it is recommended that this reference cooling load always be calculated as basic data, regardless of the actually required boundary conditions.

The cooling load calculation can also be used for variiable room air temperatures - e.g. freely-variable temperature, or temperature which floats as a function of external air temperature. (The last is not recommended as control strategy!)

For rooms which need to be air-conditioned in zones because of considerable differences in local loads, the calculation should be carried out separately for the individual zones (Computer method). The calculation data given here are focussed to Central European conditions, i.e. with solar radiation at 50° latitude, true local time (solar time) and the mean atmospheric turbidities occurring here, insofar as they refer to external thermal load, i.e. the cooling load fraction which is due to climatological conditions. (The potentially considerable temporal deviation in relation to Central European summer time {MESZ - mitteleuropäische Sommerzeit) should be taken into consideration).

Recently, a more precise definition of turbidity data became possible as a result of Statistical analyses.

The given air temperatures (see climate zone map) arise from recent Statistical evaluations of observations from a large number of German weather stations.

Since the effect of heat storage on cooling load was explained quantitatively by means of a number of Operations up to around 1980, only calculation Operations with storage are now permitted. The design in relation to the most critical quasi steady State case is retained, as the cooling load, through the thermal storage capacity of the building, is dependent not only on the instantaneous values of the thermal room load, but also on their past history, and the establishment of the steady State also helps in this standardization (see "starting calculation" notes in Section 7.12).