By creating a constant value, a fixed value can be described as the property of a state. The operating parameter should then hold this value at every moment, that the corresponding operating state is currently present. Possible application of constant values are constant volumetric flow rates for fan stages or a fixed temperature of the supply air of a ventilation system.
Also specific data of a building or general values could be added as constant values such as the building area or primary energy factors.
It might be useful to consider a range of tolerance when using constant values in definitions. For example for the compliance of a fixed temperature value of the supply air, always a certain range of tolerance should be considered, for example +/- 1K. This allows small divergence from the constant value, and better represents actual operating conditions.