Overestimation of the required pressure in the cold water source in the installation with flat stations
|Type of article||TIP&TRICK|
|Source for translation||2023-06-02|
During calculations of the installation with flat stations the following diagnostic message may appear:
- The Vs value calculated for the water supply installation connected to the flat station is higher than the value entered in the V̇HW Appartment field. Calculations further take into account the entered value.
This hint relates to the determining the required pressure at the source of the water supply system. The key parameter in such calculations for installations with flat stations is Hot water outflow (Vs). The program offers two ways to take this value into account by specifying in the General data window Manner of defining: Hot water outflow:
- User specified - value of Hot water outflow declared manually;
- Acc. to calc. of the module: Water supply systems - value of Hot water outflow calculated by the Tap water systems module.
For more information, see: Designing installations with flat stations
The message appears when User specified method is chosen. The value V̇HW Appartment set in the General data window or in data table of Flat station affects the pressure losses in the primary heating circuit supplying the flat stations and the heating output of heat exchanger.
For the calculation of pressure losses in the tap water circuit the value Vs computed accordingly Tap water systems module is taken, regardless of which method of calculation is chosen.
The value Vs is typically higher than the value V̇HW Appartment. This is the reason of overestimation of the required pressure in the cold water source.
The following steps can be taken to reduce the required pressure in the cold water source:
- Adjustment of Normative outflow (HW)(Qn HW) for single points of use;
- Exclusion of Qn HW value for the selected point by specifying Not considered in the Demand type field;
- Choosing for calculations the water supply standard DIN 1988-300.