...
Some diversity standards like the DIN 1988-300 (Based on DIN 1988-300) define
standard temperature regimes [e.g. for DIN 1988-300 : 15°C (cold water) - 60°C (hot water)]
standard flow rates for tapping points [e.g. for DIN 1988-300 : VDHW = 0,15 l/s]
Let’s take the example of the shower for DIN 1988-300.
standard regime
With the standard temperature regime as defined by the standard, the shower tapflow tap flow would result in 0,15 l/s @60°C and 0,15 l/s @15°C
This results in an overall flow of 0,30 l/s @ 37,5°C. Thast’s That’s the “goal situation“ we want to design to.
...
Suppose the designer wants to deviate from the standard, and wants to apply a custom temperature regime, e.g. 10°C - 50°C.
If we don’t change the hot water flowrate, we will not be able to reach this “goal situation” without exceeding a hot water flow rate of 0,15l/s : we can reach 0,30l/s @ 30°C or we can reach 0,27l/s @37,5°C, but we cannot reach 0,30 l/s @ 37,5°C.
...
The equations we have to solve for the example to reach the same goal situations are :
VDHW + VCHW DCW = 0,30 l/s
50°C * VDHW + 10°C * VDCW = 37,5°C * 0,30 l/s
...