The presented hydraulic diagrams do not replace the design of central heating installation
and are used for illustrative purpose only!
Additionally, the minimum diameters of boiler flow pipes and mixing valve connections should be
observed. The minimum values of hydraulic system diameters, depending on power of the
connected boiler, are given in Table 5.
The heating system must feature an emptying outlet placed at the lowest point of the circuit and as
close as possible to the inlet of the returning water.
Boiler's output /
Circuit output
Copper pipes,
minimum diameter
Steel pipes, minimum
diameter
Mixing valve
14 ÷ 29 kW
35 mm
1¼”
DN 32
30 ÷ 50 kW
42 mm
1½”
DN 40
upper 51 kW
50 mm
2”
DN 50
Table 5. Guidelines regarding the heating circuits
The data above have been quoted for information only! Regardless, the water circuit attached
to the boiler must comply with the regulations in force, the industry standards and the
construction principles. It must facilitate proper and safe operation of the heating systems.
The installation must be inspected by appropriate authorities if local or national regulations
require this.
Holz Master Manual
wer. 22/05/2012/EN/V1.0
HKS LAZAR
str.24