3 | Design Information
14
M1820921_en | Installation instructions Dual fuel boiler SP Dual compact
3.6 Domestic hot water
Unless contrary to other national regulations, the latest versions of the following
standards and guidelines apply:
Austria:
Germany:
ÖNORM H 5195
VDI 2035
Switzerland:
Italy:
SWKI BT 102-01
UNI 8065
Observe the standards and also follow the recommendations below:
r
Aim for a pH value of between 8.2 and 10.0. If the central heating water comes into
contact with aluminium, the pH value must be between 8.0 and 8.5
r
Use prepared water which complies with the standards cited above for filling and
make-up water
r
Avoid leaks and use a closed heating system to maintain water quality during
operation
r
When filling with make-up water, always bleed the filling hose before connecting, in
order to prevent air from entering the system
Advantages of prepared water:
▪ Complies with the applicable standards
▪ Less of a drop in output due to reduced limescale build-up
▪ Less corrosion due to fewer aggressive substances
▪ Long-term cost savings thanks to improved energy efficiency
Permitted water hardness for the fill and make-up water in accordance with VDI
2035:
Overall
heat output
Total hardness at
<20 l/kW minimum
individual heat output
1)
Total hardness at
>20 ≤50 l/kW minimum
individual heat output
1)
Total hardness at
>50 l/kW minimum
individual heat output
1)
kW
°dH
mol/m³
°dH
mol/m³
°dH
mol/m³
≤50
no demand or
11.2
2
0.11
0.02
<16.8
2)
<3
2)
>50 ≤200
11.2
2
8.4
1.5
>200 ≤600
8.4
1.5
0.11
0.02
>600
0.11
0.02
1. From specific system volume (litres nominal capacity/heat output; for multi-boiler systems use the smallest individual heat output)
2. In the case of systems with central heating boilers and for systems with electric heating elements
