Preventing Water Side Corrosion - Viessmann Vitomax LW Operating And Service Instructions

Standard values for water quality

Preventing water side corrosion

General information
Oxygen is introduced into the heating system with the
fill water when the system is filled initially and during
any subsequent top-ups.
This oxygen reacts with materials without causing any
damage to the system.
After a certain time in operation, the water in the sys-
tem turns black because there is no more free oxygen
present in the system.
As there is now no oxygen in the heating water, the
materials of the heating system and boiler are protec-
ted from corrosion on the heating water side.
!
Please note
The ingress of oxygen can cause damage as a
consequence of oxygen corrosion.
Prevent the ingress of oxygen by means of suit-
able measures.
Protecting the heating water from oxygen ingress
■ Prevent continuous oxygen ingress and the entry of
airborne oxygen into the system during operation.
■ Apply technical rules, specifically VDI Guideline
2035-2.
Ensure that the heating system is designed correctly
■
(dimensions, system pressure).
■ Operate the heating system in line with regulations.
■ Equip sealed unvented systems with a diaphragm
expansion vessel or similar.
Recommendation for diaphragm expansion vessel
Check the pre-charge pressure during the annual serv-
ice or sooner.
Pressure maintaining systems and corrosion
See chapter "General design information" in the
technical guide
All manuals and user guides at all-guides.com
(cont.)
Operate the system with positive pressure
■
■
■
Only use gas-impermeable components for the
systems.
■
■
■
Additional protection against oxygen ingress
■
■
Use of aluminium components
Note that different conditions may apply.
Corrosion protection with chemicals:
Obtain a safety declaration from the chemical manu-
facturer regarding the interaction of the chemicals with
the materials used in the steam boiler, the hot water
boiler and the other components of the heating sys-
tem.
Recommendation
Consult the relevant contractor regarding water treat-
ment.
In the entire boiler system
On the pump suction side
In every system operating state
If using permeable components, separate the sys-
tems (heat exchangers).
In permeable components such as underfloor heat-
ing systems, only use impermeable plastic pipes.
Separate the water flowing through the plastic pipes
from the boiler and other heating circuits with a heat
exchanger made from corrosion-resistant material.
Add an oxygen binder (in excess of 5 - 10 mg
Na SO /l).
2 3
Adjust the pH value of the heating water to 8.2 - 9.5.
Detailed information
VDI Guideline 2035-2 and EN 14868
Operating information
13