REMKO CMF-120-1P - Manual (Page 21)

Corrosion protection
Oxygen always plays a role if
metal materials in a heating system
corrode. pH values and the salt
content also play a major role.
The challenge: A licenced plumber
who would like to be able to
guarantee his customers a hot
water heating system not at risk of
corrosion from oxygen - without
the use of chemicals - must pay
attention to the following: Cor-
rect system design by the heating
contractor/planner.
Subject to the installed materi-
als: filling the heating system with
demineralised softwater or fully
deionised water, checking the pH
value after 8 to 12 weeks.
Overall
output in kW
Total hardness [°dH]
subject to the specific system volume
<20 l/kW
>20 l/kW and
<50 l/kW
>50 l/kW
to 50 kW <16.8 °dH <11.2 °dH <0.11 °dH
Reference values for the hot water in accordance with VDI 2035 Part 2
low-salt saline
Electrical conductivity at
25°C
μS/cm < 100 100-1500
Oxygen content mg/l < 0,1 < 0,02
pH value at 25°C 8,2 - 10,0*)
See the following table for the requirements in accordance with VDI
2035 Part 1 with regard to total hardness.
The following table provides the allowed oxygen content in connection
with the salt content.
*) For aluminium and aluminium alloys the pH value range is limited:
the pH value at 25°C is 8.2-8.5 (max. 9.0 for aluminium alloys)
Water treatment with chemi-
cals is not necessary
Adding chemicals to treat water
should only be done as an exception.
VDI 2035 Part 2 requires explicitly
under Point 8.4.1 that all water
treatment be explained and docu-
mented in the system log book.
This has reasons: The improper
use of chemicals often leads to the
failure of elastomer materials, to
blockages and deposits because of sludge formation, to defective
floating seals in pumps and finally
to the formation of biofilm which
can cause microbial influenced cor-
rosion or significantly impair heat
transfer.
Incidentally: For low-salt water and
the correct pH value, even oxygen
concentrations up to 0.5 mg/l can
be tolerated for short periods.
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