REMKO CMF 320 Duo - Manual (Page 18)

REMKO CMF - DUO
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:
1. Correct system design by the
heating contractor/planner.
2. 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
1. to the failure of elastomer ma-
terials,
2. to blockages and deposits be-
cause of sludge formation,
3. to defective floating seals in
pumps and
4. finally to the formation of bio-
film which can cause microbial in-
fluenced corrosion or significantly
impair heat transfer.
For low-salt water and the
correct pH value, even oxy-
gen concentrations up to 0.5
mg/l can be tolerated for short
periods.
NOTE
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