Water Quality - Viessmann Vitomax HS M73 Operating And Service Instructions

Saline boiler feedwater requirements
Permissible direct conductivity of the boiler water, subject to pressure; feedwater conductivity
7000
6000
4000
2000
0 10
Operating pressure in bar
Fig. 2 Direct conductivity
Conversion:
= 5.6 °dH
3
1 mol/m
1 °dH 3
= 0.179 mol/m
1 mval/kg = 2.8 °dH
Recommendation
Addition of phosphate, although not always necessary.
15 B
160
A
140
10 B
120
5 B
100
0.5B
80
60
40
20
0 10 20 30
Operating pressure in bar
Fig. 3 Silicic acid content
This level of alkalinity is not permissible
A
K - value in mmol/l
B
S 8.2
Recommendation
Operation with salt-free boiler feedwater is also possi-
ble as an alternative to operation with saline boiler
feedwater.
Conditioning
General comments
Certain feedwater and boiler water characteristics
must be improved (conditioned) through chemical
treatment.
Aim of the conditioning:
■ Support for the formation of magnetic layers or other
protective oxidisation layers
■ Reducing corrosion, as the pH value is optimised
■ Stabilising the hardness and preventing or reducing
scaling and deposits
Chemical binding of residual oxygen
■
Constituents of conventional conditioning agents: E.g.
sodium and potassium hydroxide, sodium phosphate
and sodium sulphite, ammonia and diamide
(cont.)
20
40
20 bar.
>
30 40
Note
In some countries or production processes, the use of
some of these chemicals may be restricted.
Conductivity
Saline
■ Feedwater with an electrical conductivity of
30 S/cm (e.g. downstream of a softening system)
> µ
Low salt
Feedwater with an electrical conductivity of
■
0.2 to 30 S/cm (e.g. downstream of a desalination
µ
system)

Water quality

30 S/cm
> μ
21