40 | Regulations and operating conditions
UNIMAT6 720 807 794 (2013/04)
Low pressure hot water boilers with operating
temperatures up to 110 °C
Subject to the total boiler output, the requirements of
water quality from Tab. 23 are to be followed. If these
requirements are not maintained, water treatment is
necessary.
In systems with a total boiler output of above 100 kW,
the volume of fill and top-up water should be measured.
Furthermore, records should be kept when top-up water
is added. The concentration of calcium hydrogen
carbonate in the top-up water should also be noted.
For the UNIMAT UT-L boilers, adhere to the
requirements of the latest VdTÜV Directive
(VdTÜV 1466).
UNIMAT UT-L boiler Boilers in Group II
Water-chemical operating mode
1)
1) Systems with heavily branched pipework, i.e. in industrial and district heating systems, those with longer stagnation periods (even for
parts of the heating network), those operating at strongly fluctuating pressures and temperatures as well as systems with components
made from diverse materials, should ideally be operated with water of a low salt content.
Low salt content Low salt content Saline
Electrical conductivity of the circulating
water
μS/cm
10–30 > 30–100 > 100–1500
Fill and top-up water
General requirements
Colourless, clear and free of undissolved substances
pH value at 25 °C
8–10 8–10.5 8.5–10.5
Alkaline earths (total hardness) mmol/l
dH
< 0.02
< 0.1
< 0.02
< 0.1
< 0.02
< 0.1
Oxygen (O
2
)mg/l< 0.1 < 0.1 < 0.1
Circulating water
General requirements
Colourless, clear and free of undissolved substances
pH value
2)
at 25 °C
2) For operation with a low salt content, adjust the pH value or the p value with trisodium phosphate. For saline operation, the alkalinity
usually adjusts itself by the composition of the fill water. If this is not the case, adjust the pH value with trisodium phosphate and, if
required, by adding sodium hydroxide. Never use ammonia. If copper components are installed in the hot water network, the pH value
of the circulating water must not be above 9.5.
9–10 9–10.5 9.5–10.5
Acidic capacity K
S 8.2
2)
(p value) mmol/l – 0.1–0.5 0.5–5
Alkaline earths (total hardness) mmol/l
dH
< 0.02
< 0.1
< 0.02
< 0.1
< 0.02
< 0.1
Oxygen
3)
(O
2
)
3) In constant heating operation, the limits are usually maintained automatically. If this is the case, oxygen binders are not obligatory. If
the limits are exceeded, a range of physical and chemical processes are available. Typical chemical agents are diamide and sodium
sulphite. Amines that form a film are not oxygen binders. Establish the application and type of oxygen binder for each specific system.
mg/l < 0.1 < 0.05 < 0.02
Phosphate
2)3)
(PO
4
)mg/l3–6 5–10 5–15
Electrical conductivity at 25 °C μS/cm
10–30 > 30–100 > 100–1500
Diamide
3)
(N
2
H
4
)mg/l0.2–1 0.2–2 0.3–3
Sodium sulphite
3)
(Na
2
SO
3
)mg/l– – 5–10
Table 23 Water quality requirements for UNIMAT UT-L boilers
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