4 Regulations and operating conditions
6 720 646 864 (12/2010) – Technical guide Logano GE315, GE515 and GE615
27
4.8.2 Terminology
Scaling
is the formation of stubborn deposits on walls in contact
with water inside hot water heating systems. These
deposits are made up of substances contained in the
water, essentially calcium carbonate.
Heating water
is all the water used for heating purposes in a hot water
heating system.
Fill water
is the water used to fill the entire heating system on the
heating water side for the first time and with which it is
then heated up.
Top-up water
is any water used to top up the system on the heating
water side after the first time it is heated up.
Specific system volume
is the quotient of the entire volume of a hot water heating
system on the heating water side and the installed output
(with multi boiler systems, use the lowest individual
output).
Operating temperature
is the temperature captured at the flow connector of the
heat source in a hot water heating system when operating
correctly.
Quantity of limescale that can be separated
m(CaCO
3
)
S
is the maximum quantity of calcium carbonate (CaCO
3
)
that can be separated in a hot water heating system.
Sum of alkaline earths (total hardness)
is the total concentration of calcium and magnesium ions
in the fill or top-up water.
Heat contracting
is the transfer for a limited time and scope of the
production and provision of heating energy to a third party
(contractor), who acts in their own name and at their own
costs. The contractor sets up or adopts and runs heat
production systems, which may include heat distribution
networks for supplying heating energy on the basis of
long term contracts.
4.8.3 Scaling in hot water heating systems
As a consequence of scaling, the heat transfer from heat
sources in hot water heating systems is reduced due to
scale deposits. Particularly with heat transfer surfaces
that are indirectly heated, local overheating can occur,
leading to the formation of cracks in some places as well
as boiling noises. The scale deposits can also cause a
reduction of the cross-section and increased pressure
drop.
As a consequence of this effect, the output will be
reduced. The formation of such layers should therefore be
kept as low as possible for trouble-free and economic
operation.
For heating systems with permissible operating
temperatures of up to 100 °C, the requirements of VDI
guideline 2035, sheet 1, December 2005 apply.
4.8.4 Requirements of the fill, top-up and heating water for boilers made of ferrous materials
The fill and top-up water has to meet certain requirements
depending on the total boiler output and the resulting
water volume of a heating system.
If the water available is not within the required range given
in the table below, either the water must be treated or the
maximum water volume V
max
must be calculated
(Æ example 1, page 28).
Total boiler output
Ca(HCO
3
)
2
concentration of the fill
and top-up water
Max. volume of fill and top-up water
V
max
(see adjacent section:
water volume V
max
) Heating water
[kW] [mol/ m³] [m³] [pH value]
Q < 50
1)
no requirements V
max
: no requirements 8.2 – 9.5
50 ≤ Q ≤ 200
1)
≤ 2.0 V
max
= 3 times the system volume 8.2 – 9.5
200 ≤ Q ≤ 600
1)
≤ 1.5 V
max
= 3 times the system volume 8.2 – 9.5
Q > 600 < 0.02 8.2 – 9.5
Q – 8.2 – 9.5
Tab. 12 Requirements of the fill, top-up and heating water for boilers made of ferrous materials
1) In systems with a specific volume > 20 l/kW, the requirements of the next group up apply
V
max
0,0313
Q
Ca HCO(
3
)
2
-------------------------------- -
×=
V
max
0,0313
Q
Ca HCO(
3
)
2
-------------------------------- -
×=
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