System Design Of Hot Water Heating; Systems; Measures On The Water Side For Hot Water Heating Systems; Operating Measures For Hot Water - Buderus Logano GE315 Technical Manual

4 Regulations and operating conditions
Information about the calcium hydrogen carbonate
concentration of the mains water can be obtained from
your water supply utility. If the water analysis does not
include this information, the calcium hydrogen carbonate
concentration CA(HCO
3
carbonate hardness and the calcium hardness, or from
the acid capacity K and calcium ions as follows:
S4,3
Example 1:
Calculation of the maximum permissible fill and top-up
volume V for a heating system with a total boiler output
max
Q of 1.5 MW.
The water analysis figures for carbonate hardness and
calcium hardness are given in the older unit of
measurement °dH.
Carbonate hardness: 15.7 °dH
Calcium hardness: 11.9 °dH
The following is calculated from the carbonate hardness:
Ca(HCO ) = 15.7 °dH × 0.179 = 2.81 mol/ m³
3 2
The following is calculated from the calcium hardness:
Ca(HCO ) = 11.9 °dH × 0.179 = 2.13 mol/ m³
3 2
The lower figure resulting from the calcium hardness is
used to calculate the maximum permissible water volume
V .
max
=
V 0,0313
max
4.8.5

System design of hot water heating

systems

When designing hot water heating systems, always take
the following into account:
• Install shut-off valves at regular intervals. This should
prevent the need to drain all the heating water if repairs
are necessary or if the system is extended.
• In systems > 50 kW, install a water meter to record the
volume of fill and top-up water. We recommend
keeping an operating log (e.g.
• If the specific system volume is > 20 l/kW heating
output (with multi boiler systems use the lowest
individual output), apply the requirements of the next
group up in terms of total heating output (as per
previous table). If this is significantly exceeded
(> 50 l/kW), soften the sum of alkaline earths
= 0.02 mol/ m³.
• If softening is required, ensure that a sufficient volume
of softened or desalinated water is available for the
initial filling, refills and substantial top-ups (e.g. use a
mobile system or tank vehicle). If a softening system
has not been used for some time, it may be necessary
to discard the initial bed volume in the container.
28
) can be determined from the
2
1500 kW
3
× ------------------------------- -
=
22 m
3
2,13 mol/m
page 29).
6 720 646 864 (12/2010) – Technical guide Logano GE315, GE515 and GE615
4.8.6 Measures on the water side for hot water

heating systems

Softening
Softening is a preferred procedure to prevent the scaling,
as it permanently removes the alkaline earths (calcium and
magnesium ions) from the system (
Hardness stabilisation
Hardness stabilisation means adding conditioners to the
heating water which influence limescale separation in
such a way that scaling does not occur. This does not
remove the causes of limescale. Additional measures are
required with regard to selection, dosage, monitoring and
disposal of the additives and conditioned heating water.
When selecting the conditioners, ensure that neither they
nor any products causing a reaction will cause corrosion
damage.
Since hardness stabilisation should not cause the
formation of sludge, do not use products containing
phosphates.
Follow the instructions provided by the manufacturer and
supplier of the hardness stabilisers.
If the heating water is also used to heat DHW, follow the
relevant regulations in DIN 1988-4 and DIN-EN 1717.
4.8.7 Operating measures for hot water heating
systems
Please note the following points:
• Commission a system in stages, starting with the
lowest output of the boiler and a high heating water
throughput. This prevents a local concentration of
limescale deposits on the heating surfaces of the heat
exchanger.
• In multi boiler systems, we recommend commissioning
all the boilers at once so that the limescale does not
settle on the heat transfer surface of just one boiler.
• For extensions and repairs, it is important to only drain
the required sections of the system.
• If measures are required on the water side, it is very
important that the first time the heating system is filled
for commissioning, treated water is used. This also
applies to any modifications, e.g. following repairs or
extensions, and for all top-up water volumes.
page 29).