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7.3 Heating System Connection
The heating system connections on the heat pump have a 1" in-
ternal thread. Use a spanner to firmly grip the transitions when
connecting the heat pump.
The connection on the heating side can also be made towards
the right. To do this, the left and right bottom front panels must
be removed. The two connecting pipes, including pipe sup-
ports, must be moved from the left to the right side of the de-
vice. The front panels must then be re-mounted the opposite
way around.
Before connecting the heating water system to the heat pump,
the heating system must be flushed to remove any impurities,
residue from sealants, etc. Any accumulation of deposits in the
liquifier could cause the heat pump to completely break down.
For systems in which the heating water flow can be shut off via
the radiator or thermostat valves, an overflow valve must be in-
stalled in a heating bypass behind the heat pump by the cus-
tomer. This ensures a minimum heating water flow rate through
the heat pump and helps to avoid faults.
Once the heating system has been installed, it must be filled,
de-aerated and pressure-tested.
NOTE
Pump units with check valves maintain the specified flow
directions. If there is incorrect distribution or breaking off of
the volume flow, these units (and the check valves in
particular) must be checked! The use of check valves are
mandatory in the event of several heating circuits or parallel
connections for heat pumps in order to avoid incorrect
distribution.
7.4 Water Quality in Heating
Systems
7.4.1 Scale Formation
Scale formation in heating systems cannot be avoided, but in
systems with flow temperatures below 60 °C the problem is so
small that it is negligible. With high-temperature heat pumps
and in particular with bivalent systems in the higher perfor-
mance range (heat pump + boiler combination), flow tempera-
tures of 60 °C and more can be achieved. One preferred
method for preventing scale formation is softening because
this permanently removes alkaline earths (calcium and magne-
sium ions) from the heating system.
The following values for water quality in heating water and cold
water must be observed and checked during an on-site check:
Degree of hardness
Conductivity
pH value
Filterable materials
The following (limit) values must absolutely be observed:
Maximum degree of hardness in filling water and supple-
mentary water 11 dGH.
The conductivity in demineralised water (DM water) (low-
salt) may not be greater than 100 μS/cm.
The conductivity in partially demineralised water (saline)
may not be greater than 500 μS/cm.
The pH value must be between 8.2 and 9.
The limit value for filterable materials in heating water is <
30 mg/l
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If necessary, for example in bivalent systems, the specifications
listed in the table below must also be observed, or the precise
guidelines for filling water and supplementary water and the
total hardness must be taken from the table in accordance with
VDI 2035 – Sheet 1.
NOTE
The specific volumes of a heating system must be determined
before filling the system.
The saturation index SI is used to determine whether water has
a tendency towards lime dissolution or lime separation. This
shows whether the pH value corresponds to a neutral pH point
or by how much it undershoots it due to excess acid or by how
much it exceeds it due to carbonic acid deficit. At a saturation
index below 0, the water is aggressive and will tend towards
corrosion. At a saturation index above 0, the water is calcare-
ous.
The saturation index SI should be between - 0.2 < 0 < 0.2
Filling and supplementary water as well as heating water, depending on
heat output
Overall heat output in kW
specific water content
heat generator > 0.3 k per kW
specific water content
heat generator > 0.3 k per kW
(e.g. circulating water heaters)
and systems with electric heat-
ing elements
> 50 kW to 200 kW
> 200 kW to 600 kW
Heating water, depending on heating output
Operating mode
Containing salt
1. For the purpose of calculating the specific system volume, the smallest indi-
vidual heat output is to be used for systems with several heat generators.
2. In systems with several heat generators with different specific water con-
tents, the smallest specific water content is decisive.
3. Full softening is recommended for systems with aluminium alloys.
Fig. 7.1:Guideline values for filling and supplementary in accordance with
VDI 2035
CAUTION!
When using demineralised water, ensure that the minimum
permissible pH value of 8.2 is not undershot. Failure to comply
with this value can result in the heat pump being destroyed.
452169.66.06b · FD 0411
Total alkaline earths in mol/m³
(Total hardness in dGH)
20
Specific system volume in l/kW
50
none
2
50
2
3.0 (16.8)
2.0 (11.2)
1.5 (8.4)
> 600 kW
< 0.05 (0.3)
Electrical conductivity in µS/cm
3
Low-salt
clear, free from sedimentary substances
English
20 to 50
50
1
Heat output
3.0 (16.8)
1.5 (8.4)
< 0.05 (0.3)
1.0 (5.6)
< 0.05 (0.3)
> 10 to 100
> 100 to 1500
Appearance
EN-9
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