Water hardness
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9
Water hardness
Determine permissible water
hardness for the
heating water according to ÖNORM H 5195-1
Instructions for determination:
1. Determine the water content of the heat producer
(in litres) and divide by its output (in kW). If the
result is larger than 0.3 l/kW, Table 1 applies. If the
value is smaller or equal to 0.3 l/kW, Table 2
applies.
2. Divide the total heating water volume (in litres) by
the output (in kW) of the smallest heat producer.
The result is the specific water content and this
determines the column within the previously
calculated table.
3. Read the data for the permissible water hardness
from the respective line using the total output of the
heat producer.
Example: A module with a 45 kW boiler and
1000 litre total water volume
1. For the module, the ratio of water content to output
is less than 0.3 l/kW => Table 2.
2. The maximum output of the module is 45 kW. With
a total heating water volume of 1,000 litres, for
example, a specific water content of 22.2 l/kW
results => average column in Table 2.
3. The total output of the module is 45 kW; therefore,
only the data from the first line (≤ 50 kW) are
relevant.
The permissible water hardness in this example is 5.6
°dH.
Table 1
Heat producer with large (> 0.3 l/
kW) water content
Table 2
Heat producer with small (≤ 0.3 l/
kW) water content
Specific water content
(litres/kW)
< 20 l/kW
≥ 20 /kW
< 50 l/kW
≥ 50 l/kW
< 20 l/kW
≥ 20 l/kW
< 50 l/kW
≥ 50 l/kW
Total output of the heat
producer
≤ 50 kW
16.8 °dH
11.2 °dH
5.6 °dH
11.2 °dH
5.6 °dH
0.6 °dH
> 50 kW
≤ 200 kW
11.2 °dH
5.6 °dH
2.8 °dH
5.6 °dH
2.8 °dH
0.6 °dH
> 200 kW
≤ 600 kW
5.6 °dH
2.8 °dH
0.6 °dH
2.8 °dH
0.6 °dH
0.6 °dH
> 600 kW
2.8 °dH
0.6 °dH
0.6 °dH
0.6 °dH
0.6 °dH
0.6 °dH
