Ecodan EHPT17X-UKHLEWS Installation Manual page 25

If the interlock operation of primary and secondary pump is available ensure minimum water volume in primary and
secondary circuit. If the interlock of operation of primary and secondary pump is not available ensure minimum water volume
in only primary circuit. In case of shortage of minimum water volume install a buffer tank.
SIZING EXPANSION VESSELS
Expansion vessel volume must fit the local system water volume.
To size an expansion vessel for the heating circuit the following formula and graph can be used.
V =
P¹ + 0.098
1 −
P² + 0.098
ε × G
Expansion vessel sizing
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20
15
10
5
0
0 50 100
System water volume [L]
Where;
V : Necessary expansion vessel volume [L]
ε : Water expansion coeffi cient
G : Total volume of water in the system [L]
P¹ : Expansion vessel setting pressure [MPa]
P² : Max. pressure during operation [MPa]
Graph below is for the following values
ε : at 70 °C = 0.0229
P¹ : 0.1 MPa
P² : 0.3 MPa
*A 30% safety margin has been added.
150 200 250 300 350 400
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