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Piping Work
Setting capacity and pre-pressure of the expansion vessel
When it is required to change the default precharge pressure of the expansion vessel(1 bar), keep in mind the
following guidelines:
•
Use only dry nitrogen or air to set the expansion vessel
pressure.
•
Inappropriate setting of the expansion vessel precharge
pressure will lead to malfunction of the system.
•
Therefore, the pressure should only be adjusted by an
competent installer.
Installation
height
difference(a)
<7m
No precharge pressure adjustment required.
Actions required:
• Precharge pressure must be increased,
calculate the appropriate value following by
>7m
"Calculating the precharge pressure of the
expansion vessel".
• Check if the water volume is lower than
maximum allowed water volume.
(a) Installation height difference: height difference(m) between the highest point of the water circuit and the
indoor unit. If the unit is located at the highest point of the installation, the installation height is considered 0m.
•
When Expansion vessel has a capacity 8 liters and 1bar pre-charged. Water volume of total system for
reliable performance is minimum 30 liters.
Calculating the precharge pressure of the expansion vessel
The pre-pressure(Pg) to be set depends on the maximum installation height difference(H) and is calculated as
below :
Pg=(H/10+0.3) bar
Water volume
< 220 Litres
> 220 Litres
Actions required:
• Pressure must be decreased, calculate
according to "Calculating the pre-pressure of
the expansion vessel".
• Check if the water volume is lower than
maximum allowed water volume.
Expansion vessel of the unit too small for the
installation.
25
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