20
HBI. 1011. 4138500_00
0
Total minimum volume
of the water, 20 litres
Total pre-set volume of
the water, 280 litres
50
0.0
0.5
1.0
1.5
2.0
2.5
100 150 200 250 300 350 400
15. VOLUME OF THE WATER AND EXPANSION VESSEL PRESSURE
The calculation method for the pressure of the expan-
sion vessel necessary for regulation is the following:
If the volume of the water system changes during in-
stallation, check whether the pre-load pressure of the
expansion vessel must be regulated by applying the
following formula:
P
g
= (H/10+0.3) bar
H = the difference between the place of installation of
the indoor unit and the highest point of the hydraulic
system.
Make sure that the volume of the hydraulic system is
lower than the maximum requested in the fi gure shown.
If this is not the case, the expansion vessel does not sat-
isfy the installation requisites.
Difference in height
of installation
1
Volume of the water (see drawing above)
<280L >280L
H < 7m Regulation is not necessary
• The pre-set pressure must be regulated using
the formula above.
• Check whether the volume of the water is
below the maximum. (With the aid of the figure
above).
H > 7m
• The pre-set pressure must be regulated on the basis of
the formula above.
• Control whether the volume of the water is below the
maximum. (With the aid of the figure above).
The expansion vessel is too small and regulation
cannot be performed.
(1)
NOTE: The difference in installation
height is the difference between the
place of installation of the indoor unit
and the highest point of the hydraulic
system. If the indoor unit is positioned
in the highest point, the difference will
be considered 0 m.
Example 1: The indoor unit is installed
5 m below the outdoor unit and the
total volume of the hydraulic system
is 100 l.
With reference to the fi gure above, it
is not necessary to regulate the pres-
sure of the expansion vessel.
Example 2: The indoor unit is installed
in the highest point of the hydraulic
system and the total volume of the
water is 350 l.
1. As the volume of the hydraulic sys-
tem is 280 l, the expansion pressure
vessel must be regulated, which must
be lower.
2. The formula used to calculate the
pressure is the following:
Pg = (H/10+0.3) bar = (0/10+0.3) =
0.3bar
3. The maximum volume of the hy-
draulic system is about 410 l. As the
effective volume of the hydraulic sys-
tem is 350 l, the expansion vessel satis-
fi es installation requisites.
4. Regulate the pre-load pressure of
the expansion vessel from 1.0 bar to
0.3 bar.
Total maximum volume of the water (litres)
Pre-load pressure in the
expansion vessel (bar)
Notes:
The expansion vessel contains 10 litres and has a pre-load pressure
of 1 bar.
The total volume of the water of 280 litres is pre-set. If it must be
changed due to the installation conditions, the pre-load pressure
must be regulated to guarantee suitable functioning.
If the indoor unit is positioned in the highest point, no regulation is
necessary.
The minimum total volume of the water is 20 litres.
Use nitrogen gas to regulate the pre-load pressure, contact a cer-
tifi ed installer.
H
Indoor unit
Highest point of the
hydraulic system
drawing purely indicative
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