To determine the maximum allowed water volume in the entire circuit, proceed as follows:
Determine the calculated pre-pressure (Pg) for the corresponding maximum water volume using the Figure 3-3.1.
Figure 3-3.1: Maximum water volume
A1: System without glycol for 1-phase 12~16kW and
3-phase 12~16kW unit
A2: System without glycol for the 5/7kW unit
Check that the total water volume in the entire water circuit is lower than this value. If this is not the case,
the expansion vessel inside the unit is too small for the installation.
Example
The unit(16kW) is installed at the highest point in the water circuit. The total water volume in the water circuit is 150L.
Since 150L is more than 72L, the pre-pressure must be decreased, refer to Table 3-3:1.
The required pre-pressure is: Pg(bar) = (H(m)/10+0.3) bar = (0/10+0.3) bar = 0.3 bar
The corresponding maximum water volume can be read from the Figure 3-1.7 is approximately 160L
Since the total water volume (150L) is below the maximum water volume (160L), the expansion vessel suffices for the
installation.
When it is required to change the default pre-pressure of the expansion vessel (1.5 bars), following guidelines:
Use only dry nitrogen to set the expansion vessel pre-pressure.
Inappropriate setting of the expansion vessel pre-pressure will lead to malfunctioning of the system. Pre-pressure
should only be adjusted by a licensed installer.
If the expansion vessel of unit is too small for the installation, an additional expansion vessel is needed.
Calculate the pre-pressure of the expansion vessel: Pg(bar) = (H(m)/10+0.3) bar
The expansion vessel equipped in the unit should adjust the pre-pressure also.
Calculate the volume needed of the additional expansion vessel: V1=0.0693*Vwater/(2.5-Pg)-V0
Vwater: the volume of water in the system
V0: the volume of expansion vessel which the unit is equipped (For 5~9kW, V0=2L; For 10~16kW, V0=5L)
3.3
Water Circuit Connection
Water connections must be made correctly in accordance with the labels on the outdoor unit, with respect to the water
inlet and water outlet. If air, moisture or dust gets in the water circuit, problems may occur. Therefore, always take into
account the following when connecting the water circuit:
Use clean pipes only.
Hold the pipe end downwards when removing burrs
Cover the pipe end when inserting it through a wall to prevent dust and dirt entering.
Use a good thread sealant for sealing the connections. The sealing must be able to withstand the pressures and
temperatures of the system.
0.3
0.8
1.3
1.8
2.3
2.8
20
70
120
170
Pr
e
ss
u
re
(b
a
r)
Maximum water volume(L)
A1
A2
56
