7. Hydraulic Performance
13
THERMA V Split Type
Hydro Box Unit
7.2 Water Volume and Expansion Vessel Pressure
Expansion vessel inside Hydro Box Unit is included which is 8 liter capacity with 1 bar pre-pressure. That means,
according to the volume-pressure graph, total water volume of 230 liter is supported as default. If total water volume
is changed because of installation condition, the pre-pressure should be adjusted to secure proper operation.
• Minimum total water volume is 20 liter.
• Pre-pressure is adjusted by the total water volume. If the indoor unit is located at the highestposition of the water
circuit, adjustment is not required.
• To adjust pre-pressure, use nitrogen gas by certificated installer.
Adjusting pre-pressure of expansion vessel
• Step 1. Refer "Volume-Height" table.
H : difference between indoor unit and the highest water pipe
V : total water volume of installation scene
If installation scene is belong to Case A, go to Step 2.
Otherwise, if it is Case B, do nothing. (pre-pressure adjustment is not required.)
Otherwise, if it is Case C, go to Step 3.
• Step 2. Adjust pre-pressure by following equation.
Pre-pressure [bar] = (0.1xH+0.3) [bar]where H : difference between indoor unit and the highest water pipe0.3
: minimum water pressure to secure product operation
• Step 3. Volume of expansion vessel is less than installation scene.
Please install additional expansion vessel at the external water circuit.
V 230 ˜ V ˻ 230 ˜
H 7m
Case B Case A
H ˻ 7m
Case A Case C
Maximum total water volume (liter)
Pre-pressure in Expansion vessel (bar)
20 60 100 140 180 220 260 300 340 360
2.4
2.1
1.7
1.4
1.0
0.7
0.3
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