Installation and operating instruction
Hydraulic unit WWP LS 8 ... 16-B
12 Project planning
83306902 2/2017-05 La
83-88
12 Project planning
12.1 Expansion vessel and system pressure
The unit is equipped with an integrated expansion vessel:
Contents 18 litres,
inlet pressure 0.75 bar.
Use the following table to verify whether an additional expansion vessel should
be installed.
Example
A maximum flow temperature of 50 °C and an installation elevation of 7.5 metres
would result in a maximum system content of 500 litres. An additional expansion
vessel must be installed if this volume is exceeded.
Installation elevation
5 m
7.5 m
10 m
12.5 m
15 m
Flow temperature
Maximum admissible total water content [litres]
max 40 °C
820
700
620
420
300
max 50 °C
620
500
410
280
190
max 60 °C
440
360
290
190
140
Expansion vessel inlet pressure
The inlet pressure is calculated from the static ceiling of the system:
10 metres static height = 1.0 bar inlet pressure
The static height is determined by the difference in height between the expansion
vessel connection and the highest point of the system.
If the static height is less than 5 metres (e. g. with a one-storey building or roof
heating centre), an inlet pressure of minimum 0.5 bar must be selected.
If the hydraulic unit is installed at a higher point of the building (e. g. in the loft), the
inlet pressure should also be set to minimum 0.5 bar.
Determine static height.
Calculate inlet pressure.
Check inlet pressure in the expansion vessel and adjust to calculated value if ne-
cessary.
System pressure
Set the system pressure 0.5 bar above the adjusted inlet pressure of the expan-
sion vessel.
Example
Example 1
Example 2
Static height
8 metres
1 metre
Expansion vessel inlet pressure
0.8 bar
0.5 bar
System pressure
1.3 bar
1.0 bar
