Installation and operating instruction
Gas condensing unit WTC-GB 15-B Compact and WTC-GB 25-B Compact
13 Project planning
83309302 1/2018-05 La
165-196
13 Project planning
13.1 Expansion vessel and system pressure
The unit is equipped with an integrated expansion vessel:
Contents 10 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 260 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
max 70 °C
330
260
220
140
100
max 80 °C
260
210
170
110
80
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.
Determine static height.
Calculate inlet pressure.
Check inlet pressure in the expansion vessel and adjust to calculated value if ne-
cessary.
The valve of the expansion vessel is located behind the display and operating unit
(system device) [ch. 3.3.1].
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