Hydraulic Balancing Line - Bosch UT-L 1 Technical Manual

56 | System examples
9.3.3

Hydraulic balancing line

A hydraulic balancing line (low loss header) is used to
hydraulically separate the boiler circuit and the heating
circuits.
Installing a hydraulic balancing line has many
advantages:
• Trouble-free sizing of the boiler circuit pump and
actuators
• Prevention of mutual influence of the flow rates in the
heat source and heat consumer circuits
• Heat sources and heat consumers are only supplied
with the allocated flow rates.
• Can be used in single and multi boiler systems,
independent of the heating circuit control system
• Actuators on both sides of the hydraulic balancing line
work best when correctly sized.
• The hydraulic balancing line can also be used as a dirt
separator if sized accordingly ( page 48).
• Divided into primary and secondary sides if there is a
large pressure loss on the water side and long
distances between the boiler and heating circuits
Sizing the low loss header
Correct sizing is very important if the hydraulic balancing
line is to function correctly. To ensure good separation
with the simultaneous function as a dirt separator, size
the line in such a way that there is virtually no pressure
loss between the flow and return. With the nominal
water volume, flow velocities of 0.1 m/s to 0.2 m/s can
be expected. This makes simultaneous usage as a dirt
separator possible. In order that the heating circuit flow
temperature can be captured, provide a sensor well,
200 mm to 300 mm long, in the upper area of the
hydraulic balancing line on the heating circuit side.
V
---------------- -
D =
F. 8 Formula for sizing the low loss header
D Diameter of the hydraulic balancing line in m
V Total boiler circuit flow rate in m
Kges
v Total boiler circuit flow rate in m/s
6 720 807 794 (2013/04)
1
Kges
× --------------
v 2827
3
/h
Example
Given
• Total flow rate V = 223.6 m
Kges
• Flow velocity (assumed) v = 0.2 m/s
Result
• Diameter of the hydraulic balancing line D ≈ 0.63 m
D
VK
RK
4
Fig. 37 Schematic diagram of a hydraulic balancing line
[RH] Heating return
[RK] Boiler return
[VH] Heating circuit flow
[VK] Boiler flow
[1] Female connection for an automatic air vent valve
[2] Female connection for a sensor well ½ "
[3] Perforated partition
[4] Quick-acting valve
3
/h
1
2
3
VH
5 × D
3–4 × D
RH
D
6 720 640 417-19.1il
UNIMAT