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7.1.3
Dimensioning a standard low loss header
X Boiler-side connection
Y System-side connection
The low-oss header serves to isolate the boiler circuit from the system cir
cuit. The resistance of the low-oss header must be very low. The rate of
flow in the low-oss header must not exceed 0.25 m/s. Please refer to the
table for the correct dimensions of a standard low-loss header.
Nominal out
put
Capacity Q
d
D ∅ or D ⎕
H
A
B
kW
m
3
/h at ΔT = 20° C "
"
mm
mm
mm
mm
300
12.9
2
6 (DN 150)
140 x 140
453
604
752
450
19.4
2.5
8 (DN 200
170 x 170
555
740
898
600
25.8
2.5
10 (DN 250) 190 x 190
641
854
1022
750
32.3
3
10 (DN 250) 220 x 220
716
955
1131
900
38.7
4
12 (DN 300) 240 x 240
785
1046
1229
1050
45.2
4
12 (DN 300) 260 x 260
848
1130
1320
1200
51.6
4
12 (DN 300) 270 x 270
906
1208
1404
7.1.4
Boiler and system pumps
ΔP Boiler resistance (mbar)
Q Flow rate (m
3
/h)
The total output of the system pump(s) must not be more than the com
bined capacity Q of the boiler pumps Otherwise, with full take-up, the sys
tem pump will pump part of the system return water straight to the system
flow. This means that the flow temperature to the system will be lower than
the flow temperature from the boilers. In addition, the selected system
pump must be able to overcome the hydraulic resistance from the system.
Important
A pump is available as an accessory for the MCA 160.
7.1.5
Non-return valve
Install (spring-loaded) non-return valves in the boilers' return pipes to
avoid water flowing back to the boilers that are not in operation. This pre
vents unwanted water loss.
Fig.42
Low-loss header
AD-0000856-01
X
Y
1/2”
1/2”
D
A
d
H
B
Fig.43
Boiler resistance
AD-0000857-02
170
300
250
200
150
100
50
0
0
1
2
3
4
5
6
7
8
9
10
6,5
[m
3
/h]
Q
T = 20 K
7 Appendix
7680446 - v.01 - 14082017
MCA
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