20
Instructions for the installer
Boiler Model
Max water flow rate
Demanded in l/h ( t=15 K)
Δ
Max water flow rate
Demanded in l/h ( t=20 K)
Δ
440
550
660 770 900
18243
22804 27365 31926 36487
24326
30404 36487 42570 48647
3.9 -
DETERMINATION OF PRIMARY BOILER PUMP OR BOILER SYSTEM PUMP
The size of the pumps must be determined
by installers or technical engineers
according to boiler data and system design.
The water side resistance curve of the boiler
is shown in the following diagram.
The pump is not an integral part of the boiler.
It is recommended to choose a pump with
the rate and delivery head at about 2/3 of its
characteristic heating curve.
The boiler pump must have a delivery head which can ensure
the water flow rate as shown in the diagram “Water pressure
losses”.
The following table gives an indication of the pump’s flow rate
in function of the
Δ
t of the primary circuit if the installation has
a mixing header.
For a
DT 20 K, of a MODULEX 900 boiler, the max. water flow rate requested is
36289 l/h
.
From the graph of the boiler’s pressure losses, it can be determined that the pump must be able
to guarantee a delivery head of at least 1,8 m/H
2
O.
0
0,4
0,2
0,6
0,8
1
1,4
1,2
1,6
1,8
2
2,4
2,2
2,6
2,8
3
3,4
3,2
3,6
3,8
4
4,4
4,2
4,6
4,8
5
5,4
5,2
5,6
5,8
6
0
2000
4000
6000
8000
10000 12000 14000 16000
20000 22000 24000
28000 30000 32000 34000 36000 38000 40000 42000 44000 46000 48000 50000 52000 54000
18000
900 EXT
770 EXT
660 EXT
440 EXT 550 EXT
WATER FLOW
(l/h)
P
re
s
s
u
re
L
o
s
s
e
s
(
m
/H
)
2
O
NOTE: The use of a mixing header fitted between the boiler circuit and the system circuit is
always advisable. It becomes INDISPENSABLE if the system requires flow rates superior to the
maximum permitted boiler flow rates, which is to say lower than 15K.