Planning
18 | WOLF GmbH 3066501_201910
4.4.1
Suction line in the single line system
i
Two-line systems must be converted to single line systems.
These older systems are no longer considered state-of-the-art and lead to accelerated oil ageing
and the ingress of air into the oil.
Suitable materials
Use suitable materials for oil lines. In the case of copper pipes, only metallic cutting ring fittings with
support sleeves are permissible. They are a reliable means of preventing air intake.
Max. line lengths
The maximum possible suction line length results from the pressure losses on the pipes and fittings and
the inlet height. The line length includes all vertical and horizontal pipes. The maximum suction line length
recommended by WOLF is 40 m.
+H
-H
A
B
Fig. 4.3
Floating suction
A
Oil pump lower than tank
B
Oil pump higher than tank
q
Oil pump
w
Floating suction
e
Anti-lift valve
The following table can be used for sizing the suction line length. When sizing the line lengths, the
individual resistances (filter, non-return valve) and six 90° bends are already taken into account.
Type
Throughput
Internal
diameter of
line
Inlet height H (m)
kg/h
mm
+4
+3
+2
+1
0
-1
-2
-3
COB-2-15
COB-2-20
COB-2-29
Up to 2.5
4
40
40
40
40
40
35
25
13
COB-2-40
Up to 3.7
4
40
40
40
38
29
22
15
9
Table 4.5 Calculation of inlet height
If the suction height or the maximum suction line length for low-lying tanks is greater than indicated in
Table 4.5 Calculation of inlet height
, an oil supply unit with an intermediate vessel is required in the
immediate vicinity of the heat generator. It must be possible to control the oil supply unit independently
of the heat exchanger, i.e. no signal pick-up on the heat generator for this purpose. When connecting a
feed pump in the supply line, the pressure must not exceed 0.5 bar. The oil supply from the intermediate
vessel is driven by the oil pump of the appliance.
Suction
Use floating or raised suction.
Floating suction is not permitted for underground oil tanks or for oil tanks for which a special draw-off
device is prescribed by the manufacturer.
