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5.12.4 Pressurised one-pipe systems
Pressurised one-pipe systems (Fig. 21) have a positive fuel pres-
sure on intake to the burner.
Usually the tank is higher than the burner, or the fuel pumping
systems are on the outside of the boiler.
In order to obtain one pipe working it is necessary to unscrew the
return plug 2), remove the by-pass screw 3) and then screw the
plug 2) in again with a tightening torque of 0.5 Nm.
H
metres
0.5
1
1.5
2
H
metres
0
0.5
1
1.5
2
3
3.5
S9666
L meters
Ø (8 mm)
Ø (10 mm)
10
20
20
40
40
80
60
100
A
L meters
Øi 8 mm
Øi 10 mm
35
100
30
100
25
100
20
90
15
70
8
30
6
20
Installation
H
= Difference of level
L
= Maximum suction line length
Ø
= Inner diameter of the pipe
The installer must ensure that the supply pressure
is not above 0.5 bar.
Above that level, the pump seal is subject to too
WARNING
much stress.
In the system in Fig. 21, the table shows the maximum approxi-
mate lengths for the supply line, depending on the difference in
level, length, and the diameter of the fuel conduit.
5.12.5 Priming pump
In the system of Fig. 21 just loosen the connection of the vacuom-
eter 6) and wait for the fuel to come out.
In the systems A and B of Fig. 22 start the burner and wait for the
priming. Should lockout occur prior to the arrival of the fuel, await
at least 20 seconds before repeating the operation.
The pump vacuum should not exceed a maximum of 0.4 bar (30
cm Hg).
Beyond this limit gas is released from the oil.
The pipes must all be perfectly sealed.
Fig. 21
WARNING
5.12.6 Vacuum systems
Depressurised systems (Fig. 22) have a negative fuel pressure
(depression) at the burner intake.
Usually the tank is lower than the burner.
Tab. E
H
= Difference of level
L
= Maximum suction line length
Ø
= Inner diameter of the pipe
Tab. F
21
GB
B
S9667
Fig. 22
20136933
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