Navien LCB700-21RS, Installation & Operation Manual

Page: 31 / 96

Connecting the Oil Supply 31
Double Pipe Sub-Gravity Feed System
With the storage tank outlet below the burner, a two pipe system should be used. The return pipe should be at the same level in the tank
as the supply pipe, both being 75 to 100 mm above the base of the tank. The pipe ends should be a sufficient distance apart so as to
prevent any sediment from being disturbed by the return entering the supply pipe.
Make sure that the bottom of the tank is more than 3.5 m below the burner.
A non-return valve should be fitted in the supply pipe together with the filter and fire valve. A non-return valve should be fitted in the
return pipe if the top of the tank is above the burner.
The pump vacuum should not exceed 0.4 bar. Beyond this limit gas is released from the oil.
For guidance on the installation of top outlet fuel tanks and suction oil supply sizing, see OFTEC technical book 3.
Min. 1 m
Oil
Storage Tank
0.7 m
M
ax. 3.5 m
Oil Strainer and
Water Separator
Fi
re
V
alv
e
(BS 5410)
Non-
Return
V
alv
e
Boiler
Oil
Filter
Oil
Pump
Non-
Return
Valve
Head
Max. Oil Pipe Length
Φ10
ੈ
Φ12
ੈ
0 m 50 m 100 m
-0.5 m 45 m 30 m
-1.0 m 40 m 95 m
-1.5 m 30 m 80 m
-2.0 m 25 m 65 m
-2.5 m 20 m 50 m
-3.0 m 15 m 35 m
-3.5 m 10 m 20 m