Page 8 - Webster Service Manual

There are two basic types of installation for fuel units:
one-pipe systems or two-pipe systems.
The first of these, a one-pipe system, should not be
confused with a single-stage fuel unit. A one-pipe sys-
tem can be installed employing either a single-stage or
a two stage fuel unit. It is used where a gravity flow of
oil is available.
In a one pipe (single- or two-stage) system, the internal
pumping capacity exceeds nozzle requirements. The
excess flow is bypassed by the internal regulating valve
and is recirculated within the pump. In the one-pipe con-
nection, inlet line flow equals nozzle flow rate.
The second basic type is known as a two-pipe system
and should always be used wherever the oil supply
level is below the fuel unit, whether it be a single or two-
stage fuel unit.
On a two-pipe system there is a second pipe, called a
return line, between the fuel unit and the tank.
excess oil over and above that required by the nozzle is
bypassed at the valve and returned to the tank.
A single-stage unit on a two-pipe system can be used
on lifts up to 10” HG. On the other hand, a two-stage
with a two-pipe system may be used on lifts up to 15” HG.
Existing Inside Tank Installation- One Pipe System
Tank Above Burner Level
With the conventional one pipe gravity feed installation
both furnace and water heater can be operated of f the
same suction line. Merely tee of f the present line to
water heater as shown in drawing below making sure oil
supply is above burner level at all times.
Existing Outside Tank Installation—
Tank Above Burner Level
The water heater may be added to the system by con-
necting the suction line to the furnace suction line as