Component Description And Operation - PHP Heat Wagon LVF90A Service Manual

Component Description and Operation

Fuel Pump
The fuel pump draws fuel from the fuel tank and pressurizes it to a high level.
Pump pressures vary by manufacturer and model, but typically fall into a
range of 80 to 160 pounds per square inch, or PSI.
The pump is driven by the heater motor. The motor rotates the pump by one
of three means: direct motor shaft to pump shaft, a coupler to connect the
shafts, or a belt drive.
The pump contains several "ports" or openings. The inlet port draws the fuel
from the tank into the pump. The outlet port carries the pressurized fuel to
the spray nozzle. The return or bypass port returns a portion of the fuel back
to the fuel tank. The gauge port allows for the attachment of a high pressure
fuel gauge to check and adjust pressure. The pressure adjustment port usually
contains a screw to adjust pump pressure. The exact arrangement of these
ports may vary from one manufacturer to another.
Fuel Filter
Several different types of fuel filters are found on high pressure oil heaters.
They all remove impurities from the fuel before they can enter and damage
the fuel pump.
Canister filters are located in the inlet line between the tank and the pump.
Inside the canister is a removable filter cartridge that can be cleaned or
replaced as needed.
Inlet line mesh filters use a metal mesh screen located at the end of the inlet
line down in the fuel tank.
Most pumps contain an internal filter located where the inlet line enters the
pump.
Motor
The motor powers the fuel pump and also turns the fan. Some motors con-
tain an internal centrifugal switch. This switch allows current to flow to the
fuel solenoid valve when the motor reaches full speed. Most motors have an
internal thermal and current protector to prevent damage should the fan or
pump lock up. These motors also contain a reset button which should only
be activated with power removed from the heater.
Safety Control
The safety control monitors the presence of flame within the combustion
chamber. A light sensing photocell is connected to the safety control. When
flame is seen, power is allowed to continue thru the safety control to run the
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