Liquid and Air Systems

b. Regulator Valve. The regulator valve, mounted

M.2, or M.3 fuel oil or JP-4 fuel as a combustible. The

electrical requirement is 24 volts-direct current (dc).

in the control head, consists of two parts-one is a

Refer to figure 71.5 for specifications.

solenoid-operated shut-off valve and the other is a high-

low pressure regulator which varies the pressure of the

150. Liquid and Air Systems

fuel being supplied to the nozzle assembly for high- or

a. Liquid Flow System. The liquid flow system

low-fire operation.

operates in conjunction with the combustion air flow

c. Nozzle Assembly. The nozzle assembly is

system to transfer the heat of combustion from the

contained in a tee, which is connected to the regulator

burner to the liquid to be heated. The combustion

valve outlet port by an elbow. The nozzle is a thin plate

chamber provides passages through which the liquid

orifice through which fuel is metered to the burner, and

flows. The combustion air is circulated around these

works with the regulator valve to assure a constant,

passages so that the chamber functions as a heat

smooth metered flow of fuel regardless of the fuel used.

exchanger. The liquid is forced into the inlet port at the

Burner.

The burner is of the modified

side of the combustion chamber by an externally

vaporizing-pot type with a porous ceramic burner wick

mounted liquid pump. It leaves the heater through the

mounted in its base. Fuel enters the burner through the

fitting at the top of the combustion chamber. The liquid

fuel inlet connection, saturates the wick, and combustion

pump is powered by the electrical circuit of the heater.

occurs in the burner throat and the combustion

b. Combustion Air System. The combustion air

chamber.

system provides the air to maintain combustion. The air

system consists of a blower motor fan and the

152. Electrical System

necessary air passages. The air enters the heater

through the larger opening in the heater base, passes

(fig. 71.7).

through the combustion air blower shell and into the

The heater electrical system controls the operations

burner. The air mixes with the fuel vapor in the burner

of the fuel, liquid, and air systems throughout the

and combustion occurs.

The hot, contaminated

complete heater cycle. It also provides safeguards

combustion air passes through ports at the far end of the

against electrical and mechanical failures. The remotely

combustion chamber, into the secondary heat

mounted control box assembly controls the circuits from

exchanger. During this time, much of its heat is

the power source to the heater and the fuel pump

transferred to the liquid. The air leaves the heater

through a connecting cable assembly.

through the centrally located exhaust opening.

a. Control Box Assembly.

(1) The control box assembly contains a circuit

151. Fuel Systems

breaker, control switch, and indicator lamp.

(2) The circuit breaker protects the system if an

(fig. 71.6).

electrical failure occurs. Located in the

power circuit to the system, the circuit

The heater fuel system provides a constant flow

breaker can disconnect the system entirely

of liquid fuel to the burner for combustion, and operates

when the reset button is pulled out. Never

in conjunction with the heater electrical system. Fuel is

pull the reset button, however, while the

supplied through a fuel pump and filter to the heater,

heater is in operation, since this will

and reaches the combustion chamber through the

eliminate the heater purging cycle.

regulator valve and nozzle.

(3) The control switch is a double-pole, double-

a. Fuel Pump. The fuel pump is electrically

throw switch with "ON-HI, OFF, ON-LO"

connected to the heater operating circuits and supplies

positions. The heater starts operating when

fuel at low pressure to the regulator valve. The pump is

the thermostat calls for heat after the switch

self-priming, requiring no bleeding or adjustment on first

is moved

start.

AGO 5667A