c. Motor/Fan Subassembly. This unit contains a DC motor, a fan (heated air), and a wheel blower assembly
(combustion air). The drive shaft of the DC motor extends out each end of motor.
(1) A fan is attached to one end drive shaft. This fan brings in air from outside the heater and forces airflow
across the heat exchanger. The heated air is discharged into the area to be heated. This airflow is breathable and safe
and completely isolated from combustion gases.
(2) A wheel blower assembly is attached to the opposite end of the drive shaft. This blower brings in air from
outside the heater and forces airflow into the burner assembly to support combustion within the burner and heat
exchanger. Hot combustion air and gases, driven by this blower, are forced through the heat exchanger. Hot
combustion air and gases are safely exhausted outside of the area being heated.
d. Burner Assembly. Within this unit fuel is mixed with combustion air and ignited. Fuel flow, air flow, and ignition
continues as long as the heater controls do not sense an unsafe condition and the temperature requirements of the
thermostat have not been met. Combustion air and gases expand and are forced, by new incoming combustion air, into
the heat exchanger.
e. Heat Exchanger Assembly. Within the heat exchanger, the heat given off by the combustion of the fuel and air is
safely transferred to the heated air being discharged to the area where the thermostat is installed. This unit also provides
a mounting area for the burner assembly and additional room for combustion to occur. This hot mix of air and gases is
then safely exhausted outside of the area being heated.
(1) The 28 VDC power source is received through power receptacle J1 pins A and C (B is ground), then through
fuse F1 and reset circuit breaker CB when switch S1 is pressed ON. With S1 OFF, 28 VDC is supplied to coil of relay K2
(2) Then 28 VDC goes through thermostat receptacle J2 pins A and C if thermostat is set above ambient
temperature of the enclosure to be heated.
(3) Then 28 VDC goes through deenergized contacts of K1 to glow plug GP1 and coil L3 to heat the burner
chamber. 28 VDC is also present from K1 deenergized contacts to K3 coil.
(4) With CB1 reset switch on, 28 VDC is supplied to electronic time delay (ETD) in ECU.
(5) When K3 in ECU energizes, 28 VDC is supplied through closed contacts of overheat switch S4 causing igniter
to spark providing ignition.
(6) When flame switch S2 closes, relays K1 and K2 energize, glow plug GP1 stops heating, and motor B1 starts;
ground is applied to ETD.
b. Stopping. The heater will stop under the following conditions:
(1) When the thermostat reaches its desired setting removing 28 VDC from J2.
(2) When overheat switch S4 opens, ignition stops.
(3) When fuel supply is gone, ignition stops.
(4) When ON-OFF switch S1 is placed in OFF position, or reset switch CB1 opens.
(5) Blower B1 will run until flame switch S2 opens or relay K3 deenergizes.