Fluid Circulation Pump
©Aqua-Hot®
250-D03 Diesel Series Service Manual
REV 220302
p. 43
Diesel Burner is turned
to the ON position on
the interior control
panel.
After approximately 10-
25 seconds, the Fuel
Solenoid Valve opens,
and fuel is sprayed
into the Combustion
Chamber through the
Fuel Nozzle.
The motor, which turns
the Combustion Air
Blower and drives the
Fuel Pump, will begin to
operate.
NOTE:
If the Aqua-Hot’s coolant
temperature is approximately
190°F or higher, the Motor
will not operate. Only when the
coolant temperature is below
160°F and the ETS Module is
calling for heat will the motor
begin to operate.
Once the ignited air-fuel
mixture (FLAME) is
observed by the Flame
Sensor, the Ignition coil
will automatically switch
OFF. The combustion
process now continues
to operate unassisted.
The combustion process
will continue to operate in
this manner until one of
the following occurs:
• The ETS Module,
which senses
coolant temperature,
reaches the preset
temperature of
approximately 190°F
• The Aqua-Hot’s diesel
burner is turned OFF.
Once the heater
switches to OFF,
thermostatically or
manually, the Fuel
Solenoid Valve closes,
which interrupts the
supply of diesel fuel to
the Fuel Nozzle.
The Motor will continue
to run for approximately 3
additional minutes. This
process is referred to as
the Purge Cycle, which
cools the heater’s internal
components and purges
the Combustion Chamber
of any residual exhaust
gases.
NOTE:
When the diesel burner
is switched OFF by the ETS
Module, the Motor will shut off
once the 3 minute Purge cycle
has completed. The diesel
burner will automatically
turn back ON once the
coolant reaches the preset
temperature of approximately
160°F.
The Diesel Burner is
operational anytime
the operator moves the
it to the ON position.
The Diesel Burner will
automatically maintain
the coolant temperature
in the Aqua-Hot’s boiler
tank without additional
involvement from the
operator.
Diesel Burner Operational Flow Chart
Diesel Burner Operation
