TM 9-4520-272-14&P
0003 00
Heated air from the heat exchanger is then forced out the heated air outlet and into the outlet air duct. The
outlet air duct delivers heated air from the LCFH to the shelter.
The LCFH can operate in three different modes: manual (MAN), ventilation air only (VENT), and automatic
(AUTO). In Manual mode, the heater senses temperature via a sensor located at the heated air outlet and
maintains a pre-determined set temperature (225 0F). The heater will then cycle on and off to maintain that
temperature. In Ventilation Air Only mode, the diesel engine drives the air inlet fan and delivers unheated
air to the shelter. In Automatic mode, the heater reacts to the temperature sensed by the thermistor at the
operator control panel. The heater attempts to maintain a set temperature as selected by the operator
using the temperature control on the operator control panel.
During heater operation, the operator control panel is hung inside the shelter out of the direct path of the
heated air outlet or the cold air from the shelter entrance. If the heater mode switch has been set to AUTO,
the thermistor on the control panel monitors the temperature of the shelter interior and sends a signal to
the heater that controls the firing of the burner assembly. The burner is then instructed to operate at full
heat output, half heat output, or no heat output.
Fault detection circuitry designed into the heater constantly monitors heater status. If a problem should
occur, the system will proceed to the shut down mode and then into post purge mode. A fault code will be
displayed on the LED display of the operator control panel.
When the heater is to be shut down, the power switch is placed in the OFF position. The heater will then
go through a shut down sequence that includes a purge mode to ensure that all residual fumes have been
removed from the heater, followed by engine shutdown.
END OF WORK PACKAGE
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