TM-9-2540-207-14&P Sustainment Manual for A20 Heater for M113 2540-01-396-2826 Download
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TM 9-2540-207-14&P 1-4 1.2.6 Ventilation Air Ventilation air is drawn from within the vehicle at the Heater Inlet by a high flow Vent Fan. The vent air stream is heated as it flows past the Burner and the Heat Exchanger before it is discharged out of the heater outlet. In high heat mode the temperature of the outlet air is about 250°F higher than the inlet air. For example, if the inlet air is -40°F, then the outlet air will be about 210°F. In low heat mode the vent air flow remains the same, but the outlet air temperature is about 125°F higher than the inlet air. The amount of heat produced will begin to be automatically reduced if the outlet air temperature exceeds 325°F. If the outlet air temperature exceeds 345°F, the heater will force a shut down, and enter purge mode. The heated outlet air may be discharged into a duct that distributes the heated air throughout the vehicle. Such an air duct should be 8" inside diameter, and be rated for 350°F under continuous operation. The duct must allow unobstructed air flow. Note: The ducting should be directed away from walls or obstructions to allow clear re-circulation of vent air. 1.2.7 Exhaust The exhaust temperature of the heater always exceeds 500°F in run mode and can reach temperatures as high as 1,300°F. The Heater Exhaust Tube connects to a 2" inside diameter duct. The duct must be rated for at least 1,100°F continuous operation, be leak tight, and secured from movement. 1.2.8 Enclosure Two semi-circular shells, top and bottom, are used to enclose the heater. A seam on each side of the enclosure is used to minimize ventilation air leakage and maximize structural strength. A Top Housing protrudes from the Top Shell of the heater. This Top Housing contains most of the fuel system, combustion air system and diagnostic display components. The Top Housing can be accessed directly by removing the Top Cover.