A-A-52545 Heaters, Vehicular Compartment 28 Volt, DcThis CID covers two types of heaters of 28 volt (V) direct current (dc) nominal rating, used for heating crew and engine compartments of military vehicles or equipment. Type I heaters are intended for use on military vehicles or equipment which may be required to operate in an ambient temperature to minus 65 degrees Fahrenheit (-65 Degrees F); from which a supply of gasoline is available; when heated air is required without the vehicle engine being operated. Type II heaters are intended for use on military vehicles or equipment from which a supply of heated circulating liquid (engine coolant) is available, which may be required to operate in an ambient temperature to -25 Degrees F.

Pages 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11

A-A-52545B

2.6.1.7 Endurance. The heater shall operate without a breakdown of the heat exchanger, electrical motor, combustion air blower wheel, ventilating air blower wheel, or fuel control valve during not less than 500 hours of continuous use, operating at ambient temperatures as low as -65°F, alternately at high and low heat settings, for 24 hour periods and cycling 20 minutes "ON" and 10 minutes "OFF".

2.6.1.8 Safety. All heaters shall comply to DOT standards cited in 49 CFR, section 177.834 in effect on date of manufacture.

2.6.2 Type II heaters.

2.6.2.1 Heat output and air discharge. The heat output and air discharge rate shall be not less than values in table III, as determined per SAE J638 procedure.

TABLE III. Type II heat output and air discharge.

2.6.2.2 Cycling. The heater shall have no coolant leakage from the coolant circulation system when cycled at 20 cycles per minute, pressure rise and fall from 0 to 32 pounds per square inch (psi), for 2500 total cycles. Cycling shall be accomplished at ambient temperature of -25 +5°F.

2.6.2.3 Endurance. The heater shall operate without a breakdown of the heat exchanger, electric motor or fan during not less than 250 hours of continuous operation with a coolant temperature of 180 +5°F with zero back pressure, and not less than 250 hours with 1.6 inches of H₂O back pressure. Starting time to full load shall be 10 seconds maximum.

2.6.3 Type I and II heaters.

2.6.3.1 Voltage. The heater shall start and operate satisfactorily at an applied voltage of 20 to 28.5 Vdc.

2.7 Environmental.

2.7.1 Low temperature operation. Type I heaters shall have operational stability at temperatures to -65 +5°F and type II heaters shall have operational stability at temperatures to -25°F.