TM 5-4520-256-14
2-7. OPERATING PROCEDURES - Continued.
b. Heating Mode Operation. (Refer to Figure 2-9).
CAUTION
Do not attempt to operate the heater unit in the heating mode for more than 10 minutes when the
ambient temperature is above +70°F (+21.1°C). Failure to comply may result in damage to
equipment.
(1) Perform the setup procedures in paragraph 2-6.
(2) Press the circuit breaker (CB1) (4).
(3) Press the RESET button (1).
(4) Set the OFF/VENT/HEAT selector switch S1 (5) to VENT for 60 seconds to allow the centrifugal fan to build.
up speed.
(5) Push toggle switch S7 (3) upward to ON position for 10 seconds to purge fuel lines of air. Fuel pressure gage
(6) indication will drop while switch is in ON position and will return to approximately 10 psig when released.
(6) Check the FUEL pressure gage (6). Gage should indicate 10 psig.
NOTE
If the ambient air temperature is below 0°F (-17.8°C) then wait 30 to 45 seconds prior to
performing step (7). For optimum heating, open fresh air damper about 25% of full open. At
temperatures below 0°F (-17.8°C), reduce fresh air damper opening to about 10% of full open.
CAUTION
After the burner lights up, lift the cover on the rear of the unit and observe the flame through the
sightglass located on the rear of the heater unit below the exhaust pipe. If the flame is not
bright, notify unit maintenance to adjust the fuel pressure.
(7) Set the OFF/VENT/HEAT switch S1 (5) to the HEAT position to ignite the burner.
(8) Check the fuel pressure gage (6). Gage should indicate fuel pressure required for the elevation and frequency
(50 or 60 Hz) at which the heater unit is being used. (See Table 2-4).
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