c. Shutdown. (Refer to Figure 2-9).
*A hot shutdown occurs when the heater and centrifugal fan are turned off at the same time when
in heater mode. Avoid turning off the fan and heater at the same time. Always set the
OFF/VENT/HEAT switch to VENT for at least 3 minutes when shutting down the heater unit from
heating mode. Failure to comply may damage heater and under some conditions, a safety
* If a power failure occurs when the heater is firing, immediately set the OFF/VENT/HEAT selector
switch (S 1) to OFF. Disconnect both the return and supply air ducts from the shelter and turn
parallel to the heater unit duct outlets. If available. insert the nozzle of a CO2 fire extinguisher in
the supply air duct and discharge CO, in short blasts of one or two seconds for six to ten blasts.
When cooling aids are not available, it is best to leave the heater unit stand idle for 15 to 30
minutes with the ducts removed and the makeup air door open. In that length of time, the
residual heat in the heat exchanger will have dissipated and the heater unit can be restarted
when power is available.
(1) If OFF/VENT/HEAT selector switch S1 (5) is not set on VENT, place it into VENT position and wait for three
(2) Set the OFF/VENT/HEAT selector switch S1(5) to OFF to shutdown unit.
c. For moving the heater short distances. refer to paragraph 3-43.1.
2-22 Change 6