ARMY TM 9-4120-380-14
NAVY EE-000-BA-MMA-010/7053-AC
AIR FORCE TO 35E9-136-21
e.
Fault Detection/Protection Circuits. The air conditioner is equipped with one external equipment protection
heat fault detection circuit and two internal unit temperature over-limit protection circuits:
(1)
Heat fault detection resulting in automatic switch over to a backup air conditioner is provided by the
heat fault thermostat (S8) If the return air temperature exceeds the setting of 82 degrees F at the
thermostat (S8), the heat fault slave relay (K15) is energized. This results in the heat fault relay (K10)
de-energizing, enabling the fault to be reported at the remote status terminal board (TB2) and the
latching relay (K11) energizing to shut down the air conditioner and to enable the backup unit.
(2)
Internal air conditioner over-temperature protection is provided by the first and second stage heat limit
switches (S9 and S10). If the first and/or second stage heating elements (HR1/HR2) remain on after
the thermostat (S2) should have deactivated them. and internal air conditioner unit temperature rises
above 160 degrees F (71 degrees C), the first and second stage heat limit switches will open. The first
and second stage heater contactors (K4 and K5) will de-energize and disconnect power from the
heating elements (HR1 and HR2)
4.21 VENT (CIRCULATE) FUNCTION. When the MODE SELECT switch (S1) is set to VENT, all heating and cool- mg
functions are disabled, except that the four fault relays (K7, K8, K9 and K10) are energized to prevent the air conditioner
from reporting itself faulted at the remote status terminal board (I32)
The evaporator fan motor contactor (K2) is energized, applying power to the evaporator fan motor (B2), and the
CIRCULATE indicator (DS4) is lighted on the control panel. Equipment protection is provided by the evaporator fan
motor thermal switch (S6) which, when opened at a preset limit by maternal fan motor heat, de-energized the evaporator
fan motor contactor (K2) and shuts down the evaporator fan motor (B2). The fault is not reported and the backup air
conditioner is not enabled.
The thermal switch (S6) will automatically reset when the maternal fan motor temperature decreases within a preset
range, energizing the evaporator fan motor contactor (K2) and restarting the evaporator fan motor B2).
4-34
