TM 1-1510-262-10
The rear evaporator blower is protected by a circuit breaker located on the DC power distribution panel, located
beneath the aisle way.
(3) High and low pressure limit switches. High and low pressure limit switches are provided to prevent
compressor operation beyond operational limits. When the low or high pressure switches are activated, compres-
sor operation will be terminated. When compressor operation has been terminated by limit switch activation, the
system should be thoroughly checked before returning it to service.
(4) Thermal sense switch. A thermal sense switch is installed on the forward evaporator. This sense
switch actuates a hot gas bypass valve which bypasses a portion of the refrigerant from the forward evaporator,
thereby preventing icing of the evaporator.
(5) Condenser blower. A vane-axial blower draws air through the condenser when aircraft is on the
ground. The blower is protected by a 50 ampere circuit breaker located beneath the aisle way. When the cabin
temperature mode selector switch is set to the AC COLD OPN position during ground operation, the condenser
blower will be off initially, and will remain off until compressor discharge pressure equals the pressure setting of the
blower control high pressure switch. The blower will remain in operation until system pressure drops to equal the
setting of the blower control low pressure switch.
(6) Air conditioning cold operation bypass valve. Selecting the A/C COLD OPN mode on the cabin
temperature mode selector switch permits the operation of the air conditioning system by overriding the refrigerant
low pressure switch. This allows the air conditioning system to operate in the manual mode. Starting the compres-
sor in this optional mode at low ambient temperature will decrease the operational life of the compressor by ive
hours each time the air conditioning system is started below 10 C using this mode (AC COLD OPN ). If the air con-
ditioning system has been operating in the normal mode during light, and due to decreasing ambient temperatures
make it necessary to switch to the AC cold operation mode, there will be no degradation in the mean time between
failures for the compressor.
(7) Air conditioner cold operation. Cold air conditioner operation mode is provided to allow the air con-
ditioner to operate in the event of a hot cabin and an outside air temperature of less than 10 C. At an OAT of less
than 10 C, a green advisory annunciator placarded AC COLD OPN , located on the caution/advisory annunciator
panel (Fig. 2-42), will illuminate. This advises the crew that if air conditioning is required, the cabin temperature
mode switch must be in the A/C COLD OPN position. This causes the air conditioner compressor to run continu-
ously and the temperature controller to operate the bypass valve.
b. Normal Operation.
(1)
Automatic cooling mode.
Bleed air valve switches -- OPEN , LEFT , and RIGHT.
(a)
Cabin temperature mode selector switch -- AUTO.
(b)
(c)
Cabin temperature control rheostat -- As required.
(d)
Cabin, cockpit and defrost air knobs -- As required.
(2) Manual cooling mode.
(a) Bleed air valve switches -- OPEN , LEFT , and RIGHT.
NOTE
For maximum cooling on the ground, set the bleed air valve switches to the PNEU ONLY position.
(b) Cabin temperature mode selector switch -- MAN COOL.
(3)
Air conditioning cold operation mode. (Used if ambient temperature is between +10 C and -25 C).
NOTE
Setting the cabin temperature mode selector switch to the A/C COLD OPN position at ambient tem-
peratures below -25 C may cause the air conditioning system to exceed the compressor low pres-
sure limit switch setting, terminating compressor operation, and thereby rendering the system in-
operative for the remainder of the light.
(a) Bleed air valve switches -- OPEN , LEFT , and RIGHT.
2-68
