TM 55-1510-220-10
(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 on the ground as well
as in flight. The current limiter for this blower is located
on the DC distribution panel in the lower equipment bay.
When the cabin temperature mode selector switch is set
to the A/ C COLD OPN position, the condenser blower
will be off, and will remain off until the condenser blower
control high pressure switch senses a compressor
discharge pressure equal to the pressure it is set to.
The condenser blower will then remain in operation until
the low pressure switch senses that the system pressure
has dropped to the pressure it is set to.
(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.
NOTE
Starting the compressor in this
optional mode at low ambient
temperatures will decrease the
operational life of the compressor
by five hours each time the air
conditioning system is started
using this mode (A/C COLD OPN).
If the air conditioning system has been operating
in the normal mode during flight, and due to decreasing
ambient temperatures make it necessary to switch to the
A/C cold operation mode. there will be no degredation
in the mean time between failures of the compressor.
(7)
Air conditioner cold operation advisory
annunciator light. A green advisory annunciator light
placarded
A/C
COLD
OPN,
located
on
the
caution/advisory
annunciator
panel
(fig.
2-6),
illuminates when the air conditioning system is operating
in cold mode, or when ambient temperatures require
switching to cold mode if air conditioning system
operation is to be continued.
b.
Normal Operation.
(1)
Automatic cooling mode.
1.
Bleed air valve switches OPEN, LEFT
and RIGHT.
2.
Cabin temperature mode selector switch
AUTO.
3.
Cabin temperature control rheostat As
required.
4.
Cabin, cockpit and defrost air knobs As
required.
(2)
Manual cooling mode.
1.
Bleed air valve switches OPEN, LEFT
and RIGHT.
NOTE
For maximum cooling on the
ground, set the bleed air valve
switches to the ENVIRO OFF
position.
2.
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
temperatures below -25°C may
cause the air conditioning system
to exceed the compressor low
pressure
limit
switch
setting,
terminating
compressor
operation, and thereby rendering
the system inoperative for the
remainder of the flight.
1.
Bleed air valve switches OPEN, LEFT
and RIGHT.
2.
Cabin temperature mode selector switch
A/C COLD OPN.
3.
Cabin temperature control rheostat As
required.
4.
Cabin, cockpit and defrost air knobs As
required.
2-70. UNPRESSURIZED VENTILATION.
Ventilation is provided by two sources. One
source is through the bleed air heating system in both
the pressurized and unpressurized mode. The second
source of ventilation is obtained from ram air through
the condenser section in the nose through a check valve
in the vent blower plenum. Ventilation from this source
is in the unpressurized mode only with the CABIN
PRESS DUMP
Change 2 2-57
