King Air C90GTi, Pilot Training Manual

Page: 253 / 557

The ELEC HEAT switch (Figure 11-18), in
the ENVIRONMENTAL group in the copi-
lot’s sub-panel, has three positions: GND
MAX–NORM–OFF. This switch is solenoid-
held in GND MAX position on the ground
and drops to NORM position when the land-
ing gear safety switch is opened at lift-off.
It provides maximum electric heat for ini-
tial warmup of the cabin. If use of all elec-
t r i c a l h e a t i n g e l e m e n t s i s n o t d e s i r e d f o r
initial war mup, as in the GND MAX posi-
tion, the switch may be placed in the NORM
position, using only four elements. In the
NORM position the four heating elements
automatically supplement bleed-air heating,
in conjunction with the cabin ther mostat.
The OFF position turns off all electric heat,
leaving only bleed air to supply cabin heat.
COOLING SYSTEM
Cabin cooling is provided by a refrigerant-
gas vapor-cycle refrigeration system con-
sisting of:
• Belt-driven compressor, installed in
the nose
• Condenser coil
• Condenser blower
• Evaporator
• Receiver-dr yer
• Expansion valve
• Cabin heat control valve
It is routed (Figure 11-19) to the condenser
coil, receiver-dryer, expansion valve, cabin
heat control valve, and evaporator, which
are all in the nose of the air plane. The rated
o u t p u t o f t h e s t a n d a r d i n s t a l l a t i o n i n t h e
fuselage nose is 16,000 BTU.
The evaporator utilizes a solenoid-operated,
hot-gas-cabin heat control valve to prevent
icing. A 33°F ther mal switch on the evapo-
rator controls the valve solenoid.
The vent blower blows recirculated cabin air
t h r o u g h t h e eva p o r a t o r, i n t o t h e m i x i n g
plenum, and into both the floor-outlet and
ceiling outlet ducts. If the cooling mode is
o p erat in g , refrig era n t w il l b e c ircu l ati n g
through the evaporator and the air leaving it
will be cool. All the air entering the ceiling-
outlet duct will be cool. This air is discharged
KING AIR C90GTi/C90GTx PILOT TRAINING MANUAL
11-10
FOR TRAINING PURPOSES ONLY
11
AIR
CONDITIONING
Figure 11-18. Elec Heat Switch
EVAPORATOR
AIR PLENUM
VENT BLOWER
COMPRESSOR
AND MOTOR
RECEIVER-DRYER
(IN WHEEL WELL)
CONDENSER
SIGHT GAGE
PRESSURE
BULKHEAD
MIXING
PLENUM
Figure 11-19. Cooling System
Components in Nose