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air duct if a failure causes the temperature control modulating valve to
open too wide. The temperature limiter has a spring loaded poppet valve
which opens if an overheat condition occurs in the conditioned air duct.
The open poppet valve vents the servo pressure normally supplied to the
temperature control modulating valve causing that valve to close. A
greater portion of cold air then enters the conditioned air duct and lowers
the duct temperature. When the temperature decreases to a safe level, the
poppet valve closes and the system returns to normal operation. If the
cause of the overheat condition is still present, the temperature limiter
will continue to cycle to limit the temperature in the conditioned air duct,
SECTION 2
Page 10
Mar 01/85
canatiair
chaiienQer
OPERATING MANUAL
PSP 606
COCKPIT AND CABIN TEMPERATURE MODE SELECTOR SWITCHES
Three-position selector switches used to select mode to control operation of
the temperature control modulating valves.
NORMAL - Controls temperature control modulating valve automatically
with reference to fan/sensor, duct temperature sensor and temperature
control switch.
STANDBY—Controls temperature control modulating valve automatically
with reference to duct temperature sensor and temperature control switch.
MAN—Automatic mode is inoperative. Temperature control modulating
valve is controlled by temperature control switch.
CABIN TEMPERATURE INDICATOR
COCKPIT AND CABIN TEMP CONTROL SWITCHES
Rotary switches used to select desired cabin or flight compartment
temperature.
Temperature Control Panel SECTION 2
Figure 5 Page 11
Mar 01/85
cacnhaadllaeinr ger
OPERATING MANUAL
PSP 606
A cabin temperature indicator is provided on the temperature control
panel. The indicator is connected to a temperature sensing bulb in the
cabin and has a range from -40 to 40°C (-40 to 104°F) in 5°C increments.
Footwarmer and Demister
The footwarmer and demister system is independent of the normal
environmental control system and is used to supplement flight compartment
heating and to provide a means of demisting the inside surface of the
windshields.
The air supply for the footwarmer and demist system is taken from the bleed
air manifold through a pressure regulator and shutoff valve, and a heat
exchanger. During normal operation, bleed air is taken from the right
engine. However, a similar supply is available from the left engine for
standby/emergency use. The standby supply is also passed through a
pressure regulator and shutoff valve.
The pressure regulator and shutoff valves are controlled by a CKPT HEAT
switch in the flight compartment. The CKPT HEAT switch has three
positions, NORM, STBY and OFF. The NORM position controls the operation of
the right pressure regulator and shutoff valve, and the STBY position
controls the operation of the left pressure regulator and shutoff valve. A
check valve is located in the supply line from the right engine to prevent
reverse air flow to the engine.
The heat exchanger cools the bleed air to a temperature of 49°C (120°F);
ram air is the cooling medium. The flow of ram air is controlled by a
modulating valve which in turn is controlled by a heat sensing unit. When
the aircraft is on the ground, cooling air for the heat exchanger is
provided by a fan which operates whenever the aircraft weight is on the
landing gear, and the CKPT HEAT switch is set to NORM or STBY.
In an emergency, the air from the footwarmer and demist system may be fed
into the cabin and flight compartment by operation of a normally closed
shutoff valve. The shutoff valve feeds air into the crossover duct between
the conditioned air ducts and is controlled by an emergency pressurization
switch/light on the cabin pressurization control panel.
If an overheat condition occurs in the duct downstream of the heat
exchanger, a heat-sensitive switch operates. When the switch operates, an
electrical circuit is completed to close automatically whichever pressure
regulator and shutoff valve is open, and isolate the cause of the
overheat. If emergency pressurization has been selected, the pressure
regulator and shutoff valve remains open.
Avionics Cooling
The avionics equipment is located in the underfloor area of the cabin on
both sides of the fuselage between the flight compartment rear bulkhead and
the wing centre section front spar. Cooling for this area is provided by
the flow of exhaust air from the flight compartment towards the outflow
valves.
SECTION 2
Page 12
Jun 12/86
canadair
chauertQer
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