Air Conditioning Components
MIXER UNIT
The mixer unit mixes air from packs and re-circulated air from the cabin
prior to distribution to each zone. The mixer unit, installed under the cabin floor, uses cabin air, which has entered the underfloor area and has been drawn through recirculation filters by recirculation fans. This air is mixed with conditioned air from the packs. The quantity of cabin air mixed with conditioned air varies from 37% to 51%.
MIXER UNIT TEMPERATURE SENSORS
There are two mixer unit temperature sensors, one on either side of the mixer unit. They indicate the actual temperature of the mixer unit to the Zone Controller (ZC). Each mixer unit temperature sensor has two thermistors, one connected to the primary computer and the other to the secondary computer.
MIXER UNIT FLAP
The mixer unit flap supplies sufficient air to the flight deck if pack 1 P/B is selected off. An electrically operated mixer unit flap is installed to
make sure that sufficient fresh air is delivered to the cockpit in case of pack 1 failure.
TRIM AIR PRV
The trim air Pressure Regulating Valve (PRV) is pneumatically operated and electrically controlled by a solenoid. The solenoid controls the ON/OFF function. A limit switch indicates the CLOSED/NOT CLOSED position to the ZC and the ECAM system. The trim air PRV regulates the pressure of the air supplied to the trim air valves to 4 psi above the
cabin pressure. The ON/OFF function solenoid de-energizes when the HOT AIR P/B is set to OFF or when any duct temperature is above 88°C (190°F). This closes the valve.
HOT AIR PRESSURE SWITCH
Due to a malfunction of the trim air PRV, the hot air pressure switchbsignals overpressure to the secondary computer of the ZC for ECAM display and the Centralized Fault Display System (CFDS). If pressure in the system exceeds 6.5 psi above the cabin pressure, the ZC activates the ECAM system. This signal stays until the pressure falls below 5 psi.
TRIM AIR VALVES
The trim air valves allow the zone temperature to be adjusted by modulating the hot airflow added to air from the mixer unit. The trim air valves close when the trim air PRV closes. The butterfly of the trim air valves is controlled by a stepper motor. The trim air valve position determination is based on the step counting principle.
DUCT TEMPERATURE SENSORS
Each duct temperature sensor detects duct temperature for the corresponding zone temperature control, indication and overheat detection to the ZC. Each duct temperature sensor consists of two thermistors, one connected to the primary computer and the other to the secondary
computer. Each thermistor gives control, indication and overheat detection (starting at 80°C (176°F) with an amber ECAM duct temperature indication).
ZONE TEMPERATURE SENSORS
Each zone sensor detects the related zone temperature for zone temperature control and indication on the ECAM display. Each zone
temperature sensor has two thermistors, one connected to the primary computer and the other to the secondary computer.
There are two mixer unit temperature sensors, one on either side of the mixer unit. They indicate the actual temperature of the mixer unit to the Zone Controller (ZC). Each mixer unit temperature sensor has two thermistors, one connected to the primary computer and the other to the secondary computer.
MIXER UNIT FLAP
The mixer unit flap supplies sufficient air to the flight deck if pack 1 P/B is selected off. An electrically operated mixer unit flap is installed to
make sure that sufficient fresh air is delivered to the cockpit in case of pack 1 failure.
TRIM AIR PRV
The trim air Pressure Regulating Valve (PRV) is pneumatically operated and electrically controlled by a solenoid. The solenoid controls the ON/OFF function. A limit switch indicates the CLOSED/NOT CLOSED position to the ZC and the ECAM system. The trim air PRV regulates the pressure of the air supplied to the trim air valves to 4 psi above the
cabin pressure. The ON/OFF function solenoid de-energizes when the HOT AIR P/B is set to OFF or when any duct temperature is above 88°C (190°F). This closes the valve.
HOT AIR PRESSURE SWITCH
Due to a malfunction of the trim air PRV, the hot air pressure switchbsignals overpressure to the secondary computer of the ZC for ECAM display and the Centralized Fault Display System (CFDS). If pressure in the system exceeds 6.5 psi above the cabin pressure, the ZC activates the ECAM system. This signal stays until the pressure falls below 5 psi.
TRIM AIR VALVES
The trim air valves allow the zone temperature to be adjusted by modulating the hot airflow added to air from the mixer unit. The trim air valves close when the trim air PRV closes. The butterfly of the trim air valves is controlled by a stepper motor. The trim air valve position determination is based on the step counting principle.
DUCT TEMPERATURE SENSORS
Each duct temperature sensor detects duct temperature for the corresponding zone temperature control, indication and overheat detection to the ZC. Each duct temperature sensor consists of two thermistors, one connected to the primary computer and the other to the secondary
computer. Each thermistor gives control, indication and overheat detection (starting at 80°C (176°F) with an amber ECAM duct temperature indication).
ZONE TEMPERATURE SENSORS
Each zone sensor detects the related zone temperature for zone temperature control and indication on the ECAM display. Each zone
temperature sensor has two thermistors, one connected to the primary computer and the other to the secondary computer.
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