Air Conditioning System Description And Principles Of Operation; Air Conditioning System Troubleshooting - Piper PA-44-180 SEMINOLE Maintenance Manual

COOLING. (PA-44-180T ONLY.)
GENERAL.

AIR CONDITIONING SYSTEM DESCRIPTION AND PRINCIPLES OF OPERATION.

The air conditioning installation is a recirculating, independent unit consisting of a compressor, evaporator,
condenser, receiver-dehydrator, circulating fan, thermal expansion valve and related plumbing.
Air is filtered, dehumidified and cooled by the evaporator. The evaporator is mounted in a fabricated housing,
along with the receiver-dehydrator, pressure switch, circulating fan and thermal expansion valve. This housing is
located at the rear of the cabin aft of the baggage area. The compressor is a piston type unit mounted at the front
of the port engine. A V-belt connection drives the compressor through a magnetic clutch. The condenser is
installed in the tail cone between stations 156.00 and 191.00.
The system is protected by a pressure switch which automatically controls the condenser maximum head
pressures by temporarily de-clutching the compressor in the event the pressure becomes excessively high.
The air conditioner controls are located on the right side of the aircraft instrument panel and consist of an air
conditioning ON-OFF control, a two-position fan control (LOW-HIGH) and a temperature control.
The air conditioning system uses Refrigerant 12. The refrigerant enters the compressor as a vapor. The
compressor pressurizes the heat laden vapor until its pressure and heat reach a point much hotter than the outside
air then pumps the vapor to the condenser where it is cooled and changed to a liquid. The liquid then passes to
the receiver-dehydrator. The function of the receiver-dehydrator is to filter, remove any moisture and insure a
steady now of liquid refrigerant into the evaporator through the expansion valve. The expansion valve is a
temperature controlled metering value which regulates the flow of liquid refrigerant to the evaporator to allow all
the liquid to evaporate and return to the compressor at a reduced pressure. From the evaporator, the refrigerant
vapor returns to the compressor where the process is repeated.
TROUBLESHOOTING.
A troubleshooting chart is provided to assist in locating and correcting possible malfunctions in the cooling
system.
The air conditioning system should be operated at least once a month to prevent
sticking valves and to keep the system lubricated
PIPER AIRCRAFT
PA - 4 4 - 1 8 0 / 1 8 0 T
AIRPLANE MAINTENANCE MANUAL
— Note —
1G15
2 1 - 5 1 - 0 2
Page 21-48
Revised: May 15, 1989