Piper PA-32R-301T SARATOGA S, Maintenance Manual

Page: 151 / 956

COOLING (cont.)
B. Air Conditioning (cont.)
(1) Description and Operation. (Refer to Figure 2)
This installation consists of a compressor with its special brackets and associated hardware, an
evaporator, a condenser, a receiver-dehydrator, circulating fan, thermal expansion valve, and relat-
ed plumbing.
The evaporator filters, dehumidifies and cools the air. The evaporator is mounted in a fabricated
housing along with the receiver-dehydrator, circulating fan, thermal expansion valve and related
plumbing. This housing is located at the rear of the cabin, aft of the baggage area. The compressor
is a two cylinder, piston type compressor which is supported by special brackets at the front of the
engine. A V-belt connected to the engine ring gear drives the compressor through a magnetic
clutch. The condenser is installed on a hinge mounted door that is located on the bottom portion
of the fuselage tail section. The condenser door is hinge mounted to allow extension into the
airstream during system operation. The condenser door is electrically activated to provide the
following positions, (system on - fully extended; system off - fully retracted).
The system is protected by a Ranco type pressure switch which automatically controls the
condenser maximum head pressure by temporarily de-clutching the compressor in the event
the pressure becomes excessively high. The controls are located on the aircraft instrument panel
adjacent to the heater and defroster levers, and consist of an Air Conditioning control, a fan
control to govern the cold air velocity, and a temperature control.
The system is such that there is no increase in drag to the aircraft during its take-off flight
conditions. During maximum power demands the compressor is de-clutched and the condenser
door is automatically retracted.
The air conditioning system in this aircraft is a recirculating, independent unit. It filters,
dehumidifies and cools the air as it cycles through the evaporator. The unit is operated from
controls mounted on the right side of the instrument panel. The air conditioning master switch
has two positions, ON-OFF. When the AIR COND position is selected the compressor clutch
engages, the condenser scoop opens and the circulating fan is turned on. The temperature is
controlled by a thermostat operated by the temperature control selector. A two position fan switch
(LOW-HIGH) operates the blower. The fan may be operated to circulate air without using the air
conditioning unit.
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. The compressor then pumps the vapor to the condenser where it cools
and changes to a liquid. The liquid then passes to the receiver-dehydrator. Its function is to filter,
remove any moisture and insure a steady flow of liquid refrigerant into the evaporator through the
expansion valve. The expansion valve is a temperature controlled metering valve which regulates
the flow of the liquid refrigerant to the evaporator. The evaporator absorbs the heat from the air
passing over the coils. From the evaporator the refrigerant vapor returns to the compressor where
the cycle is repeated.
— NOTE —
The air conditioning system should be operated at least once a
month to prevent sticking valves and keep the system
lubricated.
PIPER AIRCRAFT
PA-32R-301/301T
MAINTENANCE MANUAL
21-50-00
Page 21-10
Reissued: July 1, 1993
1H17