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24-40
AIR CONDITIONING
from the refrigerant manifold. Insert the free end of
this
test
hose into an exhaust system outlet. Open the
right-hand gauge
set
manifold valve a fraction of a
turn to
let
the sweep-test charge escape slowly. Allow
the system to discharge until the discharge pressure
gauge registers zero. Open the left-hand gauge valve
to allow any refrigerant trapped in the suction side of
the system to escape.
REPLAC E THE RECEIVER-DRIER-STRAIN ER
CAUTION:
Replacement
receiverdrier-strainer
units must be sealed while in storage. The drier
used in these units is so hungry for moisture that
they can saturate quickly upon exposure to the at-
mosphere. When installing a drier, have
all
tools
and supplies ready for quick reassembly to avoid
keeping the system open any longer than necessary.
EVACUATE THE SYSTEM
Whenever the system has been opened to atmos-
phere, it is absolutely essential that the system be
swept with refrigerant and evacuated or "vacuumed"
to remove all the air and the moisture. If any ap-
preciable amount of air remains in the system when
it is charged, the trapped air will concentrate near
the top of the condenser and cause abnormally high
discharge pressures. Air in the system will reduce the
condenser's ability to condense the refrigerant gas
and supply adequate liquid refrigerant to the evapo-
rator. To evacuate the system, proceed as follows:
(1)
Connect the gauge set manifold
to
the compres-
sor and the long test hose from the gauge
set
mani-
fold center connection to the vacuum pump, Tool
C-3652, as shown in Figure
53.
(2) Open both gauge set manifold valves and the
needle valve.
(3) Start the vacuum pump and operate until the
evaporator suction gauge registers at least
26
inches
of vacuum. If the system is tight and the pump in
DISCHARGE
COMPRESSOR
EFRIGERANT
NY 1003A
Fig. 54-Complete
System Charging
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