Make sure that all refrigerant gas has been discharged from the system before proceeding.
c. The inner end of each service valve is connected to the refrigeration piping with a flare nut. Disconnect by
unscrewing the flare nut.
d. Two screws and lock washers hold each valve body to the floor of the fresh air intake chamber. Gain access to
these screws by removing the condenser fan guard and impeller in the following manner.
(1) Remove eight screws and
lock washers from the rim
of the condenser fan guard, and remove the fan
Loosen two setscrews
in the hub
of the condenser fan impeller, and pull off the impeller. Use two jack-
screws in the threaded holes in the face of the hub if necessary to remove the impeller.
e. Remove two screws and lock washers from below each service valve body, and remove the valves.
Install the system service valves in the air conditioner as directed in the following procedure:
a. Screw the flare nut onto the connecting end finger tight.
b. Install two screws in each valve body through the floor of the fresh air chamber from below.
c. Tighten the flare nuts.
d. Replace the filter-drier, leak-test, evacuate and charge the system as instructed in paragraphs 5.53
Section XV. THERMAL EXPANSION VALVES
Two thermal expansion valves amused in the F18T-2 Air Conditioner. One meters liquid refrigerant into the evaporator
coil, through a distributor which disperses the liquid refrigerant into several parts of the coil. The other injects liquid
refrigerant into the recirculating gas in the bypass circuit to maintain the temperature of the gas below its extreme limit.
Both valves respond to temperature changes in the refrigerant suction line to which their remote bulbs are attached. The
effects of pressure-drop across the evaporator coil are canceled by a pressure equalization line from the evaporator
thermal expansion valve to the downstream (suction) end of the evaporator coil just beyond the sensing bulb. This
pressure equalization permits the valve to respond more quickly to temperature variations alone. Since pressure-drop in
the liquid quench circuit is insignificant, the liquid injection expansion valve is equalized internally. Both valves are
hermetically sealed to their sensing bulbs and capillary tubes.
To gain access to the two thermal expansion valves, and their associated sensing bulbs, proceed as follows:
a. Remove 18 screws and washers from the four sides of the fabric cover, and remove the cover.
b. Remove 15 screws and packing washers from the top surface of the top panel, and five screws from the rear
flange. Remove the top panel.
c. Remove eight screws and lock washers from the condenser from guard, and remove the fan guard.
d L o o s e n two setscrews in the hub of the condenser fan impeller, and pull off the impeller. Use two jackscrews
in the holes in the face of the hub to start removal, if-necessary.