TM 9-4120-388-14
5-20. LIQUID QUENCH EXPANSION - Continued.
(4) Be sure that service valve and gage connection to low (suction) side are open. Note pressure indicated on
gage and temperature indicated on thermometer.
(5) Set the TEMPerature control thermostat knob to full INCREASE (clockwise). Start the air conditioner in
for at least 20 minutes. If pressure is not within above limits, test operation of pressure regulating valve
NOTE
Except in a very hot climate, with room air temperature above 90F (32.2C), the refrig-
eration system will be in a bypass cycle with a maximum volume of hot discharge vapor
being recirculated back to suction side of compressor through pressure regulator valve
and quench valve.
(6) Observe that temperature indicated remains stable for a minimum of two minutes, then find saturation tem-
perature for pressure indicated on gage, using Table 5-2. For example: The saturation temperature for a
refrigerant pressure of 69 psig (48.5 kg/mm2) is 40F (4.4C).
(7) Compare the saturation temperature with indicated temperature. The indicated temperature should be 255F
(13.9 2.2C) higher than the saturation temperature. For example: With a 40 saturation temperature, the
thermometer should read 65 5F. If indicated temperature is not within above limits, quench valve is not func-
tioning properly and should be adjusted:
NOTE
If valve does not need adjustment, skip (8) below.
(8) If the superheat setting is not within the limits shown above, adjust the liquid quench expansion valve as
follows:
(a) Remove the hexagonal seal cap from the side of the power assembly.
(b) Turn the adjusting stem two complete turns to change the superheat setting by 1F (0.55C). Turn the
stem clockwise to increase superheat span; counterclockwise to decrease it. Do not change more
than two full turns at one time, then wait at least 2 minutes for temperature to stabilize and recheck
pressure and temperature before further adjustment. If valve cannot be properly adjusted, replace the
valve.
(c) When the proper setting is obtained, install the seal cap.
(9) Turn unit OFF.
(1O) Remove thermometer.
(11 ) Cover the sensing bulb and suction line with insulation tubing that was removed in step (2) above. Secure
tubing in place using tape (item 14, Appendix E.)
(12) Close service valves on unit.
(13) Remove gages or service manifold from service valves.
(14) Install hose connection protective caps.
(15) Secure service valve cover with four screws and flat washers.
Removal.
c.
(1) Discharge the refrigerant system per paragraph 5-7.
(2) Unwrap insulation tubing from suction line so that sensing bulb is exposed. Note location and position of
bulb for reinstallation. Loosen screws and nuts in clamps. Pull bulb out of clamps.
(3) Remove two cap screws, Iockwashers, flat washers, and spacers that attach valve body to bracket and
power assembly.
5-45
