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TM5-4120-377-14
NOTE
The optimum superheat setting for the evaporator expansion valve is
the saturation temperature of the refrigerant at operating suction
setting will provide maximum efficiency of the evaporator coil.
10°F (5.55°C) above
line pressure. This
(7) Slip the sensing bulb into its mounting loop clamps. Be sure the bulb is installed in its original
position and tighten the nuts and screws. Be sure the sensing bulb is making metal-to-metal contact with the
suction line.
(8) Attach an accurate thermometer to an exposed surface of the suction return line adjacent to the
sensing bulb; use a small gob of thermal mastic to improve conductivity.
(9) Rewrap insulation on the suction return line, being sure to cover the sensing bulb.
(10) Start the air conditioner in the COOL mode with the thermostat set at fully DECREASE
(counterclockwise) and allow it to run about 30 minutes, then check to be sure the temperature in the suction
line has stabilized and the thermometer reading remains unchanged for at least 2 minutes.
(11) Note the pressure on the gage connected to the low pressure (suction) service valve. Find the
saturation temperature for the pressure gage reading (See table 5-1.) and compare with the thermometer
reading. The thermometer temperature should be 10 ± 1°F (5.55 ± 0.55°C) higher than the saturation
temperature found on the chart.
(12) If the superheat setting is not within the limits shown above, adjust the 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 1°F (0.55°C). 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.
(13) When the proper setting is obtained:
(a)
(b)
(c)
(d)
Turn unit OFF.
Replace hexagonal seal cap.
Remove thermometer.
Cover the bulb and suction line with insulation tubing.
Secure insulation tubing with tape, item 11, Appendix E.
(e) Close service valves on unit.
(f) Remove gages or service manifold from service valves.
(g) Install hose connection protective caps.
(h) Using screwdriver, secure service valve cover with four screws and flat washers.
c. Removal
(1) Discharge the refrigerant system per paragraph 5-6.
(2) Unwrap insulation from suction line so that sensing bulb is exposed. Loosen screws and nuts in
clamps. Pull bulb out of clamps.
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