TM 9-4120-371-14
NOTE
The optimum superheat setting for the evaporator expansion valve is 10F (5.55C)
above the saturation temperature of the refrigerant at operating suction line pressure.
This setting will provide maximum efficiency of the evaporator coil.
(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 metalto-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) Re-wrap 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 (counter
clockwise) 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 51.) and compare with the thermometer
reading. The thermometer temperature should be 101F (5.550.55C) 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 1F (0.55C).
Turn the stem clockwise to increase superheat span; counter clockwise 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) If the proper setting is obtained:
Turn unit OFF.
(a)
Replace hexagonal seal cap.
*(b)
Remove thermometer.
(c)
(d)
Cover the bulb and suction line with insulation tubing and secure with tape, item 11, Appendix E.
Close service valves on unit.
(e)
(f)
Remove gages or service manifold from service valves.
Install hose connection protective caps.
(g)
(h)
Using screwdriver, secure service valve cover with four screws and flat washers.
**(14) If the superheat reading is not within the limits of step (11) above, replace expansion valve.
*Effective for Keco Model F18T-2S, and A.R.E. Model CVP-20-5/6-08.
**Effective for Keco Model F1 8T-2SA.
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