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Page Title: EXPANSION VALVE CONT.
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TM5-4120-387-14 (6) With one hand still on the suction return line, remove the sensing bulb from the container and warm it in the other palm. If a temperature drop is not felt in the suction return line by the time the sensing bulb no longer feels cold to the hand, the expansion valve is not opening and should be replaced. As soon as a temperature drop is felt, turn the air conditioner to OFF. NOTE The  optimum  superheat  setting  for  the  evaporator  expansion valve is 10°F (5.55°C) 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 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 ±l°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) Turn unit OFF. (b) Replace hexagonal seal cap. 5-60

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