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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.
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