Removal. - TM-5-4110-234-140157

TM5-4110-234-14

TO 40R7-5-7-1

(1)

Remove insulation from a spot on the suction line near the sensing bulb of the expansion valve.

(2) Install an accurate thermometer or the probe of a thermocouple on the bare spot, using a small amount

of thermal mastic, if available, to improve conductivity. Tap the thermometer bulb or thermocouple junction in position.

Cover with insulating material.

(3)

Adjust suction crank case pressure regulating valve so that it is wide open.

(4) Operate the unit for approximately 30 minutes and take a reading from the thermometer or

thermocouple on the suction line.

(5) Take a reading from the suction pressure gage on the control panel. Add two pounds to the reading to

allow for the pressure drop in the suction line. This sum will equal the approximate suction line pressure at the sensing

bulb.

(6) Convert pressure obtained in step (5) to saturated evaporator temperature by using a temperature-

pressure chart. See Table 5-1.

(7)

Subtract the temperature obtained in step (6) from temperature obtained in step (4). The difference is

superheat.

NOTE

Subtracting the difference between the temperature at the inlet and outlet of the evaporator is not an

accurate measure of superheat. This method is not recommended since any evaporator pressure drop

will result in an erroneous superheat indication.

(8) Remove the protective cap from the expansion valve (fig. 5-8). Use two wrenches, one on the cap, and

one on the hex of the valve body.

(9) To reduce superheat, turn the adjusting stem counterclockwise; to increase superheat, turn stem

clockwise. Make no more than one turn of the stem at a time and observe the change in superheat closely to prevent

overshooting the desired setting. As much as 30 minutes may be required for the new balance to take place after an

adjustment is made. The correct superheat setting for this unit is 6 degrees F (3.30C).

(10) Replace the protective cap on the valve adjusting stem.

(11) Remove the thermometer or the thermocouple probe from the suction service line and replace the

insulating material. Adjust the crankcase pressure regulating valve per paragraph 5-25 b.

Removal.

(1)

Pump down the system (para 5-6).

(2)

Slowly disconnect flare fittings from expansion valve to release any remaining refrigerant pressure.

(3)

Note the position of the sensing bulb and loosen the clamp holding thermal bulb to suction line.

Remove the bulb.

(4)

Remove expansion valve.

Installation.

(1)

Connect the expansion valve to the system by tightening the flare fittings.

(2)

Insert the thermal bulb in the clamp in the same position as the one that was removed. Make sure it

makes good contact with the suction line. Tighten the clamp.

(3)

Replace the drier (See para 5-19.)

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