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D. Removal and Replacement of Expansion Valve
Moisture in the refrigeration circuit may exceed drier capacity and freeze up at the
expansion valve.
CAUTION
1. Always install a new drier every time the sealed refrigeration system is
opened.
2. Do not replace the drier until after all other repair or replacement has been
made. Install the new drier with the arrow on the drier in the direction of the
refrigerant flow.
3. When brazing, protect the valve body and drier by using wet cloths to prevent
the valve body and drier from overheating. Do not allow the valve body or
drier to exceed 250°F (121°C).
1) Raise the front panel, then move the power switch to the "OFF" position and unplug the
unit.
2) Remove the evaporator case cover and panels.
3) Recover the refrigerant and store it in an approved container.
4) Remove the insulation and the expansion valve bulb on the suction line.
5) Remove the expansion valve cover and disconnect the expansion valve. Place the new
expansion valve in position.
6) Remove the drier, then place the new drier in position.
7) Braze all fittings while purging with nitrogen gas flowing at a pressure of 3 to 4 PSIG.
See "V.A.2. Brazing."
8) Use an electronic leak detector or soap bubbles to check for leaks. Add a trace of
refrigerant to the system (if using an electronic leak detector), and then raise the
pressure using nitrogen gas (140 PSIG). DO NOT use R-134a as a mixture with
pressurized air for leak testing.
9) Evacuate the system, and charge it with refrigerant. See "V.A.3. Evacuation and
Recharge (R-134a)." See the nameplate for the required refrigerant charge.
10) Attach the expansion valve bulb to the suction line in the same location as the previous
bulb. The bulb should be between the 10 and 2 o'clock position on the tube. Be sure to
secure the bulb with the clamp and holder and to insulate it.
11) Place the expansion valve cover in position.
12) Replace the evaporator case cover and panels in their correct positions.
13) Plug the unit back in. Move the power switch to the "ON" position.
14) Close the front panel.
