TEST - TM-5-4120-393-140254

TM 5-4120-393-14

5-20. Expansion Valve (Liquid Quench) (cont)

Set the TEMPerature control thermostat knob fully INCREASE (clockwise). Start the air conditioner in COOL mode.

Note that suction pressure drops to 58 2 psi (4.0 0.14kg/cm ). Allow compressor to run for at least 20 minutes. If

the pressure is not within the above limits, test the operation of the pressure regulator valve (see para 5-24) before

proceeding with quench valve test.

NOTE

Except in a very hot climate, with room temperature above 90 F (32.2 C), the

refrigeration system will be in a bypass cycle with a maximum volume of hot

discharge vapor being recirculated back to suction side of compressor through

pressure regulator valve and quench valve.

Observe that temperature indicated remains stable for a minimum of two minutes, then find saturation temperature for

pressure indicated on gage, using table 5-1. For example, the saturation temperature for a refrigerant pressure of 69

psig (4.85 kg/cm ) is 40 (4.4C).

Compare the saturation temperature with indicated temperature. The indicated temperature sho uld be 25 5F (13.9

2.2C) higher than the saturation temperature. If indicated temperature is not within above limits, quench valve is

not functioning properly and should be replaced.

Turn unit OFF.

Remove thermometer.

10. Reinstall and tape in place tubing insulation that was removed from suction line tubing. If it was damaged, replace

with tubing insulation, item 17, Appendix E.

11. Close service valve on unit.

12. Remove gages or service manifold from service valves.

13. Install valve stem and hose connection protective caps.

5-48