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 TM 55-1905-220-14-8
4-29. AIR CONDITIONING SYSTEM - MAINTENANCE INSTRUCTIONS (Continued).
(c) The differential adjustment, inside the switch case, governs the cut-out point but does not
affect the cut-in point. Turning the differential screw clockwise widens the differential.
(d) Recommended switch settings are given in paragraph 4-29a.
Proceed as follows to set
switches:
1 Setting high pressure control switch.
a
Turn differential screw to minimum (counterclockwise) and range screw to high limit
(clockwise).
b Start compressor and control discharge pressure by throttling condenser water flow.
c Raise discharge pressure to about 10 psi (68.9 kPa) above cut-in point. Turn range screw
counterclockwise until contacts open, stopping compressor. When discharge pressure
drops to cut-in point, turn range screw slowly clockwise until contacts close, starting
compressor. The cut-in point is now set.
d
With the compressor running, turn differential screw (clockwise) to wide limit. Raise
discharge pressure to cut-out point and turn differential screw counterclockwise until
contacts open, stopping compressor. The cut-out point is now set.
e Control discharge pressure and check switch settings and operation.
2 Setting low pressure control switch.
a
Turn differential adjustment clockwise to maximum position and range screw
counterclockwise to low limit.
b Start compressor and control suction pressure by throttling the compressor suction stop
valve.
4-890
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