TM 9-4110-254-14
2-1. OPERATING CONTROLS AND INDICATORS. - Continued
5 Pressure Gage (DISCHARGE PRESSURE). Indicates the pressure of the refrigerant gas leaving the
compressor. The pressure gage should generally indicate between 160 and 270 psi (1104 and 1863 kPa), at
start up and/or operation in high temperatures, this range can go higher. The inner scale indicates the
temperature of the refrigerant at any given pressure.
6 Compound Gage (SUCTION PRESSURE). Indicates the pressure of the refrigerant gas entering the
compressor. The compound gage should generally indicate between 0 and 15 psi (0 and 104 kPa), during
pump down and/or operation m low temperatures, this range can go lower. The inner scale indicates the
temperature of the refrigerant at any given pressure.
7 Sight Indicator (REFRIGERANT SIGHT GLASS). Provides a port through which the refrigerant may be
observed as it passes through the liquid line of the refrigeration system. The center indicator changes color
as it reacts to moisture m the refrigerant. The sight indicator port should be clear, indicating liquid refrigerant
passing through it. An occasional flash of bubbles is normal as the refrigerant system automatically adjusts to
changing conditions. The center indicator should be green or chartreuse m color.
8 Sight Glass (COMPRESSOR OIL SIGHT GLASS). Provides a port through which the oil level in the
compressor may be observed The sight glass port should show an oil level between 1/4 and 1/2 up the port.
Bubbles in or on the oil surface is normal.
9 Hourmeter (HOURMETER). Indicates the total number of hours the compressor has operated.
10 Indicator (DEFROST IN PROGRESS). Indicates, by illuminating, when the refrigeration unit is operating in a
defrost cycle.
2-2
