TM 9-4110-258-13
2.1 OPERATING CONTROLS AND INDICATORS. - Continued
4
Thermometer (REFRIGERATION TEMPERATURE). Indicates the refrigerator enclosure temperature. The
thermometer should indicate within 15F (7C) of the temperature set on the remote bulb thermostat.
5
Pressure Gauge (DISCHARGE PRESSURE). Indicates the pressure of the refrigerant gas leaving the
compressor. The pressure gauge should generally indicate between 165 and 250 psi (1138 and 1725 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 Gauge (SUCTION PRESSURE). Indicates the pressure of the refrigerant gas entering the
compressor. The compound gauge should generally indicate between 0 and 15 psi (O and 103.5 kPa), at
shutdown and/or operation in 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 in 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 in 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 and 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.
11
Indicator (REFRIGERATION CYCLE ON). Indicates, by illuminating when the refrigeration cycle is on
12
Indicator (HEATING CYCLE ON). Indicates, by illuminating when the heating cycle is on.
2-2
