3-2
Unit Instruments
Operating Instructions
CRR-20 & CRR-40, September 1999
condenser coil temperature input to cycle the
condenser fan between ON and OFF.
2.
WATER PRESSURE SWITCH (OPTION). When water
pressure greater than 117 +/- 21, 1.17 +/- 0.21 bar, 17 +/-
3 psig is provided to the condenser-receiver tank, the
water pressure switch opens. This causes the controller to
stop condenser fan operation. When the water pressure
decreases below 35 +/- 21 kPa, 0.35 +/- 0.21 bar, 5 +/- 3
psig, the switch closes, causing the controller to place the
unit on air-cooled condenser fan operation.
NOTE: Water-cooled condenser operation
requires a water flow of 19 to 38 l/min. (5 to 10
gal./min.).
Unit Instruments
1.
STATUS INDICATOR LEDs are located on the
µ
P-D
controller and signal the following:
• Cool
• Defrost
• Modulation
• Supply
• Null
• Return
• Heat
• Power Limit
• In-Range
• Alarm
The In-range LED illuminates when the controlling
air sensor temperature is between 1.7 C (3.0 F) above set-
point and 2.5 C (4.5 F) below setpoint. The controller
inhibits the out-of-range alarm during defrost.
NOTE: The controller will not respond to an out-
of-range condition for 75 minutes to avoid nui-
sance alarms.
2.
RECEIVER TANK SIGHT GLASS. A sight glass on the
receiver tank contains three small balls that indicate the
level of refrigerant in the tank for checking the refrigerant
charge. A moisture indicator in the sight glass changes
color to indicate the level of moisture in the system.
Check the color of the indicator against the color decal in
the sight glass. The dry eye in the sight glass is LIGHT
GREEN when the system is dry and YELLOW when the
system is wet (contains excessive moisture).
3.
COMPRESSOR OIL SIGHT GLASS. A compressor oil
sight glass indicates the relative level of compressor oil in
the compressor sump.
4.
SUCTION PRESSURE GAUGE (OPTION). A suction
pressure gauge indicates the refrigerant pressure in the
suction line returning to the compressor. See “Normal R-
134a System Suction Pressures” table in the Refrigeration
Maintenance and Service Operations chapter for normal
suction pressure readings.
5.
DISCHARGE PRESSURE GAUGE (OPTION). A dis-
charge pressure gauge indicates the refrigerant pressure in
the discharge line leaving the compressor.
6.
THERMISTOR LEAD (OPTION). A thermistor lead is
located in the unit control box to provide air temperature
verification. The bulb of the thermistor lead is attached to
the return or supply air sensor in the evaporator section.
7.
REMOTE MONITOR CONNECTOR, 4-PIN (OPTION).
A receptacle is provided on the side of the control box for
connecting the ship’s 4-pin bridge light system to the unit.
The connector provided circuits for Compressor On,
Defrost and In-range. The remote in-range light is activat-
ed when the controlling air sensor temperature is between
1.7 C (3.0 F) above setpoint and 2.5 C (4.5 F) below set-
point.
8.
RECORDING THERMOMETER (OPTION). The
recording thermometer indicates and permanently records
the temperature of the air returning to the evaporator sec-
tion on a calibrated chart.
9.
POWER LINE COMMUNICATIONS MODEM
(OPTION). Several models remote monitoring modems
are available to provide remote monitoring via the power
cable. High speed transmission reads all controller infor-
mation.
• Thermo King modem is installed in a self-enclosed box
bolted above the compressor.
• Sabroe Controls modem is installed in the electrical con-
trol box.
• RTE modem is installed in the electrical control box.
Receiver Tank Sight Glass
1.
Moisture Indicator:
Light Green = Dry
Yellow = Wet
2.
Outer ring is color coded. Compare to indicator.
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