LOW OIL PRESSURE.-- An abnormally low oil
REFRIGERATION AND
AIR-CONDITIONING SYSTEMS
pressure will close the pressure switch (PS4) and, after
the relay (6TR) has closed, energize the relay (17CR).
As an EM, you must have a knowledge of the
The 17CR contacts close, illuminating the LOW OIL
refrigeration and air-conditioning systems. In this
PRESSURE light on the annunciator panel and
section, you will learn about starting, operating, and
energizing 2CR. The 2CR contacts initiate a safety
stopping some types of refrigeration systems.
shutdown and maintain the indication through 17CR.
LOW INJECTION WATER PRESSURE.-- An
abnormally low injection water pressure will close the
REFRIGERATION SYSTEM
pressure switch (PS3) and, if 6TR has closed, energize
the relay (16CR). The 16CR contacts close,
illuminating the LOW INJECTION WATER
The function of the ship's stores refrigeration
PRESSURE light on the annunciator panel and
system is to provide refrigeration in the freeze and chill
energizing 2CR. The 2CR initiates a safety shutdown
storerooms to preserve perishable foods. The
and maintains the indication through 16CR.
refrigerant is supplied by two refrigeration plants. The
plants can be operated singly or together.
LEVEL.-- An
HIGH
CONDENSATE
excessively high condensate level in the dehydrator
sump causes the level switch (LS6) to close, energizing
Plant Components
13CR and lighting the HIGH CONDENSATE LEVEL
light on the annunciator panel. The 13CR also energizes
STR, which will time closed to energize 2CR and initiate
Each plant consists of a 1. l-ton reciprocating
a safety shutdown.
compressor assembly, motor controller, condenser,
receiver, dehydrator, heat exchanger, gauge board, and
Whenever the compressor drive motor is shut down
associated controls. The refrigeration plants supply
by the de-energizing and opening of the motor contactor
refrigerant (R-12) to the cooling coils located in the
(M), the solenoid valves (SV1 and SV7) are
three storage spaces. The storage spaces are the freeze
simultaneously de-energized.
storeroom and two chill storerooms. The freeze
storeroom is maintained at 0F. The chill storerooms
Solenoid valve SV1 closes in the injection (fresh)
are normally maintained at 33F.
water supply line to stop the flow of injection
water to the compressor intake.
Table 5-3 contains a list of the safety control
switches, the magnetic relays, the contractors, and the
Solenoid valve SV7 opens in the condensate
indicating devices of the 1.1 -ton refrigeration
drain line to drain the condensate sump and
compressor assembly. It shows the location, functions,
repressurize the compressor.
and settings of the individual units.
MAINTENANCE
Plant Operation
Scheduled maintenance should be performed
according to the Planned Maintenance System (PMS).
The compressor can only be energized from the
motor controller, which is located in the auxiliary
machinery room or reefer flats. Besides providing
start/stop operation of the plant, the controller has a
SUMMARY
two-position selector switch labeled LOCAL and
NORMAL. The difference in plant operation between
The air compressor discussed in this section
the two positions is that in the NORMAL position the
contains information on the basic operating principles
plant can be shut down from either the remote or local
of most compressors seen in the Fleet. While the
location.
compressor aboard your ship may not be this type, the
To help you understand the refrigeration
principles discussed here should prove valuable to you
in maintaining those found aboard any ship.
plant operation, refer to the wiring diagram in
5-20
