ARMY TM 9-6115-604-12
NAVY NAVFAC P-8-633-12
Coolant Level Warning Switch S13. Coolant level warning switch S13 is a solid state capacitor activated
device that is mounted near the top front of the radiator and is visible when the radiator shutter is opened.
Proper radiator coolant level holds the normally closed switch open. If coolant falls below proper level,
switch S13 closes to energize coolant level alarm slave relay K22 Relay K22 will energize annunciator
alarm system. Annunciator horn LS1 sounds and annunciator panel light A9DS15 flashes while the
generator set continues to run.
Coolant Level Shutdown Switch S14. Coolant level shutdown switch S14 is a solid state capacitor
activated device that is mounted near the top front of the radiator and is visible when the radiator shutter is
opened. Proper radiator coolant level holds the normally closed switch open. To an extent, a below
normal coolant level will also hold the switch open. If coolant level falls to a level that the coolant
temperature switch WT2 is compromised, coolant level shutdown switch S14 will close to energize coolant
level shutdown relay K21. Relay K21 does not trip an annunciator system circuit. An alarm will have
already been annunciated as a result of the closing action of coolant level warning switch S13. Instead,
relay K21 energizes fault shutdown relays K20A and K20B directly. Relays K20A and K20B shut down the
generator set as described in step (4), above.
Coolant Temperature Warning Switch WT2. Coolant temperature warning switch WT2 is mounted on the
thermostat housing on the left side of the engine. If coolant temperature rinses to 206 to 216°F (97 to
99 C), the normally open switch WT2 will close to energize self-latching relay A10K3 in the annunciator
alarm system. Horn LS1 will sound and annunciator panel light A9DS3 will flash while the generator set
continues to run. The operator is expected to investigate the cause for the alarm and, If possible, effect a
remedy before coolant temperature rises high enough to trigger a generator set shutdown via coolant
temperature shutdown switch WT1. Probable causes for high coolant temperature include restricted air
flow to the radiator, a broken engine fan belt, blockage In the cooling system, a malfunctioning water
pump, or overload. Regarding air flow restrictions, the operator should be sure that the radiator louvers
are open to allow exhaust air to exit and that the shutter door assemblies are open to admit air.
Coolant Temperature Shutdown Switch WT1. Coolant temperature shutdown switch WT1 is mounted on
the thermostat housing on the left side of the engine. If coolant temperature rises to 215 to 219°F (102 to
104°C), the normally open switch WT1 will close to energize fault shutdown relays K20A and K20B.
Relays K20A and K206 shut down the generator set as described in step (4), above. Coolant temperature
shutdown switch WT1 does not trip an annunciator alarm system circuit. An alarm will have already been
annunciated as a result of the closing action of coolant temperature alarm switch WT2.
Fuel Level Transmitter MT4. Fuel level transmitter MT4 is mounted through the top of the generator set fuel tank
and is accessible through the floor of the control room. MT4 is a float-actuated potentiometer in series between
battery ground and FUEL LEVEL gage M4 on cabinet C door. The resistance of MT4 will vary from 0 ohms to 30
ohms as the fuel level vanes from full to empty. The resultant variation in dc current through FUEL LEVEL gage
M4 is used to provide a visual indication of fuel level.
Generator Set Shutdown Circuits. The generator set may shut down automatically in response to a fault
condition signal from the DC or AC system, or it may be shut down manually. DC shutdown circuits are
described in step d, above. AC shutdown circuits are described in paragraph 4-33. Manual shutdown methods
are explained below. There are three ways to manually shut down the generator set by using MASTER SWITCH
S9 on cabinet C door; by using EMERGENCY SHUTDOWN pushbutton S7 on cabinet C door, and by using the
EMERGENCY SHUT- DOWN control on the skid base. The following steps describe the operation of these
MASTER SWITCH S9. MASTER SWITCH S9 is located on cabinet C door and is used to shut down the
generator set in accordance with Chapter 2 of this manual. Setting switch S9 to STOP will disconnect battery
positive from generator set DC control circuits.
The following events occur immediately and simultaneously.
Shutdown relay K14 will be connected to battery positive through switch S9, the relay will energize
and latch for as long as engine speed remains above 1200 rpm. Normally closed contacts of relay
K14 will open to cut off battery positive from generator set DC control circuits.