TP-6811 7/16 57Section 4 Cooling System
4.10 Cooling Fans
4.10.1 Fan Operation
The generator cooling system includes three electric
fans to provide cooling air flow. See Figure 4-3 for the
fan locations. Two fans are mounted on the radiator
assembly to cool the engine jacket water circuit. The
third fan draws air through the generator enclosure to
remove heat generated by the alternator and radiant
heat from the engine.
The electric fans are powered by the 12 VDC starting
battery and engine-mounted battery charging
alternator. Each fan is protected by a 30 amp fuse. The
fans are operated in high-speed and low-speed modes
based on genset operating temperatures. The fan
operating speeds are driven by five relays controlled by
the RDC2 controller. The fuses and relays are housed in
the fuse/relay terminal block. See Figure 4-6.
The radiator fans are operated in low-speed mode by
configuring the relays to connect the two r adiator fans in
series across the 12-volt battery supply system,
supplying each fan approximately one-half the supply
voltage. For high-speed fan operation, the fans are
connected in parallel across the power supply,
supplying each fan the full 12-volt battery supply. The
RDC2 controls operating speed based on engine
coolant temperature. The fans are set to low-speed
mode on generator set startup (for a minimum of the first
10 seconds of operation). High-speed operation is
selected when the coolant temperature exceeds 93_C
(200_F). If the coolant temperature returns to an
operating temperature below 79_C (175_F), the fans
return to low-speed operation.
The engine compartment fan is operated in low-speed
mode by configuring the relays to connect the fan in
series with a power resistor which is housed within
protective covers behind the fuse/relay terminal block.
For high-speed fan operation, the fan is connected
directly across the 12 VDC battery supply. The RDC2
controls operating speed based on engine compartment
temperature, as measured by the engine compartment
temperature sensor located on the bulkhead wall
adjacent to the engine compartment fan. The fan is set
to low-speed mode on engine startup (for a minimum of
the first 10 seconds of operation). High-speed operation
is selected when engine compartment temperature
exceeds 57_C (135_F). If the engine compartment
temperature returns to an operating temperature below
46_C(115_F), the fan returns to low-speed operation.
Note: The engine compartment fan continues to run for
2 minutes after the engine stops to evacuate
residual engine and exhaust system heat.
1
GM78527
1. Fan fuse/relay box location
Figure 4-6 Fan Fuses and Relays
Sensor
Temperature, _C(_F)
High Speed Low Speed
Coolant 93 (200) 79 (175)
Engine
Compartment
57 (135) 46 (115)
Figure 4-7 Fan Operating Temperatures
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