Generac Power Systems 8 kW LP - Manual (Page 27)

GENERAL INFORMATION
sEctioN 1.6
ENGiNE-GENErator ProtEctiVE DEVicEs
General
Standby electric power generators will often run
unattended for long periods of time. Such operating
parameters as (a) battery voltage, (b) engine oil pres-
sure, (c) engine temperature, (d) engine operating
speed, and (e) engine cranking and startup are not
monitored by an operator during automatic operation.
Because engine operation will not be monitored, the
use of engine protective safety devices is required to
prevent engine damage in the event of a problem.
Generator engines mount several engine protec-
tive devices. These devices work in conjunction with
a circuit board, to protect the engine against such
operating faults as (a) low battery, (b) low engine oil
pressure, (c) high temperature, (d) overspeed, and
(e) overcrank. On occurrence of any one or more of
those operating faults, circuit board action will effect
an engine shutdown.
loW Battery
The microprocessor will continually monitor the bat-
tery voltage and turn on the Low Battery Warning
if the battery voltage falls below 10.8 volts for one
(1) minute. No other action is taken on a low battery
condition. Low battery voltage is a non-latching alarm
which will automatically clear if the battery voltage
rises above 11.0 volts. Battery voltage is NOT moni-
tored during the crank cycle.
loW oil preSSure ShutdoWn
See Figure 1. An oil pressure switch is mounted on
the engine oil filter adapter. This switch has normally
closed contacts that are held open by engine oil pres-
sure during cranking and startup. Should oil pressure
drop below approximately 5 psi, the switch contacts
will close. On closure of the switch contacts, a Wire
86 circuit from the circuit board will be connected to
ground. Circuit board action will then de-energize
a “run relay” (on the circuit board). The run relay’s
normally open contacts will then open and a 12 volts
DC power supply to a Wire 14 circuit will then be
terminated. This will result in closure of a fuel shutoff
solenoid and loss of engine ignition.
hiGh temperature SWitch
This switch’s contacts (Figure 1) close if the tempera-
ture should exceed approximately 144° C (293° F),
initiating an engine shutdown. The generator will auto-
matically restart and the fault on the generator control
panel will reset once the temperature has returned to
a safe operating level.
oVerSpeed ShutdoWn
During engine cranking and operation, the circuit
board receives AC voltage and frequency signals
from the ignition magneto, via Wire 18. Should the
speed exceed approximately 72 Hz (4320 rpm),
circuit board action will de-energize a “run relay”
(mounted on the circuit board). The relay’s contacts
will open, to terminate engine ignition and close a
fuel shutoff solenoid. The engine will then shut down.
This feature protects the engine-generator against
damaging overspeeds.
note: the circuit board also uses rpm sensing to
terminate engine cranking.
rpm SenSor Failure
During cranking, if the board does not see a valid
RPM signal within three (3) seconds, it will shut down
and latch out on RPM sensor loss.
During running, if the RPM signal is lost for one full
second the board will shut down the engine, wait 15
seconds, then re-crank the engine.
• If an RPM signal is not detected within the first three
(3) seconds of cranking, the control board will shut
the engine down and latch out on RPM sensor loss.
• If the RPM signal is detected the engine will start
and run normally. If the RPM signal is subsequently
lost again, the control board will try one more re-
crank attempt before latching out and flashing the
overspeed LED or RPM Sensor Failure.
OIL FILTER
OIL
DRAIN
HOSE
LOW OIL SWITCH HIGH TEMP SWITCH
LOOS
EN
Figure 1. Engine Protective Switches on an
Air-Cooled Engine
Part 1
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