Siemens SG020 - Manual (Page 8)

ENGINE PROTECTIVE DEVICES
The standby generator may be required to operate for
long periods of time without an operator on hand to
monitor such engine conditions as coolant tempera-
ture, oil pressure or rpm. For that reason, the engine
has several devices designed to protect it against
potentially damaging conditions by automatically
shutting down the unit when the oil pressure is too
low, the coolant temperature is too high, the coolant
level is too low, or the engine is running too fast.
NOTE:
Engine protective switches and sensors are men-
tioned here for the reader’s convenience. Also
refer to the applicable control panel manual for
additional automatic engine shutdown informa-
tion.
HIGH COOLANT TEMPERATURE SWITCH
This switches contacts close if the temperature should
exceed approximately 140° C (284° F), initiating an
engine shutdown. The generator will automatically
restart and the LED will reset once the temperature
has returned to a safe operating level.
LOW COOLANT LEVEL SENSOR
Should the engine coolant level drop below the level
of the high coolant temperature switch, it is possible
for the engine to overheat without automatic shut-
down. To prevent such overheating, the engine has a
low coolant level sensor. If the level of engine coolant
drops below the level of the low coolant level sensor,
the engine automatically shuts down.
LOW OIL PRESSURE SWITCH
This switch has normally closed contacts that are
held open by engine oil pressure during cranking and
operating. Should oil pressure drop below the 8 psi
range, switch contacts close, and the engine shuts
down. The unit should not be restarted until oil is
added, and the AUTO/OFF/MANUAL switch must be
turned to OFF and then back to AUTO.
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OVERCRANK SHUTDOWN
After a prespecified duration of cranking, this func-
tion ends the cranking if the engine has failed to
start. The overcrank LED will turn ON. Turn OFF the
AUTO/OFF/MANUAL switch, then turn switch back to
AUTO to reset the generator control board.
NOTE:
If the fault is not corrected, the overcrank feature
will continue to activate.
Approximate Crank Cycle Times
• 15 seconds ON
• 7 seconds OFF
• 7 seconds ON
• 7 seconds OFF
• Repeat for 45 seconds
Approximately 90 seconds total.
OVERSPEED SHUTDOWN
A speed circuit controls engine cranking, start-up,
operation and shutdown. Engine speed signals are
delivered to the circuit board whenever the unit is
running. Should the engine overspeed above a safe,
preset value, the circuit board initiates an automatic
engine shutdown. Contact the nearest Authorized
Dealer if this failure occurs.
RPM SENSOR LOSS SHUTDOWN
If the speed signal to the control panel is lost, engine
shutdown will occur.
DC FUSE
This fuse is located inside of the control panel. It
protects the panel wiring and components from
damaging overload. Always remove this fuse before
commencing work on the generator. The unit will
not start or crank if the fuse is blown. Replace the
fuse with one of the same size, type, and rating. (See
the exploded views and parts lists at the end of this
manual for replacement part number.)
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4-1
Standby Generator Sets
Engine Protective Devices
EngProt001 Rev. 0 08/05