Engine Protective Devices; Coolant Temperature Sensing; Low Coolant Level; Oil Pressure Sensing - Generac Power Systems QT 5.4L Owner's Manual

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.
Engine protective switches and sensors are men-
tioned here for the reader's convenience. Also refer
to the applicable control panel manual for addi-
tional automatic engine shutdown information.

COOLANT TEMPERATURE SENSING

An analog Water Temperature Sender (WTS) is locat-
ed in the engine's cooling system. This sender is con-
nected to the panel and allows the panel to monitor
and display the temperature of the coolant system.
The WTS is a resistive device whose resistance chang-
es based on coolant temperature. The resistance of
the sender results in a voltage being developed across
the sender. As the Coolant temperature increases,
the resistance will decrease, causing the voltage to
decrease. This changing voltage is converted to 4-
20mA signal by a signal conditioner module. The
corresponding 4-20mA signal is read by the control
panel and displayed as the coolant temperature.
The control panel will monitor and display the cool-
ant temperature anytime the DC input to the control
panel is present.
If the temperature exceeds approximately 140° C
(284° F), the engine shutdown will be initiated. The
generator will automatically restart and the display
will reset once the temperature has returned to an
operating level.

LOW COOLANT LEVEL

A Low Coolant Level (LCL) sensor is placed in the
generators coolant system. This sensor allows the
panel to detect a Low Coolant Level condition.
The LCL is a resistive device whose resistance changes
rapidly based on the presence or absence of coolant.
The resistance of the LCL results in a voltage being
developed across the LCL. This voltage changes as
the resistance changes. This changing voltage is con-
verted to 4-20mA signal by a signal conditioner mod-
ule. The corresponding 4-20mA signal is read by the
control panel and displayed as the low coolant level.
If the level of the engine coolant drops below the level
of the low coolant level sensor, the engine shutdown
will be initiated.
Standby Generator Sets
Engine Protective Devices
NOTE:

OIL PRESSURE SENSING

An analog Oil Pressure Sender (OPS) is used for
monitoring the engine oil pressure. This sender
allows the control panel to measure and display the
Engine oil pressure.
The OPS is a resistive device, whose resistance
changes based on engine oil pressure. The resistance
of the sender results in a voltage being developed
across the sender. As the oil pressure increases,
the resistance will decrease, causing the voltage to
decrease. This changing voltage is converted to 4-
20mA signal by a signal conditioner module. The
corresponding 4-20mA signal is read by the control
panel and displayed as the oil pressure.
The control panel will monitor and display oil pres-
sure anytime the DC input to the control panel is
present.
Should the oil pressure drop below the 8 psi range,
the engine shutdown is initiated. The unit should not
be restarted until oil is added. Turn the AUTO/OFF/
MANUAL switch to the OFF position, then back to
AUTO to restart.

OVERCRANK SHUTDOWN

When the control panel receives a start signal, it ini-
tiates the programmed starting sequence. The start
sequence consists of the number of crank attempts,
the length of each crank attempt, and the rest time
between each crank attempt. If the engine has not
started by the end of the final crank attempt, an
Overcrank alarm is generated, the control panel will
sound the alarm and display the message "Failed to
start".

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 over speed 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.)
4-1
10/05 B Rev. EngProt002