Section 1 - General Information; Equipment Description; Engine Protective Devices; Coolant Temperature Sensor - Generac Power Systems PowerManager PM-GC Manual

1.1

EQUIPMENT DESCRIPTION

In a typical standby system, a power outage will be
sensed by a transfer switch. A time delay is usually
incorporated in this signal in order to prevent nui-
sance tripping of the power system. After the time
delay has been met, the transfer equipment will send
a start signal to the generator. Once the generator is
up to speed and it's voltage and frequency are stable,
the transfer switch will automatically disconnect from
the utility bus and transfer the load to the generator
(emergency) bus. When the utility supply returns, the
load is transferred back to the utility bus after a pre-
set user selectable time. The generator will then begin
a "cool-down" cycle and shutdown.
1.2

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. Refer to
the control panel paragraphs for additional auto-
matic engine shutdown information.
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1.2.1 COOLANT TEMPERATURE SENSOR

The coolant temperature is monitored by the control
panel. If coolant temperature rises above a safe, pre-
set level the control system automatically shuts down
the engine.
◆

1.2.2 LOW COOLANT LEVEL SENSOR

If the engine coolant level drops below a safe level, it
is possible for the engine to overheat without auto-
matic shutdown. 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 control system automatical-
ly shuts down the engine.
◆

1.2.3 OIL PRESSURE SENSOR

The control system monitors engine oil pressure dur-
ing operation. If oil pressure drops below a safe level,
the system automatically shuts down the engine.
4 Generac ® Power Systems, Inc.
Section 1 — General Information
PM-GC
NOTE:
◆

1.2.4 OVERSPEED SHUTDOWN

The control system monitors engine speed during
engine cranking, start-up, operation and shutdown.
Engine speed signals are delivered to the control sys-
tem whenever the unit is running. If the engine speed
exceeds a safe, preset value, the system automatical-
ly shuts down the engine.
◆

1.2.5 OVERCRANK SHUTDOWN

After a pre-specified duration of cranking, this func-
tion ends the cranking if the engine has failed to start.
◆

1.2.6 RPM SENSOR LOSS SHUTDOWN

If the speed signal to the control panel is lost, engine
shutdown will occur.
1.3

DC FUSES

The fuses are located on the inside of the relay box.
They protect the panel wiring and components from
damaging overload. If a fuse is missing or damaged,
the power module may not start or crank. The fuses
must be replaced with fuses of the same size, type,
and rating as originally provided by Generac.
1.4

CONTROL SYSTEM COMPONENTS

◆

1.4.1 AVR POWER MODULE

The AVR power module houses the power electronics
that drive the field of the alternator. The PM-GC actu-
ally controls the field and the AVR module converts
the PM-GC output signals to required power levels.
The AVR module controls the output voltage and
voltage stability of the generator. The Dynamic
response of these parameters can only be adjusted
via Genlink with the correct security password. Each
engine has its own AVR module.

1.4.2 THROTTLE ACTUATOR MODULE

The Throttle Actuator Module houses the power elec-
tronics that drive the throttle actuator. Again, the PM-
GC actually controls the throttle actuator and the
Throttle Actuator Module converts the PM-GC output
signals to required power levels. This module con-
trols the engine speed and stability, nominally set at
60 hertz. The speed and dynamic response of these
parameters can be adjusted via Genlink. However,
the dynamic response parameters are protected by
security password.

1.4.3 BATTERY CHARGER

The engine is provided with a Generac battery charg-
er. The battery charger must be wired by the cus-
tomer to a separate 120 VAC standard utility supply.