Generac Power Systems OHVI GSH 190, Service Manual, Page: 23 / 72

5-1
SeCTIoN 5: oPTIoNAl Idle CoNTrol
GeNerAl
Some applications, such as AC generators, may be equipped
with an automatic idle control system. This type of system pro-
vides greatly improved fuel economy by running the engine at a
high governed speed only when electrical loads are connected
to the generator. When the electrical loads are disconnected,
engine speed will automatically be reduced to an idle.
oPerATING INSTruCTIoNS
BEFORE START UP
*
CAuTIoN! before cranking and starting the engine,
always set the idle control switch to oFF. Set the
switch to its oN position only after the engine has
stabilized at high governed speed (see Figure 5 .1).
ENGINE RUNNING:
To have the engine run at high governed speed only when
electrical loads are connected and turned on, set the idle
control switch to ON. The engine will decelerate to idle speed
when loads are disconnected or turned off. If you wish to have
the engine run at high governed speed at all times (with or
without loads connected), set the idle control switch to OFF.
ON
OFF
Figure 5-1. Idle Control Switch Located on a
Generator Control Panel
CIrCuIT oPerATIoN
. With Idle Control switch set to ON:
a. AC power is delivered from the generator’s AC power
windings to a circuit board, for operation of the circuit
board.
b. With electrical loads connected to the generator, cur-
rent will flow through the primary windings of a sensing
transformer. A proportional voltage and current will then
be induced into the transformer’s secondary windings.
c. Current from the transformer secondary windings is deliv-
ered to the circuit board. Circuit board action then opens
the circuit to an idle control solenoid.
d. The idle control solenoid de-energizes and engine speed
is established by the engine governor.
e. When electrical loads are disconnected or turned off, cur-
rent flow through the transformer primary windings will
terminate. Voltage and current cannot be induced into
the transformer secondary windings and the solenoid
energizes.
f. Zero current flow of the transformer secondary windings
is sensed by the circuit board. The circuit board then closes
the circuit to the idle control solenoid.
g. The energized solenoid pulls the carburetor throttle arm
against its idle speed stop screw.
The engine decelerates
to idle speed, about 2280-2400 rpm (38-40 Hertz).
2. Idle control switch set to OFF:
a. AC power is not available to the circuit board. The idle
control solenoid will then remain de-energized at all
times.
b. The engine will run at high governed speed.
A. Schematic B. Pictorial
44X
44X
44
44 33
11X
11A 110
155
81
82
22
11
22
156
STATOR POWER WINDINGS
CIRCUIT
BOARD
COIL (MAGNET)
TRANSFORMER
SWITCH
TRANSFORMER
CIRCUIT
BOARD
SWITCH
COIL
22
11A
11X 44
155
156
Figure 5-2. Idle Control System (Typical AC Generator)
5
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