Section 4: Optional Idle Control; General; Operating Instructions; Before Start-Up - Generac Power Systems GN190H Service And Repair Manual

SECTION 4: OPTIONAL IDLE CONTROL

GENERAL

Some applications, such as generators, may be equipped
with an automatic idle control system. This type of system
provides greatly improved fuel economy by running the
engine at high governed speed only when electrical loads are
connected to the generator. When the electrical loads are dis-
connected, engine speed will automatically be reduced to idle.

OPERATING INSTRUCTIONS

BEFORE START-UP:

CAUTION! Before cranking and starting the engine,
always set the idle control switch to STOP. Set the
switch to its RUN position only after the engine has
stabilized at high governed speed (see Figure 4.1).

ENGINE RUNNING:

To have the engine run at high governed speed only when
electrical loads are connected and turned on, set the idle con-
trol switch to ON. The engine wiIl 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 electrical loads connected), set the idle control switch
to OFF (Figure 4.1).
Figure 4.1 — Idle Control Switch
STATOR POWER WINDINGS
11
44X
TRANSFORMER
11X
11A
SWITCH
A. Schematic
ON
OFF
22
44
33
44
44X
22
COIL (MAGNET)
156
155
81
110
CIRCUIT
BOARD
Figure 4.2 — Idle Control System (Typical AC Generator)
1. 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, current
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
delivered 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.
f. Zero current flow of the transformer secondary wind-
ings is sensed by the circuit board. The circuit board then
closes the circuit to the idle control solenoid. The sole-
noid energizes.
g. The energized solenoid pulls the carburetor throttle arm
against its idle speed stop screw. The engine decelerates
to idle speed, about 2,280-2,400 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.
82
B. Pictorial
22

CIRCUIT OPERATION

155
156
TRANSFORMER
CIRCUIT
BOARD
SWITCH
22
11A
COIL
11X 44