Generac Power Systems 004920-0 Owner's Manual page 9

1.12.1 LOW OIL PRESSURE SWITCH
This switch is normally-closed (N.C.) but is held open
by engine oil pressure during engine running. Should
operating oil pressure drop below about 8-10 psi
(55-68 kPa), the switch contacts close and the engine
shuts down automatically (Figure 1.6).
Figure 1.6 - Low Oil Pressure Switch
1.12.2 HIGH COOLANT TEMPERATURE
SWITCH
This normally open (N.O.) thermostatic switch has
sensing tip which is immersed in captive coolant.
Should coolant temperature exceed about 230°F
(110°C), the switch contacts close, which causes the
engine to shut down automatically (Figure 1.7).
Figure 1.7 - High Coolant Temperature Switch
1.12.3 LOW COOLANT LEVEL SWITCH
Should engine coolant level drop below the level of
the high coolant temperature switch, it is possible for
the engine to overheat without automatic shutdown.
To prevent such overheating without automatic shut
down, the engine has a low coolant level sensor. If the
engine coolant drops too low, the engine automatical-
ly shuts down (Figure 1.8).
Section 1 — General Information
Generac Liquid-cooled 20 kW Generator
Figure 1.8 - Low Coolant Level Sensor
1.12.4 OVERSPEED SHUTDOWN
The circuit board on liquid cooled units receives AC
frequency (rpm) signals directly from the stator AC
power windings, via sensing leads S15 and S16.
Should AC frequency exceed about 72 Hertz, circuit
board action will automatically shutdown the engine
(Figure 1.9).
*Rated power of generator is subject to and limit-
ed by such factors as ambient temperature, alti-
tude, engine condition, and other factors. Engine
power will decrease about 3.5% for each 1000 feet
above sea level and will decrease an additional 1%
for each 10°F above 60°F . Maximum output power
of the generator is limited by maximum engine
power.
Figure 1.9 - Control Circuit Board
J2
E
A
M14 M15
M1 M1 M1 M1 M1 M1 M1 M1 M M8
C1
R1
U1
M10
SW1
BR1 U12
R56 CR1
C4
U6
R11 R10 CR7
CR37
K4
K2
K3
K1
M9
M2
CR41
1.12.5 PCB OPERATION LED'S
• LED 1 is RED. This LED will be on when UTILITY
sensing is NOT available to the circuit board. This
LED will function only when the AUTO/OFF/
MANUAL switch is set in the AUTO position.
• LED 2 is YELLOW. This LED will be on when the
circuit board battery charger is on. This LED will
cycle on and off with the battery charger, 4.85
hours on then 4.85 hours off.
• LED 3 is GREEN. This LED will flash when the cir-
cuit board has LOAD voltage available to it. This
LED will function when voltage is available across
T1 and T2.
Generac
PRE-PACKAGED STANDBY
U13 U14
C17
Q7
C18
C12
R68 R60
C21
C25
U16
C3 C24
Q9
C2
C5 U2
R12
Q1
C
U7
Q4
Q5 Q12
C23
Q2
C20
Q3
C8
Q11
C15
Q15
C10
C9 C 1 C11
LED2
C16 C7
C14
Q6
Q13
C13
R55
2002 GENERAC POWER SYSTEMS, ASSY #076009A
® Power Systems, Inc.
U15 U17
M3
Q14
C22
U5 U4 LED3
U18
U3
U19
U9 C19
U10
U8
U20
Q16
LED1
M4
CUT R83
FOR 50HZ
7