1.6 MAIN CIRCUIT BREAKER
The generator’s main circuit breaker is included with the
unit as shipped from the factory. The breaker for each
unit is described as follows:
1.7 ENGINE PROTECTIVE DEVICES
The engine has several safety switches that cause
it to automatically shut down under the following condi-
tions: low oil pressure, high coolant temperature, low
coolant level, engine overspeed and overcrank.

1.7.1 LOW OIL PRESSURE SWITCH

This switch is normally closed (N.C.) but is held open by
engine oil pressure during engine running. Should oper-
ating oil pressure drop below approximately 10 psi (68
kPa), the switch contacts close, and the engine shuts down
automatically (Figure 1.2).

Figure 1.2 – Engine Protective Devices

1.7.2 HIGH COOLANT TEMPERATURE SWITCH

This normally open (N.O.) thermostatic switch has a
sensing tip that is immersed in captive coolant. Should
the coolant temperature exceed approximately 121° C
(250° F), the switch contacts close, which causes the
engine to shut down automatically (Figure 1.2).

1.7.3 LOW COOLANT LEVEL SWITCH

Should the engine coolant level drop below the level of the
high coolant temperature switch, it is possible for the
engine to overheat without automatic shut down. To pre-
vent such overheating without automatic shut down, the
engine has a low coolant level sensor. If the engine coolant
drops too low, the engine automatically shuts down
(Figure 1.2).

1.7.4 OVERSPEED SHUTDOWN

The control module assembly (CMA) circuit board on
liquid-cooled units receives AC frequency (rpm) signals
directly from the stator AC power windings. Should AC
frequency exceed approximately 72 Hertz, circuit board
action will automatically shut down the engine.

1.7.5 OVERCRANK SHUTDOWN

After 90 seconds of crank-rest cycles (about seven sec-
onds cranking/seven seconds at rest), this function ends
cranking if the engine fails to start in that 90-second
span.

1.7.6 DC FUSE

This fuse is located on the front panel of the control sys-
tem. 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. Generac uses an
AGC fuse rated at 15 amps.
1.8 SPECIFICATIONS

1.8.1 GENERATOR

Models ..............................................0043736, 0046265
Rated Maximum Continuous
AC Power Output (kW)*..................................................40
Rated Voltage (volts) ................................................120/240
Rated Maximum Continuous
Current at240 Volts, Single-phase (amps)................................1 67
Number of Rotor Poles........................................................4
Driven Speed of Rotor (rpm)........................................1,800
Type of Stator ........................................................Four-wire
Rotor Excitation System..................................Direct Excited
Brush-type System
Stator Insulation ....................................................Class “H”
Rotor Insulation......................................................Class “F”
*Rated power of generator is subject to and limited by such factors as ambient tempera-
ture, altitude, engine condition and other factors. Engine power will decrease about 3.5
percent for each 1,000 feet above sea level; and also will decrease an additional 1 percent
for each 6° C (10° F) above 15.5° C (60° F) ambient. Maximum output power of the gener-
ator is limited by maximum engine power.
◆
Section 1 — General Information
Guardian Liquid-cooled 40 kW Generator
Generac®Power Systems, Inc. 5
Model Number Circuit Breaker Rating
0043736 200-amp breaker
0046265 200-amp breaker