Engine Protective Devices - Generac Power Systems 004742-0 Owner's Manual

Model Rating
004742-0 15,000
004744-0 20,000
004746-0 25,000
Fuel pressure for a natural gas set up should be five
inches to 14 inches of water column (0.18 to 0.5
psi) at all load ranges.
Fuel pressure for an LP vapor set up should be 11
inches to 14 inches of water column (0.4 to 0.5
psi) at all load ranges.
A seperate gas line and regulator may be needed
to assure proper gas pressure to the generator.
Improper gas pressure can cause hard starting and
affect engine durability.
Gaseous fuels such as natural and LP (propane)
!
gas are highly explosive. Even the slightest
spark can ignite such fuels and cause an explo-
sion. No leakage of fuel is permitted. Natural
gas, which is lighter than air, tends to collect in
high areas. LP gas is heavier than air and tends
to settle in low areas.
1.7

ENGINE PROTECTIVE DEVICES

The engine has several safety switches which cause
the engine to automatically shut down under the fol-
lowing conditions: low oil pressure, high coolant tem-
perature, engine overspeed, low coolant level or over-
crank (Figure 1.3).
Figure 1.3 - Engine Protective Devices
Figure 1.2 - Main Circuit Breaker
Phase Actual Current
1
1
1
* Amp Rating of C/B structured under model.
NOTE:
Section 1 - General Information
Liquid-cooled 15 kW, 20 kW and 25 kW Generators
C/B Rating*
62.5 70
83.3 90
104.2 125
1.7.1
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 1.4).
1.7.2 HIGH COOLANT TEMPERATURE SWITCH
Normally open (N.O.) thermostatic switch has sens-
ing 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 1.5).
Figure 1.5- High Coolant Temperature Switch
1.7.3
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 1.6 on page 6).
% over rating
112%
108%
120%
LOW OIL PRESSURE SWITCH
Figure 1.4 - Low Oil Pressure Switch
LOW COOLANT LEVEL SWITCH
Circuit Breaker
70A BQ2
90A BQ2
125A BQ2
5