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Generac
®
Power Systems, Inc. 5
Recommended fuels should have a Btu content of at
least 1,000 Btus per cubic foot for natural gas and at
least 2,520 Btus per cubic foot for LP gas. Ask the
fuel supplier for the Btu content of the fuel being
used.
Fuel pressure for both natural gas and liquid
propane set ups should be 11 inches to 14 inches
of water column (0.6 psi) at all load ranges.
NOTE:
A seperate gas line and regulator may be needed
to assure proper gas pressure (11-14”) to the gen-
erator. Low gas pressure can cause hard starting
and could 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 explosion. 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
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 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).
Figure 1.4 - Low Oil Pressure Switch
1.7.2 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 1.5).
Figure 1.5- High Coolant Temperature Switch
1.7.3 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 1.6 on page 6).
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Section 1 - General Information
Guardian Liquid-cooled 15 kW, 20 kW and 25 kW Generators
Model Rating Phase Actual Current C/B Rating* % over rating Circuit Breaker
004721/004722 15,000 1 62.5 70 112% 70A BQ2
004723/004724 20,000 1 83.3 90 108% 90A BQ2
004725/004726 25,000 1 104.2 125 120% 125A BQ2
* Amp Rating of CB structured under model.
Figure 1.2 - Main Circuit Breaker