Exhaust System - Generac Power Systems 004703-1 Owner's Manual

2.5.5 GASEOUS CARBURETION
LP gas vapors should be supplied to the secondary regulator inlet
at about 11 inches water column (positive pressure). The engine
pistons draw air in during the intake stroke (Figure 2.12). This air
passes through a carburetor venturi, which creates a low pressure
that is proportional to the quantity of air being pumped. The low
pressure from the carburetor venturi acts on the regulator dia-
phragm to pull the diaphragm toward the source of low pressure.
A lever attached to the diaphragm opens a valve to permit gas glow
through the carburetor.
Figure 2.12 – LP Gas Carburetion Diagram
The greater the airflow through the carburetor venturi, the lower the
pressure at the venturi throat. The lower the pressure at the venturi
throat, the greater the diaphragm movement, and the greater the
movement of the regulator valve. The more the regulator valve
opens, the greater the gas flow that is proportional to airflow
through the generator.
The following facts about the secondary regulator must be empha-
sized:
• The regulator must be sensitive to venturi throat pressure
changes throughout the operating range.
• The regulator must be properly adjusted so it will stop the flow
of gas when the engine is not running (no air flow through the
carburetor).
• The slightest airflow (and vacuum in the venturi throat) should
move the regulator valve off its seat and permit gas to flow.
2.5.6 FUEL SUPPLY LINES
• LP gas lines must be accessible, but protected against possible
damage.
• Do NOT connect electrical wiring to any LP gas fuel line or run
wiring alongside the lines.
• Route gas lines away from hot engine exhausts.
• Retain gas lines with metal clamps that do not have sharp
edges.
• Install an approved length of flexible hose between the gaseous
fuel solenoid valve and rigid fuel supply lines. The flexible line
must be nonmetallic, nonorganic and nonconductive. It must be
approved for use with LP gas.

 Gaseous fuel lines between the tank and the
secondary regulator are under a positive pres-
sure (about 11 inches water column). Gas pres-
sure at the outlet side of the secondary regula-
tor, however, is a negative pressure and can
draw flame inside a line or fitting and cause an
explosion.
2.5.7 EXCESS FLOW VALVE
LP gas tanks should have an excess flow valve, according to NFPA
501C. This valve and the gas lines must be carefully sized so the
valve will close when a fuel line is severed or broken. Consult
the Natural-LP Gas Association for information and limitations of
excess flow valves.
Manual shutoff valves on the supply tank and elsewhere in the sys-
tem must be fully open when operating the generator. The excess
flow valve functions properly only if all valves are fully open.
2.5.8 LEAKAGE TESTS
Do not place the generator into service until the gas system has
been properly tested for leaks. To test the system, a separate
source of 12 volts DC to open the gaseous fuel solenoid valve is
needed.
The leak test must comply fully with NFPA, Paragraph 318. All con-
nections, hoses, valve regulators, fittings, and other fuel system
parts must be tested under gas or air pressure of not less than
90 psi (620 kPa), while using soap and water or an equivalent
solution to check for leaks. Other approved methods of testing for
leaks may be used, if appropriate. DO NOT USE ANY FLAME TO
TEST FOR LEAKS.
2.6

EXHAUST SYSTEM

The generator exhaust system must be safely and properly
installed. Only approved mufflers and other exhaust system parts
must be used. A properly installed exhaust system must be vapor
tight, quiet and completely safe.
Generator engine exhaust contains DEADLY
carbon Monoxide, an odorless, colorless poi-
sonous gas. Breathing carbon monoxide can
cause: dizziness, throbbing temples, nausea,
muscular twitching, headache, vomiting, weak-
ness and sleepiness, inability to think clearly,
fainting, unconsciousness or even death. If you
experience any carbon monoxide poisoning
symptoms, move into fresh air and immediately
seek medical attention.
Never operate the generator set with the vehi-
cle inside any garage or other enclosed area.
Installation
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