27
Figure 2.9 – Typical Propane Gas Fuel System
2.4.2 SOME IMPORTANT CONSIDERATIONS
When installing an LP gas system, consider seriously
the following items:
• All fittings, lines, hoses and clamps must be
tight and free of leaks. Apply a pipe sealant to
threads when assembling threaded connections.
This reduces the possibility of leakage.
• Test the entire fuel system for leaks using approved
test methods.
• Optimum gas pressure at the inlet to the gaseous
fuel solenoid valve and secondary regulator is 11
inches water column.
• The installer’s fuel supply connection point is at
the gaseous fuel solenoid valve. This is a 3/4-inch
(female) connection. Provide a suitable 3/4-inch
NPT (male) connector to attach to the fuel supply
line.
• Use a length of approved flexible fuel hose between
the gaseous fuel solenoid valve and rigid gas pip-
ing. The flexible line should be at least 6 inches
longer than necessary.
2.4.3 VAPOR
WITHDRAWAL
LP gas is stored in pressure tanks as a liquid. The
gas systems used with these generators were designed
only for vapor withdrawal type systems. Vapor with-
drawal systems use the gas vapors that form above
the liquid fuel in the tank. Do NOT attempt to use the
generator with any liquid withdrawal type system.
2.4.4 PRIMARY
REGULATOR
Gas pressure delivered to the solenoid valve must be
properly regulated by means of a primary gas regu-
lator. Mount the primary regulator at the gas tank
outlet or in the supply line from the gas tank. The
following rules apply:
• For best results, the primary regulator supplies
gaseous fuel to the secondary regulator at 11 inch-
es water column. Do NOT exceed 14 inches water
column.
• The installer must be sure the primary regulator is
rated at sufficient gas flow to operate the generator
plus all other gas appliances in the circuit.
NOTE:
Recommended MINIMUM gas flow rate for these
air-cooled generators is 40 cubic feet per hour.
If an existing primary gas regulator does not have
a sufficient flow capacity for the generator and
other gas appliances in the circuit, (a) install a
primary regulator with adequate flow rate, or (b)
install a separate regulator only and rated at least
40 cubic feet per hour. The inlet side of any pri-
mary regulator that supplies the generator must
connect directly to a gas pressure tank. Do NOT
tee the generator line into a gas circuit feeding
other areas.
2.4.5 GASEOUS
CARBURETION
LP gas vapors should be supplied to the secondary
regulator inlet at about 11 inches water column (posi-
tive pressure). The engine pistons draw air in dur-
ing the intake stroke (Figure 2.10). 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 diaphragm 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 2.10 – LP Gas Carburetion Diagram
Section 2 – Installation
Recreational Vehicle Generator
