Section 2 – Installation
Recreational Vehicle Generator
• Use a length of approved flexible fuel hose between | Figure 2.10 – LP Gas Carburetion Diagram |
the gaseous fuel solenoid valve and rigid gas pip- |
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ing. The flexible line should be at least 6 inches |
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longer than necessary. |
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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 all air- cooled generators is 40 cubic feet per hour.
The greater the airflow through the carburetor ven- turi, 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 move- ment of the regulator valve. The more the regulator valve opens, the greater the gas flow that is propor- tional to airflow through the generator.
The following facts about the secondary regulator must be emphasized:
•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.
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.
2.4.6 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 nonmetal- lic, nonorganic and nonconductive. It must be approved for use with LP gas.
2.4.7 excess flow valve
LP gas tanks should have an excess flow valve, according to NFPA 501C, Paragraph
Manual shutoff valves on the supply tank and else- where in the system must be fully open when oper- ating the generator. The excess flow valve functions properly only if all valves are fully open.
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