Installation Guidelines for Spark-Ignited Stationary Emergency Generators 17
Section 5 Gaseous Fuel Systems
Gaseous fuels, such as LP and natural gas, are highly volatile and their vapors are explosive. LP gas is
heavier than air and will settle in low areas. Natural gas is lighter than air and will settle in high areas. Even
the slightest spark can ignite these fuels and cause an explosion.
5.1 — General
Consult a local gas distributor or licensed plumber/installer when installing a gaseous fuel supply system or refer to
information published by various federal agencies. For a list of some of these publications, see Subsection 1.7.
5.1.1— Fuel System Conversion
Industrial units come from the factory configured and EPA certified with the fuel system ordered. Any one of the follow-
ing gaseous fuel systems may be installed:
• Natural Gas (NG)
• LP-Vapor Withdrawal
To convert to a different fuel (for example, from NG to LP-Gas Vapor), see the owner's manual or an independent
authorized service dealer.
5.2 — Gaseous Fuel Properties
5.2.1— Natural Gas
Natural gas is lighter than air. It is found in the gaseous state at normal ambient temperatures and pressures. It is
highly explosive and can be ignited by the slightest spark. For this reason, fuel lines must be free of leaks and ade-
quate ventilation is absolutely essential. Local fuel/gas codes dictate the maximum pressure under which natural gas
can be delivered to a site or structure. The supply pressure from the utility meter/regulator is usually not the same as
that required by the generator set, so a separate primary regulator providing the correct pressure and volume of fuel to
the generator set is required. If the local utility source pressure is less than that required by the generator, it is up to the
local utility to provide the volume of gas at the required pressure.
5.2.2— Propane Vapor (LPV)
Liquefied Petroleum gas is heavier than air. The gas vapors are explosive and can be ignited by the slightest spark. LP
Vapor is supplied by liquid propane stored in tanks. Propane exists in its liquid form at or below its boiling point (-44º
F)
as well as when it is stored under pressure. LP tank pressure is dependent on the ambient temperature and the liquid
volume in the tank, and can be over 200 psi. A first-stage regulator at the tank reduces the gas pressure to a lower line
pressure value. This line pressure is then reduced to the correct operating pressure and volume for the generator set
through the use of a second-stage regulator.
5.3 — Gaseous Fuel Systems
5.3.1— Natural Gas System
The local utility will usually provide the piping (meter and pressure regulator) from the main distribution line to the gen-
erator site. The local utility is also responsible for providing gas at sufficient volume and pressure to operate the pri-
mary regulator, so that the regulator can provide the correct volume of gas at the required pressure to the generator.
From the primary regulator, gas flows to the generator connection point, which is the end of the manufacturer supplied
flexible fuel line. The flexible fuel line can be connected directly to the generator connection point (perpendicular to the
frame rail), or by an elbow and short nipple to the frame rail itself (to run parallel to the frame rail). The nipple and elbow
used must be the same pipe size as the flexible fuel line and generator connection point. Install a flexible fuel line
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