Gaseous Fuel Systems
16 Installation Guidelines For Spark-Ignited Stationary Generators
Liquid Propane Gas
LP gas is heavier than air. The LP gas vapors are explo-
sive and can be ignited by the slightest spark. LP gas is
sup
plied by liquid propane stored in tanks. Propane
exists in its liquid form at or below its boiling point (-44 º
F
[-42 °C]) as well as when stored under pressure. LP tank
pressure is dependent on ambient temperature and the
liquid volume in the tank, and can be over 200 psi (1,379
kPa). A first-stage regulator at the tank reduces fuel pres-
sure to a lower line pressure value. This line pressure is
then
reduced to the correct operating pressure and vol-
ume for the generator through the use of a second-stage
r
egulator included with the unit.
Definitions
The following definitions are provided for use in this manual:
Term Description
Allowable Pressure
Drop
Design pressure loss in the system under maximum probable flow conditions, from point of delivery to
inlet connection of generator, shall be such that supply pressure at the generator is greater than or equal
to the minimum pressure required by generator at its full load capacity.
Authority Having
Jurisdiction (AHJ)
(NFP
A-54)
An organization, office, or individual responsible for enforcing requirements of a code or standard, or for
approving equipment, materials, an installation, or a procedure.
Cubic Foot (ft
3
) of
Gas (NFPA-54)
Amount of gas that would occupy 1 ft
3
(0.03 m
3
) when at a temperature of 600 °F (316 °C) saturated with
water vapor and under a pressure equivalent to 30 in water column (7.47 kPa).
Generator
Connection Point
Connection point for fuel supply system to
generator is the end of the manufacturer supplied flexible fuel
line fitting, which connects to fitting through base frame rail. An elbow and short nipple can be incorpo-
rated to allow the flexible fuel line to be positioned parallel
to unit base frame. Size of fuel connection point
is shown in each unit’s installation drawing; size of the flexible fuel line (and any elbow and nipple) must
be equal to or larger than this connection point. Flexible fuel line must be installed straight without bend-
ing, twisting, or kinking.
psi & psig Measure of pressure in pounds per square inch and pounds per square inch gauge.
In of Water
Column
Measure of gaseous fuel pressure
in inches of water column: 14 in water column = 3.48 kPa
Primary Regulator
A pressure regulator installed between the service regulator (NG) or first-stage regulator (LP gas) sized to
provide pressure and volume required by generator at its full rated load capacity.
Regulator (for LP gas)
First-Stage
Regulator
A pressure regulator for LP gas service designed to reduce pressure from
a container to 10.0 psig or less.
High-Pressure
Regulator
A pressure regulator for LP gas liquid or vapor service designed
to reduce pressure from container to a
lower pressure in excess of 1.0 psig.
Second-Stage
Regulator
A pressure regulator for LP gas service designed to reduce first-stage regulator outlet pressure to 14 in
water column (3.48 kPa) or less. For generator purposes, this is also referred to as the primary regulator.
Regulator (for NG)
Pressure Regulator Device placed in a fuel line for reduci
ng, controlling, and maintaining pressure in downstream piping.
Service Regulator A pressure regulator installed by the servicing fuel supplier to
reduce and limit the service line fuel pres-
sure to delivery pressure.
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