Fuel Factors; Fuel Pressure; Power Loss; Fuel Pipe Sizing - Briggs & Stratton FORTRESS Manual De Instalación Y Operación

Fuel Factors

An important consideration affecting the entire installation
is the type of fuel used by your generator. The system was
factory tested and adjusted using natural gas, but can be
converted to use LP vapor. For proper engine function,
factors that are inherent to each of these fuels, your
location and the duration of possible utility interruptions are
important considerations in the following fuel guidelines:
• Use clean, dry fuel, free of moisture or any
particulate material. Using fuels outside the
following recommended values may cause
performance problems.
• In engines set up to run on propane (LP),
commercial grade HD5 propane with a minimum
fuel energy of 2500 BTUs/ft3 with maximum
propylene content of 5% and butane and heavier
gas content of 2.5% and minimum propane content
of 90% is required.
Natural gas rating will depend on specific fuel but typical
derates are between 10 to 20% off the LP gas rating.
Natural gas or LP engines are certified to operate on
natural or liquid propane gas. The emissions control
system for this engine is EM (Engine Modifications).
WARNING Propane and Natural Gas are extremely
flammable and explosive, which could cause
burns, fire or explosion resulting in death or
serious injury.
• The residential generator is equipped with an automatic safety
gas "fuel shut-off" valve.
• DO NOT operate the equipment if the "fuel shut-off" valve is
missing or inoperative.
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Fuel Pressure

Both LP vapor and natural gas fuel supply pressure at the
generator's fuel inlet port should be between the following
levels at full load with all gas appliances turned on and
operating.
• NG is 3.5-7" W.C.
• LP is 11-14" W.C.
Ensure that all gas line shutoff valves are OPEN and that
adequate fuel pressure is available whenever automatic
operation is desired.

Power Loss

Air density is less at high altitudes, resulting in less
available engine power. Specifically, engine power will
decrease 3.5% for each 1,000 feet (300 m) above sea
level and 1% for each 10° F (5.6°C) above 77°F (25°C).
Generators located in these conditions must have their
transfer switch adjusted appropriately for this power
decrease. See Automatic Transfer Switch manual on how
to adjust for the power decrease.

Fuel Pipe Sizing

There are numerous on-line or otherwise-published
references for fuel pipe sizing. For example, NFPA 54 -
National Fuel Gas Code, 2006 (Item #: 320-6031-06) is a
common resource.
The installer should consider the specific gravity of gas
and compensate for a nominal amount of restriction from
bends, fittings, etc. If an unusual number of fittings, bends,
or other restrictions are used, refer to federal and local
codes for guidance.
• Installed piping must be properly purged and
leak tested, in accordance with applicable codes
and standards.