Siemens 30 kW Manual De Usuario

The standby generator may be equipped with one of 
the following fuel systems:

•  Natural gas fuel system
•  Propane vapor (PV) fuel system
The Manual Drawing Listing that is affixed to the 
unit includes the “Identification Code,” which may be 
used to identify the type of fuel system installed on 
the unit.

Recommended fuels should have a Btu content of at 
least 1,000 Btus per cubic foot for natural gas; or at 
least 2,520 Btus per cubic foot for LP gas. Ask the 
fuel supplier for the Btu content of the fuel.

Required fuel pressure for natural gas is 5 inches 
to 14 inches water column (0.18 to 0.5 psi); and 
for liquid propane, 5 inches to 14 inches of water 
column (0.18 to 0.5 psi).

NOTE:

Any piping used to connect the generator to the 
fuel supply should be of adequate size to ensure 
the fuel pressure NEVER drops below five inches 
water column for natural gas or 5 inches water 
column for propane vapor for all load ranges.

NOTE:

It is the responsibility of the installer to make sure 
that only the correct recommended fuel is sup-
plied to the generator fuel system. Thereafter, the 
owner/operator must make certain that only the 
proper fuel is supplied.

Natural gas is supplied in its vapor state. In most 
cases, the gas distribution company provides piping 
from the main gas distribution line to the standby 
generator site. The following information applies to 
natural gas fuel systems.

•  Gas pressure in a building is usually regulated by 

national, state and local codes.

• To reduce gas pressure to a safe level before 

the gas enters a building, a primary regulator is 
needed. The natural gas supplier may or may not 
supply such a regulator.

•  It is the responsibility of the gas supplier to make 

sure sufficient gas pressure is available to operate 
the primary regulator.

• Gas pressure at the inlet to the fuel shutoff sole-

noid should not exceed approximately 14 inches 
water column (0.5 psi). Optimum pressure at the 
fuel shutoff solenoid is 11 inches water column 
(0.4 psi).

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This type of system utilizes the vapors formed above 
the liquid fuel in the supply tank. Approximately 10 
to 20 percent of the tank capacity is needed for fuel 
expansion from the liquid to the vapor state. The 
vapor withdrawal system is generally best suited for 
smaller engines that require less fuel. The installer 
should be aware of the following:

• The natural gas and LP gas systems are similar. 

However, the natural gas system delivers gas at a 
pressure of approximately five inches water col-
umn to the carburetor.

• When ambient temperatures are low and engine 

fuel consumption is high, the vapor withdrawal 
system may not function efficiently.

• Ambient temperatures around the supply tank 

must be high enough to sustain adequate vaporiza-
tion, or the system will not deliver the needed fuel 
volume.

•  In addition to the cooling effects of ambient air, the 

vaporization process itself provides an additional 
cooling effect.

LP is supplied as a liquid in pressure tanks. It is 
usually made up of propane, butane, or a mixture of 
the two gases. Propane tends to vaporize readily even 
at temperatures as low as -20° F (-29° C). However, 
butane reverts to its liquid state when temperatures 
drop below 32° F (0° C).

LP in a liquid withdrawal system must be converted 
to its gaseous state before it is introduced into the 
engine carburetor. A vaporizer-converter is generally 
used to accomplish this. In such a converter, heated 
engine coolant is ported through the converter to 
provide the necessary heat for conversion of the fuel 
from a liquid to a gaseous state.

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FuelSys001  Rev.

 0  08/05