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The
household
appliances are typically designed to operate at 0.1-0.2 psi and
normally include a regulator to drop the incoming line pressure to this
level. Natural gas pressure at many homes served by old lines is
0.2-0.3 psi. Newer service lines may operate at 2-50 psi. For these
systems, the gas meter includes a regulator that reduces the pressure
to 0.2-0.25 psi. Some large industrial, commercial, and electric
generation customers receive pressurized NG directly from interstate
pipelines.
NATURAL GAS GENERATORS
The term "generator" in electric industry casually refers to a device
containing a combination of an engine with an electric generator head
assembled
together as a single piece of equipment called genset. The gensets
whose engine is fueled by NG typically cost about the same as
propane-fueled devices and generally are cheaper than diesels. You can
find them for
sale at about $200-300 per kilowatt. Normally, permanently installed
backup power systems are selected based on the type of the
fuel you already use for the heating. Therefore a natural gas generator
is an obvious choice of back up power device for the houses connected
to an NG line. Besides private homes, NG gensets are utilized in
commercial installations, although for such applications diesels are
more common because of their higher reliability.
The main advantage of an NG powered device is it's hooked up directly
to the home's gas line, so
you don't have to store any fuel. It can provide emergency power for as
long as the fuel is available (except for some breaks for oil change
and other required periodic service). The leading US manufacturers of
NG gensets are Generac, Briggs & Stratton, Cummins Onan, and
Kohler. Coleman no longer makes gensets, and the assets of Coleman's
Powermate were acquired by a company called PRAMAC. Generac-made models
are also sold under brand names Guardian and Carrier. Generac
Guardian series
has
probably the broadest line of automatic systems with the power ranging
from 8 to
20 kW for residential air cooled models and 25 to 60 kW for commercial
water cooled. GE is offering a line of systems with Briggs &
Stratton-built engines. NG gensets are available both online and from
local dealers. If you are looking to buy a home generator and would
like to deal with a dealer who can handle both delivery, installation
and possibly financing, complete a quick questionnarie
to get the quotes from different dealers.
Electrical connection to the house wiring system must be done via a transfer
switch
which is usually included in the automatic systems. Most
systems for homes or commercial use are currently designed to work from
standard gas pressure of 5 to 7 inches of water
column (0.18-0.25 psi), although some high power models may need a
higher fuel pressure.
Many residential NG models are actually bi-fuel: they can also run on
propane after a simple DIY adjustment.
INSTALLATION BASICS
The manufacturing manuals normally contain a detailed installation
requirements. However, it worth to know certain basics in advance. All
generators must be operated outdoors
only.
The layout, installation and all the connections should be done by
qualified professionals. Prior to the installation you should consult
local fuel suppliers or the fire department to check the codes and
regulations. Local codes may mandate a specific routing of gas line
piping. Generally, the system should be located as close as possible to
the fuel supply and to the main electrical service panel. The exhaust
should be kept away from windows and doors. Install the generator on
high ground where water levels will not rise and endanger it and allow
sufficient room on all sides for servicing.
The genset must be installed on a level surface. It is typically placed
on pea gravel or crushed stone. Check local codes if a concrete base
slab is required.
The pipe sizing, construction and layout must comply with NFPA 54. At
least one manual shut-off valve must be installed in the gaseous fuel
supply line. The fuel connection should be made a licensed plumber.
Make sure he uses AGA approved pipes and a proper pipe sealant or joint
compound. Remember that natural gas is highly explosive. Even the
slightest spark can ignite such fuels and cause an explosion. All
installed gaseous fuel piping must be purged and leak tested prior to
initial start-up in accordance with local codes, standards and
regulations. When connecting the gas line to the generator use the
flexible fuel line to ensure that vibration will not cause a leak at
the connection points. Never bend the flexible fuel line (it must not
be bent beyond 10 degrees). Note that natural gas, which is lighter
than air, tends to collect in high areas if it leaks. Where the fuel
line is to enter the generator, install a T-fitting to allow for the
pressure monitoring. Once the system is installed, verify that the fuel
pressure never drops below minimum, which is typically 5 inches WC or
0.18psi. For the ratings of top brands and selection recommendations
see Standby
Generator Review.
Note: I have a material connection with Amazon.com- see Disclosure.
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