The demand factor varies considerably for
different types of loads. services, and structures. The
National Electrical Code®. Article 220. provides the
requirements for determining demand factors.
Demand factors for some military structures are given
in table 3-2.
Example: A machine shop has a total connected
load of 50.3 kilowatts. The demand factor for this type
of structure is taken at 0.70. The maximum demand is
50.3 × 0.70 = 35.21 kilowatts.
Generators are not permitted to be closer than 25
feet to a load; however, in setting up the generator, try
to place the equipment near points of large demand to
reduce the size of wire required: to hold the line losses
to a minimum. and to afford adequate voltage control
at the remote ends of the lines.
Moving the generator may be accomplished by
lifting or pulling. The generator set comes equipped
with a lifting sling usually stored in the skid on the side
of the unit opposite the operators control panel.
You should study a plot or chart of the area on
which the individual buildingsand facilities have been
plotted. The site you select should be large enough to
meet present and anticipated needs. Then select a
location where there will be sufficient space on all
sides for servicing and operation of the unit. It should
be level. dry, and well drained. If this type of site is not
available, place the generator set on planks, logs, or
other material for a suitable base foundation.
Table 3-2.Demand Factor
Aircraft maintenance facilities
Laundry, ice plants, and bakeries
Sheltering of Generators
Although advanced base portable generators are
designed to be operated outdoors, prolonged exposure
to wind. rain. and other adverse conditions will
definitely shorten their lives. If the generators are to
remain on the site for any extended period of time, they
should be mounted on solid-concrete foundations and
installed under some type of shelter.
Presently, there are no predrawn plans for shelters
for a small advanced base generating station. The
shelter will be an on-the-spot affair, the construction of
which is determined by the equipment and material on
hand plus your ingenuity and common sense.
Before a Builder can get started on the shelter, you
will have to inform him of such things as the number of
generators to be, sheltered; the dimensions of the
generators; the method of running the generator load
cables from the generator to the distribution system
outside the building; and the arrangement of the
exhaust system, radiator discharge, and cooling air.
Installation specifications are available in the
manufacturers instruction manual that accompanies
each unit. Be sure to use them. Appropriate
consultation with the Builder regarding these speci-
fications may help minimize various installation and
piping problems and costs.
The following hints and suggestions also will be
1. Ventilation is an important factor to consider
when you are installing the units inside a building.
Every internal combustion engine is a HEAT engine.
Although heat does the work, excess amounts of heat
must be removed if the engine is to function properly.
Heat can be removed by setting the engine radiator
grille near an opening in the wall and providing another
opening directly opposite the unit. In this manner, cool
air can be drawn in and the hot air directed outdoors.
These openings can be shielded with adjustable louvers
to prevent the entrance of rain, sand, or snow. In
addition, when the engine is operating in extremely cold
weather. the temperature in the room can be controlled
by simply closing a portion of the discharge opening.
Additional doors or windows should be provided in the
shelter if the plants are installed in localities where the
summer temperatures exceed 80°F at any time.
2. Working space is another consideration. Be sure
to provide sufficient space around each unit for repairs
or disassembly and for easy access to the generator