Page last updated Oct 20, 2021 @ 10:12pm
Locating Generators
Outdoor Locations
Gensets that are housed in weather-protective enclosures are designed for installation outdoors. The following summary is from an Onan 12kW Installation Manual but most of the guidance is applicable to other sizes. Since this is only a summary, be sure to follow all the instructions contained in the Installation Manual for your specific model.
Choose a site close to the electric service and fuel supply lines
(natural gas, propane, or diesel). The image below shows a typical natural gas
installation. The main distribution panel, transfer switch and sub-panels are inside
the building in this example.
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image above to enlarge
NFPA 37 2010, section 4.1.4 Engines Located Outdoors
states, "Engines, and their weatherproof housings if provided, that are installed outdoors shall be located at least 5 ft. from openings in walls and at least 5 ft. from structures having combustible walls."
Leave at least 5 ft (or more if the housing and instructions for your
particular unit require it) all around the genset enclosure for access to the inside (NEC Art.
110-26a, Art. 110-26b). The genset must be at least 5 ft from any opening (window,
door, vent, etc.) in a wall, and the exhaust must not be able to accumulate in any
occupied area. See figure below. Note that some jurisdictions
require larger clearances such as 10 feet. Verify requirements with your
local authorities.
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image above to enlarge
Indoor Locations
We do not recommend locating generator sets indoors in residential
applications and small commercial and industrial applications. The reasons are
primarily related to safety. In addition to safety, it costs more to install a
genset indoors than for the same genset provided with the factory weatherproof housing.
Click on thumbnail
image above to enlarge
When a genset is installed indoors, the building must be designed
carefully to handle ventilation to remove heat and any fumes due to fuel, exhaust,
lubrication and starting batteries. The radiator must be provided with a duct
adapter that interfaces properly with louvers on an outside wall of the building.
Adequate air intake flow must be available not only for the radiator fan but also for
cooling the alternator. The engine exhaust piping and muffler must be tight to
prevent any leaks that would allow dangerous carbon monoxide to accumulate inside the
building. Automatic fire suppression systems may also be required. Check with
your local fire codes. You should also contact your fire insurance provider to
determine if an indoor genset is even permitted.
Even installations perfectly designed to meet all the above
requirements and all safety codes can become a hazard later. For an installation to
remain safe, it has to be regularly inspected and maintained to ensure that leaks or other
dangerous conditions do not develop with age or use. Sites that do not have a
knowledgeable maintenance staff trained to support an indoor generator set should not
install a unit inside a building.
An additional factor is the initial cost. It is impossible to
construct a building to house a genset at a cost as low as the factory housing that can be
ordered with the genset. And even if the building already exists, the design expense
and costs to adapt it for a generator set installation usually will exceed the enclosure
cost available from the genset manufacturer. For a small genset the cost of an open
unit with duct adaptor and exhaust pipe kit is as little as $400 less than the same genset
with the factory weather housing. The additional costs for just the exhaust thimble
and louvers exceed that savings.
If you decide to install a genset inside a building
here are some technical details that are typical for most designs.
* The radiator side of the genset needs to be ducted to the outside.
Typically the radiator duct area needs
to be at least 1.5X the area of the radiator.
* Intake louvers need to be mounted on the wall (usually the wall opposite the
radiator duct). The area of the
intake louvers needs to be at least 2X the area of the radiator.
* The genset will usually come with the muffler and pipe package shipped
loose. The muffler is usually anchored
to the wall or ceiling in the genset room. The engine is
then connected to the muffler using a piece of flexible
pipe. This flex will absorb most of the engine vibration
and prevent damage to the muffler mounting.
* The installer will need to purchase a wall thimble. Because the
exhaust pipe gets very hot it must be isolated
where it passes through the building wall or ceiling. The
thimble performs this function. To purchase a thimble
you will need to spacify the wall thickness and what it is
constructed of. Note that propane and natural gas
fueled gensets burn hotter than their diesel counterparts.
* The genset building should NOT be constructed of wood. It should be a
masonry building.
* Per the National Electric Code you will need at least 3 feet clearance on
all sides of the genset.
* Vibration isolators are used between the genset skid and the floor
foundation to reduce sound and vibration
transmission to the building.
As stated in the NoOutage.com LLC Terms & Conditions engine driven
generators sold by NoOutage.com LLC are not intended for indoor
operation at residential or small commercial and industrial sites because of safety risks.
The buyer and user assume all risk and liability when located and operated in such
applications.
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