Howard
J. Doss and Cornita
Tilma
Michigan State University Extension
Since
the 1930's, electrical service has been brought to virtually
ever rural area of the state and has increased the productivity
of the Michigan farmer. Electricity has proven invaluable
to the Michigan farm industry; but some rural farmers have
found that if improperly used it can be the source of fires,
injuries, and even death.
Electrical
hazards on the farm can: result in electrical shock to humans
or to livestock and possibly result in a fire within structures
or in operating equipment.
Risks
associated with electrical hazards on the farm are increased
by the presence of moisture, especially by the dampness that
is common in confined livestock areas.
Animals
are naturally grounded, making them more sensitive to low
intensity electrical currents than humans. Humans have dryer
skin than animals and normally wear shoes or boots which provide
greater resistance to electrical shock. Humans usually will
not feel an electrical shock from stray current that a well-grounded
animal does when standing on a damp concrete slab or damp
ground.
Animals
experiencing even a minor electrical shock may be reluctant
to drink from a waterer. On a dairy farm, for example, this
reduced water intake may result in less milk production and
a financial loss to the farmer.
There
are several ways to reduce the electrical hazards in farm buildings
and around work areas. You can protect yourself and your livestock
from electrical shock by following these recommendations:
- Select
a shock protection system. If you have two-conductor circuits
and a variety of tools, some with two-wire cords and plugs
and some with three-wire cords and plugs, you have four
alternatives:
- Have
an electrician install ground-fault circuit interrupters
(GFCI) permanently in each electrical circuit in the
shop and other farm buildings.
- Plug
in a portable GFCI when individual power tools are used.
- Convert
your two-conductor circuits to three-wire, grounding-type
circuits.
- Replace
your present tools with new double insulated tools (see
Figure 1).
- Get
the advice of a competent electrician who is familiar with
agricultural wiring to help you decide the safest and most
economical alternative for your farm. A combination of methods
may be your best choice.
- Purchase
tools and equipment designed to prevent shock. Look for
tools and equipment that carry the approval label of a recognized
inspection and approval agency. The label "UL Listed" indicates
that the item has been evaluated for electrical safety considerations
by the Underwriters Laboratory. The PTI "Safety Seal" indicates
approval by the Power Tool Institute. Approved tools are
equipped with three-wire, grounding-type cords and plugs
or a two-prong plug with double insulation on the tool.
Buy either type if your shop has grounding-type circuits.
Double insulated tools can reduce the risk of electrical
shock if you have two-conductor circuits, with or without
GFCI protection.
- Avoid
using grounding adapters. Grounding adapters are risky because
two-conductor circuits do not have a grounding conductor
to connect to the "pigtail" of the adapter.
- If
you find it necessary to use extension cords, refer to the
guidelines in the Electrical Cords section of this Fact
Sheet.
- Do
not abuse electrical power tools. The insulation on the
conductors inside the tool may be damaged from rough handling.
Dropping power tools, throwing them around, or picking them
up by the power cord can destroy the insulation and connections
inside the equipment. Avoid overheating. Allow tools to
cool when they become hot from continuous use or from temporary
overloads.
A
ground-fault circuit interrupter (GFCI) is a circuit breaker
designed to prevent serious shock to people or animals under
certain conditions. It can reduce the risk of shock when using
electrical tools or appliances in damp or wet areas.
The
GFCI works on the principle that the two wires supplying a
single-phase electrical load must carry the same number of
amperes (current) when the circuit is operating properly.
If a ground-fault occurs either to the grounding wire, or
through a person or animal, some of the current will take
an alternate route back to the system's grounding electrode.
One of the wires will then carry less current than the other
wire. When this occurs the GFCI will break the circuit, stopping
the flow of electricity in a fraction of a second to reduce
the electric shock hazard.
Ground-fault
circuit interrupters come in several styles. They are commonly
used as a receptacle outlet, part of an extension cord, or
can be installed in the main electrical panel to replace an
existing circuit breaker. When installed as a circuit breaker,
the GFCI offers shock protection to an entire electrical branch.
Ground-fault
circuit interrupters are available for 120-V circuits with
one hot wire and a neutral. A GFCI will work on older two-wire
electrical systems that have no ground wire. A 120-V, single-pole
GFCI fits into the same size space as a standard single-pole
breaker. There are also GFCIs for 240-V circuits using two
hot wires.
All
equipment plugged into a GFCI protected receptacle, including
any two-prong (two-wire) electrical plug, will have ground-fault
protection.
A portable
GFCI is recommended for persons using power tools in damp
or wet locations. The portable GFCI is plugged into an outlet
and the power tool is plugged into the GFCI.
Certain
conditions can result in "nuisance tripping" of a GFCI protected
circuit or receptacle.
Nuisance
tripping can be reduced by avoiding:
- Circuits
longer than 100 ft.
- Older
non-double insulated power tools that contain faulty electrical
insulation.
- Fluorescent
or other types of electric-discharge lighting fixtures.
- Extension
cords with cuts or splices where moisture has entered the
cut or splice creating a "leak" (ground fault) or path for
the current to flow outside of the wire to the ground.
- Permanently
installed electric motors.
Installing
a GFCI to prevent electrical shock from farm equipment seems
like a good idea, but nuisance tripping may become a serious
problem. The loss of a ventilation system in certain livestock
facilities can be fatal to animals. Stock waterers may freeze
in northern climates if the GFCI trips. Carefully consider
the effects of loss of power to an agricultural circuit before
installing GFCI protection. The most effective shock prevention
system for agricultural equipment and circuits is a good equipment
grounding conductor run with the circuit wires and connected
to all metal agricultural equipment.
Damaged
or improperly used cords can result in electrical shocks or
start fires. Avoid using extension cords in farming operations.
Follow these precautions if you must use an extension cord:
- Do
not use in wet areas.
- Do
not try to repair a damaged extension cord or splice two
wires together. Replace the cord.
- Keep
cords away from sharp objects, heat, oil, and solvents that
can damage insulation.
- Check
an extension cord before each use for nicks and cuts. Replace
or repair the cord if the insulation is damaged or worn.
- Use
an extension cord with correct size wiring (gauge) for the
intended use. Do not overload an extension cord or use a
"household" type extension cord to operate heavy-duty machinery.
Overloading may cause excessive heating that may result
in a fire.
- Use
a grounded wire (three-prong with a "safety grounding" wire)
for tools and machines having a grounded plug or use a portable
GFCI (ground-fault circuit interrupter).
- Buy
extension cords carrying a listing mark or certification
of a recognized independent testing laboratory.
- Be
sure the package for the cord indicates the maximum current
and/or wattage rating of the cord.
- Route
the cord to protect it from machinery and animals. Also,
people should not be able to trip over or accidentally damage
the cord.
- Two
extension cords plugged together for additional length will
reduce the amperage rating and increase the risk of an electrical
hazard.
- Extension
cords deteriorate; do not use them in place of permanent
electrical installations.
Portable
Elevators
Moving a grain auger in the elevated position may electrocute
someone if it comes into contact overhead power lines. Anyone
moving an auger should lower it first. Check the height of all
tall equipment to ensure that it will not touch overhead powerlines
during the move. Recently manufactured augers should have a
warning label attached that indicates DANGER, Electrocution
Hazard. Follow safety warnings (see Figure 2).
Mechanical
Damage to Electrical Wiring Problems
can occur when using or moving equipment inside buildings if
wiring is not securely fastened and protected. Interior wiring
should also be protected from animal damage by encasing it in
metal or plastic conduit or by elevating the wiring above the
animals' reach.
"UF"
vs. "NM" Type Electrical Wiring Type UF
cable wiring is rated for dry, damp, wet, or corrosive locations.
This type cable is permitted for surface and concealed wiring
in buildings, and for direct burial in the earth. It may not
be embedded in poured concrete.
Exercise
care if electrical conduit is used. Moist and extremely corrosive
conditions may quickly destroy metal conduit. Animals may
chew nonmetallic conduit or it may become damaged by impact
from animals or machines. Check installations frequently and
be prepared to replace damaged conduit or cable.
Type
"NM" wire should not be buried because of the potential damage
from moisture. Type "NM" electrical wire is not generally
recommended for agricultural environments associated with
animals or damp areas. Consult an electrician for specific
applications or recommendations for your farm wiring concerns.
Electrical
Fires in Agricultural Machinery Electrical
malfunctions in machinery can be a fire hazard. Combines can
be a particular problem because of the grain fines and crop
residues that are readily combustible. Check a combine's hydraulic
and fuel systems for leaks, and inspect all electrical components,
including battery terminal connections, for proper operation
before the harvest season and at least weekly during harvesting.
Shut off the machine as quickly as possible if a fire is suspected.
Turn off the ignition and remove the key to prevent electrical
current flow to the area of the fire and to prevent someone
else from restarting the engine.
If an
Accident Involving Electrical Shock or Fire Occurs Could You...?
- Turn
off or disconnect electric power to farm buildings?
- Do
family members and farm workers know how to contact fire
and rescue personnel for assistance?
To eliminate
confusion, have a complete set of directions available to
instruct emergency crews to the farm site.
Keep
the telephone number of the fire department and other emergency
services posted near the telephone to avoid any delay in reporting
an emergency.
- Ag
Safety, John Deere.
- Agricultural
Electrification - Surbrook and Mullin.
- Illustrations
courtesy of John Deere and Company, Agricultural Safety,
Fundamentals of Farm Safety, 1987.
Disclaimer
and Reproduction Information: Information in NASD does not represent
NIOSH policy. Information included in NASD appears by permission
of the author and/or copyright holder. More
NASD Review: 04/2002
Michigan State University, Agricultural Engineering Department.
Howard
J. Doss, Cornita Tilma, Agricultural Safety Specialist and
former Graduate research assistant respectively, Michigan
State University Extension, East Lansing, Michigan 48824.
5/92. Funded by the National Institute of Occupational Safety
and Health -
#UO5/CC-4506052-01
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