College of William & Mary
Extension Cord Safety & Use Guidelines
Introduction
Extension cords provide a convenient method of bringing temporary AC power to a
device that is not located near a power outlet. But, if not used properly, extension cords
lead to electrical shock hazards, equipment damage, and fire hazards. In addition,
improper cord selection can lead to use of an undersized extension cord resulting in an
overheated cord and insufficient voltage delivered to the device. This condition can
result in a device or cord failure and fire.
The U.S. Consumer Product Safety Commission (CPSC) estimates that each year,
about 4,000 injuries associated with electric extension cords are treated in hospital
emergency rooms. About half the injuries involves fractures, lacerations, contusions, or
sprains from people tripping over extension cords. CPSC also estimates that about
3,300 residential fires originate in extension cords each year, killing 50 people and
injuring about 270 other. The most frequent causes of such fires are short circuits,
overloading, damage, and/or misuse of extension cords.
The College of William and Mary is not immune to extension cord hazards. Improper
extension cord use is identified as one of the most noted electrical code and safety
findings on campus during EH&S inspections.
General Policy
The College of William and Mary has specific requirements for the use of extension
cords on campus. These requirements satisfy the VA Fire Prevention Code Section 605
to include all sub-sections. The following is the list of College requirements applicable to
all extension cord uses on campus:
1. Extension cords shall not be used as a substitute for fixed or permanent wiring.
2. Extension cords may be used for temporary applications only. “Temporary”
generally means it is associated with a one-time job or with a transient condition.
Install permanent wiring for long-term or repetitive needs. An extension cord may
be used while awaiting permanent wiring.
3. Extension cords shall not be run through holes in walls, ceilings, or floors.
4. Extension cords shall not be run through doorways or windows unless approved
by the EH&S Office.
5. Extension cords shall not be permanently attached to building surfaces.
6. Extension cords shall not be concealed by walls, ceiling, or floors.
7. All extension cords shall be clean and properly maintained with no exposed live
parts or conductors, exposed underground metal parts, splices, substantial
abrasion, or other damage that might compromise its safe usage
8. Extension cords may not be daisy-chained (one extension cord plugged into
another extension cord) (See Figure 1 below)
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College of William & Mary
Extension Cord Safety & Use Guidelines
9. Relocatable power taps shall be plugged directly into an approved permanently
installed receptacle. (See Figure 1 below)
10. Damaged extension cords shall not be spliced or repaired with electrical tape.
11. The molded plug assembly on the extension cord shall not be repaired or
replaced as this negates its Underwriter Laboratories(UL) listing.
12. Plug-in multi adapters are prohibited from use on campus.
13. Never use two-conductor extension cords (commonly referred to
as “zip cords”). All 120 VAC extension cords used at the College
must be three-conductor (grounded) - even if the device it
serves uses a two-prong plug.
14. Extension cords should not be used for heat-producing appliances such as
coffee pots, toasters, and space heaters. The load from these devices often
approaches the circuit capacity, and the added cord length increases the chance
of overheating. In addition, the appliance cord to extension cord connection is
subject to wear and tear, causing localized heating.
15. All temporary cords shall bear the approval marking of UL or other NRTL. Look
for the UL® Mark or equivalent safety standard listing on extension cords you
purchase. This means that representative samples of the cord have been tested
for forseeable safety hazards for their intended purpose.
16. Store all cords indoors when not in use. Outdoor conditions--especially sunlight-can deteriorate a cord over time.
17. Unplug an extension cord when not in use. The cord will still conduct electricity
until it is unplugged from the outlet.
18. Some indoor cords with more than one outlet have covers for the unused
openings. Use them; they prevent debris and moisture from entering the unused
outlets.
19. Do not use extension cords that are cut or damaged. Touching even a single,
exposed strand of wire can give you an electric shock or burn.
20. As a safety feature, extension cords and most appliances have polarized plugs
(one blade wider than the other). These special plugs are designed to prevent
electric shock by properly aligning circuit
conductors. If a plug does not fit, have a qualified
electrician install a new outlet.
21. Never file or cut the plug blades or grounding pin of
an extension cord or appliance to plug it into an
ungrounded outlet. Submit a Facilities
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Extension Cord Safety & Use Guidelines
Management work request to have an electrician install a new outlet with the
proper polarized connections.
22. Keep cords out of work areas. If this situation is unavoidable, secure the cord to
the floor with tape or use cord molding. Position cones or other attention-getting
warnings to alert passersby.
23. Do not permanently mount power strips to any facility surface. Note that power
strips are equipped with mounting slots and hardware. This allows you to
temporarily mount the power strip while in use. The power strip should be
removed immediately when finished with your work.
Figure 1
Offices
 Extension cord use is prohibited in offices except when used to power
holiday decorations. In these instances, the extension cord use should
not exceed 90 days and the extension cord should be unplugged and put
away immediately after the decorations have been taken down.
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College of William & Mary
Extension Cord Safety & Use Guidelines
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Relocatable power taps (RPTs) equipped with integral circuit breakers are
allowed for use in offices and there is no time restriction on their use.
Surge protection devices (SPDs) equipped with integral circuit breakers
are allowed for use in office areas where protection of sensitive
equipment is desired. Like RPTs, there is no time restriction on the use
of SPDs.
RPTs and SPDs must be plugged directly into a wall receptacle.
Do not connect two or more RPTs, SPDs, extension cords or any
combination of the three together in series. This practice is commonly
referred to as daisy chaining and it is prohibited.
Submit a work request to Facilities Management for installation of a
receptacle for the appliance. If an extension cord must be used
temporarily, choose the shortest one that will work, and at least one size
larger than the appliance cord.
Research Labs
Power strips shall not be permanently mounted to any facility surface.
For equipment racks, test benches, test carts, and similar apparatus, the
preferred method of supplying 120 VAC utility power to rack-mounted
instruments is with a special raceway power strip specifically designed for
permanent installation.
Residence Halls
 Non-fused relocatable power taps and flexible extension cords are
prohibited in residence hall rooms.
 Multi-plug adapters are also prohibited.
 Relocatable power taps (RPTs) and/or surge protection devices (SPDs)
are allowed provided they are grounded and equipped with an integral
circuit breaker.
 RPTs and SPDs must be plugged directly into a wall receptacle.
 RPTs may be used to provide additional receptacles for student items
that require less than 600 watts each.
 Students should also ensure that they do
not exceed the total watts capacity of the
RPT. You do this by adding the watts
required to power each device you plug
into the RPT and then comparing this to
the RPT specification on the package or
on the back side of the device.
 SPDs are used when protection of
sensitive electronic devices such as a
computer is desired. When SPDs are
used the same rules above for RPTs apply to SPDs.
 Improper use of an extension cord or multiplug adapter is considered a
violation of the Housing Contract and the College’s Fire and Life Safety
Program. Infractions may result in College judicial action for applicable
residents.
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College of William & Mary
Extension Cord Safety & Use Guidelines
Construction, Maintenance, Repair & Renovations
With the wide use of power tools on construction sites, flexible extension cords
often are necessary. Because they are exposed, flexible, and unsecured, they
are more susceptible to damage than fixed wiring.
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Extension cords with an equipment grounding conductor must be used at
all times.
Extension cords must be protected from damage, and not run through
doorways or windows where the doors or windows may close, causing
damage to the cord. If becomes necessary to run a cord through a
doorway or window, then additional means to protect the cord from
pinching, scraping and other damage must be provided.
Extension cords must be plugged into a circuit protected by a ground fault
circuit interrupter on wet or outdoor construction and maintenance sites,
or have the ground circuit checked for continuity in an assured grounding
conductor program.
Detachable multi-tap adapters may not be used on extension cords nor
on receptacles.
Extension cords should not be run through water or allowed to have
connections that may be exposed to puddling water.
Extension cords should be a minimum of 16 AWG and be rated for the
equipment in use. The following is a guide that might be helpful in
selecting the cord:
Extension Cord Ampere Rating
Wire Size
Single Phase Two and Three Conductor Cords
Three Phase Cords
(Copper)
16AWG
13 amps
10 amps
14AWG
18 amps
15 amps
12AWG
25 amps
20 amps
10AWG
30 amps
25 amps
8AWG
40 amps
35 amps
6AWG
55 amps
45 amps
4AWG
70 amps
60 amps
2AWG
95 amps
80 amps
Special Events
A Special Event is a one-time or infrequently occurring event outside normal
programs or activities of the sponsoring or organizing body. Special Events are
temporary and can be held indoors or outdoors. Due to the temporary nature of
these events and that they oftentimes involve outside vendors/organizations who
are unfamiliar with University electrical safety expectations, the following
provides a list of University requirements for extension cord use on campus:
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Extension Cord Safety & Use Guidelines
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All extension cords used on campus for temporary events shall be size
#12 AWG minimum, and marked for hard usage.
Cords used outdoors shall also be size #12 AWG minimum and marked
for wet locations in addition to hard usage.
Extension cords used for temporary and/or outdoor events shall have
molded connectors at each end (no repaired cords).
Extension cords used outdoors shall be plugged into a GFCI protected
outlet, contain integral GFCI protection, or be augmented with a GFCI
device or “pigtail.”
Cords with molded multiple receptacles are acceptable if the total load
does not exceed the cord ampacity.
Detachable multi-tap adapters may not be used on extension cords nor
on receptacles.
RPTs and SPDs are not permitted for use outdoors.
Extension cords shall be protected to prevent damage and to minimize
the trip hazard to event attendees.
A UL Listed TVSS may be installed OUTDOORS if evaluated to UL50
with appropriate NEMA Type rating assigned to the device.
Types of Cords
Extension Cords
Extension cords come in either two or three-wire types. Two-wire extension
cords should be used to operate one or two small appliances. Three-wire cords
are used for outdoor appliances and electric power tools. The third wire on the
cord is a ground. This type of cord should never be plugged into an ungrounded
electrical outlet. Only grounded extension cords shall be used with power tools.
One exception to this is if the power tool is double insulated.
Extension cords are intended only for temporary use (generally not to exceed 90
days) with portable equipment with one exception. Extension cords may only be
used for: remodeling, maintenance, repair or demolition of buildings and for
temporary, holiday needs. The one exception is for research projects in which
temporary electrical power and lighting, 600 volts, nominal or less, may be used
for the duration of the experimental or developmental work even if it exceeds the
90 day limit and the cord(s) is removed immediately upon completion of the
experiment.
In addition to the total electrical load, the conditions of use affect extension cord
safety. Rated capacity for an extension cord assumes it will be used in an openair and straight configuration.
As electric current passes through a wire, electrical resistance causes some
voltage drop and heating of the wire. Coiling or winding excess cord length can
concentrate this heat and overheat the cord. Similarly,
covering a cord with a rug or rag can trap heat and overheat
the cord. This trapped heat can damage the cord and lead to
a fire. Tying a knot in a cord can have a similar outcome.
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College of William & Mary
Extension Cord Safety & Use Guidelines
Relocatable Power Taps (RPT)
There are two types of RPTs. The first type is commonly referred to as a “power
strip” or “power cord.” Power strips/cords are Listed by Underwriter Laboratories
under the product category Relocatable Power Taps (RPT). The second type of
relocatable power tap is commonly referred to as a “surge protector” or “surge
suppressor.” These devices are provided with transient voltage surge
suppression (TVSS) and are Listed by Underwriter Laboratories both as a
Relocatable Power Taps (RPT) and as a Transient Voltage Surge Suppressors.
Both power strips/cords and surge protectors/suppressors are variations of an
extension cord.
The main purpose of a power strip is to
provide multiple outlets for you to plug-in
things that require electricity. Most
power strips have an On/Off indicator
light. In addition, power strips can be equipped with an integral circuit breaker.
The circuit breaker, or fuse, protects the power strip against excessive loads. If
you draw too much current because you plug in too many devices or one big
appliance like a heater then the fuse or circuit breaker will open. This prevents
the power strip from overheating that can result in a fire. All power strips used at
the College of William and Mary must be equipped with an internal circuit
breaker.
Power strips are commonly used in offices to provide multiple receptacles to
office equipment. Power strips are also used in the Residence Halls to provide
power to student electronic equipment such as computers, printers, cell phones,
and Ipod/MP3 devices. They are generally priced under $10.
Due to their size, it is often difficult
to plug more than two or three AC
adaptors into a power strip. Mini
extension cords are available to
facilitate AC adaptor connections to
the power strip receptacles. These
mini extension cords are allowed for
use on campus.
A surge protector looks very similar
to a power strip because it also
provides multiple outlets, but their
main purpose is to provide
protection from power surges.
Surge protectors should have an
indicator light on them that tells you
the surge protection component is
working. Some also have phone
and cable jacks. Surge protectors/suppressors are used to protect sensitive
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College of William & Mary
Extension Cord Safety & Use Guidelines
electronic equipment such as computers, monitors, scanners and printers from
transient over-voltages. Surge protectors are generally priced between $20$170, depending on the level of surge suppression the unit can provide and the
time it takes for the unit to react to a surge.
Surge control is important because even small surges or spikes can eventually
destroy or affect the performance of expensive electronic equipment. Damage
can occur either instantaneously or over time as smaller surges that cause the
gradual deterioration of internal circuitry. This gradual deterioration is often
referred to as “electronic rust.”
Surge protectors are equipped with a metal oxide varistor (MOV) inside the
casing. The MOV acts like an electrical sponge because it absorbs dangerous
excess voltage and prevents most of it from reaching sensitive equipment. But
like a sponge, surge protectors have a limited capacity to absorb. Once the
capacity is reached, the unit is no longer protecting the equipment and it should
be replaced. Most surge protectors will continue to function as a power strip
even though the MOV may have been destroyed by a power spike. There are
two possible hazards created when this occurs: 1) If another power surge
occurs, it can damage the equipment plugged into the surge protector; and 2) If
sufficient voltage passes through the surge protector due to a second power
spike, a resistant short may be formed that allows heating to occur inside the unit
which can lead to a fire. For these reasons Surge protection devices that do not have any visual or audible indication
that the MOV is functioning properly, as well as devices manufactured
before 1998, should be removed from serviced and disposed.
What Are Surges and Spikes?
Surges and spikes are an increase in "normal" electrical line voltage, often caused by a
sudden change or demand for more electricity, such as turning on a large appliance,
garbage disposal, air conditioner, washer, dryer, etc.
A surge typically measures less than 500V and lasts less than two seconds.
A spike, by definition, is much shorter in duration - less than one-thousandth of a
second (millisecond), but can measure into the thousands of volts.
Either type of disturbance can damage electronic equipment beyond practical repair. In
addition to change in demand for electricity, bad weather (lightning) and everyday
electric utility company switching and maintenance can produce damaging electrical
surges on the power line.
Shop Made Cords with Receptacle Boxes
Among the most common electrical violation is when a multiple receptacle box,
designed to be surface mounted, is fitted with a flexible cord and is placed on the
floor to provide power to various tools or equipment. These are not permitted
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College of William & Mary
Extension Cord Safety & Use Guidelines
and should be taken out of service. Other common problems associated with
shop made cords are the use of Romex wire for making up extension cords, the
use of the wrong size circuit breakers/overcurrent protection and the use of
equipment outdoors that are listed for dry locations only.
Flexible Cords
Flexible cords and cables are attached to appliances and should not be confused
with extension cords that supplement the regular supply cords. Flexible cords
can be used as pendants, for the wiring of fixtures, for the connection of portable
lamps and appliances, for the connection of stationary equipment that is
frequently moved, and to prevent transmission of noise or vibration and allow
movement.
Flexible cords used for pendants must be provided with strain relief. Generally
flexible cords that are designed into machinery are not a problem as long as they
are in good condition.
Cord Selection Guidelines
Extension cords must be rated “HEAVY DUTY” or
“EXTRA-HEAVY DUTY” and must be a continuous
length. Cords classified as SO, ST, and SJ meet
this requirement.
12 gauge
14 gauge
16 gauge
Extension cords must be of sufficient currentcarrying capacity to power the device(s) connected
to it (See ampacity table below). Long extension
cords require increased conductor size to
compensate for voltage drop.
A good rule of thumb is to use a cord that is one gauge heavier for every
100 feet of additional cord length.
Cord
Length
0-2
Load Ampere (Current) Rating
2-5
5-7
7-10
10-12
25 ft
16 ga
16 ga
16 ga
16 ga
14 ga
14 ga
50 ft
16 ga
16 ga
16 ga
14 ga
14 ga
12 ga
100 ft
16 ga
16 ga
14 ga
12 ga
12 ga
150 ft
16 ga
14 ga
12 ga
12 ga
200 ft
14 ga
14 ga
12 ga
10 ga
12-15
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College of William & Mary
Extension Cord Safety & Use Guidelines
Construction sites require extension cords that are specified for hard usage or
extra hard usage. Approved cords may be identified by the word “outdoor” or the
letters “WA” on the jacket.
Extension cords with molded multiple receptacles are acceptable if the total load
does not exceed the cord ampacity.
Power strips are designed for a high concentration of low ampere loads.
Allowable Cord Uses
Extension Cords
Extension cords must be of the proper type, size, and voltage and current rating
for the intended application. The cord shall not be substantially longer than
required for the application.
For 120 VAC single-phase service, only unmodified,
commercially manufactured extension cords equipped with
three-wire plugs and receptacles may be used. In general,
these cords shall have molded plugs and receptacles.
Multi-tap (“3-way”) extension cords are acceptable.
The jackets of commercially manufactured extension cords
must indicate approval by Underwriter Laboratories® or another Nationally
Recognized Testing Laboratory (NRTL).
Extension cords for special applications, such as 208 VAC or 480 VAC threephase service, may be shop-made as required. Only qualified persons may
fabricate or repair shop-made extension cords, including the installation of
connectors or plugs to the cord. All components of shop-made cords must be of
a type approved by an NRTL. For purposes of meeting this requirement,
“qualified persons” means a certified electrician employed by William and Mary or
subcontracted.
At the time of fabrication or repair, shop-made extension cords shall be tested by
qualified persons for proper wiring and grounding.
Relocatable power taps
Bench top use of RPTs on “wet” laboratory benches will be allowed only if they
are provided with GFCI protection or the RPT is hung on mounting screws above
the benchtop.
Ground Fault Circuit Interrupters (GFCI's)
The GFCI is a fast acting device that senses small current leakages to ground.
Within 1/40 of a second it shuts off the electricity and "interrupts" the current
flow. It provides effective protection against shocks and electrocution. GFCI's
are required for use on all construction sites and projects. GFCI's are also
required when work is conducted in wet or damp locations. If outlets are near
sinks, showers or water fountains a GFCI may be required.
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College of William & Mary
Extension Cord Safety & Use Guidelines
Disallowable Cord Uses
Extension cords
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Extension cords may not be used in place of permanent facility wiring.
Cords shall not be attached to building surfaces or structural members.
Cords shall not be permanently concealed in walls, ceilings, or under
floors - including raised computer floors.
Do not run cords through moisture, tied to over-head pipes, across
traveled roads, under carpets, or across areas of high foot traffic.
Extension cords may not be run through doors, ceilings, windows, holes
in walls, or through hinged door openings in enclosures. This is to prevent
“pinch” damage to the cord. If it is absolutely necessary to run an
extension cord through a doorway or open window for short-term use, the
cord must be protected from damage should the door or window slam
shut; it must be removed immediately when no longer in use; and must
not be a trip hazard.
Do not use extension cords that are frayed, cut, or damaged such that
inner conductors show, or that have outer sheaths which have pulled
loose from their molded plugs exposing the inner conductors. In
particular, do not use a cord that has a bare conductor exposed.
Detachable multi-tap adapters may not be used on extension cords nor
on receptacles.
Cords may not be repaired
Relocatable Power Taps (i.e. Power Strips and Surge Protectors)
Relocatable power taps are not intended to be series connected (daisy chained)
to other relocatable power taps or to extension cords.
Relocatable power taps use is intended for indoor use only. Therefore they shall
not be used at construction sites and similar locations.
Relocatable power taps are not intended to be permanently secured to building
structures, tables, work benches or similar structures.
Relocatable power taps are not intended to be used as a substitute for fixed
wiring.
Relocatable power taps shall be plugged directly into a permanently installed
receptacle.
The cords of relocatable power taps shall not be routed through walls, windows,
ceilings, floors or other similar openings.
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College of William & Mary
Extension Cord Safety & Use Guidelines
RPTs are never acceptable for the following uses unless they are equipped with
GFCI protection:
 Aquariums
 To power any water pumping equipment
 Use in a damp location
 Use in a cold room
 Use near a sink or other water source
RPTs may never be used in an area that may contain flammable vapors (i.e.
solvent storage room, paint cabinet, flammable cabinet, or hazardous waste
storage room) even if they are equipped with a GFCI device. These
environments require specially rated, intrinsically safe power equipment to
prevent explosions.
Equipment with a heating element should not be connected to a RPT. Examples
include:
 Hot plate
 Water bath
 Heat gun
 Coffee pot
 Toaster oven
 Space heater
 Refrigerators
 Copy machines that are not computer printers
 Office fans
 Microwave ovens
 Hair dryers
 Any other single load exceeding 600 watts
Multi-plug adapters
Multi-plug adapters are generally not fused. Therefore in many cases the only
protection against overload is the circuit fuse which may have a rating higher
than the adaptor. Power strips equipped with integral circuit breakers are
generally considered a safer alternative to "double adaptors", "two-way plugs",
"three-way plugs" or "cube taps" which plug directly into the socket.
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