Extension Cord Safety & Use Guidelines

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:

Extension cords shall not be used as a substitute for fixed or permanent wiring.
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.
Extension cords shall not be run through holes in walls, ceilings, or floors.
Extension cords shall not be run through doorways or windows unless approved by the EH&S Office.
Extension cords shall not bepermanently attached to building surfaces.
Extension cords shall not be concealed by walls, ceiling, or floors.
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
Extension cords may not be daisy-chained (one extension cord plugged into another extension cord) (See Figure 1 below)

Relocatable power taps shall be plugged directly into an approved permanently installed receptacle. (See Figure 1 below)
Damaged extension cords shall not be spliced or repaired with electrical tape.
The molded plug assembly on the extension cord shall not be repaired or replaced as this negates its Underwriter Laboratories(UL) listing.
Plug-in multi adapters are prohibited from use on campus.
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.
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.

All temporary cords shallbear 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.
Store all cords indoors when not in use. Outdoor conditions--especially sunlight-- can deteriorate a cord over time.
Unplug an extension cord when not in use. The cord will still conduct electricity until it is unplugged from the outlet.
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.
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.
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.
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 Management work request to have an electrician install a new outlet with the proper polarized connections.
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.
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.
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.

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.

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
(Copper) / Single Phase Two and Three Conductor Cords / Three Phase Cords
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

Outdoor Events

Extension cords with molded plug assemblies shall be used for outdoor events.
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 tooperate 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 open-air and straightconfiguration.

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.

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 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 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.