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How to Select the Right Electrical Extension Cord for the Job
Unless you are lucky enough to have an electrical outlet positioned exactly where you need it, you almost certainly use electrical extension cords around your home, but few of us understand just how dangerous it can be to use the wrong kind of cord. The U.S. Product Safety Commission has found that extension cords are among the most dangerous electrical devices in our homes because of improper and overloaded power cord usage. Each year, accidents from extension cords kill around 50 people, resulted in injuries requiring hospital treatment to 4,000 others and also cause over 3,000 residential fires.
The reason for this? Electrical current flowing through wires generates heat, and when too much current flows through a wire, it may overheat and melt the plastic insulation and cause short circuits and fires. This is normally not a problem when you plug an appliance directly into an outlet using its factory cord, because the manufacturer has sized the cord appropriately for its electrical current load. But if you use a light-gauge household extension cord to extend the reach of that appliance, suddenly you may be putting a load on that exension cord that is much higher than it can safely carry. The result can be disastrous.
It is critical, therefore, that you choose extension cords that are correctly sized for the use. Electrical extension cords come in many types and capacities, and its load-bearing capactity depends on two factors:
- Wire gauge: the thickness/diameter of the wire affects how much current the wire can carry and how much it heats up.
- Length: the length of the extension cord affects voltage drop.
Gauge is a numerical rating of copper wire diameter, and is identified by an American Wire Gauge (AWG) number. For example, you may see a No.12 -gauge or a No.18-gauge 120-volt extension cord. Note that in the AWG rating system, smaller numbers indicate thicker wires, while larger numbers indicate thinner wires. So, a No. 18-gauge extension cord may only be rated for 5 to 7 amperes of load and a length of up to 25 feet. A No. 10-gauge extension cord, on the other hand, may be rated for 15 amps of load and 100 feet in length.
Length of the extension cord affects voltage drop—the result of the friction or resistance the electricity experiences flowing through a long wire. You want to use the shortest extension cord possible for the job at hand. In other words, the longer the extension cord required, the heavier the wire gauge needs to be. It is a good idea to keep extension cords of various lengths on hand, so that you can use one (or a combination of cords) that is just as long as you need, without excess length.
Let's take a look at the three major types of extension cords you'll find and how to safely use them.Continue to 2 of 5 below.
02 of 05
Light-duty extension cords are those that resemble lamp wire cord. These cords should never be used with anything other than very light-duty devices. They are especially dangerous to use with space heaters and other heat-generating appliances, such as toasters or clothes irons, which draw heavy electrical loads. These cords often do not include a third wire for grounding, so should never be used with appliances that have a three-prong grounded cord.
Continue to 3 of 5 below.
- Uses: lamps, clocks, and other light-duty electrical devices drawing up to 7 amps.
- Cord length up to 25 feet: use No. 18-gauge wire
- Cord length up to 50 feet: use No. 160-gauge wire
- Cord length up to 100 feet: use No. 14-gauge wire
03 of 05
Medium-duty cords usually are grounded extension cords, which include the third wire for grounding. They have plugs that accept three-prong grounded appliance cords.
Continue to 4 of 5 below.
- Uses: televisions, computers and other devices that draw up to 10 amps of power.
- Cord length up to 25 feet: use No. 16-gauge wire.
- Cord length up to 50 feet: use No. 14-gauge wire.
- Cord length up to 100 feet: use No. 12-gauge wire.
04 of 05
Heavy-duty extension cords are suitable for drawing 10 to 15 amps of power. These are always grounded extension cords that include a third wire for grounding and have plugs with three slots for accepting grounded appliance cords.
- Uses: tools and heating appliances drawing up to 15 amps of power.
- Cord length up to 25 feet: No. 14-gauge wire.
- Cord length up to 50 feet: Use No. 12-gauge wire.
- Cord length up to 100 feet: Use No. 10-gauge wire.
Note: follow appliance manufacturers instructions regarding use of extension cords. Some manufacturers of electric ovens, clothes dryers, and space heaters may specify that extension cords should never be used with their appliances.Continue to 5 of 5 below.
05 of 05
Built-In GFCI Protection
For outdoor or below-grade use, extension cords should always be plugged into GFCI-protected outlets. Where no GFCI outlet is available, you can use an extension cord with built-in GFCI protection. Heavy-duty extensions often include this feature.