You've often used an extension cord around the home, but using the wrong type of cord can be dangerous. The U.S. Product Safety Commission found that extension cords are among the most dangerous electrical appliances in our homes because of improper usage. Each year, accidents from extension cords kill around 50 people, result in injuries requiring hospital treatment to 4,000 others and also cause over 3,000 residential fires.
Electrical extension cords come in many types and capacities. The capacity of an electrical extension cord to safely extend power is based on two factors:
- Gauge: Gauge is a measurement of the thickness / diameter of the wire
- Length: Length of the extension cord affects voltage drop
Gauge is how the copper wire is measured and is reported as a number. For example, you may see a No.12 gauge or a No.18 gauge. These numbers are tricky however in that the smaller the number the thicker
the wire, and conversely, the larger the number the thinner
the wire. So a No. 18 gauge extension cord may only be rated for 5 to 7 amps of load and a length of up to 25 feet. A No 10 gauge extension cord may be rated for 15 amps of load and 100 feet of length.
Length of the extension cord affects voltage drop. Voltage drop is result of the friction or resistance the electricity experiences flowing through a long wire. You want to use the shortest extension cord possible. Thought of another way, the longer the extension cord, the thicker (lower gauge number) the wire.
Let's take a look at the 3 major types of extension cords you'll find and how to safely use them.