Wiring Safety: Selecting The Right Wire Size

(HIT) - Knowing how to select the right wire size for circuits and extension cords can save you money, and improve your family's safety. If an extension cord is undersized, it creates a drop in voltage from one end of the wire to the other. This shortens the life of motors and other equipment, and wastes energy. Here are some wiring safety tips to help you select the right wire size:

All electrical conductors (wires) have a resistance to the flow of electricity. This resistance causes a drop in voltage from one end of the wire to the other. If the wire size is small or the circuit run is long, the resulting voltage drop can be great enough to cause problems.

Wires should be large enough to limit voltage drop to 2%, when measured from the electric panel to the specific appliance or equipment. Exceeding 2% can cause motors to overheat and fail. It also lowers the performance of lighting and heating devices, as shown in the table below.

So how do you know the correct size wire to use for a long circuit run, or the effect of running a long extension cord to an appliance? The easiest way is to use reference tables that do the calculations for you. You'll need to know the approximate length of the circuit (in feet) and the amount of electric current required by the appliance (in amps). Apply these values to reference tables that provide the minimum size conductor needed to limit voltage drop to 2%.

One source is the "Agricultural Wiring Handbook". This book contains 29 wire selection tables and other useful information to help you select the right wire size. Both copper and aluminum conductor tables are included, for circuit runs up to 2,000 feet.

To learn more about wiring safety and sizing circuits, talk with an experienced electrician or supplier of electrical materials. For information on the "Agricultural Wiring Handbook", including ordering information, visit the National Food and Energy Council Internet site at www.nfec.org or call weekdays at 1-937-383-0001.

Courtesy: Home Improvement News and Information Center