Don't Undersize Circuits Or Extension Cords

(HIT)-Knowing how to select the wire size needed 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.

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. Both copper and aluminum conductor tables are included, for circuit runs up to 2,000 feet.

To learn more about 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 site at www.nfec.org or call them weekdays at 1-937-383-0001.

Courtesy: Home Improvement News and Information Center