Introduction

To envision an electric-resistance furnace, think of a giant toaster with a fan blowing through it. As air pushed by the blower moves through the heating elements, it picks up warmth, then continues into the plenum and ducts to registers in each room.

Because no combustion occurs in an electric furnace, it doesn't require the flue or heat exchanger that gas and oil furnaces must have. Therefore, maintenance is almost nil. Operating costs, however, usually run substantially higher.

Check the anatomy drawing at right. An air-circulation switch -- often on the house thermostat, but sometimes on the furnace -- lets you run the blower continuously, if you wish. Underneath, accessible through a removable cover, there may be fuses or breakers for each of the heating elements. A transformer steps up amperage to the high levels needed for heating. Relays turn the elements on or off according to instructions from the thermostat.

If your home has a heat pump, it may have resistance-type duct heaters, like the one shown here. These mini-furnaces automatically pitch in when the temperature drops below what a heat pump can handle by itself.

The information on the next page describes the few things that can go wrong with electric-resistance furnaces and what you can do about them. Always shut off the furnace's main circuit breaker before removing the control or access panels. You'll find the breaker located next to the furnace or in your home's main service panel. Don't attempt to work on the heat elements -- that's a job for a professional.