Understanding An Electric-Resistance Furnace

by Darwin Hall

electric furnace

To envision an electric-resistance furnace, think of a giant toaster with air 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.  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.  The chart below list a 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.

Keeping Air Moving

nest thermostatIf some rooms in your home are consistently too hot or cold, don’t blame the furnace.  Instead, take on a simple “balancing” project.  To balance a forced-air system, you reduce the airflow to a room that is too warm.  Warm air then reaches cold areas, typically those furthest from the furnace.

You already may have tried balancing by partially or totally closing registers in the hotter rooms.  This cools the room off, but it doesn’t redirect the air.  Instead, look for dampers in the ductwork.

Dampers are controlled by a handle or locknut arrangement.  You may find one at the point where each duct takes off from the furnace plenum.  Not all duct systems have dampers, so consider installing them.

Identify which ducts serve each room, and label their dampers.  Close them one at a time to determine which room isn’t getting air.  Wait for a cold day to begin the balancing procedure.

If only one or two rooms have airflow problems, you might be tempted to adjust only the dampers.  Because balancing is a robbing-Peter-to pay Paul proposition, however, you’ll get better results by tuning the entire system.

troubleshooting a furnace

Watch the VideoMost electric resistance furnaces are now almost obsolete because of the cost to operate them.  Essentially, you have a large space heater for home heating.  If your home is older, this kind of unit may be present.  The main thing to remember is to make sure you oil the blower motor and keep it in good working order.

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