EUGENE WATER  &  ELECTRIC  BOARD

An electric forced air system is a single heating unit controlled by a single thermostat that supplies heat to the entire house by fan-forced air through duct work.

Ducts are often concealed in crawlspaces, attics or walls and deliver heat through an adjustable register.

The volume of air within the house is continually cycled through the system by return air ducts.

Electric forced air systems generate heat through high resistance wires called heating elements. Electricity flowing through the elements generates heat that is distributed throughout your home by a fan or blower which forces air through the elements, and directs the heated air into the ductwork.

A single thermostat controls the heating unit which turns the unit On or Off according to the set temperature. When the system turns on, electricity generates heat in the elements and the furnace fan forces air over the elements and distributes the heated air out the ducts and through the registers.

Usually, registers have built-in adjustable louvers to control the amount and direction of air flow.

The flow of electricity to the elements stops when the set temperature is reached. The fan shuts off once the unit cools down.

The air filter is the most important maintenance item in your electric forced air system because if clogged, the entire system has to work harder and run longer to deliver heat. Replace or clean the filter monthly during the heating season, and at least every three months during the remainder of the year. Many thermostats do not accurately measure the room temperature. This means that although you set the thermostat to 68 it may actually allow the room temperature to climb several degrees higher than your "set point" before shutting the system off. To check the accuracy of your thermostat, place a thermometer in a central location in the room. Check the thermometer reading against the reading on your thermostat. Are they the same? Experiment with the thermostat so you will know where to set it next time. Remember, the lower you keep the temperature setting, the lower your energy costs. Brush and vacuum fan blades and the fan enclosure area when replacing or cleaning the filter, and clean registers often with a vacuum or brush.

A technician should inspect and service your system annually. A service check should focus on:

• blower motor bearings for lubrication.
• belts (if any) for wear and tension.
• electrical connections for burned or frayed wires.
• calibration of the thermostat anticipator.
• operating amperage on motor and elements.
• overheat limit sensors.
• pressure balance of the system so that it will work at its optimum by delivering heat at every register.

Create greater system efficiency by sealing the plenum (where the ducts attach to the furnace) and ductwork at all seams and joints. By doing so, you could prevent a 15 - 40 percent loss of delivered air.

Going away for a while? If so, programmable thermostats are available to automatically "set back" the temperature while you are gone and while you sleep. You also can choose from several different types of air filters that reduce the amount of pollens and mold spores in the air.

The cost of operating the system is affected by many variables, for instance:

• leakage from air ducts affecting efficiency.
• insulation of the duct work.
• the size of the system compared to the size of your home.
• outdoor temperature and desired indoor temperature.
• the age of your home and the forced air system.
• whether or not your home is insulated.
• maintenance of the system.

Nevertheless, an example of an annual heating cost for a "typical" 1500 square foot, well-insulated house in Eugene heated by an electric forced air system is about $783 a year for heating only. This example assumes a 70 percent delivery efficiency of the system, and a $.04015 rate per kWh (kilowatt hour.)

Some basic steps in trouble shooting your system include:

• check to make sure the thermostat is on.
• check to make sure the service breaker is on.
• check for a clogged filter.
• check to see if the registers are open.

Call your service technician in cases where only cool or cold air is delivered, the system cycles on and off continually, the fan runs constantly, or the system breaker keeps "popping."