Electric Resistance Heating
Electric resistance heat can be supplied by centralized forced-air electric furnaces or by heaters in each room. Electric resistance heating converts nearly all of the energy in the electricity to heat.
Types of Electric Resistance Heaters
Electric resistance heat can be provided by electric baseboard heaters, electric wall heaters, electric radiant heat, electric space heaters, electric furnaces, or electric thermal storage systems.
With electric furnaces, heated air is delivered throughout the home through supply ducts and returned to the furnace through return ducts. Blowers (large fans) in electric furnaces move air over a group of three to seven electric resistance coils, called elements, each of which are typically rated at five kilowatts. The furnace's heating elements activate in stages to avoid overloading the home's electrical system. A built-in thermostat called a limit controller prevents overheating. This limit controller may shut the furnace off if the blower fails or if a dirty filter is blocking the airflow.
Electric Baseboard Heaters
Electric baseboard heaters are zonal heaters controlled by thermostats located within each room. Baseboard heaters contain electric heating elements encased in metal pipes. The pipes, surrounded by aluminum fins to aid heat transfer, run the length of the baseboard heater's housing, or cabinet. As air within the heater is warmed, it rises into the room, and cooler air is drawn into the bottom of the heater. Some heat is also radiated from the pipe, fins, and housing.
Electric Wall Heaters
Electric wall heaters consist of an electric element (with a reflector behind it to reflect heat into the room) and usually a fan to move air through the heater. They are most frequently installed on interior walls because installing them in an exterior wall makes that wall difficult to insulate.
Electric Thermal Storage
The most common type of electric thermal storage heater is a resistance heater with elements encased in heat-storing ceramic. Central furnaces incorporating ceramic block are also available, although they are not as common as room heaters. Storing electrically heated hot water in an insulated storage tank is another thermal storage option.
All types of electric resistance heating are controlled through some type of thermostat: baseboard heaters often use a line-voltage thermostat (the thermostat directly controls the power supplied to the heating device), while other devices use low-voltage thermostats (the thermostat uses a relay to turn the device on and off). Since baseboard heaters supply heat to each room individually, they are ideally suited to zone heating, which involves heating the occupied rooms while allowing unoccupied sections to remain cooler.
Visit the Energy Saver website for more information about electric resistance heating in homes.