electric forced air heating
Electric forced air heating systems are much like forced air
systems fueled by gas or oil. A typical electric forced air
system in a home has a furnace, made up of a heating coil
package and blower unit, that pushes warm air to registers
throughout the home via ductwork.
Advantages
• Electric furnaces are compact and easy to locate in the
home. No vents, combustion air or fuel storage are
required.
• A cooling coil can be easily added to provide air cooling
in warm weather.
• Humidification is easily achieved by adding a humidifier
in the supply ductwork.
• Air can be filtered to alleviate allergies caused by
airborne particles and to keep the house clean.
• Ductwork and registers are less intrusive in rooms than
electric baseboard heaters.
Disadvantages
• Because it’s more difficult to install zoned heating,
where room temperatures are separately controlled,
some heat is wasted.
• All forced air systems have higher capital costs and
require more maintenance than electric baseboard
heaters.
Furnaces
The most common electric forced air system is one with a
furnace unit. Furnace units are composed of a blower, air filter
and heating elements, all contained in a metal cabinet. They
also contain contactors or relays, blower controls and a hightemperature
safety cutout. Switching of the heater elements
is normally done in increments of 5 kilowatts (kW) or less to
prevent the lights dimming or flickering, which can occur when
large loads are switched.
Furnaces are available in sizes over 10 kW. For larger loads,
two or more furnaces, each located near the area they serve,
should be considered. This can provide the added advantage
of zone heating—one furnace for the bedroom wing and a
separate one for the living areas.
Temperature control
Furnaces are best controlled by low-voltage thermostats
located in an area where they will sense the average conditions
inside your whole home.
An electronic programmable thermostat will also improve
comfort and energy savings, if used correctly.
Air circulation, filtering and
ventilation
Because forced air furnace systems usually use one thermostat
to control heat in all areas, the furnace must keep all rooms
warm. In trying to provide all-around comfort, the furnace may
overheat some rooms, wasting heat.
Constant air circulation helps to alleviate this problem by
circulating sun-warmed air to other areas. However, it is better
to install zone heating, using two or more heating units and
appropriate duct work and controls. While this reduces energy
consumption, it will cost more to install.
Because forced air systems draw air through a central blower,
air can be filtered to keep the home clean and to alleviate
allergies caused by airborne particles.
If you choose to ventilate the home by introducing outside
air into the return air duct, the furnace fan can be controlled
by a dehumidistat that operates the fan intermittently. In cold
climates (winter design temperature of -10 °C or below) a
motorized damper, also controlled by the dehumidistat, should
be installed in the fresh air duct. If your budget permits, this is
also desirable in milder climates.
Recommendations for
installation
• Size equipment correctly. An under-sized furnace won’t
keep your home warm enough in cold weather. Installing
an oversized furnace (a more common mistake) results
in higher costs for the furnace and the larger ductwork
required, extra load on the service panel, and short-cycling
of the furnace.
• Ensure your unit is CSA approved.
• Ensure good duct design and installation. Employ a
contractor accredited by the Thermal Environmental
Comfort Association (TECA), who will design and install
duct systems in accordance with the Quality First Forced
Air Guidelines. For names of accredited contractors in your
area, contact the association at 1 888 577-3818.
Copyright 2008, BC Hydro. All rights reserved. May not be reproduced,
in whole or part, without the express written consent of BC Hydro.
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