Critics of radiant heat say that it can be difficult to control air temperature with a thermostat. The large heat-storage capacity of the concrete or plaster surrounding the heating cables may result in greater-than-normal fluctuations in the room air temperature, since it takes quite a while to heat up the storage mass. Also, some occupants complain about their heads being too warm in rooms that utilize ceiling radiant heat.
Supplying heat at the ceiling or floor, which are locations that typically border the outdoors or unheated spaces, can result in greater heat losses. For example, if there are any flaws in a heated concrete slab or gaps in the ceiling insulation above heating elements, a significant percent of the electric heat may escape to the outdoors without ever heating the home.
Electric Space Heaters
Electric space heaters come in a wide variety of models, either built-in or portable. These heaters may have fans to circulate heated air and may also be designed to transfer some of their heat by radiation. All of these heaters must be given adequate clearance to allow air to circulate safely.
Portable space heaters, as well as many built-in space heaters for small rooms, have built-in thermostats. Larger rooms heated with built-in electric space heaters should have low-voltage thermostats installed in an area that maintains the room's average temperature.
Portable electric space heaters can pose a significant safety hazard unless they have safety features and are used properly. Many cheaper or older portable electric space heaters are not safe for most home uses. Their red-hot elements and lack of safety features can lead to fires. When buying a portable electric space heater, select one with all of these safety features: - tip-over switch that automatically shuts off the heater if it falls over,
- protective grille to prevent anyone from touching the heating elements, and
- sealed heating elements encased in metal or ceramic.
To use your portable electric space heater safely, follow these guidelines. - Check what other appliances share the space heater's electric circuit to prevent overloading circuits.
- Avoid using extension cords.
- Inspect the cord on the heater for any cracks or worn spots, and replace the cord or heater if any are found.
- Make sure the area in which you are using the heater has a properly functioning smoke detector.
- Keep combustible objects, such as blankets, furniture, drapes, toys, etc., at least six feet (two meters) away from the heating elements.
Electric Furnaces
Electric furnaces can be a more expensive long-term heating option because of their duct heat losses. The home's air is delivered to the furnace through return ducts, and heated air is delivered back to the home through supply ducts. If these ducts run through unheated areas, they lose some of their heat through air leakage as well as heat radiation and convection from the duct's surface.
Blowers (large fans) in electric furnaces move air over a group of three to seven electric resistance coils, called elements, which are each rated at five kilowatts. The furnace's heating elements activate in stages to avoid overloading the home's electrical system. Overheating is prevented by a built-in thermostat called a limit controller. This limit controller may shut the furnace off if the blower fails or if a dirty filter is blocking air flow.
Electric Thermal Storage
Some electric utilities structure their rates in a way similar to telephone companies and charge more for electricity during the day and less at night. They do this in an attempt to reduce their "peak" demand.
If you are a customer of such a utility, you may be able to benefit from a heating system that stores electric heat during nighttime hours when rates are lower. This is called an electric thermal storage heater, and while it does not save energy, it can save you money because you can take advantage of these lower rates. However, electric thermal storage is a seldom-used type of electric heating.
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.
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