For the most part, electrical resistance heating is used for area heaters such as panel or baseboard heaters. It is also used, although less often, for central heating. The heating mechanism in a boiler or furnace is very simple. Electrical resistance coils are immersed directly into the water (for a boiler) or airstream (for a furnace). As the electrical current passes through the coils, they get hot and directly transmit their heat to the air or water. Unlike oil and gas energy, the conversion of electrical energy to heat is 100 percent. There is no heat lost to the exhaust gas because there are no exhaust gases. There is no fuel combustion with this system. Consequently, there is no need for a chimney.
From an installation point of view, electrical resistance coils are less expensive than oil or gas burners. However, for most parts of the country, they are more expensive to operate. To keep the operating expense from becoming excessive, electrically heated homes must be well insulated. In evaluating the cost of heating a house, do not depend on the owner’s assurance (“Oh, it only costs a few hundred dollars to heat the house”). Insist upon seeing the most current year’s bills.
These units are self-contained space heaters that are used to provide warmth to a single room. Sometimes they warm up two or three adjacent rooms if the doors between the rooms are kept open. The heat distribution is not very desirable from a comfort point of view. Other than a fireplace or stove, most area heaters of today will be gas-fired or electric.
Gas-fired space heaters are basically small warm-air furnaces and can operate either as gravity or forced-air units. Some of the smaller gravity heaters have an open combustion area exposing the flames. This is a potential fire hazard and is particularly undesirable when there are small children in the house. The exhaust gases from all gas-fired space heaters must be vented to the outside. In addition, the units should have the American Gas Association seal of approval. These units are controlled either automatically by a wall-mounted thermostat or manually by a calibrated knob on the gas valve. They are inexpensive to install, relatively maintenance-free, and require only periodic cleaning and adjustment.
Electrical space heaters have an advantage over central heating systems in that each room is usually individually wired, so there are as many independent heating zones as there are rooms. There are three general types of electrical area heaters: panel, baseboard, and wall. Panel heating, sometimes called radiant heating, is similar in concept to forced-hot-water panel (radiant) heating, as described in chapter 14. However, instead of hot-water pipes being embedded in the walls or ceiling, electrical resistance cables are installed with each room having a separate control. Similarly, baseboard heaters are like baseboard convectors (see chapter 14) but they contain electrical resistance coils rather than circulating hot water. They are very popular because of the ease of installation and low initial cost. They also produce a uniform heat distribution. Some baseboard heaters have a thermostat mounted directly on the unit rather than on the wall. This is not a desirable thermostat location because in many cases it will be necessary to move furniture every time a temperature change is desired. Wall heaters are compact units mounted on or recessed into a wall. Most heaters operate in conjunction with a fan that blows the warm air into the surrounding area. They are usually used to provide heat in nonhabitable areas such as a garage or workshop and are sometimes used to supplement a central heating system. These heaters do not produce a uniform heat distribution but are very responsive to a call for heat. They are usually manually controlled rather than automatically controlled.