How Radiator Heaters Work

Steam Heat

Traditional steam radiators are powered by hot water. A boiler heats water to steam, and that water flows upward into the radiator. As it cools, it turns back into water and trickles back down into the boiler. Sometimes the flow of water is helped along by pumps, particularly in large buildings.

Electric Heat

Electric radiators turn electricity directly into heat. An electric current runs through a resistor--a material that resists the flow of electricity, turning its energy into heat. This resistor is called the heating element and is always inside the radiator. In some electric radiators, the heating element is kept in a bath of oil. The heat diffuses through the oil, which helps spread it evenly to the radiator.

Dispersing the Heat

All radiators work through a process called convection. The radiator heats the air directly above and around it, causing it to expand. Because hot air is less dense, it rises into the air. New cold air fills the space the hot air just vacated and gets heated. This creates a continuous current of air, heating, rising and spreading out, then cooling and descending again. These convection currents can heat an entire room, although the heat does take time to spread

Speeding Up the Process

Because radiators only heat the air directly above and around them, many have fins to increase their surface area. These fins conduct the heat away from the heating element or steam tube. In this design, the radiator heats the air between the fins as well as the air directly above the radiator. This makes for more powerful convection currents, which spread the heat much more quickly.