Steam boilers transfer heat through radiators placed in each room, unlike forced air central heat, which involves warming and circulating air through vents throughout your home. The boiler heats water until steam rises through the system, warming the air. As the steam cools and returns to water, the pitch of the piping system carries the water back to the boiler, which reheats it to steam and the process continues. After decades of use, cast iron steam radiators can corrode and block up, causing noise, poor heating or no heating at all. With only a few tools, you can replace a central heating radiator.
Turn the boiler thermostat down all the way and turn off the electricity if applicable. Not all steam boilers operate on line voltage.
If the radiator has a drain valve underneath, open the valve and drain as much water out as possible. Note that many old radiators are rusted and plugged up and unable to drain themselves through conventional methods. Have towels handy.
Set the new radiator in place and line up the piping system.