How Does an Old Hydronic Boiler System Work?

Boiler

• A hydronic boiler is used to heat the water for a residence. Many modern homes use fuel oil, natural gas or propane as the fuel source. For homes with a hydronic boiler system, as the home is heated, the water cools. This cooled water is returned to the boiler for reheating. Any water losses are made up from your home's cold water supply. Hydronic boilers are usually in the basement and take up a fair amount of space. Although less efficient, some boilers are used to provide hot water.

Piping

• Piping is connected and arranged to transport heat from the boiler to radiators throughout the house. The piping system consists of supply pipes for carrying heated water and return pipes for heat-exhausted water going back to the boiler. In older homes, the pipes are normally made of copper, steel or cast iron. Cleaning and drainage access ports are installed in the pipes for maintenance and troubleshooting. Plastic tubing is not normally found in older systems.

Pump

• A pump with sufficient capacity is installed in close proximity to the boiler. The pump takes heated water from the boiler. It constantly circulates through the piping to radiators or convectors. More than one pump may be used depending on system design and home size. Most pumps are connected to a low-level safety cutoff. This cutoff switch shuts off the pump in the case the boiler's water level gets too low.

Radiators and Convectors

• Radiators and convectors transfer heat to the room by natural convection and direct radiation. Panel radiators, baseboard convection heaters and in-room standing radiators are available for use. Panel radiators are usually made from cast iron or steel and mounted to the wall. In-slab -- also called floor-coil -- systems are embedded into the concrete during construction. Floor radiators tend to heat evenly because heat is transferred through the floor to the rest of the room. Most radiators on an old hydronic boiler system have their own controls and allow each room to be heated independently.