The hydronic heating systems have different pipe arrangements, which can be open or closed.
The piping system distribution may be a single pipe, two pipe, or four pipes.
These pipes carry water, back and forth, throughout the system and deliver steam to the radiators to produce heat. There is no water loss in this system. The first type is the open piping system. This system has an expansion tank that opens to the atmosphere and a water loop system – hydronic heating that involves heating with the help of water instead of steam. It has a single pipe that runs throughout the system. When a room needs heat, the radiator heats the water, which, in turn, heats the area. The direct return piping allows the piping to run in a direct path, thus optimizing piping costs. Larger hydronic systems use a reverse return piping design with a closed-loop system and a return header connected to a remote hydraulic load. This design ensures the water flow and pressure distributed equally across the system. A closed piping system is sealed completely to avoid interference from atmospheric pressure. The second type is the one-pipe arrangement which uses a single pipe to serve as both the supply and the return line. This system is common in small homes. The third type is the four-pipe system. It’s simply a two-pipe heating and a two-pipe cooling system. It uses primary and secondary units in large industrial buildings, large residential areas, and larger commercial buildings where zoning is required. In this system, the primary pump circulates water continuously throughout the building through the primary circuit. Consult an HVAC technician or an HVAC contractor when purchasing, installing, or troubleshooting a hydronic system.