How does the presence of air in a hydronic heating system affect its performance?

The presence of air in a hydronic heating system negatively affects its performance in several ways. Air can collect at high points in the system, blocking the flow of water and reducing the heat output of radiators or other heat exchangers. This can cause some areas of the building to be underheated while others are overheated. Air can also cause corrosion in the system. Dissolved oxygen in the water can react with the metal components of the system, leading to rust and scale formation. This corrosion can damage the pipes, valves, and other components, reducing their lifespan and increasing the risk of leaks. Air in the system can also cause noise, such as gurgling or banging sounds, as the air moves through the pipes. This can be annoying to building occupants. Furthermore, air can reduce the efficiency of the system by reducing the heat transfer rate. Air is a poor conductor of heat, so air pockets on the heat transfer surfaces can impede the flow of heat from the water to the air. For example, air trapped in a radiator can prevent the radiator from heating up properly, even if the water circulating through it is hot. Therefore, it is important to remove air from hydronic heating systems through proper venting and air purging procedures. Automatic air vents are often installed at high points in the system to allow air to escape.