Where should a main air vent be installed in a steam heating system?

The main air vent should be installed on the steam main to effectively remove air from the system during operation. The presence of air in a steam heating system can lead to inefficiencies and performance issues, as steam must fill the space occupied by air before it can effectively heat the environment. By placing the main air vent directly on the steam main, it allows for optimal air removal from the system, ensuring that steam can circulate efficiently throughout the piping and radiators.

The installation on the steam main leverages the natural flow of steam, allowing the vent to release trapped air before steam reaches the radiators. This helps maintain proper pressure and enhances heat distribution. Furthermore, placing the air vent elsewhere, such as near the boiler, at the return line, or in the basement, would not provide the same efficiency in air removal from the steam main, potentially leading to heat retention in those areas and reduced system performance.