To ensure proper air venting from a heating or cooling coil, which connection should be at the bottom of the coil?

In a heating or cooling coil system, proper air venting is essential for efficient operation. The connection that should be located at the bottom of the coil is the drain connection. This is because any liquid, including condensation or water that may accumulate within the coil, needs to be effectively removed to prevent air pockets that can adversely affect the system's efficiency.

If there is a vent connection, it is typically placed at the highest point of the coil, allowing air to escape easily when the system is filled with fluid. Conversely, the return water connection is usually situated at the bottom of the coil to facilitate the flow of water back into the system after passing through the coil.

The supply water connection is found at the top or side. This design allows the heating or cooling medium to enter the coil so that it can interact with the air moving over the coil. Therefore, for optimal venting of any trapped air and to mitigate the risk of hydraulic issues within the system, the drain connection at the bottom is crucial.