When the return main is located above the water line in a steam heating system, what is this type of return called?

In a steam heating system, when the return main is positioned above the water line, it is referred to as a dry return. This configuration is significant because it indicates that the condensate from the steam system must flow back to the boiler without the benefit of gravity assisting its return, as the steam and condensate are separated. A dry return does not have any water or condensate in it and is often designed to ensure that steam travels efficiently through the heating system without allowing water to accumulate in the return line.

This setup can have implications for how the system operates, particularly with regard to ensuring that steam reaches the heating elements effectively and that condensate is properly managed. In contrast, a wet return would contain both steam and water, and other options like open or closed returns relate to different systems and methods for managing steam or condensate, thereby making them less applicable in this context.