When steam is supplied upwards through risers to heating units, what is the heating system referred to as?

The heating system is referred to as "upfeed" because it describes the method of supplying steam in an upward direction through risers to the heating units. In this type of system, steam flows vertically from the boiler, through risers, and into the heating units located above. This allows for effective heat transfer as the steam rises and reaches the heating elements.

Using an upfeed method ensures that steam can reach higher locations in a building without the need for complex pumping mechanisms. As steam rises, it expands and condenses into water, releasing heat energy to the heating units, which then warms the surrounding area. This mechanism is particularly efficient in maintaining consistent temperature levels throughout upper floors of a structure.

In contrast, other terms such as downfeed, sidefeed, and topfeed refer to different systems of steam distribution where the movement of steam does not involve upward flow through risers, which is why upfeed is the appropriate terminology in this context.