What statement is true concerning a one-pipe hydronic heating system?

Correct Answer: Option C — Each heating coil inlet temperature is different, as the hot water inlet temperature to each heating coil progressively drops as the water passes through each successive series-connected coil.

In a one-pipe hydronic loop, water flows through series-connected heating coils sequentially. As thermal energy transfers to each space, the circulating water temperature drops progressively, resulting in lower inlet temperatures for each successive downstream terminal unit.