🔍 Key Concepts

• Two-pipe hydronic heating system flow pattern (how supply and return mains serve each coil) • Difference between series and parallel connection of heating coils • Effect of connection type on inlet water temperature at each coil

💭 Think About

• Visualize the piping: in a two-pipe system, does each coil see water that has already passed through another coil, or does each coil get water directly from the main? • Ask yourself: in a series connection, what happens to water temperature as it flows from one coil to the next? In a parallel connection, how is the flow split? • Consider whether “separate supply teeing off a supply main” better matches a series or a parallel arrangement.

✅ Before You Answer

• Verify how series-connected coils share flow and how water temperature changes from the first to the last coil. • Verify how parallel-connected coils are piped in relation to a common supply and return main. • Confirm whether a true two-pipe hydronic system is typically designed so that all coils see the same supply temperature or a progressively cooled one.