Hydronic Heating Delta-T

In any hydronic heating system, fluid will be hotter when it leaves a boiler than when it returns. This temperature difference is known as the design temperature difference or “delta-t.” Many commercial designs incorporate very high delta-t ratings, but residential systems generally have standard ratings based on system type (20°F for baseboards and 10°F for in-floor radiant heat systems). Systems with lower delta-t designs have higher head pressure and may need larger circulator pumps. They provide more even surface temperatures for in-floor hydronic systems.