When designing hydronic circuits, most of us focus on what’s necessary for that circuit to absorb thermal energy at a heat source, carry it along like a conveyor belt and release that energy at one or more heat emitters. After all, that’s the principal objective of any hydronic heating system — regulating thermal energy transfer from source to load.
However, thermal energy isn’t the only energy being processed in hydronic systems. Electrical energy is being converted into mechanical energy. The latter is what’s referred to as “head” in the hydronics industry. Circulators convert electrical energy into head energy.