There’s no such thing as magic in hydronics. There are no magic boilers, controls, or circulators that know what to do. If someone can’t explain to you exactly how a delta (Δ) P or a ΔT variable-speed circulator works, and why, without using the word “magic” or some derivative thereof, there’s one hydronics expert I know who says, “They either went to hydronics school at Hogwarts, or they don’t really know.”