Coils and Counter-Flow: 5 Quick HVAC Questions Answered

by Dan Jacobs, May 11, 2026

The first thing to remember about coils and counter-flow is that chilled water coils are always built to be piped in counter-flow. This means that the air flows in the opposite direction as the water. For example, with counter-flow, the air flows through rows 1-8, while the water runs through rows 8-1. Water always travels through the coil in the opposite direction of the air; hence the term “counter-flow.”  Direct Expansion Coils (Evaporator Coils) are also piped in the same manner.