Chilled Water vs DX Cooling Coils Explained

Cooling coils come in two main flavours: chilled-water and direct-expansion (DX). They cool the same air but work differently.

Here's how to tell them apart and choose.

Chilled-water coils

Chilled water from a central plant circulates through the tubes, absorbing heat from the air. Common in larger buildings with central chiller plants; easy to control and zone.

DX coils

In a DX coil, refrigerant evaporates directly inside the tubes, cooling the air. Common in packaged and split systems. See DX evaporator coils.

Control and efficiency

Chilled-water systems modulate smoothly and suit large, zoned buildings. DX systems are simpler and efficient for smaller or distributed loads.

Choosing between them

Building size, layout and existing plant usually decide. Both benefit from the same quality coil construction and testing.