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Mechanical / HVACaka: CHW systemaka: hydronic cooling

Chilled Water System

In Plain English

A central cooling system that circulates cold water through pipes to cool air in multiple areas of a large building.

Definition

A central cooling system that uses chilled water produced by a chiller to distribute cooling energy to air handling units and fan coil units throughout a building. Chilled water is typically supplied at 44°F and returned at 54°F through insulated piping. Chilled water systems are preferred for large buildings because they are more efficient and flexible than direct-expansion refrigerant systems.

Why It Matters in Bidding

Chilled water systems are among the most cost- and coordination-intensive HVAC packages on large commercial projects, spanning chillers, pumps, insulated piping, controls, and air handlers, so the mechanical sub's bid hinges on accurate takeoff of these interdependent components. Because the system touches structure, electrical capacity, and roof or mechanical-room space, estimators must coordinate it across trades to avoid scope gaps and costly change orders later.

Example

Pricing a mid-rise office, the mechanical estimator takes off linear feet of insulated supply and return piping, the chilled-water pumps, and the air handling units, then coordinates the chiller's electrical load with the electrical sub before submitting the HVAC bid.

Related Terms

ChillerCooling TowerAir HandlerCoil

Frequently Asked Questions

Chilled water systems generally win on larger buildings with many zones, where their efficiency, central control, and flexibility offset higher first cost. Smaller buildings often favor direct-expansion (DX) systems because they are cheaper to install. Estimators weigh building size, zoning needs, and operating cost when comparing the two during budgeting.
A complete takeoff covers the chiller, chilled-water pumps, insulated supply and return piping with fittings and hangers, air handling and fan coil units, cooling tower or air-cooled condenser, valves, and controls. Missing the insulation, hangers, or balancing scope is a common source of underbidding on these packages.
It drives significant electrical load for chillers and pumps, requires structural support for equipment and piping, needs roof or mechanical-room space, and ties into the building automation system. Coordinating these dependencies during estimating prevents change orders and ensures each affected sub carries the right scope.

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