What Is a Chiller Plant?

The AHU cools air using chilled water coil. The FCU cools room air using chilled water. But where does all this chilled water come from?

The Chiller Plant.

Think of the chiller as the building's refrigerator compressor — but instead of cooling a small box, it cools thousands of litres of water pumped throughout the entire building.

Chiller cools water to 6–8°C
        ↓
Chilled water pumps push it through building pipes
        ↓
Reaches every AHU and FCU
        ↓
At each AHU/FCU — water absorbs heat from air
        ↓
Water returns warm (12–14°C) back to chiller
        ↓
Chiller removes that heat again
        ↓
Cycle repeats continuously

BMS Chiller Sequencing:

One chiller for light load (night, weekend).
Two chillers for medium load (morning ramp-up).
Three chillers for peak load (hot afternoon, full occupancy).

BMS decides which chillers to start, when to start them, and how to sequence pumps and cooling towers for maximum efficiency.

Related Topics

• What is BMS integration? — how a BMS connects with VFDs, energy meters, BACnet/Modbus devices and other building systems
• How to design a BMS system step by step — the complete BMS design methodology covering site survey, IO list, controller selection, sequence of operations
• What is a Building Management System (BMS)? — fundamentals of BMS controls and architecture for HVAC, lighting, energy and access
• What is BMS commissioning? — the disciplined commissioning process that turns a BMS install into a working building brain
• Browse all HVAC Systems topics — more from this section of the EnSmart BMS Library