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How a chilled-water plant cools a building.

Larger buildings often don't have a unit on the roof for every zone. Instead a central plant makes cold water and pumps it to air handlers throughout the building. Here is the loop, part by part — and what we check at each one.

Chilled-water plant schematic A chiller pumps cold water out to three air handlers and takes warmer water back. A second loop carries the heat from the chiller to a cooling tower on the roof and back. Six numbered markers match the numbered list beside the drawing. Cooling tower Chiller Air handler Air handler Air handler 1 2 3 4 5 6
The loop, numbered

Six parts, one system.

  1. ChillerTakes heat out of the building's water, making it cold. We check refrigerant pressures, approach temperatures, oil and safeties.
  2. Chilled-water pumpPushes cold water out to the building. Seals, bearings, vibration and flow.
  3. Air handlersBlow building air across coils full of cold water. Coils, filters, belts, valves and drain pans.
  4. ReturnWarmer water comes back to the chiller. The difference between supply and return tells us how hard the building is working.
  5. Condenser-water pumpCarries the heat the chiller removed out to the cooling tower.
  6. Cooling towerRejects that heat to outside air. Fill, fans, basin and water treatment coordination.
Where plants go wrong

Most problems are small ones left too long.

Fouled tubes and coils

Scale in the condenser or dirt on air handler coils make everything work harder for the same cooling.

Valves and sequences

A stuck valve or a control sequence that was never finished can leave pumps running flat out all year.

Tower water

Cooling towers need treated water. We coordinate with your water treatment provider and flag what we see.

Illustrative HVAC scene: A technician reading the gauges on a chiller in a plant room, a clipboard in hand
Illustrative HVAC scene: A pair of chilled-water pumps on concrete bases with insulated blue piping and valves
Illustrative HVAC scene: An air handler in a mechanical room with its access door open, showing the coil and filters
Businesses

Plants and packaged units

Central plants for larger buildings; rooftop and split systems for everything else.

Homes

The same idea, smaller

Your central AC moves heat out the same way — refrigerant instead of water, a condenser instead of a tower.

The drawing is a simplified schematic. Real plants add bypasses, primary and secondary loops, heat exchangers and controls; we work on the one you have.

Running a central plant?

Let's look at it together.

A walk-through of the chiller, pumps, air handlers and tower.

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