Chilled Water, Cooling Water and Condenser Water: What’s the Difference?
In a water-cooled chiller system, three different water circuits serve different functions — chilled water, cooling water (condenser water), and in some systems, condensed water. Understanding the difference is essential for anyone specifying, installing, or maintaining a chiller plant.
What is Chilled Water?
Chilled water is water that has been cooled by a chiller unit to a setpoint temperature — typically 6°C to 7°C supply, returning at 12°C to 14°C. It is circulated from the chiller to air handling units (AHUs), fan coil units (FCUs), or process equipment, where it absorbs heat and cools the space or process. The warmed water then returns to the chiller to be re-cooled.
- Typical supply temperature: 6°C – 7°C
- Typical return temperature: 12°C – 14°C
- Function: Delivers cooling to terminal units in the building or process
- Circuit type: Closed loop — no water is lost under normal operation
What is Condenser Water (Cooling Water)?
Condenser water — also called cooling water — is the water circuit that carries heat away from the chiller condenser to the cooling tower, where it is rejected to the atmosphere. It is a separate circuit from the chilled water and operates at higher temperatures.
- Typical supply temperature: 29°C – 32°C (from cooling tower to chiller)
- Typical return temperature: 35°C – 38°C (from chiller to cooling tower)
- Function: Rejects heat from the chiller refrigerant to the cooling tower
- Circuit type: Open loop — cooling tower evaporation causes water loss; makeup water required
Chilled Water vs Condenser Water — Comparison Table
| Parameter | Chilled Water | Condenser Water |
|---|---|---|
| Also called | CHW, evaporator water | CW, cooling water, condenser water |
| Temperature range | 6°C – 14°C | 29°C – 38°C |
| Function | Delivers cooling to building/process | Rejects heat to cooling tower |
| Circuit type | Closed loop | Open loop (cooling tower) |
| Water treatment | Corrosion inhibitor only | Scale, corrosion, biological treatment required |
| Water loss | None (closed loop) | Evaporation loss — makeup water required |
| Pump | Chilled water pump (CHWP) | Condenser water pump (CWP) |
| Connected to | AHUs, FCUs, process equipment | Cooling tower |
How a Chilled Water System Works
A complete water-cooled chiller plant contains both circuits working together:
- The chiller cools chilled water to setpoint (e.g. 7°C) using refrigeration
- The chilled water pump circulates cold water to AHUs and FCUs throughout the building
- At the terminal units, chilled water absorbs heat from the air and warms up (e.g. to 12°C)
- Warmed chilled water returns to the chiller evaporator to be re-cooled
- Heat absorbed by the refrigerant is rejected via the condenser to the condenser water circuit
- The condenser water pump carries warm condenser water to the cooling tower
- The cooling tower rejects heat to the atmosphere and returns cooled condenser water to the chiller
Chilled Water System Applications
| Application | Chilled Water Supply Temp | Notes |
|---|---|---|
| Commercial HVAC (offices, hotels) | 6°C – 7°C | Standard chilled water temperature |
| Hospital and healthcare | 6°C – 7°C | Redundancy required — N+1 chiller configuration |
| Data center cooling | 12°C – 18°C | Higher supply temp possible for free cooling |
| Pharmaceutical process cooling | 2°C – 15°C | Precise temperature control required |
| Food and beverage processing | 0°C – 10°C | Glycol required below 5°C |
| District cooling | 4°C – 6°C | Lower temp allows smaller pipe sizes |
Geson Chilled Water System Equipment
Geson supplies complete chilled water system equipment including water cooled chillers, chilled water pumps, cooling towers, and skid-mounted integrated packages for industrial and commercial applications.
- Water Cooled Chillers — 30RT to 4,500RT
- Air Cooled Chillers — 3RT to 300RT
- Glycol Chilled Water Systems
Frequently Asked Questions
What is chilled water?
Chilled water is water cooled to between 6°C and 12°C by a chiller and circulated to provide cooling for buildings or industrial processes. It absorbs heat at terminal units and returns to the chiller to be re-cooled.
What is the difference between chilled water and condenser water?
Chilled water delivers cooling to the building at 6°C–14°C in a closed loop. Condenser water carries heat away from the chiller to the cooling tower at 29°C–38°C in an open loop. They are two separate circuits in a water-cooled chiller system.
What temperature is chilled water?
Standard chilled water supply is 6°C–7°C, returning at 12°C–14°C. For low-temperature process cooling, glycol chilled water systems can supply as low as -45°C.
What is a chilled water system used for?
Chilled water systems are used for building air conditioning (hotels, hospitals, offices), industrial process cooling (pharmaceutical, food & beverage, plastics), data center cooling, and district cooling.