Warm-water cooling loops

What it is

Liquid cooled chips tolerate much warmer coolant than air cooled rooms need. Raising facility water temperature cuts or removes chiller hours and raises the grade of recovered heat.

ASHRAE classes

ASHRAE TC 9.9 uses classes W17, W27, W32, W40, W45 and W+, each named after the maximum facility water supply temperature in °C. Equipment claiming a class should run unthrottled across that range. Use the class to align IT, CDU and plant designs.

Examples

STULZ rates its CyberCool CDU at 32 °C facility water and 36 °C TCS supply. Trane's LiquidStack CDU 2.X supports facility inlet up to 45 °C. DCX designs its 8 MW FDU for 45 °C warm water operation.

Sourcing considerations

Warmer water needs a smaller CDU approach temperature to keep chips within limits, which means larger heat exchangers. Confirm the IT vendor's allowed TCS temperature, and agree who carries the risk if a future GPU generation needs colder water.

Questions to ask suppliers

• Target ASHRAE W class and why
• Approach temperature the CDU must achieve at that class
• IT vendor maximum TCS supply temperature
• Chiller backup hours and trim strategy
• Heat reuse offtake temperature

Start a requirement brief