Data Center Cooling Systems Design

The following are design guides for cooling systems in data centers.  This guide will show you strategies and best practices for designing mechanical systems used in data center cooling and electrical guidelines for supplying power to the data center equipment itself.  It is assumed that you have a basic understanding of air conditioning design in data centers.

Mechanical System Guidelines:

• Data centers should be designed for equipment, not people.  Use the entire ASHRAE recommended range, which is from 64 F to 81 F.
• Energy is saved if you provide warmer supply air and no humidification.  Provide the warmest supply temperature that satisfies the data center equipment inlet conditions.
• Humidification does not protect against electrostatic discharge.  Consider grounding and personnel practices instead of humidifying.
• Computer room air conditioning and air handler (CRAC/CRAH) units are controlled by return (hot aisle) conditions
• Always provide variable airflow fans for CRAC/CRAH units or air handler units (AHU’s).
• Draw return from as high as possible in the room.
• Having an overhead supply system with VAV boxes is more energy efficient than underfloor supply systems and provides a more uniform temperature control.
• Use air-side economizers for free cooling in dryer climates.  Using air-side economizers and no humidification provides very significant energy savings.
• Having contaminants in the server room is not an issue with air-side economizers.  Lawrence Berkeley National Laboratory did a study using MERV 7 filters that demonstrated that particulates were not an issue in data centers that used air-side economizers.
• Consider using direct evaporative cooling to extend the hours of free cooling.
• Connect water-side economizers in series with chillers on the chilled water side.

Electrical Guidelines

• Distributing higher voltage is more energy efficient
• Highly efficient UPS’s, transformers, PDU’s and power supplies should be specified for the loads they will see, not for full load.
• Direct current (DC) systems can reduce conversion losses
• Redundancy choices affect efficiency in electrical equipment
• On-site generation can improve reliability and efficiency

If you have any questions or are looking for more resources in this topic, please feel free to contact me.  Data center load is by far the highest energy consumer in buildings and it is only going to increase in the future.  Having the capacity to supply power to these centers is going to be an issue.