Best practice for energy efficiency

by Wayne Ward, Managing Director

Large data centres can use over 90% of their energy in operating or cooling the data storage medium. It is clear that during refurbishment and replacement of data servers, energy efficiency should be a key driver in specifying equipment.

Using lower energy servers with wider effective operating ranges has the added benefit of reducing the loads applied to the HVAC equipment. In legacy installations, it is important to plan replacement equipment with a consequential review of the environmental control set points to maximise the energy efficiency of the HVAC operation.

Following the 2015 Best Practice Guideline for the EU Code of Conduct on Data Centres, key objectives for replacement of equipment in legacy data centres should include setting policy to:

  • Include energy efficiency as a specified requirement for new or replacement installations, this may be through the use of Energy Star, SERT, SPECPower or a bespoke performance specification, considering the full system efficiency including converters and power supply characteristics.
  • Calculate data centre inventory and aim for SUE of 1.0 post replacement of legacy equipment
  • Sets specific operating temperature and humidity ranges for existing and new installations:
    • Existing: 15°C to 32°C inlet temperature (59°F “ 89.6°F) and humidity from 20% to 80% relative humidity and below 17°C maximum dew point (62.6°F)
    • New: – 10°C to 35°C inlet temperature (50°F to 95°F) and humidity within 20% relative humidity to 80% relative humidity or 21°C (69.8°F) dew point.
    • Optimal inlet temperature should be 27°C, except where this results in relative humidity outside of above range, where outlet temperature exceeds maximum of above stated range.
  • Set group energy policy in terms of Inlet Temperatures, Outlet Temperatures, Humidity and Chilled Water Temperatures, then monitor through site operational compliance assessment. Review biannually or on technology change.
  • Require a temperature range energy use analysis for all new and replacement installations to allow a full design review of corresponding cooling and ventilation requirements.
  • Ensure a programme of blanking is included in new and replacement equipment rollout, including recommissioning of cooling and ventilation as the programme proceeds.
  • Specify M&E Equipment that does not require cooling in itself during normal operation.
  • Consider the energy requirements of the installations based on a phased approach, taking into account future technology enhancements.
  • Require that old equipment is replaced in groups with corresponding recommissioning of local HVAC systems to suit new operating requirements.
  • Provide sub-metering and sensors to monitor energy use against temperature and allow detailed performance monitoring. Sub-metering should separate IT, HVAC, offices, and warehouses as much as practically possible.
  • Ensure removal of redundant equipment.
  • Require the keeping of a register with location, type and operating parameters of equipment.
  • Require consideration of layout for airflow in setting out replacement installations to prevent hot spots.
  • Require Modular High efficiency UPS installations in line with the IEC 62040 series for UPS systems.
  • Develop and implement a group-wide measuring and monitoring program to include incoming and sub-metering HH readings for at least IT equipment and HVAC. Temperature and humidity set points scheduled against energy use. Set targeting and action triggers.

If you would like to discuss potential energy saving opportunities for your data centre, please contact me on 07539 169313 or email

This article was written by

Wayne Ward
Managing Director

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