Data Center/Server Room Best Practices

Mid-Tier Data Center

< 5,000 ft.² / hundreds of servers, extensive external storage

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Mechanical Air Flow Management

Hot Aisle/Cold Aisle Layout
Blank Unused Rack Positions

Standard IT equipment racks exhaust hot air out the back and draw cooling air in the front. Openings that form holes through the rack should be blocked in some manner to prevent hot air from being pulled forward and recirculated back into the IT equipment. For more information, see Chapter 1 of the Design Guidelines Sourcebook.

Use Appropriate Air Diffusers
Position supply and returns to minimize mixing

Diffusers should be located to deliver air directly to the IT equipment. At a minimum, diffusers should not be placed such that they direct air at rack or equipment heat exhausts, but rather direct air only towards where IT equipment draws in cooling air. Supplies and floor tiles should be located only where there is load to prevent short circuiting of cooling air directly to the returns; in particular, do not place perforated floor supply tiles near computer room air conditioning units using the as a return air path. For more information, see Chapters 1 and 2 of the Design Guidelines Sourcebook.

Minimize Air Leaks in Raised Floor

Mechanical Air Handler Systems

Use Redundant Air Handler Capacity in Normal Operations

With the use of Variable Speed Drives and chilled water based air handlers, it is most efficient to maximize the number air handlers operating in parallel at any given time. Power usage drops approximately with the square of the velocity, so operating two units at 50% capacity uses a sum total less energy than a single unit at full capacity. For more information, see Chapter 3 of the Design Guidelines Sourcebook.

Configure Redundancy to Reduce Fan Power Use in Normal Operation
- When multiple small distributed units are used, redundancy must be equally distributed. Achieving N+1 redundancy can require the addition of a large number of extra units, or the oversizing of all units. A central air handler system can achieve N+1 redundancy with the addition of a single unit. The redundant capacity can be operated at all times to provide a lower air handler velocity and an overall fan power reduction, since fan power drops with the square of the velocity. Light loading. For more information, see Chapter 3 of the Design Guidelines Sourcebook.
Control Volume by Variable Speed Drive on Fans Based on Space Temperature

Mechanical Humidification

Use Widest Suitable Humidity Control Band
Centralize Humidity Control
Use Lower Power Humidification Technology

There are several options for lower power, non-isothermal humidification, including air or water pressure based 'fog' systems, air washers, and ultrasonic systems. For more information, see Chapter 7 of the Design Guidelines Sourcebook.

Mechanical Plant Operation

Use Free Cooling / Waterside Economization

Free cooling provides cooling using only the cooling tower and a heat exchanger. It is very attractive in dry climates and for facilities that have local concerns about outside air quality that may cause concern about the use of standard airside economizers.
For more information, see Chapters 4 and 6 of the Design Guidelines Sourcebook.

Monitor System Efficiency

Install reliable, accurate monitoring of key plant metrics such as such kW/ton. The first cost of monitoring can be quickly recovered by identifying common efficiency problems, such as: low refrigerant charge, non-optimal compressor mapping, incorrect sensors, incorrect pumping control, etc. Efficiency monitoring provides the information needed for facilities personnel to optimize the system's energy performance during buildout and avoid efficiency decay and troubleshoot developing equipment problems over the life of the system.
For more information, see Chapter 4 of the Design Guidelines Sourcebook.

Rightsize the Cooling Plant

Due to the critical nature of the load and unpredictability of future IT equipment loads, datacenter cooling plants are oversized. The design should recognize that the standard operating condition will be at partload and optimize for efficiency accordingly. Consistent part-load operation dictates using well know design approaches to part load efficiency such as utilizing redundant towers to improve approach, using multiple chillers with variable speed drive, variable speed pumping throughout, chiller staging optimized for partload operation, etc. For more information, see Chapter 4 of the Design Guidelines Sourcebook.

IT Equipment Selection

Specify High Efficiency Power Supplies

Server power supplies can be made significantly more efficient than currently offered. Specify power supplies that have a minimum efficiency equal to or greater than the minimum recommended power supply efficiency guidelines put forth by the industry group Server System Infrastructure (SSI) Initiative. For more information, see Chapter 8 of the Design Guidelines Sourcebook.

Consider Equipment Power Consumption in Specifications

Develop internal procedures to encourage the acquisition of the most energy efficient equipment that will meet the application requirements. Lower power consumption chips, idle mode setbacks and other features can vary the power efficiency of equivalent equipment. For more information, see Chapter 8 of the Design Guidelines Sourcebook.

Electrical Infrastructure

Maximize UPS Unit Loading

When using battery based UPSs, design the system to maximize the load factor on operating UPSs. Use of multiple smaller units can provide the same level of redundancy while still maintaining higher load factors, where UPS systems operate most efficiently. For more information, see Chapter 10 of the Design Guidelines Sourcebook.

Specify Minimum UPS Unit Efficiency at Expected Load Points

There are a wide variety of UPSs offered by a number of manufacturers at a wide range of efficiencies. Include minimum efficiencies at a number of typical load points when specifying UPSs. Compare offerings from a number of vendors to determine the best efficiency option for a given UPS topography and feature set. For more information, see Chapter 10 of the Design Guidelines Sourcebook.

Evaluate UPS Technologies for the Most Efficient

New UPS technologies that offer the potential for higher efficiencies and lower maintenance costs are in the process of being commercialized. Consider the use of systems such as flywheel or fuel cell UPSs when searching for efficient UPS options. For more information, see Chapter 10 of the Design Guidelines Sourcebook.

Lighting

Use Occupancy Sensors

Occupancy sensors can be a good option for datacenters that are infrequently occupied. Thorough area coverage with occupancy sensors or an override should be used to insure the lights stay on during installation procedures when a worker may be 'hidden' behind a rack for an extended period.

Provide Bi-Level Lighting

Provide two levels of clearly marked, easily actuated switching so the lighting level can be easily changed between normal, circulation space lighting and a higher power detail work lighting level. The higher power lighting can be normally left off but still be available for installation and other detail tasks.

Provide Task Lighting

Provide dedicated task lighting specifically for installation detail work to allow for the use of lower, circulation space and halls level lighting through the datacenter area.

Commissioning and Retrocommissioning

Perform a Peer Review

A peer review offers the benefit of having the design evaluated by a professional without the preconceived assumptions that the main designer will inevitably develop over the course of the project. Often, efficiency, reliability and cost benefits can be achieved through the simple process of having a fresh set of eyes, unencumbered by the myriad small details of the project, review the design and offer suggestions for improvement.

Engage a Commissioning Agent

Commissioning is a major task that requires considerable management and coordination throughout the design and construction process. A dedicated commissioning agent can ensure that commissioning is done in a thorough manner, with a minimum of disruption and cost.

Document Testing of All Equipment and Control Sequences

Develop a detailed testing plant for all components. The plan should encompass all expected sequence of operation conditions and states. Perform testing at with the support of all relevant trades — it is most efficient if small errors in the sequence or programming can be corrected on-the-spot rather than relegated to the back and forth of a traditional punchlist. Functional testing performed for commissioning does not take the place of equipment startup testing, control point-to-point testing or other standard installation tests.

Measure Equipment Energy Onsite

Measure and verify that major pieces of equipment meet the specified efficiency requirements. Chillers in particular can have seriously degraded cooling efficiency due to minor installation damage or errors with no outward symptoms, such as loss of capacity or unusual noise.

Provide Appropriate Budget and Scheduling for Commissioning

Commissioning is a separate, non-standard, procedure that is necessary to ensure the facility is constructed to and operating at peak efficiency. Additional time commitment beyond a standard construction project will be required from the contractors. Coordination meetings dedicated to commissioning are often required at several points during construction to ensure a smooth and effective commissioning.

Perform Full Operational Testing of All Equipment

Commissioning testing of all equipment should be performed after the full installation of the systems are complete, immediately prior to occupancy. Normal operation and all failure modes should be tested. In many critical facility cases, the use of load banks to produce a realistic load on the system is justified to ensure system reliability under design conditions.

Perform a Full Retrocommissioning

Many older datacenters may have never been commissioned, and even if they had performance degrades over time. Perform a full commissioning and correct any problems found. Where control loops have been overridden due to immediate operational concerns, such as locking out condenser water reset due to chiller instability, diagnose and correct the underlying problem to maximize system efficiency, effectiveness, and reliability.

Recalibrate All Control Sensors
Where Appropriate, Install Efficiency Monitoring Equipment

As a rule, a thorough retrocommissioning will locate a number of low-cost or no-cost areas where efficiency can be improved. However, without a simple means of continuous monitoring, the persistence of the savings is likely to be low. A number of simple metrics (cooling plant kW/ton, economizer hours of operation, humidification/dehumidification operation, etc.) should be identified and continuously monitored and displayed to allow facilities personnel to recognize when system efficiency has been compromised.