Electronics Protection - Winter 2014 - (Page 10)

Feature Increase Rack Cooling Efficiency and Solve Heat-Related Problems Cooling tends to take a back seat to other concerns when server rooms and small to mid-size data centers are first built. As computing needs grow, increased heat production can compromise equipment performance and cause shutdowns. Haphazard data center expansion creates cooling inefficiencies that magnify these heat-related problems. End users may assume that they need to increase cooling capacity, but this is expensive and often unnecessary. In most cases, low-cost rack cooling best practices will solve heat-related problems. Best practices optimize airflow, increase efficiency, prevent downtime and reduce costs. The Ideal Intake Temperature - and Why it Matters It's a common misconception that data centers need to be kept cold. In fact, manufacturers recommend IT equipment intake air temperatures at, or slightly above, room temperature for maximum reliability, availability and performance, as high as 80.6ºF. You will find that temperature recommendations vary somewhat depending on the type of data center, equipment and cooling methods employed. The recommendations listed in this document are appropriate for the majority of small to mid-size, mixed-use data centers we encounter. Allowable temperatures can drift as high as 90ºF for limited periods of time without affecting short-term operating reliability. Most IT equipment is even designed to survive temperatures above 90ºF, though it may not run reliably. However, running at these elevated temperatures will shorten the equipment's lifespan. (Long-term temperature increases are especially problematic for UPS batteries. For example, the estimated service life of a typical UPS battery decreases by 50 percent when the ambient temperature increases from 77°F to 90°F.) 77ºF is The "Sweet Spot" for IT Equipment: * Maintaining intake air temperatures below 77°F does not improve operating conditions or provide other benefits, so it's simply an unnecessary and costly waste of energy. (If temperatures naturally fall below 77°F without any associated electricity cost or temperature swings, that isn't a problem.) * Although IT equipment can run reliably with intake air temperatures above 77°F, the increased speed and power consumption of cooling fans inside the equipment tends to counteract (or even exceed) further energy and cost savings. * If you have an unusual situation where maintaining 77°F seems too costly, understanding the drawbacks of higher intake temperatures will help you balance budgetary considerations against equipment reliability and system availability. As Computing Demand Heats Up, So Do Data Centers Many data centers start out as a few racks in a computer room or network closet. As computing needs grow more equipment and higher wattages are packed into each rack, often without following a master plan. More equipment means more power consumption and more heat. At the same time, disorderly growth leads to haphazard rack layouts and unmanaged airflow. The result is a cobbledtogether environment characterized by cooling inefficiencies. When users experience malfunctions, shutdowns, premature equipment failures or other heat-related issues, they frequently assume that pumping more cold air into the room from the facility HVAC (heating, ventilation and air conditioning) system or CRAC (computer room air conditioner) will provide an easy 10 Winter 2014 * www.ElectronicsProtectionMagazine.com solution. However, a smart first step is conducting a site audit to identify where and why hot spots and cooling inefficiencies exist. This evaluation supports informed decision-making about the most effective strategy, which often turns out to be implementing low-cost cooling best practices rather than purchasing and installing additional cooling capacity. Not only is "brute force" cooling expensive and power hungry, turning down the room temperature will only provide a temporary fix for many heat-related problems, if they are fixed at all. Common Causes of Cooling Inefficiencies Efficient and effective data center cooling is not simply a matter of supplying cold air, it's actually all about separating hot air from cold air. IT equipment generates heat non-stop, so even if cold air is directed at the rack, problems will occur if the hot exhaust When hot air recirculates, it will increase from the equipment the intake air temperature. Even in a recirculates. Recirculachilly room, a server under load can feed tion will pollute the cold itself hot air until it shuts down. air supply and raise the air temperature at the equipment intakes. One of the best ways to prevent this is to contain the hot air and remove it from the rack enclosure and the room before it can mix with the cold air supply. Potential Trouble Spots * Internal and External Rack Layout: Hot air from equipment exhaust must not be allowed to recirculate and mix with cold air (a relative term, since 77º F is ideal). It is absolutely critical to arrange rack cabinets and the equipment inside them to block the recirculation of hot air. Air seeks the path of least resistance, so even a modest barrier can make a big difference. If racks are arranged front to back, or if servers and racks are mounted with too much open space around them, hot air will recirculate and increase the intake air temperature. Even in a chilly room, a server under load can feed itself hot air until it overheats and shuts down. Problems can also arise when poorly managed cabling blocks fans and interferes with airflow, or when vented side panels are used in an enclosure (or left off entirely). Without solid side panels in place, hot exhaust air will flow through the sides of the enclosure, recirculate and contaminate cold air. Room Construction, Size and Location: Natural heat dissipation through walls, ceilings and doors typically lowers room temperatures. However, if the room size is too small, the racks are densely populated, or surrounding areas aren't cool enough, dissipation may be unable to keep pace with the heat generated. If the data center has a brick exterior wall with direct sun exposure, heat transfer through dissipation is also likely to be insufficient because masonry traps heat much more than drywall, like an oven. On the other hand, if the room has interior surrounding walls heated by the HVAC system in the winter, temperatures can also rise to levels that are not optimal. And obviously, overheating can occur yearround if the computer room happens to be an unvented former http://www.ElectronicsProtectionMagazine.com

Table of Contents for the Digital Edition of Electronics Protection - Winter 2014

Editor's Choice
EMI Compliance: Choosing the Right Shielding and Gasketing
Thermal-Fluid Modeling for Flat Thin Heat Pipes/Vapor Chambers
Increase Rack Cooling Efficiency and Solve Heat-Related Problems
Seven Essential Cabinet Design Considerations for Protecting 19 Inch Electronics
A Better Alternative to Heat Pipes: Integrating Vapor Chambers Into Heat Sinks
Common IP Testing Failures and How to Avoid Them
Enclosures
EMI/EMC/RFI
Thermal
Power
Hardware
Contamination
Industry News

Electronics Protection - Winter 2014