The main areas for best practice improvements are;

Plug holes in the raised floor: Most raised-floor environments exhibit cable holes, conduit holes and other breaches that allow cold air to escape and mix with hot air. This single low-tech retrofit can save as much as 10 percent of the energy used for data centre cooling.

Install blanking panels: Any unused position in a rack needs to be covered with a blanking panel to manage airflow in a rack by preventing the hot air leaving one piece of equipment from entering the cold-air intake of other equipment in the same rack. When the panels are used effectively, supply air temperatures are lowered by as much as 22 degrees Fahrenheit, greatly reducing the electricity consumed by fans in the IT equipment and potentially alleviating hot spots in the data centre.

Coordinate CRAC units: Older CRAC (computer room air-conditioning) units operate independently with respect to cooling and dehumidifying the air. These units should be tied together with newer technologies so that their efforts are coordinated, or managers should remove humidification responsibilities from them altogether and place those responsibilities on a newer piece of technology.

Improve under floor airflow: Older data centres typically have constrained space underneath the raised floor that is not only used for the distribution of cold air, but also has served as a place for data cables and power cables. Many old data centres have accumulated such a tangle of these cables that airflow is restricted, so the under floor should be cleaned out to improve airflow.

Implement hot aisles and cold aisles: In traditional data centres, racks were set up in what is sometimes referred to as “classroom style,” where all the intakes face in a single direction. This arrangement causes the hot air exhausted from one row to mix with the cold air being drawn into the adjacent row, thereby increasing the cold-air-supply temperature in uneven and sometimes unpredictable ways. Newer rack layout practices instituted in the past 10 years demonstrate that organizing rows into hot aisles and cold aisles is better for controlling the flow of air in the data centre.

Install sensors: A small number of individual sensors can be placed in areas where temperature problems are suspected. Simple sensors store temperature data that can be manually collected and transferred into a spreadsheet, where it can be further analyzed. Even this minimal investment in instrumentation can provide great insight into the dynamics of possible data centres temperature problems and can provide a method for analyzing the results of improvements made to data centre cooling.

Implement cold-aisle or hot-aisle containment: Once a data centre has been organized around hot aisles and cold aisles, dramatically improved separation of cold supply air and hot exhaust air through containment becomes an option. For most users, hot-aisle containment or cold-aisle containment will have the single largest payback of any of these energy efficiency best practices.

Raise the temperature in the data centres: Many data centres are run colder than an efficient standard. ASHRAE (the American Society of Heating, Refrigerating, and Air-Conditioning Engineers) has increased the top end of allowable supply-side air temperatures from 77 to 80 degrees Fahrenheit. Not all data centres should be run at the top end of this temperature range, but a step-by-step increase, even to the 75 to 76 F range, would have a beneficial effect on data centre electrical use.

Install variable-speed fans and pumps: Traditional CRAC and CRAH (computer room air handler) units contain fans that run at a single speed. Emerging best practices suggest that variable-speed fans be used whenever possible. A reduction of 10 percent in fan speed yields an approximately 27 percent reduction in the fan’s electrical use, and a 20 percent reduction in speed yields electrical savings of approximately 49 percent.

Exploit “free cooling”: Free cooling is the general term for any technique that cools air without the use of chillers or refrigeration units. The two most common forms of free cooling are air-side economization and water-side economization. The amount of free cooling available depends on the local climate, and ranges from approximately 100 hours per year to more than 8,000 hours per year.

Design new data centres using modular cooling: Traditional raised-floor-perimeter air distribution systems have long been the method used to cool data centres. However, mounting evidence strongly points to the use of modular cooling (in-row or in-rack) as a more energy-efficient data centre cooling strategy

The entire report ($195) can be found on the Gartner Web site: “How to Save a Million Kilowatt Hours in Your Data Center.”

A Watt is the actual or true power used or dissipated by the device

A Volt Amp is called the apparent power and is obtained by multiplying the voltage by the current drawn by an alternating current device.

This is a small but significant difference. The Watt rating is used for measuring the power used and resultant heat. The VA is used for sizing calculations.

There are two types of load, resistive and reactive.

A light bulb is resistive but a computer or other electronic device is reactive.

If we calculated a the power used for a resistive light bulb operating at 240volts and drawing 0.25ampere it is a matter of applying a simple formula;

Power = Voltage x Current or 240 x 0.25

60 watts, the VA rating would be exactly the same.

Where the load is reactive a power factor must be used. With reactive loads a certain amount of power is absorbed by and subsequently released by the device. This power amount is called the reactive power or the difference between apparent and true power.

In an example where a computing device has an impedance of 120 Ohms using Ohms law (current = voltage/resistance) 240/120 will produce a current figure of 2 amps.

Using the same formula as above to get power

Power = Voltage x Current or 240 x 2

The apparent power would then be 480VA

Since the load is electronic, a power factor must be applied. Different devices will have different power factors; in this case the computer has a power factor of 0.9

Applying the power factor to the apparent power results in a watt figure of 480 x 0.9 = 432 watts

This difference between the apparent power and true power is reactive power, in this example 48 Volt Amps.

The vast majority of modern large computer devices now have very high power factors, usually close to 1 but smaller devices such as PC’s may be as low as 0.65

However, UPS devices do not have this high power factor. UPS devices are rated in VA with a stated power factor. The power factor is generally accepted to be 0.6 for UPS devices designed to power PC’s and other small devices.

A typical 500VA UPS would deliver 300 Watts. To complicate things even further large UPS’s now have very high power factors, approaching 1

The UPS will have both maximum VA and Watt ratings that cannot be exceeded.

Careful thought needs to be applied to the correct sizing of UPS’s taking into account the nature of the load and design specifications of the UPS itself in order to avoid errors. The safest approach is to keep the load at less than 60% of the VA rating of the UPS or seek expert advice

What is less well understood is the care required in specifying the most suitable back-up system, as an inappropriate choice will still leave a business vulnerable.

Design

Before a standby system is installed, a thorough analysis should be made of the specific application to ascertain the load, operating environment and the most appropriate design for providing critical power. This is seldom done well, if at all and consequently many standby systems installed are simply incapable of fulfilling their emergency role. Always consult a supplier with in-house design services for a total power solution.

Installation

Surprisingly often in critical applications the quality of installation has not been given sufficient attention — often as a direct result of a “lowest price tender” system. Where systems have been installed down to a price rather than up to a required quality, risks are ever-present.

Poor quality components, low quality workmanship, under sizing of cables, wrong settings on adjustable components and circuit breakers, inadequate cooling systems, poor fuel systems, etc all lead to high probability of failure.

Maintenance

Equipment needs regular maintenance to perform at its best and this should be considered a must not an option. There is always resistance to spending more than the initial cost of the equipment. Where the equipment does not display any outward signs of noise, motion or activity, as in the case of a UPS, it is easy to forget it after it has been installed. To overlook maintenance would be a grave mistake. The UPS is there to protect and support businesses in an emergency, so it has to be ready. Maintenance is an integral part of the UPS system, and should not be marketed as an extra level of insurance.

Batteries

Batteries are the heart of all back-up power systems and are the main cause of operational failures. Without continuous battery monitoring, users of the majority of static UPS systems, centralised emergency lighting systems and rectifiers are unlikely to have any warning before their system lets them down.

Age

Most organisations would not dream of using critical IT equipment beyond 3 — 5 years of age. The same organisations seldom consider upgrading or renewing a circuit breaker or a generator control system. Some standby generator systems date back 30 years and beyond. Even if a system is correctly designed, installed and maintained it could still fail due to its age. This is simply because buildings are dynamic creations, where the original criteria for the critical power installation may change over time. As part of your maintenance agreement insist on a regular assessment of the critical load and the system’s ability to support it.

Temperature

Main standby power components, diesel generators and UPS generate substantial amounts of heat. As any installation draws in its cooling air at these elevated ambient temperatures it is immediately heated further by the heat rejected from the equipment. This effect often forms a vicious circle, ultimately resulting in the standby system losing its thermal equilibrium with temperatures climbing inexorable upwards until the whole system fails. Chloride, a total service provider, carries out more than 500 load tests each year and has found that many systems installed in the UK struggle to maintain thermal equilibrium at sub 30ºC ambient temperatures. Very few systems would sustain thermal equilibrium at 35ºC and above.

Network Resilience

The National Grid considers that its period of greatest demand is in the winter, which is true given a holistic view. It is, however, not true for any “Hi-Tech” organisation where the heat generated by their equipment is a liability. In these cases the period of increased demand is in the summer when air conditioning is drawing its greatest load. National Grid openly states that it reduces the resilience of its network in summer in order to accommodate their maintenance. It follows then, that specific parts of the network, such as the commercial centres of any City, are subject to less resilience at the very point when they are at their most vulnerable.

Security

Critical power systems often have no physical security leaving systems prone to tampering or sabotage, maybe by the disaffected employee. Access control and personnel screening is often lacking, whilst night shift absenteeism and even alcohol abuse have been known to leave systems unmonitored.

Remote Monitoring

Mission critical systems are often left unattended outside normal working hours. Watching over the UPS and mains power remains essential; what happens if a weekend problem goes unnoticed until Monday morning? Companies running 24/7 remote monitoring packages for both UPS and generators are becoming an essential part of the maintenance mix, providing immediate identification of problems, pre-emptive maintenance and ‘remote fix’ capability.

Finally…

As problems experienced by critical power system end-users are very likely to be one or a combination of factors outlined here this list represents a checklist for reassessing the reliability of existing critical power systems.

Andrew Hodge is Service Sales Manager at Chloride Harath