Being Power-Wise for Mission Critical Facilities
Then and Now
Not too many years ago, it was fairly simple. The manager or operator of a data center would call you up to install a couple of computer room air conditioning (CRAC) units against the wall of the center. Then you would connect the piping, controls, and the electrical service and perform a routine start-up of the new units. Unless you sold a maintenance agreement to the customer, you and they were done.
Back then, engineers and data center operators were working under this premise: How many watts per square foot would the information technology (IT) equipment consume, therefore reject, into the room in the form of waste heat? The calculations were simple enough; the conversion from watts to Btuh was made, and the appropriate tonnage CRAC units were ordered and installed. This process worked pretty well for many years. Even though the CRAC unit placement within the space was not ideal, there was usually enough tonnage to totally saturate the room with cold air. The mindset concerning electrical costs was, “They are what they are.”
But times have changed. One of the rules of thumb in IT is Moore’s law, which states, “Every 18 months, the computing capacity, meaning work done by a computer, will double.” Therefore, the amount of heat given off by the computing equipment will rise as well.
That law and other factors drive many decisions in the IT field. As a result, the cooling of those very same data centers took on a whole new complexity. No longer may we work based on watts/square-foot calculations. Today it’s all about kilowatts (kW) per rack of IT gear. The introduction of larger-capacity, faster, and therefore hotter computers (especially blade-style servers) has forced many engineers to analyze the physics of cooling the data room.
The focus now, and going forward, is heat removal and, in particular, capturing the heat as close to the source as possible. Most of today’s CRAC and computer room air handler (CRAH) units do not sit on a wall (known as room cooling) at the perimeter of the data center. Instead, they are strategically located within the rows of IT equipment, or otherwise positioned to ingest all of the hot air possible — the higher the return air temperature is, the more efficient the overall operation is.
Many of the units themselves do not resemble air conditioners. More often than not, they look like a rack of IT equipment, with the same dimensions and the same name brand in many cases. This has taken on the name in-row cooling.
Now the current mindset regarding electrical costs seems to be, “We must be as efficient as possible in order to pay as little for power as possible.”
Ask the Right Questions
So how do you, as a service/installation/integration partner for
your IT-savvy clients, help the com-
pany save money? As always, start by asking questions.
What kind of input is your client seeking from you? Could you possibly save the client operating dollars by studying the layout of the IT gear and making placement suggestions based upon heat load?
Many existing data centers have an abundance of heat-removal capacity, read as tons (or kW) of cooling. The problem is the supply and return (as hot as you can get it) air distribution. It is highly inefficient to mix the supply and return air of any mechanical system. You wind up only extracting a portion of the heat from the room into the airstream, where it can then be transferred into the chilled water or refrigerant and, finally, expelled from the room.
Would it make sense to duct or re-duct either the supply or return air in an existing facility? Is this the only site they have in operation, or is there a disaster recovery (DR) site elsewhere?
Also, start looking around and checking out what the IT staff is installing and working on. Are the rows of equipment placed in a hot aisle-cold aisle design? Do you have to turn the setpoints down low to keep the cooling on for longer cycles? Are the CRAC units fighting each other, meaning some are cooling, some are reheating, and others are fighting the humidity setpoint? All of these are signs of inefficiency and waste.
What about containment systems, freezer strips, rack hats, end caps, etc.? All of these devices and products, including fire-proof foam blocks and rack U-space blanking panels, are an increasingly important part of mission critical environments because they keep the heat isolated, allowing the heat rejection systems to do their job to the best of their ability.
What happens if you lose a compressor due to short cycling of air due to poor perforated tile placement? Will you drop the critical load? You need to know what level of service your customer commits to provide for its customers, which is typically specified as a Tier 1, 2, 3, or 4 service level agreement (SLA). What are the expectations of uptime? Is it 99.999 percent of the time? If so, that is still 5½ minutes a year of outage — is that OK? Can you commit to responding to those requirements?
As a good partner, you must also be highly cognitive of any issues associated with the green movement. Many data centers are connected in some way to a LEED-certified building. So, what impact may that have on operations, operating procedures, chemicals for coil cleaning, etc.? Are the CRAC/CRAH units draining their condensate into a cistern for non-potable irrigation water or cooling tower make-up water?
These are just a few of the interwoven complexities of operating a green building and an efficient data center simultaneously. All of this must be happening while ensuring that a balance can be struck with the requirements listed by an ever-growing list of certification agencies (and oh, by the way, keeping the equipment energized, on-line and removing heat from the critical space).
Be a Resource
When it comes down to it, HVAC is only a slice of the pie that critical facilities managers are responsible for. As contractors, we need to make it easy on the managers to communicate their needs to us. If you learn what is driving their business, maybe you can figure out a way to help them stay on-line. Then maybe, just maybe, you will viewed as a resource. No one wants to be just a vendor or just the heating and air guy.
By showing your willingness to step outside of the normal service provider or contractor stereotype, you will become an ever-more-important partner to your customer. After all, isn’t that where we all want to be?
Publication date: 6/18/2012