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    Pacific Northwest National Laboratory
    Contracting Business/Kelly Faloon

    On the Spot and On the Job

    June 1, 2011
    Spot coolers aren’t just for emergencies anymore.

    For many years, portable air conditioners — also known as spot coolers — were thought of only as temporary solutions for emergency applications. However, these durable, versatile pieces of equipment often can be used in permanent applications, such as computer server rooms, or in manufacturing processes.

    "Spot coolers are much like cable television or microwave ovens," says Garth Tagge, a spokesperson for Spot Coolers. "As people use the product, it gains in popularity and usefulness, and the number of short- and long-term applications increase. Soon it stops being a novelty and starts being an ingrained solution."

    Spot coolers have three major applications: comfort cooling in areas where there's no existing air conditioning or where additional cooling is needed; equipment cooling, such as in computer server rooms; and process cooling in manufacturing applications. Hot parts moving down an assembly line can be cooled quickly by spot coolers, increasing the speed of the process and the productivity of the line.

    "In manufacturing process cooling, we've seen upwards of a 95% reduction in cool-down time when companies use spot coolers," says Eddie Stevenson, CIS marketing manager, MovinCool. "This allows manufacturers to assemble or package parts more quickly, and increase production capacity."

    Clark Michel is a vice president with Atlas Sales & Rentals, Inc., a distributor of portable cooling and heating equipment. He says his clients find spot coolers to be valuable in a variety of applications. These include:

    Permanent cooling in leased spaces. Many server rooms are located in leased facilities where landlords restrict or prohibit the installation of permanent HVAC equipment. Even where HVAC upgrades are allowed, lessees are understandably reluctant to invest in built-in air conditioning equipment that will be left behind in the event of a move.

    "Portable cooling provides a cost-effective solution: It allows tenants to get the cooling they need for as long as they need it," Michel says. "Portable units can be transported to the new location or returned to the supplier as the situation warrants."

    Short- or long-term portable cooling to save on capital expenditures. Operational cost reduction is virtually a universal goal in today's economy. Portable cooling equipment is available on a daily, weekly, monthly or long-term rental basis to satisfy cooling requirements without the need for an unwanted capital expenditure. "However, if a company does elect to purchase the equipment, a portable air conditioning unit can be much kinder to the pocketbook than a conventionally installed system," Michel says. "In fact, a portable unit used in a permanent server room application typically costs only 20% to 30% as much as a non-portable system of similar capacity, while still performing the required function."

    Supplemental cooling of rooms with increased heat loads. Increased heat loads are a common event in server rooms, whether due to consolidation or expansion. Upgrading an installed HVAC system can be a costly proposition. Portables can bridge the gap, providing the needed supplemental cooling without incurring a large capital expenditure.

    Emergency backup. Portable coolers are probably best known for delivering emergency cooling in the event of a power outage or a primary cooling system failure. Though rental units are often used for this purpose, some companies purchase one or more portable units to keep on hand for emergencies — especially for larger data centers. The portable units provide redundancy for installed cooling systems if a problem should occur, and can also be called into action to maintain critical temperature and humidity control when primary HVAC equipment is down for service or repair.

    Nighttime and weekend temperature setback for energy savings. Though many facilities operate only during business hours, data rooms must remain online around-the-clock. It’s a waste of energy and money to run the entire central building air conditioning system 24/7 just to keep the data room cool, yet this is sometimes what happens. Michel says a more efficient approach is to install a portable cooling unit that's dedicated to the server room, and set to operate when the central system is shut down or on nighttime or weekend setback.

    A portable air conditioner installed for this purpose will pay for itself in HVAC energy savings in no time versus running the entire building central system," he says. Stevenson adds that spot coolers used in permanent applications can often be connected to a building's existing exhaust ductwork.

    "In most cases, you can simply hook up a duct to the top of the unit and exhaust it into the ceiling space. If the main air conditioning system of the facility is running, the return plenum of that facility should be able to exhaust that hot air out of the space," he says. In cases where that's not an option, Stevenson says an accessory air plenum kit or water-cooled units are available. In addition, some units can accommodate duct runs of up to 100 ft., adding to their venting options.

    Spot coolers may have been thought of as temporary, emergency solutions. But that has changed, and the units' versatility and durability has earned them many full-time jobs — not to mention a place in the hearts of contractors and building owners alike.

    Tips on Selecting a Portable Unit

    There are two primary types of portable air conditioners used in commercial applications: Air-cooled units, which work by pumping in cool air and exhausting hot air out through ductwork; and water-cooled units, which connect to an external water source such as a central cooling tower or chiller system. Air-cooled portables are most often the system of choice because they use air to reject the heat — which is available everywhere. Water, the source for heat rejection in a water-cooled system, is less readily available but sometimes the only choice due to air-cooled heat rejection issues and floor space constraints.

    Always look for a high-quality commercial grade unit designed to deliver continuous, "24/7" cooling. The low-cost portables available from home improvement retailers may be adequate for residential use, but they do not have the cooling capacity, wide range of operation, reliability or durability needed for round-the-clock protection of critical electronics. Also, the low-cost units are limited to ducting lengths and only offer single-duct systems.

    By working with a reputable portable cooling supplier who carries multiple product lines, you can get unbiased advice on the best spot cooler for your application. A good supplier should also be able to help you make a "rent or buy" cost analysis that takes both your short- and long-term needs into account.

    Make sure the unit you choose has an automatic restart feature so it will start up again automatically in the event of a power interruption. For critical applications, have a backup generator ready in the event of a major power failure, and verify that the portable unit is designed to work on the backup circuitry. Some manufacturers incorporate fire suppression features and programmable controls. Since portable units are exposed to a wide range of conditions year-round, low ambient controls are important to prevent possible damage to the compressor due to liquid slugging.

    — Clark Michel, vice president, Atlas Sales & Rentals, Inc.