Building air-conditioning systems are more crucial than ever because more and more building operations rely on them. Without air-conditioning, computers and telecommunications equipment can heat up and get damaged. Also, occupied spaces can quickly become stifling. What's more, maintenance and engineering managers may be forced to shut down building systems and operations, thereby sustaining losses that will rapidly pile up.

Fortunately, the limited options of the past—which included opening windows, handing out fans to building occupants and circulating more outside air—have been joined by a more effective solution—portable cooling systems. These systems are not designed to completely replace building air-conditioning systems, but in the event of air-conditioning loss, they provide spot cooling to a facility's critical areas. This means that essential operations can keep on going, averting a costly shutdown.

Facility managers can employ these portable systems in many applications because they come in a range of capacities and configurations. Most units can be plugged into AC outlets while other larger units might need dedicated electrical service. Also, most systems release the removed heat through a nearby window while other units entail the placement of a heat-rejection unit outside of a facility.

While air-conditioning systems are very reliable—among the most dependable in a building—the need for backup systems remains because air-conditioning disruptions still occur. In fact, even routine maintenance on central equipment can temporarily halt air-conditioning service. Also, the air-conditioning system may fail for some reason or be derailed by breakdowns in a building's electrical service and distribution system.

For example, periods of heavy electrical demand can lead to the interruption of air-conditioning. During such times, utility companies might lower system voltage. As a result, managers are often compelled to shut down central air-conditioning systems because operating them at reduced voltage can damage system compressors. Another situation that can result in air-conditioning loss is the failure of equipment within a building's electrical distribution system. In such cases, managers may have no choice but to shut down central air-conditioning equipment to lower electrical loads. Depending on the seriousness of the equipment failure, the interruption in service could last from a few hours to several weeks.

Portable systems are also warranted because facility needs are constantly evolving, requiring changes to building air-conditioning systems. While most systems have the capacity and flexibility to easily adjust to many shifting needs, in some cases modifying the system can be time-consuming and can create brief periods during which the current air-conditioning system is insufficient.

Additionally, portable cooling systems come in handy during the performance of some maintenance activities, especially those taking place in confined spaces. For instance, the interiors of large steam boilers usually have to be examined once a year, often requiring inspectors to stay inside a boiler for several hours. To make the task less arduous and uncomfortable, portable cooling systems can be employed to deliver cooled ventilation air.

Finally, portable systems are needed when particular locations call for additional air-conditioning. For example, building occupants might be involved in a special project that entails the use of equipment with a heavy heat load. Or a certain activity going on in a particular space might call for more air-conditioning than the current system can provide. Under such temporary conditions, portable systems represent the most viable solution because modifying the building system would be too expensive.

Managers can choose from two general types of portable cooling systems—air-to-air systems and water-based systems. While small air-to-air systems can be wheeled to the particular area that needs cooling, larger air-to-air units can have capacities of up to 5 tons and are usually placed outside a building because of their size. Water-based portable cooling systems also come in capacities of up to 5 tons. And like air-to-air units, water-based ones supply conditioned air where it is required through a flexible duct.

To get the most out of such systems, managers must plan their placement and operation. First, they must pinpoint the facility's critical areas—those places in which operations need air-conditioning in order to continue. Typically considered critical are computer equipment rooms and telecommunications equipment centers. This is because without air-conditioning, computer equipment usually has to be shut down, potentially resulting in costs of up to several thousand dollars per minute. In addition, sensitive electronic equipment could be damaged if operated without cooled air.

For each critical area they list, managers must figure out the load that the portable cooling system will have to satisfy. By calculating the loads for all the critical areas they identified, managers can get an idea of the size and number of portable cooling systems they will need. Also, managers should evaluate the importance of all the different loads, devoting certain portable systems to the most crucial loads and rotating portable units among less critical loads.

Finally, managers must choose between having the equipment on site or committing to a contract to rent a system, with delivery guaranteed within a specified time in the event of a loss in air-conditioning. Managers should not wait for the cooling system to fail or to be interrupted before starting to search for a portable cooling system to rent.

Flexible and easy to use, portable cooling units provide much-needed backup to the building's air-conditioning system. But managers should keep in mind that these systems are temporary solutions, not the permanent answer to building HVAC system problems. As such, they should be removed once the air-conditioning crisis or the situation that called for portable air-conditioning is over. Though they may be tempting to use as permanent solutions, portable cooling systems provide the most benefits in a pinch.

Source: Helping Facilities Keep Their Cool
James Piper
Maintenance Solutions, Mar. 2003
http://www.facilitiesnet.com/ms/mar03/mar03HVAC.shtml