"To make a distinction, portables are different from mobile air conditioners, which are also mounted on wheels but are often towed, trailered, or trucked to a job site," said Tagge. "In addition, mobile units are usually much larger in physical size and capacity, and must be set up outside."

According to Tagge, the most familiar type of portable air conditioning is air-cooled. In his estimation, air-cooled units provide flexibility and make equipment set up and tear down fast and simple. It is his belief that air-cooled portables can fit the bill perfectly for seven out of 10 applications.

"Today, a wide range of models and types of portable air conditioners are available for sale or rent," said Tagge. "Air-cooled portables still make up the bulk of the market. However, specialty units have grown in importance and represent the fastest growing segment of the market."

TYPES AVAILABLE

"Sometimes the application prevents the inflow or outflow of air into a space," he said. "Other times, it is the venue itself."

One example of where air-cooled portables won't work is a surgery suite, he said. The air conditioning system for the surgery suite is always a dedicated, closed-loop system.

"There can't be even the slightest amount of outside air allowed to penetrate the surgery suite in order to keep it germ free," he said. "In addition, all air that circulates through surgery must be HEPA-filtered to maintain the germ-free environment."

The problem is how to add capacity to such an environment, he said. Most supplemental cooling schemes would use air outside of the existing cooling loop, making air-cooled equipment useless.

"However, many hospitals have discovered that the addition of a water-cooled portable, set up and operating during a surgery, provides exactly the added capacity that they need to keep the surgical team cool and comfortable," said Tagge. "Surgery suites contain all of the elements needed to make water-cooled units operational, including a water source and a drain."

TOUGH-TO-COOL APPLICATIONS

"Even in buildings built with air conditioning there are numerous occupants or equipment rooms located in the basement or rooms that don't have access to the return air system," he said. "This makes using air-cooled equipment nearly impossible. For these, water- cooled portables are ideal."

In regard to water-to-air split-system portables, Tagge called them "the perfect marriage between a water-cooled unit and an air-cooled unit."

"Water-to-air split-systems can be an ideal way to solve problems for which neither is ideal," he said. "They utilize a water-cooled heat exchanger located in the air-handling unit to accept the heat. The air-handling unit is placed inside the space to be cooled and provides the cool evaporator air, as well. This unit creates no positive or negative air pressure condition as it circulates only interior air through the evaporator, just like a water-cooled unit."

In this case, the heated water is then pumped through a triple hose line set to a remote fan coil condenser - much like a dry cooler or automotive radiator. The fan coil unit is placed somewhere outside the space to be cooled - and this could be outdoors or in the hallway.

"Ambient air passes over the remote condenser and the heat is rejected," explained Tagge. "The cooled water is then pumped back through the line set to the unit and the process is repeated. The third hose on the line set handles the condensate created in the process."

There is a need for water-cooled portables. There are just some applications where the introduction of makeup or exhaust air — required of air-cooled units — just cannot occur.

LARGE A/C, HEAT APPLICATIONS

When a dedicated 25-ton computer room a/c unit fails or is shut down for service, portables of 5-tons or less aren't adequate to compensate, according to Tagge.

"Often, you can get by on reduced capacity, perhaps one half of the system capacity," he said. "But wheeling in a 1-, 2- or even 5-ton unit isn't going to handle the load when a 25-ton unit is shut down or fails. Multiple portables may make up the needed tonnage but each requires floor space and its own power source - neither of which may be available."

Enter the 12-ton dual centrifugal cart-mounted air conditioner. This unit was designed for large-capacity requirements inside of commercial office space, said Tagge. With a small footprint (45 inches wide by 65 inches long and 50 inches high), it can fit into most freight elevators, through double doors, and down most hallways, he said. The size allows access to high-rise office buildings and commercial spaces.

Sometimes, the problem that you are dealing with is a space that is not too hot, but is too cool. This happens for a number of reasons, including:

"Heat pump portables look exactly like their portable a/c counterparts. In fact, all heat pump portables are also portable air conditioners," said Tagge. "They are air-cooled units that look and set up in an identical manner to the portable a/c units."

The difference is completely internal. From the outside, you can only tell the difference between a heat pump and its "cooling only" counterpart by a few extra buttons on the control panel.

"Portable air conditioning has come a long way in the last 20 years," said Tagge. "And with continuous and rapid advances in computer technology and information processing, expect to find new and flexible products emerging from the portable cooling industry."

Publication date: 07/10/2006