As the temperature outside rises this summer, warehouses can quickly be-come hot and unbearable, resulting in declining employee productivity. But it doesn't have to be that way.

To maintain a cool warehouse, air conditioners, chilled-water systems, evaporative coolers, heat pumps and fans can be pressed into service. The selection of the best equipment suited to your operation depends on many factors ranging from cooling requirements to facility size. Understanding how the various cooling systems operate and their effectiveness under a range of conditions is the key to cooling your warehouse.

When cooling a warehouse is the priority, utilizing an air conditioner is often the solution. These industrial units work much like air conditioners used at residences or offices.

Air conditioner units incorporate cold evaporator coils, hot condenser coils and a compressor pump to transfer indoor heat to the outdoors. The system passes indoor air through the evaporator coil where a heat transfer fluid, known as a refrigerant, absorbs the heat. The heat, in its gaseous form, is then carried to the condenser coil. Condensed into a liquid again, the heat is released and channeled outside. These units are either air-cooled, blowing air through the condenser coils to help dissipate the heat, or water-cooled, running water over or through the hot condenser coils.

Air- and water-cooled units can be installed as a split system or a packaged unit. Water-cooled units can also utilize a cooling tower to improve efficiency.

In a split system, the evaporator and condensing units are separated. The evaporative units reside inside the warehouse and are encased in metal cabinets called air handlers. These cabinets have a fan and are connected to ducts to blow air through the coil and then throughout the building. The condensing units are generally housed on top of the warehouse roof.

Packaged units combine the two units into one system, eliminating the need to install numerous ducts throughout the building. Because they can be installed entirely inside the warehouse, packaged systems avoid some of the problems associated with split systems, such as regional regulations prohibiting exposed equipment outdoors.

Packaged air conditioning systems are available in three configurations. Horizontal units are typically hung from the ceiling to avoid wasting valuable floor space. However, this arrangement is expensive to install and can generate high utility costs since large blowers are necessary to thrust air down to the floor. Vertical units are often mounted on the floor or have wheels for portable use. And smaller, portable units provide spot cooling in specific areas of the warehouse.

A cooling tower used in conjunction with a water-cooled air conditioner is another arrangement suitable for warehouses. A cooling tower blows air through a stream of water, causing some of it to evaporate and the entire stream of water to become cooler. The water then runs through a heat exchanger and cools the hot condenser coils of the air conditioner. While a cooling tower is expensive to install, it delivers significant energy savings, especially for large warehouses located in areas with low humidity.

Operating differently than a standard air conditioner, a chilled-water air conditioning system cools the water before pumping it into the air handlers inside a building. This system is ideal for large warehouses where the extensive piping and ducting of a split system unit is not practical.

A chilled-water system houses the entire air conditioning unit on the roof or behind the building. Once it cools water to between 40 and 45 degrees Fahrenheit, the system circulates the chilled water through pipes to the air handlers.

A completely different type of air conditioner is an evaporative cooler, a cooling system that uses the natural process of water evaporation along with a blower. This system pulls fresh outside air through wetted filters that cause the water to evaporate, cooling the air.

Evaporative coolers are much less expensive to install than standard air conditioners and use only a quarter as much energy, but they are only highly effective and energy efficient in areas of low humidity. The system also requires more maintenance because minerals from the evaporative water constantly build up as water runs over the condensing coils.

Contrary to its name, a heat pump delivers cool air as well as heat. It is an air conditioner containing a valve, two metering devices and two bypass valves. As a cooling system, it reverses the flow of fluid to remove heat from the warehouse. A heat pump system can be centrally installed in the warehouse and connected to an air duct or water system. It can also be installed with multiple units placed in various areas throughout the building to provide individual space cooling. The benefits of using a heat pump to cool a warehouse are its energy efficiency and low levels of environmental pollution.

Used as an alternative or in addition to other cooling systems, industrial fans create comfortable working environments by providing a breeze and improving air movement throughout the building. Advantages include low maintenance requirements and flexible installation.

Effective and cost-efficient in cooling warehouses of any size is a high-volume, low-speed (HVLS) fan. This type provides substantial airflow over an area as large as 20,000 square feet and creates a breeze-like effect that makes a worker's skin feel six to eight degrees cooler.

When used in conjunction with air conditioning systems, HVLS fans circulate the cool air emitted from ceiling units, transferring it to the warehouse floor. A single 24-foot ceiling fan displaces air at a rate of 125,000 cubic feet per minute-over 12 times greater than an air conditioner's displacement.

From an air conditioner with a cooling tower to an evaporative cooler to an industrial fan, the operations, installations and performance of cooling systems vary. Determine which system or combination of systems best meets the needs of your warehouse and everyone will feel cool and comfortable.

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