SPX Cooling Technologies 160 manual Operating and Environmental Considerations, System Cleanliness

/ Operating and Environmental Considerations /

Cooling towers are usually selected to produce a specific cold water temperature at the higher summertime wet-bulb temperatures. During the remainder of the year, the cooling tower is capable of producing much colder water. Unless your system will benefit from the coldest possible water temperature, you may want to consider controlling cold water temperatures to higher levels. You'll also save energy by using such control. See Marley Technical Report

#H-001A, “Cooling Tower Energy and its Management”.

Always control leaving water temperature by manipulating the quantity of air that the fan moves through the

tower. Varying the quantity of water flow is not normally recommended and can be harmful in freezing weather. You can alternately start and stop single-speed motors to keep water temperatures within an acceptable range. But your flexibility is limited by the amount of starting time per hour allowed by the motor manufacturer.

Increased flexibility can simplify your operating procedures and save you money in the long run, both on operation and on maintenance. Here are two of the more popular options:

❑Two-speed motors improve operating flexibility by increasing the number of potential operating modes. Users in northern climates will find that the tower can carry winter loads at half-speed; reducing fan power requirements

by 85+% during that time. Two-speed motors also help to control icing during wintertime operation. See Marley

Technical Report #H-003, “Operating Cooling Towers During Freezing Weather”.

Normally, two-speed motors are provided in 1800/900 RPM, single winding configuration, which is the least expensive two-speed option. They are also available in other combinations including the more expensive double winding.

❑Frequency modulation devices work well on induced draft, propeller fan cooling towers such as the Class 160.

However, their design must include the capability to lock out any critical fan speeds and the very low fan speed ranges. Consult your Marley sales representative for specific recommendations when considering variable speed control. In many cases, for example, you'll achieve the best results by using a single control to regulate the speed of several fans on a multicell tower.

■System Cleanliness

Cooling towers are very effective air washers. Atmospheric

dust able to pass through the relatively small louver openings will enter the circulating water system. Increased concentrations can intensify system maintenance by clogging

screens and strainers; and smaller particulates can coat system heat transfer surfaces. In areas of low flow velocity (such as the cold water basin), sedimentary deposits can

provide a breeding ground for bacteria.

In areas prone to dust and sedimentation, you should consider installing some means for keeping the cold water

basin clean. Typical devices include side stream filters and a variety of filtration media.

You should also plan ahead to develop a consistent, effective program of water treatment. A good water treatment program will help to assure long service life, while keeping your tower free of potentially harmful biological growths.

C a u t i o n

The cooling tower must be located at such distance and direction to avoid the possibility of contaminated tower discharge air being drawn into building fresh air intake ducts. The purchaser should obtain the services of a Licensed Professional Engineer or Registered Architect to certify that the location of the tower is in compliance with applicable air pollution, fire, and clean air codes.

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