How To Pick A Cooling Tower: Tips for a Smart Specification

By Chad Edmondson

Mechanical design engineers can protect owners from unnecessary expense, maintenance, and even liability with a carefully written specification. Our experience has shown that including the following items whenever the project or application allows will provide the best and most cost-effective long-term service:

CTI (Cooling Technology Institute) Certification. This is insurance that the tower you select meets its published performance. CTI certified cooling towers have been thoroughly tested by a CTI-licensed testing agency and are third party certified to have met thermal efficiency standards that are referenced in both ASHRAE Standards 90.1 and 189.1

Crossflow Cooling Tower Design. Crossflow towers offer easier access to drive system, allow for complete fill inspection and require less pump head to operate. They have an internal access plenum that can be fitted with an internal platform for safe and easy inspection and servicing. Counterflow tower are limited in their maintenance access but can be a good option if space is an issue.

Factory Installed Basin Sweeper Piping. Including sweeper piping in your original design specification complements the existing or any future filtration system. Owners will quickly recoup this initial cost by reducing labor, reducing water treatment and increasing the equipment efficiency and life. It is also more economical to have the piping installed at the factory than later in the field.

Mechanical Vibration Cutout Switch. This prevents downtime and component destruction that can happen due to excessive vibration. We prefer that the tower automatically shut down without an option for remote restart because this ensures that a worker actually has to inspect the tower to determine the source of the vibration before restarting it. Excessive vibration can cause serious damage in a relatively short time, so “buying time” with remote restart isn’t worth the risk.

Crossflow Tower Safety Access. Crossflow cooling towers require access to the interior and top of the cooling tower for routine maintenance. For safety reasons this typically means including an interior walkway (to prevent slippage on wet surfaces). If the cooling tower is over 20 feet tall, you may also need a ladder (possibly with a cage) and a raised service platform. All of the above may be necessary for you to meet OSHA standards as well as local codes.

Counterflow Tower Safety Access. Counterflow cooling towers, which typically do not have any open interior space, must be outfitted for servicing from the outside via an external platform and ladder.

Cold Water Basin Material of Construction. The cold water basin construction is arguably the most critical specification when it comes to extending the service life of the tower. Whenever possible it is best to specify stainless steel or polyurethane. Polyurethane basins typically offer a better warranty than stainless. We have found that for overall cooling tower lifecycle cost a stainless-steel factory assembled tower (no basin) installed on top of a field-constructed concrete sump/basin offers the longest life.

Hot Water Basin. Crossflow towers, but not counterflow towers, also have “hot water” or “distribution” basins. Stainless steel or fiberglass are preferred for extending cooling tower life.

Direct Fan Drive. Direct fan drives should be chosen for fan motors with larger horsepower. Direct drives eliminate the energy loss that occurs between the motor and fan when indirect methods are used. They also require less maintenance, have better warranties and use up to 10% less energy than indirect (belt or gear) drives.

Belt Drive. When smaller fan motors are used, a belt-type indirect drive is easier to service than a gear drives. Belt drives have fewer moving parts and do not require oil lubrication. On the other hand, gear drives must be properly aligned and serviced to avoid damage.

Casing Panels. Casing panels should be made of fiberglass or stainless steel to decrease corrosion.