Independently certified to withstand seismic and wind load forces at ALL Building locations in North America.


The eco-ATWB is an induced draft, counterflow design closed circuit cooler with a capacity range of 150 to 38280 MBH (42 to 10813 kW). Standard construction includes the patented, high efficiency  EVAPCO Ellipti-fin Coil and G-235 (Z-725 Europe) galvanized steel casing and basin. Type 304 or 316 stainless steel construction is available for the basin or the entire unit.


eco atwb closed cooler clark johnson company

Closed Circuit Coolers

eco-ATB-E Closed Circuit Coolers

evapco distributed by Clark Johnson Co

   Design Features

     Maintenance Features

      Drive Systems

      Optional Equipment

Thermal Performance

eco-ATWB Closed Circuit Cooler - Design Features


The New eco-ATWB line of Closed Circuit Coolers has been specifically designed to dramatically increase both the evaporative (latent) and dry (sensible) modes of cooling. With this new revolutionary design, the EVAPCO eco-ATWB will also save water and energy by increasing the unit’s efficiency in both the evaporative and dry  cooling modes of operation. The eco-ATWB utilizes the EVAPCO Ellipti-fin coil which features elliptical spiral fin technology to maximize the surface area available for heat transfer. The eco-ATWB is the ideal solution for: Reducing Water Consumption,Lower Energy Costs, High Dry Bulb Switchover, Super Low Sound Levels.




Principle of Operation Evaporative Mode (Latent Heat Transfer)heat mode evaporator clark johnson company In the evaporative mode, the process fluid enters the eco-ATWB cooler through the top coil connections and circulates through the finned coils. With both pumps energized, the heat from the process fluid is transferred through the coil tubes to the water cascading downward over the coils while simultaneously air is drawn upward over the coil opposite the water flow using the fan drive system (Fan on, Pump A & B on). A small portion of the water is evaporated to dissipate the heat to the atmosphere in a latent heat transfer. This mode of operation provides fan energy savings and lower leaving water temperatures by utilizing evaporative cooling.       Dry Mode (Sensible Heat Transfer)   dry mode evaporator clark johnson co In the dry mode, the recirculating spray pumps are deenergized (Fan on, Pump A & B off). The process fluid enters the eco-ATWB cooler through the top coil connection and circulates through the coil with the Fan On. Heat from the process fluid is dissipated to the atmosphere by sensible heat transfer through the tube walls to the air passing over the coils. The coils are finned to promote optimal airflow over the coil and to maximize heat transfer area. Air is drawn over the finned coils by the fan drive system. The process fluid then returns to the heat source via the bottom coil connection. This mode of operation eliminates water consumption when the dry bulb temperature is favorable.       Efficient Drift Eliminators An extremely efficient drift eliminator system is standard on the eco-ATWB  Closed Circuit Cooler. The system removes entrained water droplets from the air stream to limit the drift rate to less than 0.001% of the recirculating water rate. With a low drift rate, the eco-ATWB Closed Circuit Cooler saves valuable water and water treatment chemicals. The eco-ATWB  Closed Circuit Cooler can be located in areas where minimum water carryover is critical, such as parking lots. The drift eliminators are constructed of an inert polyvinyl chloride (PVC) plastic material which effectively eliminates corrosion of these vital components. They are assembled in sections to facilitate easy removal for inspection of the water distribution system.  Superior Air Inlet Louver and Screen DesignThe air inlet louver screens on the eco-ATWB are constructed of corrosion-freePVC. They are a two pass design that minimizes splashout and reduces the potential for algae formation inside the cooler. In single pass louver systems used by other manufacturers, circulating water droplets tend to splashout, especially when the fans are shut off. With the two pass louver system, the water droplets are captured on the inward sloping pass, minimizing splashout problems. This unique louver design completely encloses the basin area. Direct sunlight is blocked from the water inside the cooler, thereby reducing the potential of algae formation. Water treatment and maintenance costs are substantially reduced. While effectively containing the recirculating water and blocking sunlight, the louver design has a low pressure drop. The low pressure drop results in lower fan energy consumption, which reduces the operating costs of the cooler. Ellipti-fin Coil Design  The new eco-ATWB Closed Circuit Cooler utilizes Evapco's patentpending Ellipti-fin coil design which assures even greateroperating efficiency. The elliptical tube design allows for closertube spacing, resulting in greater surface area per plan areathan round-tube coil designs. In addition, the revolutionaryEllipti-fin design utilizes elliptical spiral fin coil technology andhas lower resistance to airflow than typical finned coil designs.This permits greater water loading, making the new Ellipti-fincoil the most efficient coil design available on the market.The coils are manufactured from high quality steel tubingfollowing the most stringent quality control procedures.Each circuit is inspected to ensure the material quality andthen tested before being assembled into a coil. Finally, theassembled coil is pneumatically tested at 400 psig underwater to ensure it is leak free. eco-ATWB=E Operating Benefits The eco-ATWB  maintains all of the advantages of the eco-ATW with the additional benefit of enabling simultaneous wet and dry operation. The unique Water Efficient Mode of the eco-ATWB allows for a portion of the heat load to be rejected through both evaporative cooling AND dry cooling, even at high ambienttemperatures, this further increases your ability to save water and offers additional associated cost savings through reduced water make-up, blow-down and chemical consumption. The eco-ATWB provides an ideal solution for applications where minimizing both energy and water consumption is critical. Depending on the optimum eco-Cooler you select for your job, one can operate 100% wet, 100% dry or simultaneously Wet & Dry in the Water Efficient Mode, offering unique advantages in freezing climates, higher temperature industrial cooling applications where 100% evaporative cooling is not always favorable. Multiple Water Distribution Systems   Each coil in the eco-ATWB features its own water distribution system. This allows each coil to operate in a mode independent of the other coil EVAPCO’S Zero Maintenance ZMII® Spray Nozzle remains clog-free while providing even and constant water distribution for reliable, scale-free evaporative cooling under all operating conditions. The heavy duty nylon ZMII® Spray Nozzles have a 1-5/16” diameter opening and a 1-1/2” splash plate clearance enabling EVAPCO to use 75% fewer nozzles. Furthermore, the fixed position ZMII® nozzles are mounted in corrosion-free PVC water distribution pipes that have threaded end caps. Together, these elements combine to provide unequaled coil coverage and scale prevention, and make the industry’s best performing non-corrosive, maintenance-free water distribution system. The water distribution is designed to provide a minimum 6 GPM over each square foot (4 liters per second over each square meter) of unit plan area to ensure proper flooding of the coil.   Principle of OperationEfficient DriftEliminatorsSuperior Air Inlet Louver and Screen DesignEllipti-fin Coil Designeco-ATWB Operating BenefitsMultiple Water Distribution Systems



eco-ATWB Closed Circuit Cooler - Maintenance Features


Designed for easy maintenance, the eco-ATWB- Closed Circuit Cooler leads the industry in service friendly features. The three most critical areas for closed circuit cooler maintenance are the basin, drive system, and coil. The eco-ATWB basin section is designed to allow quick and easy access from outside the cooler. Just like the basin, all service to the drive system can be safely performed from the side of the cooler, and EVAPCO's Power-Band drive system is the easiest belt drive system to maintain in the industry!

Drive System


The eco-ATWB Evaporative Cooler features the highly successful EVAPCO POWER-BAND Belt Drive System engineered for heavy-duty operation. The POWER-BAND Drive System has consistently provided trouble-free operation in the most severe duty evaporative condenser applications. In addition, the complete drive system including the fan motor is standard with a (5) Five Year Warranty.


  •     Fan Motors
  •     Fan Shaft Bearings
  •     Drive System Sheaves
  •     Power-Band Belt Drive


Fan Motors



 Closed Circuit Cooler models utilize heavy duty totally enclosed (T.E.F.C. or T.E.A.O) fan motors designed specifically for closed circuit cooler applications. In addition to the standard motors offered on each cooler, EVAPCO offers many optional motors to meet your specific needs, including:


  • Premium Efficiency Motors
  • Multi-Speed Motors
  •  Inverter-Duty Motors for VFD Applications


3', 4', 8.5' & 17' (0,9; 1,2; 2,6 & 5,2 m) wide ATWB models feature T.E.F.C. motors are located on the outside of the unit, protected by a hinged, swing away cover. 12' & 24' (3,7 & 7,3 m) wide ATWB models have T.E.A.O. motors located inside the fan section on a heavy duty motor base which swings to the outside for repair or removal.





Fan Shaft Bearings


The fan shaft bearings on the Closed Circuit Cooler are specially selected to provide long life, minimizing costly downtime. They are rated for an L-10 life of 75,000 to 135,000 hours, making them the heaviest duty pillow block bearing in the industry used for Closed Circuit Cooler duty.


Power-Band Belt Drive


The Power-Band drive is a solid-back multigroove belt system that has high lateral rigidity. The belt is designed for closed circuit cooler service, and is constructed of neoprene with polyester cords. The drive belt is sized for 150 percent of the motor nameplate horsepower ensuring long and trouble free operation.




Drive System Sheaves


Drive system sheaves located in the warm, moist atmosphere inside the cooling tower are constructed of an aluminum alloy. Those located externally are protected by a hinged cover.

Optional Equipment


The standard design of the EVAPCO eco-ATWB  provides the customer with the most efficient and easiest Closed Circuit Cooler to maintain in the industry. There are additional options which can make maintenance easier, extend the life, or enhance the performance capabilities of the Closed Circuit Cooler.



  • Sloped Access Ladders
  • Stainless Steel Water Basin
  • Electric Water Level Control
  • Electric Immersion Heaters
  • Remote Sump Configuration
  • Low Sound Solutions
  • Pulse~Pure® Water Treatment System

Clark Johnson Company, Inc.       2016