Closed Circuit Coolers

PMWQ Closed Circuit Cooler

PMWQ Closed Circuit Cooler

The PMWQ is a forced draft, axial fan design closed circuit cooler. Standard construction features the patented, high efficiency Thermal-Pak® Coil with a G-235 (Z725 Europe) galvanized steel casing and basin. Type 304 stainless steel is available for the basin and the casing.

The PMWQ product line is a result of EVAPCO's extensive experience in forced draft designs. Models are designed for easy maintenance and long, trouble free operation. These units are also designed with IBC Compliant construction and CTI Certified Thermal Performance. All features shown are available on all models.

Principle of Operation

The process fluid is circulatedthrough the coil of the closed circuit cooler. Heat from the process fluid is dissipated through the coil tubes to the water cascading downward over the tubes. Simultaneously air is pulled through the unit by the fans and travels upward over the coil opposite the water flow. A small portion of the water is evaporated which removes the heat. The warm moist air is forced to the top of the closed circuit cooler by the fan and is discharged to the atmosphere. The remaining water falls to the sump at the bottom of the cooler where it is re-circulated by the pump up through the water distribution system and back down over the coils.

IBC Compliant  



What is IBC?  

  • The International Building Code requires that evaporative cooling equipment must meet the same seismic or wind load forces as the building to which they are attached.

How does it apply? 

  • Based on project zip code and site design factors, calculations are made to determine the equivalent seismic "g force" and wind load on the unit.

What does EVAPCO offer?

  •     Standard Structural Design

                    -Projects with ≤ 1.0g seismic or 145 psf wind loads

  • Upgraded Structural Design

                    -Projects with > 1.0g seismic or 145 psf wind loads

  • The upgraded structural design package for the New ATWB is designed for 5.12g and 145psf, making it applicable to ALL building locations in North America.

Thermal-Pak Coil

Evapco Closed Circuit Coolers utilize EVAPCO's patented Thermal-Pak® coil design which assures greater operating efficiency. The elliptical tube design allows for closer tube spacing, resulting in greater surface area per plan area than round-tube coil designs. In addition, the Thermal-Pak® design has lower resistance to airflow and also permits greater water loading, making the Thermal-Pak® coil the most effective design available.

The coils are manufactured from high quality steel tubing following the most stringent quality control procedures. Each circuit is inspected to ensure the material quality and then tested before being assembled into a coil. Finally, the assembled coil is pneumatically tested at 400 psig under water to ensure it is leak free. To protect the coil against corrosion, it is placed in a heavy steel frame and then the entire assembly is dipped in molten zinc (hot-dip galvanized) at a temperature of approximately 800°F.

Note: Closed circuit coolers should only be used on sealed, pressurized systems. Continual aeration of the water in an open system can cause corrosion inside the tubes of the cooler leading to premature failure.

Efficient Drift Eliminators

The PMWQ is provided with an efficient drift eliminator system that effectively reduces entrained water droplets from the air discharge to less than 0.001% of the spray water flow rate. The eliminators are constructed of non-corrosive PVC with a multi-pass design for maximum drift reduction. They are assembled in modular sections for easy removal and access to the water distribution system. In addition to reducing drift, the eliminators also function as effective debris screens which protect the spray system from sunlight and debris.

Maintenance Free ZMII® Spray Nozzle Water Distribution System

EVAPCO's Zero Maintenance ZMII® Spray Nozzle remains clogfree 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. 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.

Fast, On-Time Shipments

The PMWQ is completely factory assembled and manufactured by a dedicated professional workforce, expert in building closed circuit coolers. Factory trained mechanics and EVAPCO's strict quality control and inspection procedures guarantee the quality of every unit shipped.

EVAPCO's controlled factory environment ensures fast on-time shipments, allowing the PMWQ to be available WHEN THE CUSTOMER WANTS IT!

Quiet Operation: Super Low Sound Fan is Standard

10 - 13 db(A) Reduction versus Standard Fan!

The Super Low Sound Fan offered by EVAPCO utilizes an extremely wide chord blade design available for sound sensitive applications where the lowest sound levels are desired. The fan is one-piece molded heavy duty FRP construction utilizing a forward swept blade design. The Super Low Sound Fan is capable of reducing the unit sound pressure levels 10dB(A) to 13dB(A), depending upon specific unit selection and measurement location. The fans are high efficiency axial propeller type and operate with no loss of thermal performance.

Corrosion Protection

G-235 Hot-Dip Galvanized Steel Construction 

The standard material of construction for evaporative cooling equipment for many years has been hot-dip galvanized steel. The purpose of galvanizing is to protect the base metal from corrosion, and the thickness of the galvanized layer directly affects the equipment life. EVAPCO has been instrumental in the development of corrosion protection technology and was the first manufacturer to use G-235 galvanized steel construction. The G-235 designation equates to a minimum of 2.35 ounces of zinc per square foot of surface area.

The EVAPCOAT Corrosion Protection System is the heaviest galvanized coating available for extended corrosion protection eliminating the need for costly, unreliable epoxy paint finishes. 

Stainless Steel Material Options 

The LRWB is standard with a stainless steel cold water basin. Optional upgrades to stainless steel water touch basins, stainless steel water touch units and all stainless steel construction are also available. 

For more information on these stainless steel options, see your local EVAPCO sales representative.

Designed for easy maintenance, the PMWQ Closed Circuit Cooler leads the industry in service friendly features. The three most critical areas for cooling tower maintenance are the basin, drive system and coil . The cold water basin is easily accessed from outside the tower via large circular access doors. All drive system components are located in the dry, entering air stream for long life and can be serviced from outside the tower. The exclusive Thermal-Pak coil is designed for trouble free maintenance and long life straight from the factory.

Fan Motor Mount

TEFC fan motors are mounted in a convenient open area for ease of belt tensioning, motor lubrication and electrical connection. The motor base can be easily adjusted then locked into position to maintain proper belt tension.

Easy Access

Mechanical Drive System Access 

The PMWQ mechanical drive system is easy to maintain. Bearing lubrication and belt adjustment can be performed from outside the unit. There is no need to remove fan screens to maintain important drive components. In addition, the locking mechanism used to maintain belt tension can also work as a wrench to adjust the belt. 

Basin Access 

The basin/fan section of a centrifugal fan unit is designed for accessibility and ease of maintenance. Fan and drive components are positioned to allow easy adjustment and cleaning. All grease fittings are in convenient locations for periodic lubrication. Large circular access doors are provided to allow entry into the basin. All float valve and strainer assemblies are located near the door for easy adjustment and cleaning. The sump is designed to catch the dirt accumulated. This can be flushed out simply with a hose. The stainless steel strainers may be easily removed for periodic cleaning.

Thermal-Pak Coil

EVAPCO’s exclusive elliptical Thermal-Pak coil is manufactured at EVAPCO from high quality steel tubing following the most stringent quality control procedures. Each circuit is inspected to assure the highest material quality and then is tested at 400 psig (2758 kPa) under water to ensure it is leak free. To protect the coil against corrosion, it is placed in a heavy steel frame and then the entire assembly is dipped in molten zinc (hot-dip galvanized) at a temperature of approximately 800º F (427º C). The tubes are pitched in the direction of fluid flow to provide good liquid drainage.

NOTE: Closed Circuit coolers should only be used on sealed, pressurized systems. Continual aeration of the water in an open system can cause corrosion inside the tubes of the cooler leading to premature failure.

Stainless Steel Strainers

One other component of evaporative cooling equipment which is subject to excessive wear and corrosion is the suction strainer. EVAPCO provides a lasting Type 304 stainless steel strainer on all units (except remote sump applications) as standard. Strainers are positioned around a large anti-vortex hood in easily handled sections.

The PMWQ Closed Circuit Cooler features the highly successful EVAPCO V-belt drive system engineered for heavy-duty operation. All drive system components including the fans, motors, sheaves, and belts are located in the dry entering air stream and are suitable for the most severe duty closed circuit cooler applications.

Fan Motors

All EVAPCO Closed Circuit Coolers come standard with premium efficient, inverter capable fan motors that can be used with variable frequency drive (VFD) systems for precise capacity control. VFD systems can control the speed of a fan motor by modulating the voltage and frequency of the motor input electrical signal. When connected to a building automation system a VFD can receive signals and vary the fan speed to meet demand loads. This popular method of capacity control can yield significant energy savings.

Evapco offers two-speed fan motors as an option for alternative capacity control. In periods of lightened loads or reduced wet bulb temperatures the fans can operate at low speed providing about 60% of full speed capacity yet consuming only about 15% of full speed power. In addition to the energy savings the sound levels of the unit can be greatly reduced by operating at low speed. These motors do not require the use of VFD systems however they can only operate at two speeds: full or low.

Belt Drive

The belt drive system consists of multigrooved V-Belts with high lateral rigidity. The belts are designed for closed circuit cooler service, and are constructed of neoprene with polyester cords. The belt drive is sized for 150 percent of the motor nameplate horsepower ensuring long and trouble free operation.

The standard design of the EVAPCO PMWQ provides the customer with the easiest Closed Circuit Cooler to maintain in the industry. There are additional options which can make maintenance easier and extend the life of the Closed Circuit Cooler. These options are listed below.

Stainless Steel Coils

EVAPCO now offers the optional TITAN COIL. Constructed with type 304L Stainless Steel, the TITAN COIL is manufactured using EVAPCO's patented elliptical tube Thermal-Pak® coil design upgraded to Xtra Tough construction featuring: Xtra Durability, Xtra Corrosion Resistance, and an Xtra long 5 YEAR Coil Warranty as standard.






Screened Bottom Panels

Protective inlet screens are provided over the unit's air intake. Screens are not provided below the fan section since most units are mounted on the roof or at ground level. It is recommended that bottom screens be added to the unit when it will be elevated. These screens can be provided by the factory at an additional cost or added by the installing contractor.

Extended Surface Coil

Closed Circuit Coolers can be provided with spiral fins on the heat exchanger coil to increase the dry performance of the unit. Dry performance is accomplished by rejecting heat to the atmosphere without the use of the spray pump and the evaporation process. Dry operation can be practical in cold climates and/or when reduced winter loads exist. The quantity of finned rows can be varied to optimize dry performance. See your local sales representative for more information. 

Stainless Steel Construction

For additional corrosion protection, several stainless steel options are available in either type 304 or for extreme applications, type 316 stainless steel. The PMWQ’s modular design allows specific areas to be enhanced from the cold water basin, to water touch panels, up to the entire unit. Combined with EVAPCO’s non-corrosive eliminators and water distribution system, this is the most effective extended corrosion protection available. Unlike costly, unreliable epoxy paint finishes, stainless steel will not peel or bubble exposing the base metal and clogging the suction strainers.

Electric Water Level Control

EVAPCO closed circuit coolers are available with an optional electric water level control system in place of the standard mechanical makeup valve and float assembly. This package provides very accurate control for the basin water level and does not require field adjustment, even under varying operating conditions.

The control was designed by EVAPCO and is manufactured exclusively for EVAPCO. It consists of multiple heavy duty stainless steel electrodes. These electrodes are mounted external to the unit in a vertical stand pipe. For winter operation, the stand pipe must be wrapped with electric heating cable and insulated to protect it from freezing.

The weather protected slow closing solenoid valve(s) for the makeup water connection is factory supplied and is ready for piping to a water supply with a pressure between 25 and 50 psig (138 kPa and 345 kPa).

Discharge Hood with Positive Closure Dampers 

When a closed circuit cooler is used in a water-to-air heat pump system or in certain process cooling applications, a method of reducing the heat loss during idle periods of wintertime operation may be required. For these cases, an optional discharge hood with positive closure dampers and damper actuator is available. 

The discharge hood with dampers is designed to minimize the heat loss from convective airflow through an idle cooler. Further reductions in heat loss may be obtained with the addition of insulation to the hood and casing, minimizing conductive heat losses. Insulation may be factory-installed on the hood and casing or field-installed by an insulation contractor. 

The discharge hood and dampers are constructed of hot-dip galvanized steel. Hoods are equipped with access panels to facilitate maintenance on the eliminators and water distribution system. The dampers, damper actuator and linkage(s) are all factory- assembled. Actuator controls and wiring are field-supplied by others. Damper actuators require 120 volt power supply. 

The system control sequence should provide for dampers to be fully open before the fans are running and closed when the fans are off; the damper actuator must be interlocked with the temperature control system for this purpose. When a centrifugal fan model uses a tapered discharge hood, the next larger size fan motor may be needed in order to overcome the additional static pressure. 

Heat loss data is provided for standard units without hoods, with hoods and with hoods and insulation. Table ratings are based on 50°F water in the coil, -10°F ambient and 45 MPH winds (fan and pump off) and can be found in the LSWB/LRWB catalog. The catalog is available electronically under the Product Features & Engineering Brochures section of this website. 

Pulse~Pure® Water Treatment System

The PMWQ is available with EVAPCO's optional Pulse~Pure® non-chemical water treatment system. The Pulse~Pure® Water Treatment System utilizes pulsed-power technology to provide CHEMICAL FREE Water Treatment and is an environmentally responsible alternative for treating water in evaporative cooled equipment. It does not release harmful by-products to the environment and eliminates costly chemicals completely from cooler drift and blowdown. The Pulse~Pure® system delivers short, high-frequency bursts of low energy electromagnetic fields to the recirculating water in the PMWQ and will:

  • Control Bacteria to Levels Well Below Most Chemical Water Treatment Programs.

  • Control the Formation of Mineral Scale on Heat-Exchange Surfaces.

  • Save Water by Operating at Higher Cycles of Concentration.

  • Yield Corrosion Rates Equivalent to Chemical Water Treatment.

More benefits of offering EVAPCO's Pulse~Pure® Water Treatment System on the new PMWQ are:

  • Optional Pulse~Pure® Factory Mounting - Factory Installation of the Pulse~Pure® System Guarantees Your Water Treatment is Installed to Factory Specifications.
  • Integral Cutting Edge Conductivity Control and Blowdown Packages that are contained in a single feeder panel:

Conductivity Control Package 

Measures Conductivity Utilizing a Non-Fouling Torodial Probe and Features:

  • One power connection of 120 volt or 460 volt is all that is required.
  • USB port for downloadable 60 day audit trail of system operation.
  • Self draining conductivity loop.

Motorized Blowdown Valve

Standard for the most reliable operation in bleed control. Three-way valve operation provides good bleed flow without a standing column of water. Because ongoing water treatment service is an absolute requirement for any evaporative cooled system, each purchase of a Pulse~Pure® Water Treatment System includes, as standard, a 1 year water treatment service and monitoring contract provided by your EVAPCO Representative. 

EVAPCO's Pulse~Pure® system offers PMWQ owners a single-source of responsibility for equipment, water treatment and service.

Freeze Protection

If the units are installed in a cold climate and operated year-round, freeze protection must be provided for the heat exchanger coil in the unit as well as for the recirculating water system.

Recirculating Water System Freeze Protection Options

Remote Sump Configuration 

The surest way to protect the recirculating water system from freezing is with a remote sump. The remote sump should be located inside the building and below the unit. When a remote sump arrangement is selected, the spray pump is provided by others and installed at the remote sump. All water in the closed circuit cooler basin should drain to the remote sump when the spray pump cycles off. 


Basin Heater Package  

If a remote sump configuration is not practical, electric basin heater packages are available to keep the pan water from freezing when the unit cycles off. Water lines to and from the unit, spray pump and related piping should be heat traced and insulated up to the overflow level to protect from freezing. The unit should not be operated dry (fans on, pump off) unless the basin is completely drained and the unit has been designed for dry operation. Consult your local sales representative when dry operation is a requirement.

Steam or Hot Water Coils 

Pan coils are available as an alternate to using electric basin heaters or a remote sump. Constructed of galvanized pipe and installed in the closed circuit cooler basin, they are supplied without controls and are ready for piping to an external steam or hot water source. Pan water heater controls should be interlocked with the water circulating pump to prevent their operation when the pump is energized.

Heat Exchanger Coil Freeze Protection Options 

The simplest and most foolproof method of protecting the heat exchanger coil from freeze-up is to use a glycol solution. If this is not possible, an auxiliary heat load must be maintained on the coil at all times so that the water temperature does not drop below 50°F when the cooler is shut down and, a minimum recommended flow rate per unit must be maintained. See the PMWQ catalog for more information. The catalog is available electronically under the Product Features & Engineering Brochures section of this website. 

If an anti-freeze solution is not used, the coil must be drained immediately whenever the pump is shut down or flow stops. Care must be taken to ensure that the piping is sized to allow the water to flow quickly from the coil. This method of freeze control should only be used in an emergency situation. Coils should not be drained for an extended period of time. Leaving the coil drained and open to the atmosphere can cause corrosion inside the tubes which may lead to premature coil failure. 

The amount of glycol required for a system will depend upon the total volume of water in the closed loop and the winter ambient conditions for the installation. The Engineering Data Tables presented in the PMWQ catalog provide the water volume contained inside the cooler coils to assist in this calculation.

Other Options

  • Ladders

  • Stainless Steel Fan Shafts

  • Vibration Switches

  • Motors – 2S/1W and 2S/2W / Mill and Chem Duty Artic Duty and Many More, Consult the Factory

PMWQ Specification59 KB


A. Drawings and general provisions of the Contract, including General and Supplementary Conditions and Division 1 Specification Sections, apply to this section.


A. This Section includes factory assembled and tested, closed-circuit forced-draft cooling tower (also known as a closed circuit cooler).


A. General: Submit the following:

     1. Certified drawings of the closed circuit cooler, sound data, recommended steel support indicating weight loadings, wiring diagrams, installation instructions, operation and maintenance instructions, and thermal performance guarantee by the manufacturer.


A. Verification of Performance:

     1. Test and certify closed circuit cooler thermal performance according to CTI Standard 201.

     2. Test and certify closed circuit cooler sound performance according to CTI ATC-128. B. Meet or Exceed energy efficiency per ASHRAE 90.1.


A. Motor/Drive System: Five (5) years comprehensive warranty against materials and workmanship including motor, fan, bearings, mechanical support, sheaves, bushings and belt.

B. Unit: One (1) year from start-up, not to exceed eighteen (18) months from shipment on the unit.


A. Manufacturers: Subject to compliance with requirements, provide cooling towers manufactured by one of the following:

     1. EVAPCO, Inc.

     2. Approved Substitute


A. Galvanized Sheet Steel complying with ASTM A 653/A 653M and having G-235 designation.

B. Optional Type 304 and/or 316 Stainless Steel as specified.


A. Description: Factory assembled and tested, forced draft closed circuit cooler complete with heat transfer coil, fan, louvers, accessories, and rigging supports.

B. Closed Circuit Cooler Characteristics and Capacities: Refer to the Closed Circuit Cooler schedule.

C. Fan(s):

     1. Type and Material: fans of FRP construction. The fans shall be factory installed, and statically and dynamically balanced for vibration free operation.

     2. Fan Housing: The complete drive system, including the electric motor, belts, bearings, fan, and drives shall be completely enclosed in a protective housing which covers the drive system.

     3. Maximum sound pressure level of ____dB(A) measured at 5 feet above the fan discharge during full speed operation in accordance with CTI Standard ATC-128.

D. Water Distribution System: Non-corrosive materials.

     1. Evenly distribute of water over heat transfer coil with pressurized spray tree. a. Pipes: Schedule 40 PVC, Non-corrosive Materials b. Nozzles: Non-clogging, nylon, threaded into branch piping.

     2. Maximum pressure at inlet shall be ____ psig.

E. IBC Compliance: The unit structure shall be designed, analyzed, and constructed in accordance with the latest edition of the International Building Code (IBC) Regulations for seismic loads up to ____ g and wind loads up to ____ psf.

F. Collection Basin Material: Heavy Gauge G-235 Galvanized Steel or Type 304 Stainless Steel (Optional) for long life and durability:

     1. Removable Type 304 Stainless Steel strainer with openings smaller than nozzle orifices.

     2. Joints: Bolted and sealed watertight. 3. Overflow, Makeup and Drain connections: G-235 Galvanized Steel (MPT and FPT).

G. Casing: Heavy Gauge G-235 Galvanized Steel or Type 304 Stainless Steel (Optional):

     1. Casing panels shall totally encase all sides of the heat transfer surface to protect it from direct exposure to environmental elements. All galvanized steel panel edges shall be coated with a 95% pure zinc compound during fabrication.

     2. Fasteners: Corrosion resistance equal to or better than materials being fastened.

     3. Joints: Sealed watertight.

     4. Welded Connections: Continuous and watertight

H. Heat Transfer Coil: Heavy Gauge G-235 Galvanized Steel encased in a steel framework, assembly hot-dip galvanized after construction. Type 304 Stainless Steel Optional. Coil assembly completely enclosed and protected from sunlight exposure, environmental elements and debris. Tubes sloped for free drainage of the coil and designed for low pressure drop. Coil assembly pneumatically tested at 400 psig under water. Coil connections beveled for weld, flanged (optional) or grooved (optional).

I. Drift Eliminators: PVC, for long life and durability resistant to rot, decay and biological attack; formed, bonded together for strength and durability in block format for easy removal and replacement; self extinguishing with flame spread rating of 5 per ASTM E84-81a; 0.001% drift rate.

J. Water Level Control: Brass mechanical makeup water valve and plastic float with an adjustable linkage.

K. Water Recirculation Pump: Close-coupled, centrifugal type with mechanical seal. The pump motor shall be ____ horsepower totally enclosed for outdoor service on ____ volts, ____ hertz, and ____ phase.


A. General requirements for motors are specified in Division 23 Section "Motors".

B. Enclosure Type: TEFC

C. Fan Motor Speed: Premium Efficient VFD Duty (Option: 2-speed)

D. Drive: Power Band Belt designed for 150% of the motor nameplate HP.

     1. Belt: V-belt type neoprene.

     2. Sheaves: Steel, taper lock design.

     3. Bearings: Heavy duty, self-aligning bearings with extended grease lines and fittings.

     4. Fan Shaft: Solid steel.

     5. Vibration Cutout Switch (Optional): Mechanical switch to de-energize fan motors if excessive vibration in NEMA 4 enclosure.


A. Access Door (Optional): A man-sized access door shall be located above the basin on both ends of the unit to allow for easy access to the pan interior.

B. Ladders (Optional): Aluminum, vertical complying with 29 CFR 1910.27.

Thermal Performance

pmwq_line_-capable_flow_table.pdf154.45 KB