Thermal Certification of Water Cooling Towers



Why is Thermal Certification Important?

Evaporative Heat Rejection equipment, a category that includes cooling towers, is used in various applications from power stations to HVAC production as a cost-effective and energy-efficient means for extracting heat from different industrial processes to cool large buildings or facilities. In most cases, cooling towers are used in areas where standard HVAC equipment would not be a viable solution, including power plants, petroleum refineries, petrochemical plants, natural gas processing plants, food processing plants, and other expansive industrial facilities.


Keeping these industrial cooling towers in working order requires a unique approach. No two cooling towers are precisely the same. Depending on the raw water source, air quality, variances in temperature, humidity levels, and operating procedures, inconsistencies may arise in thermal performance. Because of this, we are committed to providing a thermal certification program that guarantees all models in a line of Evaporative Heat Rejection Equipment from a single manufacturer will operate per the manufacturer’s published ratings.


Purchasing a CTI-Certified model ensures that the cooling tower will perform as specified. In all instances of thermal certification, the purchased model, or a model within the same line, will have been thoroughly inspected and tested by a CTI-licensed testing agency.


LEARN MORE: What is the Importance of Measuring Cooling Tower Thermal Performance?


Thermal Rating Requirements

  • Certified ratings are established based on entering wet bulb temperature for products located in a free and unobstructed environment and circulating fresh water over the fill or heat exchanger. The manufacturer shall make available published criteria defining a free and unobstructed environment.

  • Certification will also apply to multiple cell arrangements of certified models, provided the physical configuration, and airflow through each cell remains unaltered.

  • To comply with CTI standards, any cooling tower selected at random should have a thermal capacity of no less than 100% of its published standard rating when tested at any rating conditions. The thermal performance test tolerance on individual tests shall be less than or equal to -5%.

  • For closed-circuit cooling towers, the corresponding process fluid pressure drop should not be more than 100% of its published standard pressure drop at the test flow. The pressure drop test tolerance on individual tests should be less than or equal to +15%.

LEARN MORE: Purchase Standard for the Certification of Water Cooling Tower Thermal


Minimum Data Requirements for Published Ratings

Thermal Published Ratings

Upon completion of thermal testing, ratings are published to the general public. These ratings will include the operating conditions for each process fluid or refrigerant listed in the certification. When certifying thermal performance for closed circuit coolers with aqueous glycol solutions, the published ratings will also include a list of operating conditions for each glycol type.


The data may be published in IP units, SI units, or both, depending on the manufacturer’s preference. All claims to ratings for products within the scope of the CTI standard are accompanied by the statement “Rated in accordance with CTI Standard 201 RS.” All claims to ratings outside the scope of the CTI standard will include the statement “Outside the scope of CTI Standard 201 RS.” Wherever application ratings are published or printed, they will include a statement of the conditions at which the ratings apply.


Pressure Drop Published Ratings

For closed-circuit cooling towers, published ratings will include process fluid pressure drop values corresponding to a minimum of three flow rates for each type of heat exchanger coil and each fluid. For aqueous glycol solutions, fluid pressure drop values will be listed for solutions at 30% concentration by volume. The first flow rate will be within +/- 10% of the heat exchanger’s median flow rate, while the second and third flow rates will be 80% and 120% of the first flow rate. In this instance, the median flow is defined as the average of the minimum and maximum flow rates of the heat exchanger, as defined by the manufacturer.


All three flow rates will be within the flow range covered by the thermal conditions listed in the CTI Standard 201 RS. If the disclosed flow rates are outside the given model’s flow rate range, they shall be replaced with the corresponding minimum or maximum flow rate of that model’s performance table. The pressure drop shall be provided along with the corresponding quantity and size of the inlet and outlet coil connections used by the Manufacturer as standard for each of the three flow rates.


LEARN MORE: Licensed CTI Thermal Testing Agencies


How can our Thermal Certification Directory help you?

Cooling Technology Institute has published a directory of manufacturers and their lines of cooling tower models currently certified under CTI Standard 201 RS. This directory is a great tool to help our owner/operators understand which models will provide a quality performance. For more information, contact us today or purchase one of our helpful guides:




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