Cooling Tower Design Checklist: 56 Checks Before Issuing Drawings

This is a list of 56 checks for the design engineer and lead engineer: what to verify in a cooling tower design before the documentation goes to the client. It is built on the practice of Cold Energy (NCT): more than 350 installed cooling towers and membership in CTI (Cooling Technology Institute, the body that develops the world's cooling tower standards). Go from top to bottom and tick. An item with no answer is not a detail: it is the spot where the project comes back to you two years later, together with a claim. The PDF is in Russian; the key points are below in English.

What is inside the checklist?

• Design point: 11 checks.

• Tower type and system COP: 11 checks.

• Water balance and water treatment: 9 checks.

• Open-circuit pump set: 7 checks.

• Circuit hygiene: 4 checks.

• Winter and operating modes: 8 checks.

• Siting and layout: 6 checks.

References in the text are to SP 60.13330.2020 (Russian HVAC code), SP 131.13330 (Russian building climatology code) and the VNII VODGEO cooling tower design manual. The checklist is the handout for my webinar talk of 26.08.2026; the slides with tables and worked examples are a separate download: Cooling tower in design: webinar slides.

Key takeaways

There is no current code with a cooling tower calculation method. The section on recirculating water coolers was removed from the updated SP 31.13330.2021 (Russian water supply code). The industry reference is the VNII VODGEO cooling tower design manual, formally a companion to the withdrawn SNiP 2.04.02-84.

The wet-bulb temperature is taken for a specific city, and the exceedance level by water-user category. Per the manual (Table 7), Moscow is 20.8 °C at 1 % exceedance, 19.0 °C at 5 % and 17.9 °C at 10 %; St. Petersburg is 20.1 / 18.3 / 17.4 °C. Category I is 1 %, II is 5 %, III is 10 % over June to August, meaning conditions will be worse than design on 1, 5 or 10 days a year.

Siting corrections add up to a six-degree spread. Under SP 60.13330.2020, clause 8.15, the wet bulb is raised by 1.5 °C for a tower in shade, 3 °C in direct sun, and another 3 °C on a flat roof with walls no more than 3 m away on all sides. For Moscow that is 20.8 to 26.8 °C, a different unit in size and price. The manufacturer receives the already corrected value. Recirculation of the tower's own plume adds another 1 to 3 K on top of the code.

Do not set the leaving water temperature close to the wet bulb. The VNII VODGEO manual, clause 2.33, recommends an approach of at least 4–5 °C and never below 2–2.5 °C in any case, with a water range of 4–8 °C. The CTI STD-201 certifiable range: entering wet bulb 12.8–32.2 °C, water up to 51.7 °C, range at least 2.2 K.

Sometimes the chiller leaves the scheme entirely. If the process is fine with 30 to 40 °C (compressor oil, hydraulics, moulds, data-center loops with high return temperature), a closed-circuit cooling tower does the job. A chiller with a water-cooled condenser uses about 0.20 to 0.30 kW per kW of cooling; a closed-circuit tower with fans and pump uses 0.02 to 0.04 kW. If the chiller stays, a wet tower gives a condensing temperature 8 to 12 K lower than an air-cooled scheme, and each degree is 2 to 3 % of compressor power.

For an absorption chiller, size the tower on cooling plus driving heat. An absorption chiller rejects roughly twice as much heat as a compressor chiller of the same capacity and is designed for about 30 to 32 °C entering cooling water. A dry cooler cannot deliver that in summer. The working option is an open evaporative tower.

Show the client the water balance in cubic metres and rubles before the contract. Evaporation E = 0.0017 × G × Range, blowdown B = E / (N − 1), make-up M = E + B. World practice with proper water treatment is 5–10 cycles of concentration; after 6–7 the savings curve flattens while the scaling risk grows. Blowdown must be automatic: manual blowdown stops in the second month.

Size the open-circuit pump on hot water. NPSHa = Hatm + Hstatic − Hlosses − Hvapour, with a margin over NPSHr of at least 0.5–1 m. Two identical pumps in parallel usually add 30–50 % flow, not double.

Hygiene and winter are solved in the design, not in operation. The 25–45 °C range is ideal for Legionella; above 100 CFU/ml the response is hyperchlorination, cleaning and a repeat test. A closed-circuit tower can switch to a dry winter mode and run like a dry cooler. For plume abatement the dry-air share is 10–40 % at around +5 °C and 80–90 % in hard frost; this cannot be bought later.

Who is it for?

• Design engineers and lead engineers issuing a cooling tower section at design or detailed design stage.

• Owner's engineers who accept the design and want to see where it will come back with a claim.

• Process engineers: they define the water-user category and the temperature the process really needs.

FAQ

Where do you take the design wet bulb if there is no code with a cooling tower method?

The industry route is Table 7 of the VNII VODGEO manual with exceedance over June to August, but its climate records end in the late 1980s. The second route is the chain SP 60.13330.2020 → SP 131.13330: since 9 September 2025 a new edition with recent observations is in force, the wet bulb is derived from temperature and enthalpy on the psychrometric chart, and exceedance there is annual. The two routes give figures that cannot be compared directly, so the chosen route is fixed in the design brief.

How many open items are normal?

More than three open items on a project is a normal picture: part of the data comes from other disciplines and from the client. The list exists so that the questions are asked before the documentation is issued, not after start-up.

Why can't you compare offers from different suppliers as they are?

Units sized at different wet-bulb temperatures are not comparable in capacity, and the difference easily reaches tens of percent. All offers are compared at one design point.

Related articles

• How to choose an industrial cooling tower: open, closed or hybrid

• How much water does a cooling tower use, and how to cut make-up

• Cooling tower vs dry cooler: which to choose for equipment cooling

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