Respect the cold. Your tower will thank you in July.
Watch the fan exhaust. A healthy winter plume is wispy and dissipates quickly. A dangerous plume is thick, heavy, and drifts horizontally without rising. This indicates the water is entering the cold air basin at a temperature too low to melt the ice forming upstream.
Most operators assume that cold weather is a blessing for cooling. After all, if it’s freezing outside, the tower doesn’t have to work as hard to shed heat, right? This is the single most dangerous misconception in wet cooling tower management.
From the Cooling Tower Handbook, 4th Edition
For nine months of the year, the cooling tower is the unglamorous workhorse of the industrial plant—loud, wet, and largely ignored. But when the mercury dips below 32°F (0°C), this same piece of equipment transforms overnight into the plant’s most vulnerable asset. Winter operation is not about efficiency; it is about survival.
When ice forms, panic leads to silence. Silence leads to stagnation. Stagnation leads to a tower that looks less like a heat exchanger and more like a frozen waterfall. A frozen cooling tower cannot be thawed with steam hoses; it must be rebuilt in April.
As ambient temperature drops, the cooling tower’s capacity for heat rejection actually skyrockets. A tower designed to cool 100°F water down to 85°F on a 95°F summer day can easily overcool that same water to 40°F or lower on a 20°F winter night. While this sounds like a performance gain, it leads to the "Ice Paradox": The better the tower performs thermally, the faster it self-destructs structurally.
If you see ice, do not shut down. Increase heat load. Increase water flow. Do not stop the fan unless you intend to scrap the cell.