Cold Weather Cooling: A Practical Winterization Checklist for Closed-Circuit Cooling Towers

Winter is one of the most demanding seasons for cooling tower operation. When ambient temperatures drop, water that sits in basins, pipes, spray nozzles, or idle coils can freeze quickly. Because water expands as it turns to ice, even a small amount of frozen water can create serious pressure, leading to cracked components, damaged coils, and unexpected downtime.

For closed-circuit cooling towers, winter protection is especially important. These systems have two fluid paths:

A closed process loop, which should remain clean and protected

An external spray water system, which is more exposed to cold air and freezing conditions

If either side is not properly prepared, the result can be reduced efficiency, equipment damage, or a complete shutdown during cold weather.

Why Winterization Matters

A cooling tower does not stop being important just because the weather gets colder. Many industrial processes, chillers, compressors, hydraulic systems, and manufacturing lines still require stable cooling year-round.

The goal of winterization is not to ignore the cooling system, but to make sure it can operate safely and reliably in low temperatures. A good winter preparation plan should focus on three priorities:

Prevent freezing

Maintain stable operation

Avoid unnecessary energy and water waste

1. Check Basin Heaters Before Cold Weather Arrives

Basin heaters are one of the most important freeze protection components for cooling towers operating in cold climates. Their job is to keep the external spray water basin above freezing when the system is idle or running at low load.

Before winter begins, check:

Whether the basin heater is powered and functional

Whether the temperature control or thermostat is working correctly

Whether the heater capacity matches the basin size and local climate

Whether heater elements show signs of corrosion, scaling, or damage

A heater that fails during a cold night may not be noticed until damage has already occurred. Testing it early is much cheaper than replacing a cracked basin or damaged pump.

2. Use Glycol Protection for the Closed Process Loop

In closed-circuit cooling towers, the process fluid circulates inside a sealed coil. This fluid should not be exposed to outside air, but it can still be affected by very low ambient temperatures.

Adding the correct concentration of glycol helps lower the freezing point of the process fluid. This is especially useful for systems that operate outdoors, experience long idle periods, or are located in regions with severe winter temperatures.

Important points to check:

Use the correct type of glycol for your system

Maintain the recommended concentration for your lowest expected temperature

Test glycol concentration regularly

Check for leaks that could reduce protection levels

Avoid over-dilution during make-up water additions

Glycol protection should always be based on actual site conditions. The correct concentration depends on local winter temperatures, system design, and operating schedule.

3. Keep Water Moving When Possible

Moving water is much less likely to freeze than standing water. If the cooling tower must operate during cold weather, continuous or controlled water circulation can help reduce freeze risk.

Where possible:

Avoid long idle periods in freezing conditions

Keep spray pumps and process pumps running according to system requirements

Use automatic controls to prevent unnecessary shutdowns during cold periods

Make sure bypass valves and control logic are set correctly

If the system must be shut down for an extended period, simply turning it off is not enough. Standing water in vulnerable areas may still freeze and cause damage.

4. Drain Idle Systems Carefully

If the cooling tower will not be used during winter, draining may be necessary. However, draining should be done completely and carefully.

Water can remain trapped in:

Spray nozzles

Coil sections

Low points in piping

Pump casings

Basin corners

Valve pockets

Even a small amount of trapped water can freeze and expand. Before leaving a system idle, confirm that all vulnerable sections have been drained and, if needed, blown out with compressed air.

Important: Draining should only be done according to the system design and manufacturer guidance. Some systems should not be fully drained without specific precautions.

5. Protect Spray Nozzles and Distribution Systems

The spray water distribution system is often one of the most exposed parts of a cooling tower. If spray nozzles become clogged, water may not distribute evenly across the coil.

Uneven spray can create two problems:

Some areas may receive too little water, reducing cooling performance

Other areas may collect standing water, increasing freeze risk

Before winter, inspect:

Spray nozzles for blockage or wear

Spray distribution patterns

Strainers and filters

Pump performance

Pipe connections and valves

Clean distribution systems help maintain stable cooling and reduce the chance of localized freezing.

6. Reduce Cold Air Infiltration

Cold wind can increase heat loss and make freezing conditions worse. In some cases, temporary wind barriers or controlled airflow management can help reduce the impact of cold air entering the tower.

However, airflow should never be blocked completely. Cooling towers still need proper ventilation when operating. The goal is to reduce excessive cold air exposure without creating airflow problems or overheating during warmer periods.

Check:

Louvers for damage or excessive gaps

Access panels for proper sealing

Fan operation and control settings

System behavior during low-load winter operation

Any airflow adjustments should be made carefully and reviewed by qualified personnel.

7. Monitor Operation More Closely in Winter

Winter operation requires more attention than normal summer operation. Small changes in temperature, water level, pressure, or noise can be early signs of a developing problem.

Recommended monitoring points:

Process fluid inlet and outlet temperatures

Basin water temperature

Spray pump operation

Heater operation

Glycol concentration

Water level in the basin

Unusual vibration or noise

Ice buildup around the tower

If ice begins to form on louvers, fans, or structural components, it should be treated as a warning sign. Ice accumulation can affect airflow, add weight to components, and indicate that freeze protection is not sufficient.

8. Avoid Common Winter Mistakes

Some of the most common winter problems come from simple oversights.

Avoid these mistakes:

Assuming the system will protect itself without monitoring

Waiting until the first freeze to check heaters or glycol

Ignoring small temperature changes

Draining the system partially instead of completely

Using the wrong glycol type or concentration

Blocking airflow too aggressively

Running the system without checking basin heaters

Skipping post-storm or post-cold-snap inspections

Winter damage is often preventable, but only if preparation happens before the coldest weather arrives.

A Simple Winter Readiness Checklist

Use this checklist as a practical starting point:

Test basin heaters

Check heater controls and temperature settings

Verify glycol concentration in the closed loop

Inspect spray nozzles and strainers

Confirm pump operation

Check water level controls

Review freeze protection alarms

Inspect for ice buildup after cold weather events

Drain idle systems completely if required

Confirm that control logic supports safe winter operation

Schedule regular winter inspections

The Bottom Line

Winter does not have to mean equipment damage, emergency repairs, or unplanned downtime. With the right preparation, closed-circuit cooling towers can continue to provide reliable heat rejection even in cold climates.

The key is to act early. Check heaters, verify glycol protection, keep water moving when required, drain idle systems properly, and monitor operation closely during cold spells. A small amount of preventive maintenance now can help avoid major repair costs later.

If you are preparing a cooling system for winter operation and need guidance on freeze protection, glycol selection, or system inspection, contact our technical team for support.