Knowledge base
In short
A dry cooler needs little attention, but it needs it at the right time of year. Before summer the coil should be clean and the fans checked, because a dirty coil costs cooling on the hottest days. Before winter the liquid circuit must be protected against frost, units that stand idle must be drained or kept frost safe, and snow and ice must not block the fans or the air path. A short plan for both seasons keeps the unit at its rating for many years.
Most dry cooler problems we hear about are found at the two ends of the year. The first hot week shows a coil that collected a winter of dust and a spring of pollen, and the first hard frost shows a circuit that was filled or topped up with the wrong liquid. Neither is difficult to prevent. This guide walks through what a dry cooler asks for over a year, in plain words, with the winter side given more room than usual, because that is where the expensive damage happens.
Before The Heat Arrives
A dry cooler is sized for its worst day, and its worst day is in summer. Anything that has settled on the fins since the last cleaning, such as dust, seeds, leaves, insects or the fluff that some trees shed in spring, eats into exactly the margin the unit needs then. The right moment to clean is therefore late spring, after the pollen season and before the first heat, not in the middle of a heat wave when the unit cannot be taken out of service.
The cleaning itself is gentle work: water or air against the normal direction of the airflow, no hard jets and no aggressive chemicals on the fins. Our general maintenance guide for air-cooled heat exchangers covers it in more detail. What matters for a dry cooler is the habit of doing it every year at the same time, and more often on sites near roads, fields, quarries or the sea.
Fans, Liquid And The Signs To Watch
Fans are the only moving parts on most dry coolers, and they usually announce trouble early: a new noise, a vibration, a fan that no longer starts with the others or a fault message in the control panel. Each of these is worth a look the same week, because a dry cooler that loses fans quietly will still seem fine until the hot afternoon when it needs all of them.
The liquid in the circuit deserves the same attention. A level that keeps falling points to a leak somewhere in the circuit, and every top-up with plain water weakens the frost protection a little more. Checking the mixture once a year, and always after a repair or a large top-up, costs very little compared to a frozen coil.
Frost Is The Real Enemy
A dry cooler coil is made of many thin tubes, and water that freezes inside them splits them. The damage is often not visible until the circuit is warm again and the coil starts to leak from many places at once. In most cases the coil then has to be replaced, so frost protection is the one point in a dry cooler that should never be left to chance.
Circuits that run through the winter are normally filled with a water and glycol mixture suited to the coldest weather at the site. The risk comes from changes made later: a repair, a refill from the mains, a part of the circuit that was drained and filled again with water only. Units that stand idle in winter, such as standby units or seasonal cooling, need special care, because liquid that does not move freezes first. They are either filled with a proper mixture or drained completely, and a drained coil should be left drained until it is filled again with the right liquid.
Adiabatic dry coolers have one more task before winter: the water spray system must be emptied and closed for the cold season, because its pipes and pads freeze long before the main circuit does.
Snow, Ice And Too Much Cooling
Snow and ice bring their own problems. A unit standing on the ground can be buried by drifting snow or by snow cleared from a roof or a path, and fans that pull air from below then draw no air at all. Ice can form on fan guards and blades and throw the fans out of balance. Keeping the area around the unit clear and the unit raised above the expected snow level is part of the layout, not only of the winter routine.
In very cold weather a dry cooler can also cool too much. If the liquid comes back far colder than the process, the engine or the building wants, the fans should slow down or stop, and the control has to be set up so that the unit holds the temperature rather than chasing it. A control that was set up once at commissioning in summer is worth checking before the first winter.
TECS Engineering designs and builds dry coolers and radiators for engine, power plant, data center and industrial cooling. Tell us about the site climate, the liquid in the circuit and how the unit runs in winter, and the engineering team will advise on the care it needs or on a replacement coil if frost or wear has already done its work.
In Short
- Clean the coil in late spring, before the first hot week
- Watch the fans and the control panel for early signs of trouble
- Keep the frost protection of the liquid right after every top-up or repair
- Fill idle units with a proper mixture or drain them completely for winter
- Empty the water spray system of adiabatic units before the frost
- Keep snow and ice away from the fans and check the cold weather control
What To Send With An Enquiry
- The type and age of the dry cooler and a photo of the unit and its nameplate
- The liquid in the circuit and how it was last filled or topped up
- Site location, the coldest and hottest weather and how much snow falls
- Whether the unit runs through the winter or stands idle part of the year
- The problem seen, such as lost cooling, leaks, noise or overcooling
- Whether a cleaning plan, spare parts or a replacement coil is wanted
Questions We Are Often Asked
How often should a dry cooler be cleaned?
At least once a year, best in late spring before the hot season. Dusty sites, sites near trees, fields or roads and coastal sites need it more often.
Can a dry cooler freeze?
Yes. If the circuit holds plain water, or a mixture that has been weakened by top-ups, the water can freeze in the thin coil tubes and split them. A correct glycol mixture or complete draining prevents it.
Should a dry cooler be drained for the winter?
Only if it stands idle and the circuit is not protected by a suitable mixture. A drained unit must be emptied completely and stay empty until it is filled again with the right liquid.
Why does my dry cooler cool too much in winter?
In cold air the unit has far more capacity than it needs. The fans should slow down or stop, so the control settings are worth checking before the first winter.
Can a frozen dry cooler coil be repaired?
Small leaks can sometimes be repaired, but frost usually damages many tubes at once and the coil has to be replaced. TECS can design a replacement coil for an existing unit.
Contact Us
Send us the heat duty, the fluid temperatures and flow rates, the ambient conditions and the installation limits. We answer with a design proposal - or write to us on WhatsApp.
