A dry cooler is a closed-circuit heat exchanger that cools water or a glycol solution by blowing outdoor air across a finned coil, without evaporating any water and without a refrigerant circuit or compressor. Add a wetted pre-cooling section and it becomes an adiabatic cooler, which spends water only on the hottest days. Paul Industries installs, pipes, fills, starts up and maintains dry coolers, adiabatic coolers and the glycol and chilled water loops they serve, for process plants, chiller plants and data centers. This guide explains how the equipment works, how it compares with cooling towers and chillers, how to protect the loop from freezing, and what installation and upkeep involve. We install the units and build everything around them.
What is a dry cooler?
A dry cooler is an air-to-fluid heat exchanger: warm fluid flows through tubes inside a finned coil, fans move ambient air across the fins, and the fluid leaves cooler than it arrived, with all of the heat carried away as sensible heat in the air. A one-line dry cooler definition for a specification: a closed, fan-driven, finned-tube fluid cooler that rejects heat to outdoor air with no water spray. Manufacturers also call it a closed-circuit air cooler, an air-cooled fluid cooler or a glycol cooler.
The dry cooler heat exchanger itself is usually copper tube with aluminum fins, with coated fins available for coastal and corrosive sites, and headers that split the fluid across parallel tube circuits. Two pieces of equipment look similar and are often confused with it. A remote air-cooled condenser has the same fins and fans but carries refrigerant from a compressor. A closed-circuit evaporative cooler has a coil too, but it sprays recirculated water over that coil and behaves like a cooling tower. An HVAC dry cooler serving a building and a unit on a plant loop are the same machine sized for different temperatures.
How does a dry cooler work?
A dry cooler works by circulating warm fluid through a finned coil while fans draw outdoor air across it, so heat flows from the fluid to the air and the fluid returns to the load at a temperature somewhere above the outdoor dry-bulb temperature. That gap between leaving fluid and entering air is the approach. Manufacturers’ engineering data commonly shows design leaving fluid temperatures about 5 to 10 degrees Celsius (roughly 9 to 18 degrees Fahrenheit) above design ambient, with about 4 degrees Celsius as a practical minimum. A tighter approach needs much more coil and airflow, so a far bigger unit.
The physics sets a hard limit: without help, a dry cooler can never deliver fluid colder than the air entering it. Capacity depends on the difference between entering fluid and entering air temperatures, so the same unit rejects far more heat on a cold day. The controller reads the leaving fluid temperature and adjusts airflow to hold a setpoint. Units with electronically commutated (EC) fans modulate speed from a 0-10 volt or 4-20 milliamp signal across a wide range, roughly 10 to 100 percent; older units stage fixed-speed fans on and off. In cold weather a three-way bypass valve can send part of the flow around the coil so the loop does not overcool, and the fans can stop entirely.
What is adiabatic cooling?
Adiabatic cooling, in HVAC equipment, means lowering the temperature of air by evaporating water into it, so a dry cooler or air-cooled condenser receives cooler air on hot days. The plain adiabatic cooling definition: sensible heat in the air is spent evaporating water, so the air’s dry-bulb temperature falls while its moisture content rises and its total heat stays roughly constant. Meteorologists use the same word for air that cools as it rises and expands, which is a separate subject. Applied to heat rejection equipment, an adiabatic cooling system is a set of wetted pads or spray nozzles that pre-cools the air just before it reaches a coil.
What is an adiabatic cooler?
An adiabatic cooler is a dry cooler fitted with wetted pads or spray nozzles ahead of its coil, which evaporate water into the incoming air on hot days so the coil sees air several degrees cooler than ambient; the rest of the year it runs dry and uses no water. Manufacturers also sell it as an adiabatic dry cooler, an adiabatic fluid cooler or a hybrid cooler, and the closed water or glycol loop inside it is piped, filled and protected exactly as on an unwetted unit.
How does an adiabatic cooler work?
Its controller turns the wetting system on only when the outdoor temperature rises above a switchover setpoint, so the fans pull pre-cooled air across the coil during peak hours; below that setpoint the water stays off and the coil rejects heat to dry air. The limit is the outdoor wet-bulb temperature. Pad performance is rated by saturation efficiency, the temperature drop achieved divided by the gap between dry bulb and wet bulb. Full-size test programs have measured peak efficiencies of roughly 72 to 78 percent, falling as air velocity through the pad rises. As a worked example, on a 95-degree Fahrenheit afternoon with a 75-degree wet bulb, a pad running at 75 percent efficiency delivers air at about 80 degrees to the coil, a 15-degree gain in available approach. In humid climates the dry bulb and wet bulb sit close together and the gain shrinks.
Pads vs spray nozzles
Pad systems wet a corrugated media panel in front of the coil; the pad keeps water off the fins but scales and is replaced periodically. Spray systems mist water into the incoming air and add little pressure drop when dry, but any minerals that reach the fins stay there. Softened water stops hardness scale but leaves chloride and sulfate on the coil, which corrodes fins over time, so many spray designs call for low-mineral water from reverse osmosis or limit annual spray hours.
Dry cooler system components
A complete dry cooler system is more than the outdoor unit: it is the coil and fans plus the pumps, piping, expansion and air removal, fill equipment and controls that keep a closed glycol loop full, pressurized and at the right concentration.
| Component | What it does | What the installer checks |
|---|---|---|
| Finned coil and headers | Transfers heat from fluid to air across parallel tube circuits | Fin condition on arrival, header connections, vents and drains at the coil |
| Fans and motors (EC or AC) | Move air across the coil; speed sets capacity | Rotation, guards, vibration, speed response to the control signal at startup |
| Circulating pumps | Move fluid through the load and the cooler | Alignment, suction conditions, flow against the design value with glycol, not water |
| Expansion tank | Absorbs thermal expansion of the fluid and holds system pressure | Precharge set before fill, size checked for glycol expansion over the full temperature span |
| Air separator and high-point vents | Remove entrained and trapped air | Vents at every high point, separator at the warmest, lowest-pressure point |
| Glycol fill station or makeup tank | Adds premixed fluid without diluting the loop | Low-level alarm; no automatic city-water makeup into a glycol loop |
Many plants keep glycol on the outdoor side only, with a plate heat exchanger separating it from the building or process water, so the larger plant volume needs no glycol.
Dry cooler V-type vs flat-bed layouts
A flat-bed unit lays the coil horizontally under the fans; it is low, easy to rig onto a roof and suits small and medium loads. A V-type unit sets two coil banks at an angle to each other, like a V, with a row of fans along the top. The V arrangement packs far more coil face area into the same plan area, which is why large plants favor it. Whatever the layout, warm discharge air must not be drawn back into the intake; spacing and wall clearances come from the manufacturer’s data, and ignoring them costs capacity on the hottest days.
What a dry cooler does not use: water, refrigerant and compressors
Do dry coolers use water?
A basic dry cooler consumes no water in operation. The water or glycol mix inside circulates in a sealed loop and is never evaporated, so there is no makeup, blowdown or drift. Water consumption only appears when an adiabatic section is added, and then only during the hours it runs.
Do dry coolers use refrigerant?
No. A dry cooler moves heat with a liquid, not a refrigerant, so it has no refrigerant charge and no refrigerant leak checks. If the outdoor unit is connected by copper lines to a compressor indoors, it is a remote condenser, a different machine.
Do dry coolers have compressors?
No. Its only moving parts are the fans. When a process needs fluid colder than outdoor air, a separate chiller supplies the refrigeration, and the dry cooler either rejects that chiller’s heat or carries the load alone in cold weather.
Adiabatic cooling vs evaporative cooling vs dry cooling
The three approaches differ in what limits the leaving fluid temperature: a dry cooler is limited by outdoor dry bulb, an adiabatic cooler approaches the wet bulb only during hours when it is wetted, and an evaporative cooling tower works against the wet bulb all year. Cooling towers are commonly rated at 95 degrees Fahrenheit entering water, 85 degrees leaving, at a 78-degree wet bulb, a 7-degree approach, and practical tower designs mostly fall between about 5 and 10 degrees of approach.
| Factor | Dry cooler | Adiabatic cooler | Open cooling tower |
|---|---|---|---|
| Water use | None for cooling | Only above the switchover temperature, so seasonal and climate dependent | Continuous: evaporation of roughly 1 percent of flow per 10 degrees Fahrenheit of range, plus blowdown and drift |
| Achievable fluid temperature | Above outdoor dry bulb by the approach | Toward the wet bulb at peak, dry-bulb limited the rest of the year | Above wet bulb by about 5 to 10 degrees Fahrenheit |
| Energy | Highest fan power per unit of heat; raises chiller lift if it serves a condenser | Lower peak fan power and lift than dry; pump for pad or spray water | Lowest fan power; coldest condenser water for chillers |
| Maintenance | Coil cleaning, fans, glycol testing | All of the dry tasks plus pads or nozzles, sumps, drains and winterizing | Fill, basin, drift eliminators, mechanical service, frequent inspection |
| Water treatment and Legionella | Closed-loop inhibitor only; no aerosol | Water management plan for the wetting system; scale control matched to pad or spray type | Full treatment program: scale, corrosion and biocide control, Legionella risk management under ASHRAE Standard 188 |
Why does adiabatic cooling vs evaporative cooling matter for Legionella? Both put water in contact with moving air, and the CDC’s Legionella control toolkit lists evaporative air coolers and misters among devices that can grow the bacteria when uncontrolled, with growth favored between 77 and 113 degrees Fahrenheit. A tower sprays recirculated water every hour it runs, while a pad system is wet only part of the year and can be drained; both belong in the building’s water management program. Our cooling tower water treatment work covers the evaporative side of a plant that runs both.
Dry cooler vs cooling tower
A dry cooler uses no water and needs little treatment but delivers warmer fluid, while a cooling tower delivers fluid close to the wet bulb at the cost of continuous water consumption and a full treatment program. On a hot afternoon in an arid climate the wet bulb can sit 20 or more degrees Fahrenheit below the dry bulb, which is the whole advantage of evaporation. The deciding questions are the fluid temperature the load actually needs, water and sewer cost, blowdown discharge limits, freezing risk and available maintenance labor.
Adiabatic cooler vs cooling tower
An adiabatic cooler vs cooling tower comparison is a trade between water and temperature: the adiabatic unit uses water only on the hottest days and keeps the loop closed, but its leaving fluid on those days is still warmer than a tower’s, and it needs more fan power and more plot area for the same heat. It is the usual compromise where water is restricted but summer peaks would push a pure dry unit past what the load accepts.
Dry cooler vs adiabatic cooler
The dry cooler vs adiabatic cooler choice comes down to the peak design hour. If the leaving fluid temperature at design ambient dry bulb is acceptable, a dry unit is simpler, uses no water and has nothing to winterize. If not, the adiabatic section lets a smaller unit meet the peak instead of oversizing the coil for a few hours a year, at the price of water, pad upkeep and a water management plan.
Dry cooler vs chiller
A dry cooler and a chiller do different jobs: a chiller uses a refrigeration cycle to cool fluid below the outdoor temperature, while a dry cooler can only reject heat to outdoor air and therefore always delivers fluid warmer than ambient. Asking about dry cooler vs chiller is really asking whether the process can accept fluid above the outdoor temperature. Hydraulic oil coolers, compressor aftercoolers, induction equipment and warm-water liquid cooling can; fermentation, food chilling and comfort cooling cannot. Our industrial process chiller guide covers how to size the refrigeration side.
Dry cooler vs air cooled chiller
Comparing a dry cooler vs air cooled chiller shows the same split. An air-cooled chiller packages compressors, an evaporator and a condenser coil, and can make, for example, 45-degree water on a 95-degree day. A dry cooler of similar size produces fluid above 95 degrees on that day but draws only fan power. Many plants need both, or the two working together.
| Equipment | Coldest fluid it can make | Main energy use | Water use | Best fit |
|---|---|---|---|---|
| Dry cooler | Above outdoor dry bulb | Fans | None | Warm process loops, condenser loops, free cooling in cold weather |
| Air-cooled chiller | Well below ambient | Compressors and fans | None | Chilled water where no tower is wanted |
| Water-cooled chiller with tower | Well below ambient | Compressors, tower fans, condenser pumps | Continuous | Large plants where water is available and efficiency matters most |
| Chiller with dry cooler free cooling | Below ambient in summer, dry cooler alone in winter | Compressors only when needed | None | Year-round loads in climates with long cold seasons |
Chiller with dry cooler arrangements
A chiller with dry cooler heat rejection or free cooling is laid out in one of three ways. The first uses the dry cooler as the condenser loop of a water-cooled chiller: the chiller rejects its heat into a glycol loop instead of a tower. That saves all tower water, but condensing temperatures follow the dry bulb, so the chiller works harder in summer and must be selected for the warmer condenser fluid.
The second is parallel free cooling. A heat exchanger sits between the dry cooler loop and the chilled water loop, and when the outdoor air is cold enough the chillers shut off and the dry cooler carries the whole load through the exchanger. Full free cooling needs outdoor air colder than the chilled water supply setpoint by the dry cooler approach plus the exchanger approach. The third is series, or partial, free cooling: chilled water return passes through the free cooling exchanger first, the dry cooler takes whatever heat the weather allows, and the chiller trims the rest. Series piping gains the most hours because it helps whenever outdoor air can cool the return water at all, not only when it can reach the supply setpoint. Packaged chillers with a built-in free cooling coil do the same inside one cabinet; the piping and valves for all three are typical chilled water system retrofit work.
Air cooled chiller with adiabatic cooling
An air cooled chiller with adiabatic cooling has pads or sprays in front of its condenser coils, so on hot days the condenser sees cooler air, condensing pressure drops, the compressors draw less power and the machine keeps more of its capacity. An adiabatic cooling system for chillers can be factory-fitted or added as a retrofit frame, with the same water and Legionella duties as other wetted media. Our process chiller crews install and pipe both chillers and their heat rejection.
Dry coolers in data center plants
Dry coolers suit data centers because liquid-cooled IT equipment accepts warm facility water, and the warmer the water, the more of the year a dry unit alone can reject the heat. ASHRAE’s liquid cooling classes, W17 through W45 and W+, are named for the maximum facility supply temperature in degrees Celsius. At the warmer classes, a dry cooler for data center service can carry the load through most or all of the year in many climates, with adiabatic assist or trim chillers only for the hottest hours. Yard design then turns on spare units, row clearances and valving that lets one unit be drained while the loop runs.
Adiabatic cooling for data centers
Adiabatic assist lets a data center yard meet its design-day fluid temperature with fewer or smaller coolers, because the wetting system only has to cover the hours when ambient sits above the switchover point. The same coolers run dry for the rest of the year, but the peak-hour water supply, spray water treatment and a Legionella water management plan still have to be designed in, and the trade against trim chillers is water on hot afternoons versus compressor power.
Water footprint is covered on our data center water and piping page, plant arrangements on data center cooling systems, the loop the coolers ultimately serve on data center liquid cooling, and staged yard testing on data center commissioning.
Glycol concentration and freeze protection for dry cooler loops
A dry cooler loop in a freezing climate needs inhibited glycol mixed so its freeze point sits at least 5 degrees Fahrenheit (3 degrees Celsius) below the lowest expected outdoor temperature. A coil that freezes once usually needs replacing.
Glycol makers distinguish two levels. Freeze protection keeps the fluid liquid and pumpable at the stated temperature. Burst protection allows slush to form but prevents the expansion that splits tubes, provided the system has room to expand; it suits loops that sit idle in winter, not loops that must run. Typical values for one widely used inhibited propylene glycol are below.
| Lowest temperature | Freeze protection (propylene glycol, % by volume) | Burst protection (% by volume) |
|---|---|---|
| 20 F (-7 C) | 18.8 | 12.6 |
| 10 F (-12 C) | 30.4 | 20.9 |
| 0 F (-18 C) | 37.7 | 25.1 |
| -10 F (-23 C) | 44.0 | 29.3 |
| -20 F (-29 C) | 48.2 | 31.4 |
Two rules sit alongside the table. First, glycol suppliers recommend not running below about 25 percent, because dilute glycol can feed bacteria and carries too little inhibitor to protect the metals. Second, more glycol is not better: it lowers specific heat and raises viscosity, so the coil rejects less heat and the pumps work harder, and both the cooler and the pump selections must be made for the actual mix. Use inhibited industrial glycol, never automotive antifreeze; food plants use propylene glycol, as on our brewery glycol cooling page.
Mix glycol with distilled or deionized water, or buy it premixed. Supplier specifications typically limit chloride and sulfate in dilution water to under 25 parts per million each, because hard or salty water reacts with the inhibitor package and shortens fluid life. They also warn against automatic city-water makeup, which dilutes the mix unnoticed.
Dry cooler sizing inputs
Sizing a dry cooler starts from the heat load and the leaving fluid temperature the process needs at the hottest design hour, and works back through fluid, flow, ambient and approach to a coil and fan selection. On a dry cooler, industrial process duty usually adds factors a comfort system ignores, such as dirty air, round-the-clock operation and loads that grow when production is added.
| Input | Why it matters | Common mistake |
|---|---|---|
| Heat load | Sets coil and fan size | Using nameplate load instead of measured or future load |
| Fluid and glycol concentration | Glycol reduces capacity and raises pressure drop | Selecting on water, then filling with 40 percent glycol |
| Flow and temperature range | Sets tube velocity and the log mean temperature difference | Flow that does not match the pumps actually installed |
| Design ambient dry bulb | The hottest hour the unit must still meet | Using an average summer day rather than a published design percentile, such as ASHRAE 0.4 or 1 percent values |
| Approach | Smaller approach means a much larger unit | Specifying an approach tighter than the process needs |
| Altitude | Thinner air carries less heat per fan revolution | No altitude correction at high-elevation sites |
| Site layout and recirculation | Hot discharge air drawn back in raises the real entering temperature | Units packed against walls or each other |
Installing and piping a dry cooler
Installing a dry cooler correctly means setting it level on supports designed for its operating weight, piping it with isolation, air removal and drains at the right points, and flushing, testing and filling the loop before the fans ever run. Units are craned onto dunnage or a pad and anchored for wind and seismic loads as the structural engineer specifies.
Isolation valves at each unit let one cooler be serviced while the others run, air vents belong at header high points, drains at low points, and a strainer protects the coil. Pipe is typically carbon steel or copper under ASME B31.9 for building services, or to ASME B31.3 where the loop is part of a process system.
| Step | What is done | Record kept |
|---|---|---|
| 1. Set and anchor | Rig, level and anchor on dunnage or pad; check clearances | Rigging plan, anchor details |
| 2. Pipe and support | Isolation valves, vents, drains, strainer, flexible connectors | Weld or joint records, as-built markups |
| 3. Pressure test | Hydrostatic test of field piping at the specified pressure, unit isolated if its rating requires | Test report with pressure, duration and witness |
| 4. Flush and clean | Flush at velocity with temporary strainers until clean | Flush log, strainer inspection |
| 5. Fill | Premixed inhibited glycol pumped in from the low point; vent high points | Volume added, batch information |
| 6. Verify fluid | Concentration by refractometer, pH, inhibitor level | Baseline fluid report |
| 7. Start up | Fan rotation, flow balance, setpoint and bypass sequence, alarms | Startup sheet, controls checkout |
On adiabatic units we also pipe the water supply, backflow protection, drain and any treatment equipment, whether that is a water softener or an RO unit.
Dry cooler maintenance schedule
Dry cooler maintenance comes down to three things: keeping the coil clean so air can pass, keeping the fans and controls working, and keeping the glycol at the right strength and chemistry. Intervals below are typical; the manufacturer’s manual and the water management plan govern.
| Interval | Dry tasks | Adiabatic tasks |
|---|---|---|
| Monthly in season | Walk-down for debris, noise, vibration, leaks; check leaving fluid temperature against setpoint | Inspect pads or nozzles, sump and drain; verify switchover setpoint; check water treatment equipment |
| Quarterly | Check fan operation and alarms; clean strainer; check loop pressure and expansion tank | Clean nozzles or rinse pads; record water use; sample as the water management plan requires |
| Spring | Clean coil after pollen and seed season; straighten damaged fins | Recommission wetting system: flush, disinfect, refill, check controls |
| Fall | Test glycol before first freeze | Drain and winterize wetting system; protect pads |
| Annually | Glycol concentration, pH and inhibitor reserve tested by lab; check fan mounts, guards and connections; review control sequence | Replace scaled or damaged pads as needed; review water management plan |
Pressure washers bend fins and ruin the coil they are meant to save, so coil cleaning uses low pressure only. Our preventive maintenance program covers dry coolers, adiabatic units and their loops, and our industrial water treatment team handles the equipment that prepares adiabatic water.
Dry cooler troubleshooting
Most dry cooler complaints are high leaving fluid temperature, freezing or lost glycol.
| Symptom | Likely cause | Check or fix |
|---|---|---|
| Leaving fluid too warm at design ambient | Fouled coil, fan failed, recirculation of discharge air | Inspect and clean coil; check each fan; look for hot air returning to the intake |
| Capacity lower than when new | Glycol concentration raised, flow below design, air in the coil | Test concentration; measure flow; vent high points |
| Loop overcools in winter | Bypass valve stuck or sequence wrong; fans not stopping | Check valve stroke and sequence; review setpoint |
| Frozen or split coil tubes | Glycol diluted, loop stagnant in cold weather | Test glycol before winter; keep flow or drain idle units |
| Falling loop pressure | Leak, expansion tank failed or waterlogged | Find leak; check tank precharge; stop untracked makeup |
| Adiabatic unit using too much water | Switchover setpoint too low, valve passing, overflow | Reset setpoint; check solenoid and float; review sequence |
| White scale on pads or fins | Hard spray water, too little bleed | Improve water treatment; descale or replace pads |
How Paul Industries handles dry cooler and adiabatic cooler work
We rig and set dry coolers and adiabatic coolers, fabricate and install the glycol, condenser and chilled water piping that connects them, install pumps, heat exchangers, expansion and air separation equipment, and pipe water supply and treatment for adiabatic sections. We pressure test, flush and fill the loops, verify the glycol, start up the units and prove the control sequence, and then maintain them: coil cleaning, glycol testing, wetting system service and emergency repair. We handle single units and multi-unit yards alike, on new plants and replacements. To scope a project, request a quote.
Standards referenced: ASHRAE Standard 188 · ASHRAE Guideline 12 · ASME B31.9 · ASME B31.3 · ASHRAE TC 9.9 liquid cooling guidelines
Frequently asked questions
Is a dry cooler a type of fluid cooler?
Yes. The term fluid cooler also covers closed-circuit evaporative coolers, which spray water over the coil and need water treatment, so a specification should state whether the unit is dry, adiabatic or evaporative.
Is a dry cooler the same as an air-cooled condenser?
No. A remote air-cooled condenser condenses refrigerant from a compressor, and its piping is refrigerant line work. A dry cooler carries water or glycol in a closed hydronic loop, so it is piped, pressure tested and filled like any other water system.
Can a dry cooler run on plain water instead of glycol?
Yes, where it never sees freezing weather, or where the loop is drained or kept moving with a reliable freeze protection sequence. Most outdoor units in cold climates use glycol because one missed drain-down or pump trip in a freeze can split the coil.
How cold can a dry cooler get the fluid?
Only as cold as the outdoor air plus the approach. In winter that can be very cold, which is when free cooling pays off; on the design summer day the fluid leaves several degrees above ambient. Anything colder than outdoor air needs a chiller.
What glycol concentration does a dry cooler loop need?
Enough to put the freeze point at least 5 degrees Fahrenheit below the lowest expected outdoor temperature, and not less than about 25 percent so the inhibitor works and bacteria cannot grow. For inhibited propylene glycol, freeze protection to 0 degrees Fahrenheit takes roughly 38 percent by volume.
Should a dry cooler loop use propylene glycol or ethylene glycol?
Ethylene glycol gives slightly better heat transfer and lower viscosity, so it is common in closed industrial loops. Propylene glycol is lower in toxicity, so it is used in food, beverage and pharmaceutical plants and wherever a leak could reach people or product. Either must be an inhibited industrial grade.
How often should the glycol in a dry cooler loop be tested?
At least once a year with a lab analysis of concentration, pH and inhibitor reserve, and with a field refractometer before each winter and after any leak or fluid addition. Trending the results shows slow dilution or inhibitor depletion before it causes damage.
Why does glycol concentration drop over time?
Almost always because water has been added, through an automatic makeup connection, a topping-up after a leak, or a technician filling with plain water. Glycol does not evaporate from a sealed loop. Remove automatic water makeup and top up only with premixed fluid.
Adiabatic cooler vs dry cooler: which costs less to own?
It depends on climate and water price. The adiabatic unit is usually smaller for the same peak duty and draws less fan power on hot afternoons, but it adds water and sewer charges, pad or nozzle replacement, spray water treatment and seasonal draining and disinfection. Where summer peaks are moderate the plain dry unit tends to win; in hot, dry climates with affordable water the adiabatic unit often does.
At what temperature does an adiabatic cooler start using water?
At a switchover setpoint chosen during design and adjustable in the controls, typically when the unit can no longer hold its leaving fluid setpoint running dry. Setting it too low wastes water; setting it too high lets the loop drift warm on peak afternoons.
Do adiabatic coolers need a Legionella water management program?
Yes, the wetting system should be part of the site's water management program. The CDC lists evaporative air coolers among devices that can grow Legionella, and ASHRAE Standard 188 expects owners to manage water systems that can create aerosol. Draining, cleaning and disinfecting the system at season start and end are the core controls.
Can adiabatic pre-cooling be added to an existing dry cooler or air-cooled chiller?
Often, using a retrofit frame with pads or nozzles mounted ahead of the coil. The added air-side pressure drop, the water supply and drainage, and the manufacturer's position on coil warranty all need checking first, along with the control sequence that decides when the water runs.
How long do adiabatic pads last?
It depends on water quality, hours of use and how well the pads are drained and dried between uses. Pads fed hard water scale and lose efficiency far sooner than pads on treated water. Replace them when scale, sagging or torn media show up on inspection rather than on a fixed calendar.
How do you clean a dry cooler coil?
Isolate and lock out the fans, then rinse with low-pressure water or air from the leaving-air side toward the entering side so debris exits the way it came in. Use only a coil cleaner the manufacturer approves, rinse it off fully, and comb out any bent fins afterward.
Where should a dry cooler be located on a site?
Where it can draw in outdoor air that has not already passed through another unit, with the clearances the manufacturer specifies from walls, screens and other coolers. Keep it away from exhaust stacks, kitchen vents and dusty processes, and check sound at the nearest property line.
How does altitude affect dry cooler capacity?
Air at high elevation is less dense, so each fan revolution moves less mass of air and carries away less heat. Manufacturers apply an altitude correction in their selections; leaving it out at a mountain site can undersize the unit noticeably.
Is a dry cooler cheaper to run than a cooling tower?
On water, chemicals and treatment labor, yes, because it uses none for cooling. On electricity, often not: dry units need more fan power per unit of heat, and if they serve a chiller condenser the chiller works harder in summer. The total depends on water and power prices and the climate.
Do dry coolers work in winter?
Winter is when they work best. The cold air gives a large temperature difference, so fans slow down or stop and the loop may need a bypass to avoid overcooling. Glycol strength, drain valves and controls that keep fluid moving through the coil are the winter concerns.
What does replacing a dry cooler involve?
Isolating and draining the unit, recovering the glycol, rigging the old unit out and the new one in by crane, adapting the pipe connections if the new headers differ, then pressure testing, refilling, venting and starting up. A matching replacement can usually be swapped while other units in the bank keep running.
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