Why is it so important to get your hybrid wet / dry cooler cleaned and inspected
by professionals who also work on cleaning cooling towers?
A lot of people don’t bother getting their hybrid air coolers regularly inspected and
cleaned as they view it as an unnecessary expense.
However, you should carry out maintenance, so that you don’t end up with a
Legionnaires Disease outbreak. What Legionella, how is that possible?
If the auto dump valve is not working or the basin and coils are full of sludge,
Legionella bacteria will grow.
Don’t let this occur is what Coolclean say. Avoid having to have Hybrid wet / dry
air coolers treated by chemicals to kill off bacteria, by routine maintenance and
We have decided to sit down with an industry professional based in Melbourne
Victoria that could tell us more about hybrid wet / dry air coolers or Hybrid cooling towers.
Grant Nichols, Business Manager
Grant Nichols is the Business Manager at Coolclean, and he wants to discuss
how Hybrid cooler owners and managers can avoid expensive water treatment.
Grant has 25 years of experience as a cooling tower and cooling system
manager, including heavy industry, light industrial, food & beverage production,
power generation and commercial & institutional applications.
What is hybrid cooling?
Hybrid cooling approach involves using different operational modes. The coolers
combine dry cooling with evaporative wet cooling, to provide the heat rejection all
year round, to reduce water and energy consumption, and to eliminate expensive
water treatment. They are also called Adiabatic coolers.
Evaporative cooling for hot days and dry cooling for most of the year to conserve
water. Hybrid fluid coolers optimise water and energy savings with EC fans.
Hybrid cooler working principle
Globally, we are all becoming more conscious of our water consumption as
freshwater is recognized as a critical natural resource.
By utilizing hybrid cooling solutions using wet / dry cooling for process and HVAC
situations these units can dramatically reduce annual water consumption.
Hybrid coolers are specifically designed to avoid visible plumes in cold, humid, or
ambient conditions, when local constraints require this technology, such as at
HVAC, airports, commercial buildings, Hospitals, Industrial factories, Food
manufacturing, Shopping centres.
Hybrid wet / dry air Coolers V Cooling Towers:
In Victoria, its law that all cooling tower interior surfaces to be cleaned twice a
year, six monthly. Cooling tower owners (landlords, building managers) must
inspect their cooling water systems monthly and ensure that their cooling towers
are periodically inspected, and the interior cleaned every six months.
It is also law to chemically treat, sample, test, service monthly, audit, complete
risk management plans, for cooling towers to control Legionnaires Disease
How Hybrid coolers got around these regulations:
The Hybrid coolers are a wet / dry air-cooled system. The coil has cooling
provided by dry air and wet air via the wet evaporative section. When the outside
air temperature gets hot, the wet evaporative section comes on. Water trickles
through the evaporative Celdek pads which get soaked with cool water. The fan
that is drawing air through the dry air-cooled coil is now getting the hot air of the
day cooled before it goes through the coil.
Where there is water, bacteria can grow so the Hybrid air coolers rely on the wet
section basin water being automatically being drained by activating a dump valve.
The wet section basin does collect dirt which becomes mud, and this does not
get dumped. The water distribution nozzles block with mud. Legionella growth
Types of Hybrid wet / dry air coolers:
Dry cooler with wet trim:
In dry coolers, a top priority is water savings, the dry cooler with wet trim puts the
dry cooling coil in series such as Evapco or BAC with the evaporative cooling
coil, and the dry coil is a persistent part of the cooling system, rather than
alternating on or off. Process fluid passes from the dry coil into the wet section
coil located below the pressurized water distribution system, where depending on
the current unit load, is cooled through evaporative cooling, or continued dry heat
Wet cooler with dry trim
The BAC wet Hybrid cooler is capable of running a wet and dry evaporative mode
simultaneously by having separate spray sections above the coils. The coils can
either utilize evaporative or dry cooling, rather than at once. Depending on
capacity needs, the Trillium Series unit can run either entirely in dry mode, 50%
of the unit in wet mode, or the entire unit in wet mode, the result being a
significant drop in water consumption compared to wholly evaporative cooling
Hybrid Cooler – Working in dry mode
Hybrid Cooler – Working in wet mode
Hybrid cooler cleaning maintenance
Hybrid cooler, like a normal Evapco or BAC cooling tower, require regular
maintenance and attention (every 6 months), especially if it is to last long and
function at its most optimum capacity. While these are specifically designed to be
low-maintenance, and even if they are built from top-notch materials that are
resistant to all minor types of damage, regular upkeep ensures that any existing
and unseen damage is immediately discovered and properly addressed.
Why the Modular Hybrid cooler maintenance important?
Over time, nutrients, airborne dirt, and inefficient operation will cause the
temperature of the hybrid cooler / HXV Adiabatic cooler to rise and debris to
collect within different components of cooler. If not properly cleaned, these
contaminants can cause blockages and corrosion, impair the operating efficiency
and lead to significant damage and possibly failure of the system.
Built up dirt, sludge, mould and other biological matter in wetted cooling
We found out that regular maintenance of various series of wet / dry hybrid
coolers ensures health and safety, performance, durability, efficiency, and
compliance. Failure to do so can be costly and extremely dangerous. Coolclean
recommends routine checks to maintain the condition of your Hybrid or Adiabatic
cooler. This will help you get the most out of your equipment while also providing
a clean, safe, and compliant work environment.
Grant Nichols said I once saw a wet / dry hybrid cooler in country regional
Victoria that had not been cleaned properly for around 2 years. It was full of
25mm of sludge through the basin and into the cooling coil. This resulted in
severe corrosion and failure of steel coil, as the sludge allowed bacteria to grow
and breed in the mud. Bacteria consumes nutrients from with the sludge and as a
by-product, discharges an acidic waste that is very corrosive. It attacks, steel,
stainless steel, aluminium, and copper very quickly, to the point of failure. Failure
of coils shuts the system down and releases the refrigerant or fluid into the basin.
Bacteria corrodes aluminium and copper coil fins very quickly
It was a safe place for Legionella bacteria to grow as there was no water
Coolclean’ s full-inclusive cleaning service in Victoria and Melbourne that
The Steps Required to Clean a Hybrid Cooler:
Step 1: Safely procedure
The first step before cleaning a wet dry hybrid cooling tower is to inspect the unit.
Ensure that there is safe access to all access panels and that they can be
removed safely. Check the isolation procedures for the site, complete the SWMS
and JSEA, understanding permits such as confined space entry requirements,
working at heights, using EWP / scaffold, correct wastewater disposal, and
understanding the building or site rules can be accomplished.
Step 2: Hybrid Cooling Tower Treatment process. Pre-Disinfection
Carry out the disinfection of the hybrid cooler for at least a one-hour period.
The Victorian state law states that 10ppm, of free chlorine must be held within a
pH range of 7 to 7.6 for a minimum of one hour.
The bacteria/fungus that grow in wet dry hybrid coolers may cause harm or
illness to humans, and so it is necessary to disinfect with proper chemicals
This makes the cleaning process safer and easier while eliminating excessive
Step 3: Wet Dry Hybrid Cooler interior cleaning
All Interior components and surfaces such as cooling pads, water nozzles, splash
louvers, coils, casings, and basin surfaces need to be thoroughly cleaned and
sanitized to function properly. Coolclean takes photos and attaches them to the
service report that is provided. This ensures nothing was damaged or done
incorrectly in the process.
Severe corrosive damage of the cooling coil caused by sludge and bacteria
Internal pads removed for cleaning. Please note how they are dirty and bent which
severely reduces the cooling performance
One of the wetted pads had fallen in, exposing the water distribution pipeline.
Note: These holes are very small and can block easily. Maintenance in critical.
Step 4: Reassemble
Ensure all components of the hybrid / Adiabatic cooler that were disassembled
are properly reassembled into place. To prevent faults such as water splashing,
water loss, bacterial growth, electric motor failure, and damage to a chiller, heat
exchanger, or process.
Step 5: Final hybrid Cooler Post Disinfection
After the cleaning and inspection are completed, bacteria have been successfully
disturbed so it must be disinfected to eliminate regrowth by a final disinfection
Carry out the disinfection of the hybrid cooler for at least a one-hour period
The Victorian state law states that 10ppm, of free chlorine, must be held within a
pH range of 7 to 7.6 for a minimum of one hour.
This step is enforced as Legionella Bacteria could have been living and growing
deep in the coil, the pads, on casing surfaces, and in pockets of dirt in the basin.
Making the final disinfection procedure critical to the maintenance steps.
Step 6: Hybrid Cooler Cleaning Service Reporting
The after-cleaning safety report is created with the data that has been taken from
examining and cleaning the hybrid cooler. Also included are the levels of chlorine
and Ph, as well as when the hybrid cooler needed to be treated again based on
these results. Photos are added from the interior cleaning process of
the components and surfaces such as the cooling pads, basin casing and coil.
Apart from the after-service reporting, it’s important to mention that Coolclean
sells a range of hybrid cooler parts such as the evaporative Celdek pads, ball
float valves, strainers, auto dump valves they can sell and install.
So, make sure your hybrid cooler or Adiabatic evaporative
cooling is a safe item of cooling equipment, keep up to date with
your maintenance and if you are ever unsure of the best thing to
do, call the Hybrid cooler professional, it’s that easy. Coolclean
cooling system experts are always looking out for their clients,
providing the highest quality service possible.
Unit 21, 21-22 National Drive, Hallam VIC 3803
+61 03 8765 9500