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How to Select an Evaporative Cooler for Australian Conditions

Much of AUSTRALIA is hot and dry for much of the time and it is not surprising that evaporative cooling is very popular in ADELAIDE, MELBOURNE, PERTH and most inland areas.

  To install ducted evaporative air-conditioning is a major purchase, which typically costs from $3,000 to $6,000 (depending on size, location, controls and other factors). Hence it is worth making sure that your money is spent as wisely as possible. Although you can't be guaranteed a successful installation, the following tips should lead to a satisfactory outcome. These tips are of a general nature, and it is up to you to ensure they apply in your case.

WHAT SHOULD I LOOK FOR IN A COOLER?

CENTRIFUGAL or AXIAL fan?
A CENTRIFUGAL fan is a drum shaped fan. It is generally:

HOWEVER they:

An AXIAL fan is a propeller shaped fan. It is generally:

HOWEVER it is:

RECOMMENDATION:
For a large cooler I favour a centrifugal fan, as the installation is more likely to be successful. However there are some (particularly the smaller) axial coolers on the market that are satisfactory. (refer for instance to the COOLMAX )

SHOULD I HAVE CELDEK or WOODWOOL pads?
CELDEK pads are manufactured from corrugated paper with a binder.

HOWEVER:

WOODWOOL, (often referred to as Aspen), is manufactured by shredding timber. The better quality woodwool is made from Poplars grown above the snow line. Woodwool pads need to be firmly and evenly packed.

HOWEVER:

RECOMMENDATION:
I recommend CELDEK pads, except for those few areas where the poor quality water causes a problem for CELDEK.

THICKNESS of PADS
Pad thickness is vital to get good performance. CELDEK pads in conventionally designed coolers should preferably be at least 75mm thick, if the airflow is even, or 90 to 100 mm thick otherwise. WOODWOOL pads should be generally be at least 50 mm thick.
 

MATERIAL OF CONSTRUCTION

The most important criterion is resistance to corrosion. The best from this point of view are:

Coolers with a large amount of powder coated or even galvanised steel where it can be readily splashed should generally be avoided.

THE COOLER BRAND
To develop a high quality evaporative cooler requires a considerable investment in research and development. Generally only a large manufacturer can support this. Most small manufacturers do not have the expertise to do the testing needed to ensure a product performs as expected. Speak with your friends who have evaporative cooling, or ask to see testimonials from satisfied owners.

THE CONTRACTOR.
It is the contractor or dealer who will make or break an installation. A good unit, installed by an inexperienced contractor will not satisfy you. Among other things, check:

DESIRABLE FEATURES.
For decades the standard cooler had a two-speed motor, a pump switch, and a continuous bleed system. These features make a simple reliable cooler. However, the number of features and options available today can be very confusing. The following comments are my personal opinions, based on my extensive but not exhaustive experience.

VARIABLE SPEED:
This has become the standard for residential units. The main benefit is that the minimum speed is less than the minimum on a two-speed unit. This is highly desirable at night, as a two-speed unit can often be too cold when it is on, even though the house will quickly heat up when you turn the cooler off. In addition, a variable speed cooler can be set to give exactly the cooling you want.

AUTOMATIC CONTROL:
Electronic thermostats are available to vary the fan speed automatically, and switch the pump and fan on and off. Although those currently available still sometimes need a minor adjustment of the setting, they do a good job of maintaining comfort. Some contractors supply a mechanical thermostat in lieu of the electronic thermostat, however they are not as useful, as they don't vary the fan speed, or control the pump. On a wall or window mounted cooler automatic control is not usually necessary.

AUTOMATIC SHUTOFF DAMPERS:
These are flaps in the discharge of the fan, or in the duct, which open when the fan starts, and close when the fan is switched off. They reduce the loss of heat through the cooler when it is not working. This eliminates the need to cover the cooler with a bag at the end of summer. Some types have a latch to keep them closed and eliminate 'chattering' in gusty conditions. Some of these fold out of the direct air stream when working, and hence cause no loss of airflow. Others remain in the direct airflow and hence do cause a small loss of airflow.

SALINITY BASED WATER QUALITY SYSTEMS:
When water evaporates the salt that was in that water doesn't, and builds up in the cooler. This leads to increased corrosion of  metal components and a reduction in cooling performance. There is also a build up of dust and pollens washed out of the pads, or in the water supply. The traditional way of getting rid of that salt is with a constant bleed off of water. However, more bleed off is needed in hotter weather, or when the supply water is saltier.  To match the bleed to the need, measurement of the salinity of the water in the cooler can be used to control how much water is discharged, and when it is discharged. These systems work well in most areas, but for very hard water, they can use more water than is economically feasible. Some have a setting to allow a higher concentration of salt in those areas. (However if the higher setting is used, the cooler will need to be cleaned more frequently) for a small cooler salinity control is not economically justified, and a traditional bleed system is satisfactory.

DRAIN SYSTEMS:
When the cooler is not being used for a period of time, algae and similar things can grow in the tank. To prevent this some manufacturers offer a drain system. When the cooler is not going to run for a time, the tank empties and the water supply is shut off. Check that the manufacturer has included a timer, to ensure that you don't lose water every time the cooler fan or pump switches off.

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