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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