Why is sizing an evap air conditioner important?
Under sizing air-conditioners by dealers trying to cut costs and by manufacturers overstating the cooling capacity of their units has lead to numerous dis-satisfied evaporative air-conditioner owners.
This negative reputation of evaps has damaged sales of evaporative air-conditioning.
CoolBreeze offers a Performance Guarantee – if you size the unit according to the ComCool sizing guide – if the customer is not satisfied, CoolBreeze will upsize the unit at no cost.
Old school
If you’ve been in the air-conditioning industry for more than 10 years, you’re probably familiar with the “30 air-changes an hour” method of sizing evap air-cons.
What is it and is it still relevant?
How to do it
The 30 air-change per hour method requires you to measure the volume of the rooms to be cooled – length x width by height (in m3) of each room, then total the room volumes.
The manufacturer would nominate the cubic metre per hour rating of each model.
You would then multiply your total room volume by 30.
You would then select the model that was greater than the room total.
So now that you know how to do it – please forget it!
Does it work?
There are a couple of fundamental flaws with the 30 air-changes per hour method.
Even if the capacity provided by the manufacturer was correct – it was based on what’s know as ‘free-discharge’ – basically it just a measure of the air volume straight out the bottom of the air-conditioner and doesn’t take into account factors such as duct length, size and resistance, dropper design or Y piece design.
Is it relevant today?
Evaporative air-conditioning really took off in Australia in the late 80s and early 90s.
At that time, massive housing growth was fuelled by cheap construction methods and materials.
In the early 2000s governments across Australia introduced minimum energy efficiency ratings for homes.
In 2008, as the GFC hit, Kevin Rudd stimulated the economy with his Home Insulation Scheme.
The current energy rating is 6 stars.
A 6 star home is 24% more energy efficient than a 5 star home.
What this means…
An air conditioner sized using the 30 air-change per hour method that suited an un-insulated 1980s home will be massively oversized for a modern 6 star rated home.
You may lose the sale because your quoted price will be way higher than other companies that have sized the home correctly.
What about kilowatts?
An Australian Standard was developed to measure the kilowatt rating of evaporative air-conditioners under controlled conditions.
Unfortunately, the standard has some loop holes that can be exploited to give unrealistic cooling capacities.
It becomes a theoretical measure rather than a consistent method of testing or comparing models.
The other failing of the kilowatt system is that it doesn’t give a ‘like for like’ comparison with refrigerated air-conditioning (also a theoretical measure) because with evap air-conditioning, much of the cooling effect is provided by the heat transfer to the air that is expelled from the home.
So how should evaps be sized correctly?
- Measure the length, width and height of the rooms to be cooled.
- Use the multipliers on the ComCool chart for factors such as home orientation, location, etc.
- Total the room volumes
- Select the CoolBreeze unit that rated higher than the room totals.
- Rest assured that CoolBreeze backs your sizing with a Performance Guarantee.
Is there an easy way?
There is a short-cut that suits most modern homes in ‘normal’ situations – that’s is without huge areas of west facing glass etc.
All you have to do is measure the length and width of each room to be cooled.
Based on a standard ceiling height of 2.4m, add the total square metres of the rooms.
Select a Coolbreeze unit with a model number that is greater than the total room area.
- Total Room Area less than 95m2 – use CoolBreeze D095
- Total Room Area between 95m2 and 125m2 – use CoolBreeze D125
- Total Room Area between 126m2 and 160m2 – use CoolBreeze D160
- Total Room Area between 161m2 and 195m2 – use CoolBreeze D195
- Total Room Area between 196m2 and 230m2 – use CoolBreeze D230
- Total Room Area between 231m2 and 255m2 – use CoolBreeze D255
You can’t get much easier than that!
While the model number of CoolBreeze units represents the total cooling area (in m2) that the units is guaranteed to cool NOT ALL OTHER BRAND’S MODEL NUMBERS represent their cooling capacity.
One manufacturers largest unit is not necessarily equivalent to another’s largest unit – you need to know the airflow and filter pad volume to do an accurate comparison. See the resource page of this website for information on specifications of several popular evap brands, For example:
- The CoolBreeze D230 has an airflow of 2890 l/sec and a pad volume of 480 litres.
- A Breezeair EXH220 has an airflow of 2450 l/sec* and pad volume of 360 litres.
- That’s 18% less air and 33% less pad material.
So clearly, the CoolBreeze has a much greater guaranteed cooling capacity than the Breezair.
*airflow taken from 2016 Breezair brochure.