Guidelines and Sizing

Triforce Electrical

Air-Conditioning Guidelines & Sizing

Choosing the right size air-conditioning unit and finding the perfect location for absolute efficiency in your home (meeting all legal requirements) can be a headache. Never fear! Triforce Electrical and Air is here!  We have considered all the variables for you and put together an easy to understand guide.

Selecting the right unit

In order to help you choose the perfect unit for your home, make a note of the following factors:

  • Room size
  • Ceiling height
  • Is the roof space insulated?
  • Are the wall cavities insulated?
  • Are there large glass windows and/or doors? Do they get direct sunlight? Are they glazed or double glazed?
  • Does the room get direct western sunlight?

What air conditioner size do you need?

In a standard insulated QLD home, you will usually require a 2.5kW system for a bedroom and 7kW for your lounge room. You’re unlikely to require other sizes unless your home is uninsulated, has lots of windows, is western facing or has significantly high ceilings. You can reduce the load on the air-conditioners by closing all your blinds and shutters, but most Queenslanders love the sunshine and want to take full advantage of its beauty, so this will make a difference on the size of the unit you need.

Don’t forget that you will need to have a regular 12-monthly air-conditioning service to keep your unit in tip top shape!

For all the technical people out there who want the specifics

Firstly decide on the size of the area that needs to be cooled. Do this by measuring the room: multiply the room’s width by its length (LxW), then multiply this value by 140 to get the number of watts required. Why 140? Here at Triforce we think the magic number to promote efficient cooling and heating is 1.4kW per 10 square meter (140 watts) – which is what we will use for our example.

A 4m by 3m room = 12 square meters
You will require a minimum of 1-1.5kW per 10 square meters of space in a regular insulated home with standard ceiling height.

Let’s use the room example above:
Wattage required: 12 x 140 = 1680watts (1.68Kw)

Therefore, a 2.5kW system will provide adequate and ample cooling for a room of 12 square meters. Why not a smaller unit? You still need to add in the factors of windows, doors, sunlight, home positioning and days with extreme temperatures (when you will need your system the most).

Room sizeExampleApprox. capacityPrice guide* (incl. basic installation)
Small (up to 20m2)Bedroom, study, small kitchen2–2.5kWFrom $1249
Medium (21–40m2)Bedroom with ensuite, small lounge3.5–5kWFrom $1858
Large (41–60m2)Large bedroom, mid-sized lounge, large kitchen6-7kW From $2598
Extra large (61+m2)Open-plan areas, large lounges8-9kW From $3147

* prices based on Mitsubishi electric, our most recommended product. Basic installation is “back to back”. Cost varies for other types of units and installation requirements. Please enquire to find out more.

What about heating?

Most split systems have an extra kW power rating for heating compared to cooling. Therefore, if the system is able to cool the room efficiently it will also heat it easily.

How much space is required for installation?

Most people don’t give this question any consideration, but it’s another important aspect of a quality installation. Here are the minimum spaces needed for an efficient installation.

  • Small units require 900mm (w) x 300mm (l) of empty wall space
  • Large units require 1150mm (w) x 350mm L) of empty wall space
  • The largest outdoor unit is 800mm wide x 1100 high, so you want roughly 300mm minimum clearance in every direction

You also need to think about what is on the other side of the wall.

I’m confused, what else can I do?

Send us some photos of your home and we can work out where to put your air-conditioning unit for you. If you have a basic floor plan this can also really help us map out and plan logistics. It’s important to let us know of any possible dilemmas there may be before installation so we can quote properly, have to right staff numbers on the job and allow efficient time for installation.


Back to back install
This is the most standard type of installation and the most basic. Your unit is placed on the inside wall with the outside condenser directly behind it on the outside wall.
Side Exit Install (right)

Pipes will leave the unit from the right-hand side. There may be a small amount of ducting on the internal wall. This will be connected to the condenser that will be located directly on the other side of the external wall.

High Set Installation

The internal unit needs to be installed above single story height and needs to be connected to the condensers below. Maximum pipe length for all installs is 5m.


There are standard brackets, placed 1m off the ground and high brackets placed 2m off the ground.

Up and Over Installation with condensate pump

These installs require pipes to be taken up through the ceiling (up to 10m) to the location of the outdoor unit. They are mostly for air-conditioners that are placed on internal walls (they don’t have an external wall directly behind the unit). Some of these installations may also require extra gas to cover the length of pipe. A condensate pump may also be required in order to effectively drain water from the indoor unit to the outside of your home. We have one of these installation’s in our bedroom.

Decommissioning of old units

This is the safe removal of old air conditioners, gas and all associated waste.

Is there enough space for the outdoor unit?

In the modern world there is a drastic increase in higher density living with small 400m2 blocks and units. Your neighbours are on your fence lines. To avoid nuisance noise complaints and council fines it is vital to ensure your units are being placed in appropriate places for everyone around you.

Outdoor units require a maximum space of 800mm wide x 1100 high, with 300mm minimum clearance in every direction. You also have to consider what they are going to be sitting on – concrete, PVC floor, poly-floor or brackets. Some examples of outdoor spaces are shown below.

Regulations in QLD

1. Peak Smart Devices

You may notice that some air conditioners on the market are specific to QLD. This is because in QLD there are strict regulations around energy usage and efficiency. One of these restrictions is the option for DRED technology (Demand Response Enabled Device). This is better known as Energex’s Peak Smart device and allows Energex to remotely operate your air-conditioner in an economy mode when the power grid is not coping via a “peak smart event”. As the QLD electrical grid is robust, this may only happen a couple times of the year.

The good news is that when you install a peak smart air-conditioner, you get cash-back rewards as a thank you for being environmentally friendly. For more information on this please visit the Energex website.

For every peak smart installation, you will need to fill out the online reward application form and upload it, along with our installation certificate, to the Energex website to claim your rebate.

2. The QLD laws against noise

Queensland is hot! The humidity and heat waves are unbearable at times and more residents are installing air-conditioners in their homes. With this increase in sales of air-conditioners, noise complaints have also more than doubled.

The Environmental Protection Regulations (1998) includes a section on noise limits for air conditioners. Local city councils are responsible for enforcing these limits and if your unit exceeds recommended noise limits you may be hit with a fine. The allowable noise levels are:

  • 7:00am to 10:00pm – noise no louder than 50dB(A)
  • 10:00pm to 7:00am – noise no more than 5dB(A) above background noise or 40dB(A) (whichever is higher)

All air-conditioning manufactures have a legal obligation to display the outside sound power level on their units, so you have an idea on what to expect; the higher the number, the louder the unit. To reduce nuisance noise complaints, the location of the outside units are of vital importance. In some cases units may have to be encased with barriers or enclosures.

3. QLD Energy Efficiency Standards

The Queensland Building Development Code (QDC) 4.1 – Sustainable buildings, states that all new or replacement air-conditioners installed in all new or existing buildings (classes 1-10) must have a minimum tested average Energy Efficiency Ratio (EER) of 2.9 or higher for cooling. For an excellent source of information click here.

For more information on why you need a regular air-conditioning service or help selecting an air-conditioning unit for your home, call Triforce Electrical and Air on 0412 922 265 or send us an email to discuss your requirements.


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