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Frequently Asked Questions

Here are some questions people often ask about their air conditioners.  If your questions are not answered here, fell free to give us a call and we’re always more than happy to provide all the advice you need.


What size unit should I purchase?

The amount of wattage you will need depends on the size of the room(s) you want to heat/cool and the heat load which is determined by environmental factors such as the amount of windows and sunlight in the room, weather conditions and what type of insulation you have.  Generally, the bigger the area you have, the more power you will need to service it.  Optimum Air is more than happy to give you all the advice you need in this regard.


What is an inverter system?

An inverter system lets your air conditioner alter the speed of its motors (compressors) in response to cooling demand. The result is a controllable and energy efficient system that is not only cheaper to run, but also uses a smaller power supply.

See our web page on Inverter Systems.


What is the difference between a split system and a room air conditioner?

A split system has an indoor and outdoor unit that is connected together. They provide quieter and more efficient air conditioning than a single room air conditioner. They work by having the condenser (the noisy bit) in the outside unit and then having one or more indoor units that contain the fans.

A package unit (room air conditioner) requires no external components and has to be installed through a window or hole in a wall. These units are good for small rooms, but some people find them bulky and unattractive.  They are also much noisier than a split system because the condenser is located immediately behind the outlet, whereas a split system's condenser can be located away from the rooms being cooled.

Make sure you check out our web pages on Wall Splits, Multi-Splits, and Ducted Systems.


What is the difference between a split system and a multi split system?

A split system has an indoor and outdoor part that is connected together. Meanwhile a multi split system has just the one outdoor part that is connected throughout the house through multiple indoor parts installed in each room. So while a split system powers up the one room, a multi split system powers up multiple rooms from one outdoor unit.

What is the difference between a split system and a ducted system?

Nowadays, almost all air conditioners are split systems.  In fact virtually all ducted systems are a kind of split system.

The term "split system" refers to a type of air conditioner where the compressor is connected to an indoor unit via pipes.  The actual type of air conditioner can be either a wall-hung system or ducted system.  The ducted system transfers its conditioned air through ductwork.  The wall-hung system has an indoor unit connected directly to the outdoor unit with pipes, and conditioned air comes directly out of the indoor unit without the need for any ducting.  Of course, this means the wall-hung indoor unit can only condition one room or area.  To condition more than one area a wall-hung unit would need to have multiple indoor units.  To condition multiple areas with a ducted system you still need only one indoor unit - the conditioned air from it is transported using the ducting.

Some people refer to "split systems" when they really mean "wall-hung split systems".  It is just a shortening of the term.  A "split system ducted" air conditioner is, likewise, usually referred to as simply a "ducted air conditioner".

Again, see our web pages on Wall Splits, Multi-Splits, and Ducted Systems.


Is a cooling-only system better than a heating/cooling system?

Cooling-only systems are not necessarily better than combined cooling/heating systems, but they are generally cheaper to buy. Air conditioners that can both heat and cool are known as reverse-cycle systems.  This is because the normal cycle is to pump heat from indoors to the outside.  By reversing this cycle, the heat can be pumped from outside to inside, and thus the unit becomes a heater.  This can save you money because just the one appliance performs both heating and cooling, obviating the need to buy a separate heater.


How often do I have to clean my filters?

Return air filters require regular cleaning.  The frequency depends on how dusty the house is.  If not cleaned the unit can ice up and stop working.  The condenser (outdoor unit) also needs to be dust free with an unobstructed air flow.  If you do this three or four times a year, that's almost always sufficient.  Optimum Air can design a maintenance programme for you to make sure that filter cleaning (along with regular checkups) are done and give you complete peace of mind.

See our separate web page in the Service section on Cleaning your Filter


Should a thermostat be set to "auto" or "cool" / "heat"?

Today, most air conditioners have an "auto" setting on the thermostat that makes the fan operate only when the temperature requires it.  This is generally the most used and efficient setting because programmable thermostats maintain a steady temperature and reduce energy use by only working when needed.

Using "auto" means the air conditioner itself is allowed to decide whether to heat or cool.  For instance if it’s 30° outside, you’ll probably want the machine to cool, and the "auto" setting will do this.  If it’s 10° outside, naturally the desired operation is heating.

If the indoor and outdoor temperatures are roughly the same, however, this can sometimes confuse the "auto" setting.  In this case you might like to over-ride the auto setting by specifically letting the machine know that you want it to cool or heat (or possibly just de-humidify) by using the relevant setting.


Can I leave doors and windows open while operating the unit?

You can leave windows and doors open, but it’s not a good idea if you’re trying to heat or cool the room.  For tips on saving money on running your air conditioner, please see our separate web page of Tips for Efficient Operation.


It says on the air conditioner that it uses 6,000 watts of current (thus requiring a 25 amp circuit), yet the manual says the machine only has a rating of only 2,500 watts.  What is going on here?

Electrical input wattage and refrigeration wattage are two different things.  The important thing to note is the refrigeration rating, which is how effective the machine is in pumping heat.  In fact machines of the same cooling/heating rating might use more or less electricity to achieve this.  The less input energy used to achieve the same refrigeration rating, the better.  This is how the Energy Star ratings are calculated.  This gives the efficiency of a machine in a way most people can understand: the more stars, the better.


What do "R22", "R410a", "R407c" and "R417a" mean?

These labels refers to the type of refrigerant gas the air conditioner uses.  Older hydrochlorofluorocarbon (HCFC) based refrigerants are in the process of being phased out due to their ozone depleting potential.  That means the current air conditioning refrigerant R22 has a phased reduction until 2015.

The main replacement that is being introduced is hydrofluorocarbon (HFC) R410a which has an ODP of zero. Unfortunately it has a higher direct greenhouse warming potential than R22 but indirectly it's less damaging to the ozone layer. R22 manufacturing by-products caused a far higher total greenhouse warming potential.

R407c is another of the R22 replacements that requires polyol ester oil.

R417a is a drop in replacement for R22 systems that requires no changes and uses the existing mineral oil.  This will become the simplest replacement as R22 is phased out.

If you are considering purchasing a new air conditioner, it's worth shopping for an R410a or R407c unit. They’re marginally more efficient, better for the environment and will be more future proof in terms of servicing.

If you have an old air conditioner or refrigerator it is important to dispose of it properly.  If the refrigerant is released into the atmosphere the damage to the ozone layer and greenhouse warming potential is roughly equivalent to operating a medium-sized four cylinder car continuously for six months!  The refrigerant gas can be reclaimed (pumped out) and disposed of in a safe way by a licensed refrigerant handler, such as Optimum Air Conditioning.


I hear that you can catch Legionnaire’s Disease from air conditioning.  Should I worry?

Legionnaire’s Disease has been overblown by the media.  You CANNOT catch Legionnaire’s Disease from a domestic air conditioner.  This disease is formed in cooling towers which are only used in very large commercial operations such as in office blocks and shopping centres.

Cooling towers can provide an ideal place for legionella bacteria to grow (temperatures between 28° to 40°C) and the operation of the towers causes drift which aerosols the bacteria allowing people to breathe it in. There is, however, probably more danger in handling potting mix than from a cooling tower because by law, all towers have to be regularly maintained and treated with biocide.


Should outdoor units be covered in winter?

Outdoor units are designed to withstand seasonal changes so do not need to be covered.  The heat pumps inside the unit operate year round and if you cover them, it may cause damage.


If an outdoor unit needs replacing, should the indoor unit be replaced too?

Generally it is a good idea to replace the entire system when a major component of the system fails to operate correctly and cannot be repaired.  That's because air conditioning and heating units are designed to operate as a complete, matched system.  In fact it can sometimes be downright impossible to obtain an indoor or outdoor unit to match its counterpart if the unit is more than a few years old.


Can plants or shrubs be planted around an outdoor unit?

Yes. However, make sure there is plenty of room around the outdoor unit so air can freely flow in and out of it.  Without room for air circulation, the unit can overheat and damage itself. It's also a good idea to trim shrubbery and limbs back because they can cause damage if leaves or twigs are sucked into the outdoor unit.


What is the average life expectancy of an air conditioner?

The typical life expectancy of an air conditioner is about 10-15  years. When the air conditioner starts having problems that are not cost-effective to fix, it may well be time to replace it.  Be wary of spending more than 50% of the replacement value of a machine on repairs.  If the machine should need a similar repair within a few years, you may as well have bought a new one at the time of the first problem.  Modern machines are usually far more efficient than old systems.  This is an added bonus of replacement: the machine you replace it with will almost certainly use less electricity than the old one.


I am trying to cut and paste text from this website into my word processor and it appears invisible!  What do I need to do?

The text on this website is white.  If you paste it into a word processor with a white background, the text will be there, but since it's white on white you won't be able to see it.  Either highlight the pasted text and turn the text colour to black, or alternatively, when you paste the text don't use a normal paste operation.  Choose "Paste Special", and then paste the text as "unformatted text" (or "normal paragraphs") into your word processor.  Footnote: the above is no longer true, we've changed all the colours on the website and the text is now black!  The above point does apply to some other websites, however.

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Copyright © 2010 Optimum Air Conditioning   [Last modified: Tuesday, 07 December 2010 10:56:45 PM]