The difference between a single and three phase air conditioner

Air Conditioning FAQs

When choosing an air conditioner, one of the options on offer is between a single or 3 phase power supply. These types refer to the amount of power delivered to your property via underground or overhead power lines on the street.

Single phase is the standard method of distribution of electric power; most homes or apartments will run on this phase of power. Three phase power is generally for commercial and industrial situations. However, if you are in a larger property with appliances that draw a lot of power, three phase can be installed to avoid power fluctuations. Air conditioning with higher capacities may require a 3 phase power source.

Your property’s single phase or 3 phase power source will dictate the air conditioner that will be appropriate for your home.

How do I know what phase power I have?

Determining the power phase of your property is easily done. You need to:

  • Locate your central switchboard. This switchboard is usually easily accessible, either inside the house or at the front of your property
  • Open the switchboard and locate the breaker labelled ‘Main Switch’; this will identify which phase of power you have access to.

Note: A single circuit breaker indicates single phase power whereas three circuit breakers joined together by one switch indicates three phase power.

How do single and three phase power work?

Active wires in your power source are known as ‘phases’, with neutral wires earthed at the switchboard. The difference between the two of these phases lies in their names. Put simply;

  • A single phase power source has two wires: active and neutral.
  • A three phase power source has four wires: three active and one neutral.

Again, the single phase current is commonly used as the source of heating, cooling and lighting in most households and non-industrial businesses. A 3 phase current offers power density, particularly appropriate for large businesses in manufacturing and industry.

Why would my home need 3 phase power?

If you are trying to run large machines or devices off a single phase power base there will not be enough power supply to meet your demand. This can result in the circuit breaker continually switching itself off as it is overloaded.

You’ll need a three phase power source if you have (or are aiming to install):

  • A 15+ kW capacity air conditioning system.
  • Multiple fridges and freezers.
  • A large home, where family members may be using multiple appliances at peak times.
  • Lifestyle or vocational devices that consume a lot of electricity. For example, a big ceramics kiln, large motors, garage workshop equipment or welding rigs.
  • A pool with a large filter pump.

Splitting an electricity load into three phases reduces the load on one phase and allows multiple air conditioners to use their own phase. This can lead to cost savings as this type of motor is more efficient in terms of electricity transmission. However, if one transformer fails, it can lead to a complete shutdown of the entire system with costly repair bills.

Choosing the correct phase for your family’s lifestyle should be quite straightforward as it will be based on the capacity of your electricity use. If you are unsure which phase your require it is always a good idea to consult with your installer.


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