Heating your home with reverse cycle air conditioning

How a reverse cycle system heats

A reverse cycle air conditioner does not make heat. It moves heat that is already in the outside air into your home, using the same refrigeration process as your fridge, run the other way. A reversing valve switches the flow of refrigerant, so one direction heats and the other cools. The same machine is also called a heat pump.

There is heat energy in the outside air even on a cold winter morning, and moving it indoors takes far less electricity than making heat. An electric heater turns one unit of electricity into one unit of heat. A reverse cycle air conditioner delivers roughly three units of heat for each unit of electricity. Inverter models, which vary the compressor speed rather than switching on and off, are more efficient again.

How it compares with electric and gas heaters

A plug-in electric heater turns one unit of electricity into one unit of heat and warms only the spot it sits in. A reverse cycle air conditioner delivers roughly three units of heat for the same electricity and warms a whole room, or the whole house on a ducted system. Many households that heated with gas now heat with reverse cycle instead. What you save depends on your tariff and how you run it.

On safety, gas heating burns fuel, so it carries a combustion risk and a carbon monoxide risk. Portable electric heaters are a common cause of household fires in winter. The outer shell gets hot and dust inside the unit can start a fire. A reverse cycle system has no flame, produces no combustion gases and is fixed in place rather than sitting on the floor.

Winter set points and zoning

Set the thermostat to 18 to 20 degrees in winter and check the room after 30 minutes before you nudge it. The Department of Resources, Energy and Tourism's Good Energy Practice Guides put every extra degree above that range at up to 10 per cent more on the heating part of your bill.

Heat the rooms you are using and not the rest. On a ducted system, switch off the zones for empty rooms, for example living areas by day and bedrooms at night. On a split system, close the doors to the rest of the house. A multi-split gives each room its own control.

Keep windows and doors closed while it runs, and use the timer so it is off when nobody is home. Open curtains by day, close them at night, and seal draughts.

Keep the filters clean

A clogged filter makes the fan work harder to pull air through, and the system gives less heat for more electricity. Clean or replace the filters every month or two while the system is in regular use, and more often with pets or dust. As a rough guide, swapping a clogged filter for a clean one can save 5 to 15 per cent of the system's energy use.

The coils and fins need a professional, so have the system serviced once a year, which also picks up mould, rust and grime. Outside, keep leaves and shrubs at least half a metre clear of the outdoor unit. Your quote from an accredited member states the recommended servicing frequency, and what a service should include has its own guide.

When to replace an old system

Air conditioners age like any other machine and eventually need replacing. An older system can use many times the power of a new one for the same heating and cooling, so a unit that still runs is not always worth keeping. Check the Energy Rating Label on the old system. More stars means higher efficiency. A new system also brings a fresh manufacturer's warranty and modern controls.

Have the replacement sized by an approved calculation, not a rule of thumb. A unit that is too big for the space works harder and costs more to run. Every accredited member must work out the capacity your home needs that way and put it in the written quote. The six things a quote must include are on The ACDA Standard page.

If a new installation is not right

Tell the member first and give them the chance to fix it. An equipment fault is a manufacturer's warranty matter, and your member can help you lodge the claim.

If the installation itself may fall short of the ACDA Standards, complete the Dispute Resolution Form: your details, the member's details, what was installed and when, and what the problem is. Attach your quote, your invoice and any photographs. Send it to the Dispute Resolution Committee at PO Box 253, Emu Plains NSW 2750, or [email protected]. ACDA then engages a Chartered Engineer to investigate and arranges for defects to be corrected.

The Guarantee is a written workmanship guarantee on new domestic installations by an accredited member, on contracts up to $25,000 including GST, with independent Chartered Engineer review. It is not an equipment warranty or a price guarantee, and it sits alongside your rights under Australian Consumer Law. ACDA is an industry association, not a regulator. The full process is on The ACDA Standard page.

Before winter

• Set the thermostat to 18 to 20 degrees and check the room after 30 minutes.
• Close doors to rooms you are not heating and switch off empty zones.
• Clean or replace the filters, then every month or two while in use.
• Point the louvres towards the floor.
• Clear leaves and shrubs half a metre from the outdoor unit.
• Book a service if it has not had one in the past year.
• Put the portable heaters away.

An accredited member sizes a replacement by an approved calculation and quotes it in writing. The written workmanship Guarantee covers new domestic installations by a member on contracts up to $25,000 including GST.