An isolator switch is a manual switch that disconnects an appliance or circuit from the power supply so it can be shut down or worked on safely. It has no automatic trip, so unlike a circuit breaker it never turns itself off. In Australian homes you find them beside air conditioners, ovens, hot water systems, pool pumps and solar inverters.
Most people notice theirs for the first time when the air conditioning stops working and they spot a grey box with a turning handle on the wall next to the outdoor unit.
What does an isolator switch do?
It cuts the power at the appliance itself, so nobody has to walk back to the switchboard to make the equipment safe. A technician servicing an outdoor air conditioning unit needs to know the power cannot be switched back on at the board while their hands are inside it. Many isolators can be padlocked in the off position for exactly that reason.
The Wiring Rules, AS/NZS 3000, require a means of isolation for fixed equipment such as air conditioning. For an outdoor condenser that normally means an isolator mounted on the wall or a stand right beside the unit, where it can be seen and reached by whoever is working on it.
Is an isolator switch the same as a circuit breaker?
No. A circuit breaker turns off automatically when it detects too much current, while an isolator only turns off when someone turns it. They do different jobs, and an appliance with an isolator still has its own breaker back at the switchboard.
| Feature | Isolator switch | Circuit breaker |
|---|---|---|
| Turns off by itself | Never | Yes, on an overload or short circuit |
| Protects the cable | No | Yes |
| Main job | Safe manual disconnection | Protection against too much current |
| Usual location | At the appliance, or as the main switch | In the switchboard |
| Can be locked off | Often | Only with an add-on lock clip |
A safety switch, or RCD, is a third device again. It trips when current leaks to earth, which is what protects people from electric shock. The main switch on many older Sydney boards is a plain isolator, but on some it is actually an RCD, which is why a main switch that keeps dropping out is worth a closer look. We cover how to tell them apart in why the main switch trips but the breakers stay on.
Where will you find isolator switches in a home?
Anywhere a hard-wired appliance needs to be shut off on the spot. In a typical Sydney house, the common locations are:
- Air conditioner outdoor unit. A rotary isolator on the wall or a stand beside the condenser. Ducted systems often have another one near the indoor unit in the roof space.
- Electric oven and cooktop. A wall switch near the kitchen, sometimes tucked inside an adjacent cupboard.
- Electric hot water system. Beside the tank, or as a labelled switch at the switchboard.
- Pool and spa equipment. A weatherproof isolator near the pump and heater.
- Solar inverter. AC and DC isolators beside the inverter, and on older systems another one on the roof.
- The switchboard. The main switch is itself an isolator for the whole house.
What are the different types of isolator switch?
Most isolators fitted outside homes are rotary, double pole and weatherproof.
- Rotary. Operated by a turning handle marked ON and OFF, or I and O. This is the usual style on air conditioners.
- Double pole. Breaks both the active and the neutral conductors, where a single pole switch breaks the active only. Appliances on three-phase power use three or four pole isolators.
- Weatherproof. Built for outdoor mounting with an IP rating, commonly IP56 or IP66. Our guide to outdoor power points explains what those ratings mean.
- DC isolator. Made for the direct current that comes off solar panels. DC is harder to switch off cleanly than AC, so a DC isolator is a different product and the two are not interchangeable.
Isolators also carry a current rating. It must be at least as high as the circuit it isolates, so the electrician matches it to the breaker and the appliance rather than picking a standard size.
Isolator cracked, scorched or not working?
DM Electrical replaces failed isolators on air conditioners, ovens, hot water and pool equipment, and checks the wiring behind them for heat or water damage. Based in Brookvale, Level 1 and Level 2 ASP accredited, working across the Northern Beaches and wider Sydney.
Why do air conditioner isolator switches fail?
An outdoor isolator sits in sun and rain all year, and once its cover cracks or a seal perishes, moisture gets inside and corrodes the contacts. On the Northern Beaches and other coastal suburbs, salt air speeds this up. A corroded contact heats up under load, and over time it can burn the switch and the cable ends inside it.
Signs your aircon isolator needs attention:
- The air conditioner will not start, even though its breaker at the switchboard is on.
- A breaker or safety switch trips when it rains, or after the unit has been running for a while.
- The housing is cracked, faded, chalky or brittle.
- The handle feels loose, or turns without a firm click.
- There are scorch marks, melted plastic, a burning smell or a buzzing sound.
If you see scorching or smell burning, do not touch the isolator. Turn the air conditioning off at the switchboard and call an electrician. Our emergency electrician team attends burnt fittings 24/7. Replacing an isolator is a small job, but in NSW it is licensed electrical work, and the cable behind it needs checking too.
Should you turn off the aircon isolator over winter?
You can, but check the manual first, because many split and ducted systems want the power back on for several hours before they start again. A lot of outdoor units have a small heater that keeps the compressor oil warm while the system sits idle. After a long shutdown, restoring power well before you switch the system on gives that heater time to work. The standby power saved is small, so plenty of people leave it on.
Whatever you decide, always turn the unit off with its remote or wall controller first, then turn the isolator. Switching an isolator while the compressor is running wears the contacts faster.
What about solar isolator switches?
A solar system has DC isolators that disconnect the panels from the inverter, and problems with them are a job for a solar specialist. Many older Australian systems have a DC isolator on the roof beside the panels as well as one next to the inverter. Rooftop isolators have a history of water getting in and overheating, and current installation standards generally no longer require one on the roof.
Solar panels produce power whenever there is daylight, so the DC side of the system stays live even with the main switch off. If an isolator on the roof or beside the inverter is discoloured, cracked or showing a fault, contact your solar installer. For the AC side of the system and the switchboard it connects to, our switchboard upgrade page explains what a modern board includes.
Frequently asked questions
Can an isolator switch trip?
No. A plain isolator has no trip mechanism, so it only changes position when someone turns it. If an appliance has lost power and its isolator is still on, check the circuit breaker and safety switch at the switchboard.
Can I replace an isolator switch myself?
No. In NSW, replacing an isolator is electrical wiring work that must be done by a licensed electrician, who will also check the cable and connections for heat or water damage.
Is it safe to use an isolator switch to turn off my air conditioner?
Yes, as long as you turn the unit off with its remote or controller first. Switching the isolator while the compressor is running puts unnecessary wear on the contacts.
Why is there an isolator switch next to my oven?
A hard-wired oven or cooktop needs a way to be disconnected locally, so the isolating switch lets you or a technician cut power to it without going to the switchboard.
The bottom line
An isolator switch is a simple manual off switch that makes an appliance safe to service, and it never trips on its own. The ones outside on air conditioners wear out first, especially near the coast. If yours is cracked, scorched or the appliance has stopped working with the breaker still on, get in touch and we will check it and the wiring behind it.