Frequently Asked Questions on RCDs

What is an RCD and how does it work?
Why two RCDs?
Is an RCD the same as a circuit breaker?
How do I tell the difference between an RCD and a circuit breaker?
Why does my house not have RCDs?
Where are the RCDs fitted?
What if I want to buy a house and no RCDs are fitted?
What if the property I own, or want to buy, only has one RCD? Is that enough?
If I buy a house with RCDs fitted, how can I tell if they meet the regulations?
If RCDs are fitted, how can I check if they are operating correctly?
Who can install RCDs and how much will it cost?
RCDs must be installed to meet the AS/NZS 3000:2007, Wiring Rules – what does this mean?
With respect to the recent legislation to retrofit RCDs into tenanted properties and at point of sale for residential properties, if I install RCDs, I will also have to rewire light and power circuits in the installation so the RCDs will not ‘nuisance trip’. This will be very expensive for the home owner. Can these types of installations be exempt from the legislation?
If I install RCDs, do I have to submit a Notice of Completion for the work?
With respect to the recent legislation to retrofit RCDs into tenanted properties and at point of sale for residential properties, do I need two RCDs for house services?
If I am asked to verify that an installation has a minimum of two RCDs, do I have to submit a Notice of Completion for this checking work?
Do RCDs have to be fitted to park homes where the owner owns the building but not the land (which is subject to a lease)?
Do RCDs need to be fitted in caravan parks?
Are RCDs required to be fitted to a caravan?

1. What is an RCD and how does it work?

An RCD is a safety device that monitors electrical current flowing within a circuit from the meter box or distribution board. It works on the principle that the electricity current flowing in must be equal to the current flowing out of the circuit.

If the RCD detects an imbalance in the electrical current, indicating a leakage to earth, e.g. current flows through someone’s body to earth, the RCD immediately cuts the electricity supply to prevent electrocution.

RCDs are extremely sensitive, disconnecting within 10 to 50 milliseconds of detecting a leakage current. This is usually set at 30 milliamps for homes but may be less in other situations, such as hospitals.

2. Why two RCDs?

The household circuits need to be divided evenly between a minimum of two RCDs to ensure some light and power remains if one operates. Two RCDs also reduce the possibility of tripping due to some appliances which have low levels of earth leakage.

3. Is an RCD the same as a circuit breaker?

No. Many homes already have circuit breakers installed. However, circuit breakers only protect against overloading and short circuits. They do not prevent electrocution.

4. How do I tell the difference between an RCD and a circuit breaker?

An RCD looks like a circuit breaker but also has a test button. The attached photograph shows two circuit breakers compared with an RCD (note the test button).
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Combined RCD/circuit breaker are available also. These devices provide protection from overload, short circuit and electrocution. They also have a test button.

5. Why does my house not have RCDs?

Since 2000, it has been compulsory for all new homes to have a minimum of two RCDs fitted to protect the power and lighting circuits as part of the initial electrical installation.

However, homes built before 2000 were not required to have two RCDs fitted.

Also from 1992 to 1999 only one RCD was fitted to protect some of the power points and not the lighting circuits.

6. Where are the RCDs fitted?

RCDs are required to be fitted at the origin of the power and lighting circuits which will be at the main meter box or distribution board for the residence.

7. What if I want to buy a house and no RCDs are fitted?

From 9 August 2009, a minimum of two RCDs must be installed in every residential property before it can be sold. If you are considering buying a property, check the main meter box of the home for the RCDs before you sign the offer and acceptance form. RCDs can be identified by the test button (See picture).

If there are no RCDs, you should include a condition in the real estate agent’s Offer and Acceptance Form that the property must have a minimum of two RCDs installed to protect all power point and lighting final subcircuits to comply with AS/NZS 3000:2007, Wiring Rules. The settlement agent should then ensure that this condition is met before the sale takes place.

Properties built after 2000 should already have a minimum of two RCDs fitted.

8. What if the property I own, or want to buy, only has one RCD? Is that enough?

No. A second RCD must be installed and the power point and lighting circuits divided between the two RCDs. If you own the property, contact a licensed electrical contractor to arrange for a second RCD to be installed. If you are the purchaser you need to include the installation of a second RCD as a condition in the Offer and Acceptance Form.

9. If I buy a house with RCDs fitted, how can I tell if they meet the regulations?

A licensed electrical contractor is the best person to advise if your RCDs meet the regulations.

However, you can do a simple check to determine if your residence is protected in accordance with the new legislation as follows:

Plug a small lamp into a power point and make sure it works. Leave it turned on.
Make sure that electricity is connected to the property and the main switch is in the on position. The lamp should be on.
Turn off all electronic equipment (computers and televisions) etc
Push the test button on each RCD. Do not hold your finger on the test button. The RCD should operate (turn off). If it does not operate, it must be checked by an electrical contractor.
After pushing the test button and the RCDs have turned off check that the small lamp is now off. Also check that all the lights and power points do not operate. To do this, plug the small lamp into all the power points and turn the power point on. If the lamp turns on a licensed electrical contractor must be engaged to correct the wiring.
When finished testing, turn the RCDs back on and check that the lamp works when plugged into a power point.

10. If RCDs are fitted, how can I check if they are operating correctly?

All RCDs are manufactured with a test button. Homeowners and tenants should press the test button every three months.

Pushing the test button simulates an earth leakage fault and indicates whether or not the device is operating correctly. Electrical clocks and timing devices may have to be reset after the test button has been pushed and the RCD turned back on.

11. Who can install RCDs and how much will it cost?

Any licensed electrical contractor can supply and fit RCDs. As a guide, it should cost no more than $500 to supply and fit two single-phase RCDs in an average-sized 4×2 home. Ask a licensed electrical contractor for a no-obligation price quotation.

12. RCDs must be installed to meet the AS/NZS 3000:2007, Wiring Rules – what does this mean?

AS/NZS 3000:2007, Wiring Rules is the minimum safety standard that all electrical installing work must meet in Australia and New Zealand. All licensed electrical contractors will have a copy of this standard and are familiar with its requirements.

13. With respect to the recent legislation to retrofit RCDs into tenanted properties and at point of sale for residential properties, if I install RCDs, I will also have to rewire light and power circuits in the installation so the RCDs will not ‘nuisance trip’. This will be very expensive for the home owner. Can these types of installations be exempt from the legislation?

No. If the circuit wiring is in such a state of deterioration, it should be replaced anyway. Cost is not a valid reason to compromise electrical safety.

14. If I install RCDs, do I have to submit a Notice of Completion for the work?

Yes, if the RCD is fitted to protect more than one final sub-circuit. Also, the electrical contractor must prepare an Electrical Safety Certificate for this work. The certificate must be delivered to the person for whom the work was carried out.

15. With respect to the recent legislation to retrofit RCDs into tenanted properties and at point of sale for residential properties, do I need two RCDs for house services?

No. House services power and light circuits need only be protected by one RCD. Similarly, in a residence with a shed, power and light circuits for the shed need only be protected by one RCD. The actual residence requires a minimum of two RCDs to protect the power and light circuits.

16. If I am asked to verify that an installation has a minimum of two RCDs, do I have to submit a Notice of Completion for this checking work?

No. If you are merely confirming that the installation has a minimum of two RCDs, you need only deliver an Electrical Safety Certificate for this checking. Sample wording for this checking work is along the lines of “Inspected installation. Confirmed two RCDs are installed to protect all socket outlets and lighting final sub circuits in accordance with AS/NZS 3000:2007 Wiring Rules”.

17. Do RCDs have to be fitted to Park Homes where the owner owns the building but not the land (which is subject to a lease)?

The owner only needs to fit two RCDs if the building is sold or rented. Most of these cabins are supplied by a flexible cord and inlet socket. In this case, one RCD is acceptable in a cabin supplied by one inlet socket. At least two would be required if there are two or more inlet sockets.

18. Do RCDs need to be fitted in Caravan Parks?

Caravan parks are classed as residential premises, so they fall under the new RCD laws. The onsite permanently wired cabins require two RCDs when they are sold, leased or rented. An exemption can be issued for one RCD where the cabin does not have a meter box or the meter box does not have sufficient space to install two RCDs.

All the lighting and socket outlet circuits in the caravan park (with sites that are sold, rented or leased) must be protected by RCDs as the caravan park is a residential premises. Clearly only one RCD is necessary to protect an individual socket outlet supplying a caravan.

19. Are RCDs required to be fitted to a Caravan?

Caravans require RCDs if sold, rented or leased. One RCD is acceptable in a caravan supplied by one inlet socket. At least two would be required if there are two or more inlet sockets.