Residual current devices (RCDs)
Whether you’re buying or building a new home, safety is one of the highest priorities. While there are many areas to consider in this regard, power is one of the most important, due to the potential electrical hazards that can occur if electricity running through the property has any problems.
A residual current device – better known as an RCD – is the solution. This article aims to explain what RCDs are, how they work, their importance, testing procedures, and the different types available.
What are RCDs and how do they work?
RCD is the acronym for Residual Current Devices – however, most people will likely know them as safety switches. They work by monitoring the flow of current through electrical wires to ensure that the current is equal in the neutral and active wires.
When the flow of electricity runs to the ground in an unintended way, this is known as an Earth leakage. A residual current device provides essential safety protection against electric shocks and fires caused by events such as a short circuit. While they are commonly found on switchboards, you can buy a portable RCD for certain situations.
Electrical installations can deteriorate with age and use. For this reason, they should be inspected and tested periodically relative to their use and environment to verify compliance with the pertinent laws.
An RCD consistently checks the electric current flowing through the circuits it is set to. If it detects an abnormality in the electrical path – such as when a person has touched a live part – the RCD will turn the circuit off in order to significantly reduce the risk of harm.
RCDs are designed so that these switches turn the power off almost instantly. This also provides electrical safety when an RCD is protecting a power tool since the operator is much less likely to receive a fatal electric shock if the tool, cord, or socket happens to get wet.
RCDs are installed at the meter box and distribution board of your home. These are the main sources of electricity that supply a building’s power and lighting. Some older homes may only have one RCD monitoring the primary electrical power supply, however, two RCDs are now required.
Why are RCDs important?
Under Australian law, all new homes built are now required to be fitted with a minimum of two residual current devices protecting the final sub-circuits to socket outlets and lighting circuits. There are some variances in the laws covering RCDs from state to state hence people looking to sell, buy or rent a property should seek the advice of a local authority.
Failure to adhere to these safety switch requirements can result in significant penalties if the land title is transferred to another party. It is good practice for property managers and real estate agents to inform potential vendors that RCDs must be installed before the transfer of ownership of the property.
Even considering the legal requirements of installing residual current devices, they’re still a critical element of any property. Of twenty-nine deaths in Western Australia over seventeen years, before the RCD laws went into effect, twenty-three could have been prevented if the building in question had been fitted with residual current devices.
An RCD should be removed and replaced as soon as an inspection or test identifies that an RCD fails to comply with the standards. The property owner – or another party in charge of site safety – is responsible for the decision of taking disposal, removal, or other corrective actions.
An electrician cannot force a building owner or tenant to replace an RCD, but they cannot keep such an RCD in service. In this situation, circuits can be doubled up in switchboards to temporarily bypass the RCD while keeping the power running to all circuits.
As with any safety features of a property, every residual current device needs to be tested. It is recommended that these be tested quarterly (every three months). RCDs have a ‘test’ button on the front of the device that you can press and release to perform a test. The test will only check to see if an electrical supply is connected to the RCD.
If you are a person with the management of a workplace, you must make sure that RCDs used at work are tested regularly by a competent person to make sure they are working effectively. Records of RCD tests need to be kept on record until the device is next tested or disposed of.
The Department of Mines, Industry Regulation and Safety provided the following steps in doing the proper testing of RCDs:
Plug a small lamp into a power outlet and make sure it works. Be sure to leave it turned on.
- Make sure that electricity is connected to your property and that the main switch is in the “on” position. The lamp should still be on.
- Turn off all electronic equipment within the property including computers and televisions.
- Push the test button on each RCD, but make sure not to hold your finger on the test button. The RCD should operate correctly and turn off. If it does not, it must be checked by an electrical contractor.
- After pushing the test button and the RCDs have turned off, check that the small lamp you turned on is now off. Also, check that all the lights and power points aren’t operational. To do this, plug the small lamp into every power socket and turn them on. If the lamp turns on, a licensed electrical contractor must be engaged to correct the possible wiring fault.
- When finished testing, turn the RCDs back on and check that the lamp works when plugged into a power point.
When testing an RCD at a work office, it is recommended to carry this out after hours before the office opens, or you will need to advise your staff that the power will be disrupted for each circuit and that their computers will need to be turned off.
A tested RCD can help put your mind at ease when it comes to the safety of your workers. RCD testing – when performed by a qualified electrician – can ensure that your RCDs are fault-free and can be relied upon to function when needed.
It is important to note that having RCD’s fitted in a home does not provide 100% protection from electrocution. As with anything else in your home, exercising care and common sense when dealing with electrics is the best way to keep yourself as safe as possible. Switch off the power when handling electrical wiring and use a pipe and wire detector before drilling holes in walls.
If you are ever unsure, talking to an experienced electrician can provide you with safety information to keep you and others safe.
What types of RCDs are available?
RCDs come in many different shapes and sizes that have different levels of functionality. You may need to seek technical advice from a competent industry professional about the kinds of RCDs that are right for your home.
There are four major types of RCDs: Meter Box Mounted RCDs, Combination RCD and circuit breakers, Portable RCDs, and PowerPoint RCDs.
Meter box mounted RCDs
The law requires that RCDs be fitted to the home’s power circuits. You can often find this type of RCD located alongside circuit breakers. You need two of these to ensure light remains if one of your RCDs operates.
Combination RCD and circuit breakers
These devices combine RCDs and circuit breakers. They protect your home’s appliances and electrical circuits. They also prevent electrocution. These are a good option when you need to do retro-fitting and there is little space available.
Portable RCDs are found attached directly to a power board. These types of RCDs are convenient, however, it should be considered that they can only provide protection to appliances directly connected to them. However, they are perfect for people using power tools that are not protected by the meter box or power point RCDs.
Power point RCDs
These devices are fitted to your home’s first power point right after the meter box. They are perfect for protecting electrical appliances in specific areas of your home.
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