Should Every Circuit in My Home Have Its Own RCBO?

For many modern homes, giving each final subcircuit its own RCBO is an excellent way to improve protection and fault isolation. It does not mean every part of the electrical system should automatically use the same device, or that an existing switchboard should be converted without first assessing the wiring.

The aim is to give each circuit the correct protection for what it supplies.

What does an RCBO do?

An RCBO combines two forms of protection in one device.

The circuit-breaker component protects the circuit wiring against overloads and short circuits. The RCD component detects certain types of current leakage and provides additional protection against electric shock.

When each final circuit has its own RCBO, that protection is contained within the individual circuit. If a fault develops, the affected circuit is more likely to disconnect without unnecessarily turning off other parts of the home.

Why individual RCBOs can be valuable

Older switchboards commonly have one RCD protecting several separate circuit-breakers. This arrangement can still provide RCD protection when it has been correctly designed, installed and tested. WorkSafe guidance recognises that one RCD may protect multiple final subcircuits within the limits established by the wiring rules. WorkSafe’s electrical guidance explains this relationship.

The practical disadvantage is that a problem on one circuit can disconnect every circuit sharing that RCD.

For example, a fault involving an outdoor socket might also turn off unrelated lighting, kitchen sockets or appliances. When circuits have individual RCBOs, the disruption is generally limited to the circuit with the problem.

Individual RCBOs can also make fault-finding clearer. Instead of investigating several circuits connected to one RCD, the electrician has a much better indication of where the issue is located.

Shared protection can contribute to nuisance tripping

Most modern electrical equipment produces a small amount of normal leakage current. When several circuits share one RCD, those small amounts can accumulate.

No individual appliance may have a serious problem, but their combined leakage can bring the shared RCD closer to its operating point. That can contribute to intermittent or nuisance tripping, particularly as more electronic equipment is added to the home.

Individual RCBOs separate that leakage between circuits. This can improve reliability and prevent one group of appliances from affecting another.

Not every circuit has identical requirements

Installing the same RCBO on every circuit without considering what each circuit supplies is not good switchboard design.

The device must be selected to suit the cable, circuit rating, connected equipment and type of residual current that may be present. Equipment such as EV chargers, solar systems, batteries, induction cooking and variable-speed appliances can have specific protection requirements.

EV charging is a good example. Current WorkSafe guidance requires protection that is compatible with the charging equipment and the types of leakage current it may produce. WorkSafe’s 2026 EV charging addendum sets out these particular considerations.

Main switches, submains and specialised equipment also need to be considered differently from ordinary final circuits. The objective is correct and coordinated protection, not simply a row of matching devices.

The existing wiring needs to be tested first

Many Dunedin homes have electrical systems that have been altered gradually over several decades. Circuit descriptions may be unclear, neutrals may be shared between circuits, and the condition of the wiring can vary throughout the home.

Modern RCBO protection can expose an existing wiring issue that an older fuse or circuit-breaker did not detect. If a new RCBO trips after installation, it does not necessarily mean the new device is faulty. It may be identifying leakage, an incorrect neutral arrangement or another condition that needs attention.

That is why circuit testing and verification should come before deciding on the final switchboard layout.

Does an older home have to be converted?

An older switchboard is not automatically unsafe or unlawful simply because every circuit does not have an individual RCBO. Existing installations need to be considered in the context of their age, condition, previous alterations and current use.

New circuits and alterations need to meet the requirements that apply to the work being completed. Maintenance and replacement of existing installations can be treated differently under the Electricity (Safety) Regulations 2010.

The better question is whether the existing protection remains suitable for the home today and for any changes being planned.

Remember to leave room for what comes next

Individual RCBOs can make a switchboard safer, clearer and easier to manage, but the board must also have enough physical capacity for future circuits and equipment.

Space may be needed for surge protection, EV charging, solar, battery storage, heating, load management or a future renovation. Replacing old equipment while leaving the new board crowded can create another limitation later.

A Power Integrity Review™ can assess the home’s Capacity, Protection, Distribution, Condition and Future Ready position before the switchboard design is decided.

The takeaway

Individual RCBO protection across final circuits is usually a strong choice for a modern residential switchboard. It improves fault isolation, reduces the number of circuits affected by one problem and creates a clearer electrical foundation.

However, “one RCBO for every circuit” should not be treated as a blanket specification. The right result comes from testing the existing wiring, understanding each circuit and selecting protection that suits the equipment it supplies.

Safer circuits. More room for what comes next.