AS/NZS 3000 · Switchboard

Switchboard layout: RCDs, RCBOs and the circuit schedule

The switchboard is where a floor plan full of power points turns into a finite list of circuits. Getting the board right — enough ways, RCDs arranged as the Wiring Rules require, a schedule that says what each device does — is what makes an installation maintainable ten years later.

Reading time: 9 min·Updated: October 2026·By Planelico

What a switchboard diagram is

A switchboard diagram shows what sits inside the board and what each device feeds. It is a different drawing from the floor plan: the plan says where things are, the board diagram says how they are supplied and protected. A complete set of documents for a home usually has both, plus the circuit schedule that ties them together.

If you only ever produce one of the two, produce the floor plan. But a board diagram is what stops two electricians quoting for two different installations — one assuming two RCDs, the other one RCBO per circuit.

What is inside the board

Main switch

Isolates the whole installation and must be clearly and durably marked so anyone can operate it in an emergency (clause 2.3.3).

RCDs

Each 30 mA RCD protects a group of no more than three circuits in a home (clause 2.6.2.4). A full RCBO board replaces them with one combined device per circuit.

Circuit breakers

One per final subcircuit, rated for its cable and load: typically 20 A for power, 10 A for lighting.

Neutral and earth bars, MEN link

Where conductors terminate. The MEN connection between neutral and earth sits at the main switchboard, in an accessible position.

Labels and schedule

Each device identified against the circuit it protects, and the date of first energisation recorded at the board.

Spare ways

Empty positions left for later — solar, a battery, an EV charger. Worth planning deliberately rather than discovering you have none.

Older switchboards can contain materials, such as asbestos-containing backing panels, that need precautions when the board is replaced. Mention the age of the board when you ask for quotes.

RCDs: three circuits each, at least two

In New Zealand, final subcircuits supplying power points, lighting points and directly connected hand-held equipment in a home need 30 mA RCD protection, installed at the switchboard where the circuit starts (clause 2.6.3.3.1). RCDs must switch both active and neutral and be Type A or better (clause 2.6.2.2.3); an EV charging circuit gets its own Type B RCD (clause 7.9.3).

Clause 2.6.2.4 then decides the layout: no more than three final subcircuits on any one RCD in a home, at least two RCDs as soon as there is more than one circuit, and lighting circuits shared between RCDs. The aim is simple: one trip should never leave the whole house without power or light.

Several RCDs or full RCBO

This is the main decision, and it has real consequences for how the house behaves when something goes wrong.

	RCDs, three circuits each	Full RCBO
Cost of the board	Lower	Higher
Effect of an earth fault	Up to three circuits trip together	Only the faulty circuit trips
Fault-finding	Split the circuits and retest to isolate the cause	The tripped device names the circuit
Fridge or freezer	Shares its RCD with up to two other circuits	Inherently separate
Board size	RCDs take extra modules	One device per circuit
Usual choice for	Limited upgrades on a budget	Rewires, extensions and new builds

How many ways do you need?

Count the final subcircuits your layout actually requires, then add what the board itself consumes and a genuine allowance for the future. A three-bedroom house typically needs two or more lighting circuits, power circuits by area, a kitchen circuit, the cooktop, the oven, the water heater and air conditioning — before anyone mentions an EV charger, solar or a battery. With three circuits per RCD at most, that is four or five RCDs, or one RCBO per circuit.

Spare ways are cheap at installation and expensive afterwards. Adding a circuit to a full board often means a new board — and replacing all its protection brings every circuit up to current RCD requirements.

A reasonable rule of thumb: size the board so that a quarter of its ways are still free the day the installation is certified.

The circuit schedule

The schedule is the list of devices and what each one does. At design stage it records your intent; on completion the electrician confirms it with the installed devices and test results, and keeps it at the board.

A design-stage schedule for the house described above might look like this:

Way	Circuit description	Rating	Cable
1	RCD 1 — 30 mA Type A	40 A	—
2	Lighting — living areas	10 A	1.5 mm² TPS
3	Power — living, dining	20 A	2.5 mm² TPS
4	Cooktop	32 A	6 mm² TPS
5	RCD 2 — 30 mA Type A	40 A	—
6	Lighting — bedrooms	10 A	1.5 mm² TPS
7	Power — bedrooms	20 A	2.5 mm² TPS
8	Kitchen power	20 A	2.5 mm² TPS
9	RCD 3 — 30 mA Type A	40 A	—
10	Oven	20 A	2.5 mm² TPS
11	Water heater	20 A	2.5 mm² TPS
12	Air conditioning	20 A	2.5 mm² TPS
13	EV charger — Type B RCBO, 30 mA	32 A	6 mm² TPS
14	Spare	—	—

An illustration, not a specification. Device ratings and cable sizes have to be calculated for the real installation — its loads, cable routes, grouping and installation methods under AS/NZS 3008.

Generating the board from your floor plan

Working the circuit list out by hand from a plan is tedious and easy to get wrong. Planelico derives it: once the fittings are placed and the rooms are qualified, it proposes the circuit split, the RCD distribution and a modular board layout with spare capacity.

1
Place the fittings on the plan
Power points, lighting points, switches, appliance supplies — everything that will eventually hang off a way in the board.
2
Qualify each room
Telling Planelico that a room is a kitchen, a bathroom or a bedroom is what lets it reason about dedicated circuits and constraints.
3
Let Planelico group the circuits
It groups nearby fittings into final subcircuits, keeps appliances that need their own supply separate, and places at most three circuits behind each 30 mA RCD, with lighting shared between them.
4
Review and adjust
Rename circuits, move a fitting to another circuit, force a dedicated circuit. The generated split is a starting point, not a verdict.
5
Export the board layout and schedule
A modular row layout with spare capacity, plus the circuit schedule, exported alongside the annotated plan in one PDF.

Frequently asked questions

How many circuits can share one RCD?

No more than three in a home, with at least two RCDs as soon as there is more than one circuit, and lighting circuits shared between RCDs (AS/NZS 3000 clause 2.6.2.4).

How many ways should a switchboard have?

Count your final subcircuits, add the RCDs (two modules each in single phase) and the main switch, then leave genuine spare capacity. With three circuits per RCD at most, a typical house quickly needs four or five RCDs, or one RCBO per circuit — size the enclosure for that, with room for solar, a battery or an EV charger.

Is a full RCBO board worth the extra cost?

It usually is on a rewire or a new build. With one RCBO per circuit, a fault takes out that circuit alone, and fault-finding becomes much quicker. On a limited switchboard upgrade, several RCDs with three circuits each can still be a reasonable choice.

Can I replace a switchboard myself?

No. Switchboard work must be done by a licensed electrical worker, and replacing all the circuit protection on a board brings RCD protection for every circuit it supplies (clause 2.6.3.3.4).

Does Planelico produce a certified circuit schedule?

No, and no software should claim to. Planelico produces the design intent — the circuits, their grouping and the proposed switchboard layout — in a form your electrician can review and price. The certified documents are completed on installation, with the test results, by the electrician who certifies the work.

Get the circuit list out of your floor plan

Place your fittings, qualify the rooms, and let Planelico propose the circuits and the switchboard layout.

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