The Complete Guide to Switchboards

What a switchboard does

A switchboard receives incoming supply, protects it and distributes it to the final circuits of an installation. It carries the main switch, the protective devices (RCBOs, MCBs, RCDs), the busbar arrangement and — on a main switchboard — the metering pre-wire that links to the network's meter. Everything from a domestic consumer unit to an industrial main switchboard is a variation on this job.

EVO Electric fabricates and supplies switchboards from our Sydney factory to the trade. We do not install — this guide is written to help electricians, contractors and builders specify and order boards that arrive ready to terminate.

Main switchboards versus distribution boards

The two terms get used loosely, but they do different jobs in an installation.

On a small residential job the main switchboard and distribution board are often one enclosure. On commercial and industrial sites they are separate assemblies linked by submains.

Single phase versus three phase

The phase configuration is the single biggest fork in a switchboard specification. Single phase suits most homes; three phase spreads heavy loads across three supply phases and is triggered by high-demand equipment.

• —Single phase — standard domestic and light commercial; one active, one neutral.
• —Three phase — three actives and a neutral; needed for ducted air conditioning, EV chargers, pool heat pumps, workshops and larger commercial loads.
• —Moving to three phase changes the main switch, the service protection (MPD instead of SPD) and the metering pre-wire to a polyphase meter.

Once maximum demand approaches the limit of a single-phase service, a three-phase board future-proofs the installation and spreads load evenly across the phases.

Pre-wired boards save site time

A pre-wired switchboard arrives with the main switch, RCBOs, service protection, neutral links, sub-board and metering pre-wire already assembled and tested. It turns a day of board building into a mount-and-terminate job, and it removes the most common causes of inspection defects before the board leaves the factory.

• —Factory assembly and testing under controlled conditions.
• —Consistent labelling and layout across a project's boards.
• —Fewer site defects — no missing links, mislabelled circuits or crowded terminations.
• —Ideal for volume housing where every board is near-identical.

Enclosure materials and IP ratings

Like meter boxes, switchboard enclosures are specified for their environment. The material sets the corrosion life and the IP rating sets the ingress protection.

Compliance: AS/NZS 61439

The AS/NZS 61439 series is the standard for low-voltage switchgear and controlgear assemblies. It replaced the old 3439 series and sets design verification, temperature-rise, short-circuit and clearance requirements for the assembly as built — not just its individual components. The assembly manufacturer verifies the design; the installer verifies the installation.

• —Confirm the fault rating suits the supply.
• —Check segregation matches the tenancy and metering layout.
• —Verify labels match the circuit schedule.
• —Ensure sealing provisions are in place for the network sections.

Buying from a fabricator who builds to 61439-aligned construction keeps the compliance chain intact when the certifier asks — and gives you a local contact who can answer a temperature-rise or segregation query directly.

Labelling and documentation

A compliant switchboard is only as good as its labelling. Every protective device, main switch and submain should be clearly and durably labelled to match the circuit schedule, and the board should carry the manufacturer's rating information. Poor labelling is a frequent defect and a genuine safety issue during fault-finding.

How to order a custom switchboard

Custom boards are specified from a schedule and a layout. The clearer the brief, the fewer revisions and the faster the build. A good custom switchboard enquiry includes the following.

• —Supply details — single or three phase, service capacity, fault level.
• —Main switch and protective device schedule with ratings.
• —Metering requirements — direct-connect or CT metering, number of meters.
• —Enclosure size, material, IP rating and mounting method.
• —Segregation, tenancy split and any sub-board requirements.
• —Delivery date and whether staged delivery suits the program.

Because EVO fabricates locally in Sydney, spec changes mid-project are a phone call and a few days rather than a container and a month. Request a quote with your board schedule and we will build and test it before dispatch.

Frequently Asked Questions