Spearwood Switchboard Upgrade: From Mixed Fuses to RCBO Protection

It started with a call about power circuit breakers that kept tripping.

The cause: overloaded circuits

On site, the cause was overload. Once I opened the board and looked behind the panel, I found three power circuits linked together on each of the three 16A power circuit breakers: nine power circuits sharing three breakers.

The board itself had grown over the years: ceramic fuses, DETA and Merlin Gerin breakers of different ages, and only partial safety-switch coverage.

The client also wanted two new circuits for two split-system air conditioners, which was impossible on the old panel. I suggested an upgrade, and the client accepted.

What I changed

• Replaced the old board with a Clipsal MAX9 enclosure
• Split the nine power circuits so each has its own 16A RCBO
• Put the oven circuit and the hot water booster on their own RCBOs as well
• Left two 16A RCBOs wired up and ready for the two future air conditioners
• Every circuit is protected by its own labelled RCBO, combining circuit-breaker and 30mA safety-switch protection
• Separated the grid and inverter supply main switches, and identified the solar and three-phase circuits

Before. Ceramic fuses alongside DETA and Merlin Gerin breakers of different ages, and only partial RCD coverage. A board that had grown circuit by circuit rather than being designed.

After. A Clipsal MAX9 enclosure, one labelled RCBO per circuit, and the grid, inverter, solar and three-phase supplies each clearly identified.

The earth stake that was not there

I could not locate the original earth stake anywhere around the house. It was as if it had never existed. So I ran a new main earth and installed a new earth stake.

Testing

Before handing over, I tested the earthing, the insulation resistance and the polarity.

The result

Each power circuit now has its own breaker instead of sharing one with two others, every circuit has safety-switch protection, the house has a proper earth, and two RCBOs are already wired and waiting for the air conditioners. About seven hours from start to finish.

Breakers tripping at your place?

Repeated tripping is a sign worth taking seriously, and the cause is not always obvious from the front of the board. For what to check yourself first, see RCD tripped? No power in the house? For background on old fuse boards and modern protection, read the old fuse box guide, or see switchboard upgrades.