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AS/NZS 5033 Amd2-2018

The Problem: Panels That Stay Live

A solar PV array on a rooftop remains electrically energised as long as daylight reaches the panels — regardless of whether the inverter is off, the main switch is open, or the building is on fire. A string of 14 panels in full sun produces 550 V DC and enough current to sustain a lethal arc. This reality requires specific emergency provisions under the 2018 amendment to AS/NZS 5033.

What Rapid Shutdown Means in Practice

Rapid shutdown is the ability to reduce the DC voltage at the array to a safe level (typically ≤30 V) within a defined time period after initiating shutdown. It protects firefighters working on or near the roof from live DC conductors.

Method

How It Works

Cost

Module-level power electronics (MLPE)

Microinverters or power optimisers shut down at panel level on signal

High — adds per-panel electronics

String-level shutdown relay

Contactor in combiner box opens on signal, de-energising the string

Moderate — contactor + control wiring

Inverter-integrated shutdown

Inverter opens internal DC disconnect on grid loss or manual trigger

Low — if inverter supports it

Emergency Isolation Switch — Mandatory Requirements

Every grid-connected solar installation in Australia must have a lockable AC isolation switch that is:

  • Clearly labelled "Solar PV System Isolation Switch"

  • Located adjacent to the electricity meter or main switchboard

  • Accessible to emergency services without entering the building

  • Red in colour or with a red surround to distinguish it from general load switches

Note: Operating this switch only de-energises the AC side. The DC array cables remain live — this is the communication challenge to fire brigades. Installer must provide a site diagram showing cable routes and array location at the isolation switch.

Engr. Jason Morales — Founder, SolarEnergyPH


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