AS/NZS 5033:2021 is the mandatory Australian standard for the installation and safety requirements of photovoltaic (PV) arrays. Every grid-connected solar installation in Australia must comply, and CEC accreditation guidelines directly reference AS/NZS 5033 requirements. Electrical inspectors and DNSPs use the standard to assess installation quality. See Solar Energy in Australia for more.
This guide explains what the standard requires, what changed in the 2021 update, and how the key requirements affect installation practice.
What AS/NZS 5033 Covers
AS/NZS 5033 covers the DC portion of a solar PV installation — from the modules through to the inverter DC terminals. The standard is divided into key sections:
| Section | Coverage |
|---|---|
| System design and documentation | Design requirements, site assessment documentation |
| DC cables and wiring | Cable types, ratings, installation methods |
| Overcurrent protection | String fusing, array fusing, combiner box requirements |
| Arc fault detection | AFCI (Arc Fault Circuit Interrupter) requirements |
| DC disconnection | DC main switch, string isolation requirements |
| Earthing and bonding | Frame earthing, equipotential bonding, earthing conductor sizing |
| Labelling | Warning labels, disconnection point labels, emergency information |
| Commissioning | Tests required before energising |
DC Cable Requirements
Cable types: DC cables must be rated for outdoor UV exposure and for the maximum DC voltage of the system. Suitable cable types include:
- PV-specific cable to IEC 62930 (common TUV-certified “solar cable”) — recommended for string runs
- AS/NZS 5000.1 compliant cable — where suitable for the voltage and UV exposure
Cable sizing: DC cables are sized based on:
- Maximum continuous current (125% of the string short-circuit current for string cables)
- Voltage drop limits (AS/NZS 5033 recommends maximum 3% voltage drop on the DC side)
- Short-circuit current withstand rating
Double insulation: Single-insulated cable must be installed in conduit or otherwise protected from mechanical damage. Double-insulated cable (standard PV cable) can be installed exposed on racking, subject to UV rating and physical protection requirements.
Conduit: Where DC cabling passes through roof spaces, conduits, or anywhere not in open air on the racking, appropriate conduit or cable management must be used.
String Protection (Overcurrent Protection)
String fusing protects against reverse current — current from parallel strings flowing through a faulted string in the opposite direction to normal.
When string fusing is required:
String fusing is required when the maximum reverse current in a faulted string could exceed the string cable rating or the module’s maximum overcurrent protection rating. The practical trigger is typically when three or more strings are connected in parallel to the same MPPT input.
| Number of Parallel Strings | String Fusing Typically Required? |
|---|---|
| 1 string per MPPT | No |
| 2 strings per MPPT | Depends on module Isc and cable rating — check calculation |
| 3+ strings per MPPT | Yes, typically required |
Fuse specifications: DC string fuses must be:
- Rated for DC (not AC) — AC fuses are not suitable for DC circuits due to arc extinction behaviour
- Voltage-rated to at least the string open-circuit voltage (with temperature correction)
- Current-rated at 1.25–2× the string short-circuit current (see CEC guidelines for specific values)
Combiner boxes: Combiner boxes must be IP55 or higher for outdoor installation, rated for the maximum DC voltage and current, and fitted with appropriate DC string fuses.
Arc Fault Detection
AS/NZS 5033:2021 introduced mandatory requirements for arc fault detection — a change from the 2014 standard. Arc faults in DC wiring are a fire risk because DC arcs do not self-extinguish as AC arcs do.
AFCI (Arc Fault Circuit Interrupter) requirement: AFCI devices or inverters with built-in arc fault detection must be installed. Many modern inverters now include arc fault detection as a standard feature — verify the inverter’s AFCI capabilities before specifying for Australian installations.
Where required: The specific trigger conditions for mandatory AFCI are defined in the standard based on system voltage, location, and roof type. AS/NZS 5033:2021 should be consulted directly for the applicable thresholds.
Earthing and Equipotential Bonding
What must be earthed:
- All metal mounting structures and racking rails
- All metal module frames (where accessible — most modern modules with plastic frames may have different requirements)
- Combiner box enclosures
- Inverter enclosures (inverter manufacturer requirements also apply)
Earthing conductor sizing: The earthing conductor must be sized to safely carry the maximum fault current that could flow in the event of an insulation fault. This is typically sized using the protective conductor sizing rules from AS/NZS 3000.
DC system earthing: Modern transformerless inverters use an unearthed (isolated) DC system — the inverter’s ground fault protection monitors for faults. The array frames and structure must still be earthed; only the DC conductors themselves are isolated. If a positive or negative conductor is intentionally earthed (less common now), specific inverter and protection requirements apply.
Labelling Requirements
AS/NZS 5033:2021 requires specific labels at defined locations:
| Label Location | Required Information |
|---|---|
| DC main switch | “Solar Array DC Isolator — Do not operate under load” (or equivalent) |
| Inverter input | Warning: DC voltage and shock hazard |
| Combiner box | Number of strings, voltage, current ratings |
| Emergency shutdown | Location of PV array DC isolator and AC isolator |
| Roof (where array is not visible from ground) | Warning label indicating PV array is present |
| Switchboard | AC isolator labelling for solar circuit |
Labels must be permanent, legible from operating distance, and resistant to UV and weather.
Commissioning Tests
Before the system is energised, commissioning tests must be completed and documented:
| Test | What to Measure | Why |
|---|---|---|
| String open-circuit voltage (Voc) | Measured at each string | Verify modules are connected correctly, identify polarity reversal or damage |
| String polarity | Positive and negative confirmation | Prevent reverse-polarity connection to inverter |
| String short-circuit current (Isc) | Measured at each string (if safe to do so) | Verify module count and shading |
| Insulation resistance | DC conductors to earth | Identify insulation damage before energising |
| Earth continuity | Metal structures to earth | Verify earthing connections |
| Labelling verification | Check all required labels are in place | — |
Commissioning records must be retained in the system file and provided to the DNSP or network authority on request.
Key Change in 2021: Arc Fault Detection
The most significant addition to AS/NZS 5033:2021 compared to the 2014 version is the mandatory arc fault detection requirement. If you are specifying inverters for Australian installations, verify that the inverter includes AS/NZS 5033:2021-compliant arc fault detection. This affects inverter selection and should be confirmed at the design stage.
What AS/NZS 5033 Does NOT Cover
- AC wiring from inverter to switchboard: Covered by AS/NZS 3000 Wiring Rules
- Inverter grid connection settings: Covered by AS 4777.2:2020
- Battery storage installation: Covered by AS/NZS 5139:2019
- Structural requirements for mounting: Generally covered by building standards and installer design responsibility
Generate AS/NZS 5033-Compliant Design Documentation
SurgePV produces string sizing calculations, DC cable sizing, and single-line diagrams that reflect AS/NZS 5033:2021 requirements — giving Australian CEC-accredited installers documentation that supports DNSP applications and electrical inspections.
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Frequently Asked Questions
What does AS/NZS 5033:2021 cover?
The DC side of a solar PV installation — cable sizing, string protection fusing, arc fault detection, earthing, disconnection devices, labelling, and commissioning tests.
What changed in the 2021 version?
The major addition is mandatory arc fault detection (AFCI). Other updates include clarified earthing requirements, updated system voltage provisions (up to 1500 V DC for specific conditions), and additional battery integration requirements.
When is string fusing required?
Typically when 3 or more strings are connected in parallel to the same MPPT input. The exact threshold depends on the module’s short-circuit current and cable rating — check the CEC guidelines and standard calculation method.
What commissioning tests are required?
String Voc, string polarity, insulation resistance, and earth continuity. All measurements must be documented before the system is energised.
Does AS/NZS 5033 cover battery storage?
No. Battery storage installation is covered by AS/NZS 5139:2019. Where solar and battery are co-installed, both standards apply.
