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AS/NZS 5033-2014 Amd2-2018
AS/NZS 5033 — The Primary Solar Standard
If there is one standard that every Australian solar installer must know thoroughly, it is AS/NZS 5033: Installation and safety requirements for photovoltaic (PV) arrays. This standard specifically addresses everything from the solar panels to the point where the DC circuit enters the inverter — and a few things beyond.
The current version is AS/NZS 5033-2014 with Amendment 2 (2018), which introduced significant updates including arc fault protection requirements, additional labelling mandates, and updated string sizing rules.
Part 1 — String Sizing and Array Design
Maximum System Voltage — The Critical Limit
The maximum DC system voltage is the most important design limit in a PV array. Exceeding it can destroy the inverter, violate the building standard, and create a lethal arc hazard.
Installation Type | Max System Voltage | Requirement |
|---|---|---|
Residential building (attached to or part of) | 600 V DC | AS/NZS 5033 Cl. 2.2 |
Commercial, industrial, or non-residential | 1000 V DC | Enhanced safety measures required |
Ground-mounted (not part of a building) | 1500 V DC | Additional isolation requirements |
The system voltage is calculated as the Open Circuit Voltage (VOC) corrected for minimum site temperature:
Voc,max = Voc(STC) × Nseries × [1 + β(Tmin - 25)]
Where: β = voltage temperature coefficient (%/°C) • Tmin = lowest expected site temperature (°C)
For Sydney, the design minimum temperature is typically 2°C. For alpine areas or Tasmania, use -5°C to -10°C. A 450W panel with VOC = 37.5V and β = -0.27%/°C in a 14-panel string at 2°C gives: VOC = 37.5 × 14 × [1 + (-0.0027)(2-25)] = 37.5 × 14 × 1.062 = 557 V DC — safely within the 600V residential limit.
String Fusing and Overcurrent Protection
String fusing is required when the number of parallel strings could cause overcurrent through a faulted string cable. AS/NZS 5033 sets the threshold:
No fusing required — when ≤2 strings are paralleled AND the cable is rated ≥ 1.35 × ISC × (n-1) where n is the number of parallel strings
String fusing required — when ≥3 strings are paralleled, or when the cable is not rated for the fault current from parallel strings
String fuses must be DC-rated (AC fuses cannot safely interrupt DC arc faults)
Maximum fuse rating: the lesser of the module's maximum series fuse rating or 1.5 × module ISC
Part 2 — DC Wiring Requirements
Cable Routing and Segregation
DC positive and negative conductors must be routed in the same conduit or cable management system to minimise the loop area (reduces lightning-induced transients)
DC cables must not be routed through fire-rated walls or floors unless in metal conduit with appropriate fire stops
DC cables must be protected from mechanical damage — in conduit, trunking, or cable ties every 300 mm in accessible areas
Where DC cables run inside the building (roof cavity, walls), they must be in conduit or otherwise protected against physical damage and rodent attack
Connectors — MC4 and Compatibility
Only use connectors rated and tested for PV use (IEC 62852)
Mixed connector brands (e.g., one MC4-compatible brand with another) are prohibited — mating connectors must be from the same manufacturer
Connectors must be fully mated (audible click) and not under tensile load
Never disconnect a live, loaded MC4 connector — an arc will form in DC circuits without a fuse or disconnect in series
Part 3 — Isolation and Disconnection
Isolation Point | Requirement | Location |
|---|---|---|
Array DC isolator | Load-break, lockable, rated for max system voltage and ISC × 1.25 | At or near the array — accessible without going onto roof where possible |
Inverter DC disconnect | Required adjacent to the inverter (most inverters have internal DC disconnect) | Within 1 m of inverter |
Array sub-array isolators | Required for arrays >1500 V DC or at installer's discretion | At each sub-array combiner box |
Part 4 — Labelling Requirements
Amendment 2 (2018) significantly expanded the labelling requirements. Every label must be:
Durable, UV-resistant, and permanently attached
Visible without opening enclosures where possible
In English (additional languages permitted)
Label | Location | Content Required |
|---|---|---|
PV Array Warning | All DC junction boxes, combiner boxes | "CAUTION — PV ARRAY — Do not disconnect under load" |
Dual Supply Warning | Main switchboard | "SOLAR PV SYSTEM INSTALLED — Two or more supply sources" |
Rapid Shutdown | Adjacent to solar isolation switch | Solar isolation switch location and operation instructions |
Maximum System Voltage | Array DC isolator | Max VOC at minimum temperature (calculated value) |
Array Configuration | Near inverter | Number of strings, panels per string, rated current |
Engr. Jason Morales — Founder, SolarEnergyPH
