AS/NZS 5033:2021 – The Importance in PV Installations

The AS/NZS 5033:2021 standard is comprehensive safety and installation guidelines for photovoltaic (PV) array electrical systems. As the solar energy industry continues to grow, this is very important. Published in November 2021, the updated standard introduces significant changes aimed at enhancing consumer safety and streamlining system design and installation practices. Here’s a detailed overview of the key updates and requirements.

Key Changes in AS/NZS 5033:2021

Transition and Acceptance
AS/NZS 5033:2021 was published on November 19, 2021. Installers had a grace period of six months to switch from the standard of 2014 where they were allowed to completely comply with either the standard of 2014 or 2021. From 20 May 2022, the standard AS/NZS 5033:2021 was in effect. It should also be pointed out that you cannot do a mix and match. It has to comply to either one of the standards on system design and installation.
Voltage Limits
The domestic PV installations have increased their maximum voltage from 600V d.c. to 1000V d.c. The voltage level has aligned with international standards. Due to regulatory stipulations in AS/NZS 4777.1:2016, the 600V limit remains in place for houses and apartments that are domestic dwellings until the standard is revised. Commercial and industrial PV systems can now operate at 1500V d.c., which makes the use of larger systems possible, but temperature corrections for maximum voltage still need to be considered with a multiplication factor from Table 4.1 of the standard.
String Current and Array Calculations
AS/NZS 5033:2021 introduces new formulas for the maximum string and array currents, which are ISTRING MAX and IARRAY, respectively. These calculations are important for proper equipment ratings and ensuring system safety:
  • Calculate the maximum string current using the formula:
    ISTRING MAX = 1.25 × KI × ISC MOD
    Where KI is typically 1 unless bifacial modules are used, and ISC MOD is the module’s short circuit current.
  • Verify the inverter’s backfeed current (IBF TOTAL) and compare it to the string current. Most SMA inverters will have zero backfeed current.
  • Determine the maximum array current:
    IARRAY = SA × ISTRING MAX
    Where SA is the number of strings in the array.
  • Verify that the maximum array current is lower than the rated short circuit current of the inverter.
String Protection and Fusing
String fuses sizing technique is further improved. Previous methods included sizing the lower and upper limit of the string fuses at 1.5 and 2.4 times the module short circuit current. The above can now be summarized:
In must be at least 1.2 × ISTRING MAX, yet at most equal to or not exceeding the maximum overcurrent protection rating for that module (IMOD MAX OCPR).
The design principle is the same but may be represented differently in the new standard. In that regard, designers should ensure that the fuse selection will comply with the updated parameters, especially in cases involving bifacial modules or d.c. conditioning units (DCUs).
Cable Installation Requirements
The updated standard emphasizes stricter guidelines for cable installations, especially in ceiling spaces:
  • Cables should be secured and should not be mounted less than 0.6 meters of the ceiling surface unless the cables are secured to the roof structure.
  • Cable placement is also restricted by other factors including a 50mm clearance from roofing material and certain clearances near external walls or disconnection points.
  • Signage is applicable when cables are installed within an accessible roof or floor space, which shall indicate warnings and labels as applicable to the standard.
Disconnection of Rooftop DC Isolators
The most eagerly awaited deletions in AS/NZS 5033:2021 is the Mandatory Rooftop DC isolators. Rooftop isolators have been among the biggest causes of hazards. It has been reported widely that fire issues are frequent occurrences with these isolators. Removing them, however brings along new requirements:
  • Installers need to comply with new recommendations regarding disconnection points, cable routing, and system isolation.
  • Systems with microinverters, two or fewer strings in parallel, or particular configurations with string fusing will have unique demands for isolators and disconnection devices.
Limited Access for Ground-Mounted Arrays
The standard includes a requirement for limited access to ground mounted PV arrays, regardless of voltage. All ground mounting systems, including small domestic installations, must have, for example, fencing when the PV modules are lower than 2.5 meters from the ground.
Optimisers and Voltage Calculations
AS/NZS 5033:2021 includes a provision to include DCUs, such as optimisers, in system design. When determining maximum string voltages, DCU maximum output voltages are accounted for. For inverter types, such as SolarEdge, further allowances are afforded with compliance to IEC 62548, which describes the regulation of inverter controlled voltage.
Exclusions and Special Applications
As photovoltaic arrays in a vehicle, transportable structures, and boats fall under an exclusion of AS/NZS 5033:2021; this is instead complied to through AS/NZS 3001 or AS/NZS 3004. Large PV systems over 240 kW are required to meet all provisions of the standard, doing away with any previous provision for engineering-based variations.

AS/NZS 5033:2021 is a comprehensive update aimed at improving safety and future-proofing PV installations. Although it may cause some adjustments in design and installation practices, it is necessary to keep up with international standards and consumer safety. Installers and designers must familiarize themselves with these changes to remain compliant and leverage the full benefits of the new standard. Always consult with your state regulator and stay updated on any amendments or additional guidance. The standard can be purchased from Standards Australia, SAI Global, or Techstreet.

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