Solar installation standard - how the recent changes affect you

The AS/NZS 5033:2014 - Installation and Safety Requirements for Photovoltaic (PV) Arrays standard has just been updated and the changes came into effect on 6 February 2015. This article details the key updates and explains how they affect installers.

The latest update includes several positive changes and clarifications but, compared with the 2012 release, the changes are minimal. Standard updates like these are a necessary hurdle for an industry that is constantly growing in size and experience, and encounters an ever-broadening range of products. Global Sustainable Energy Solutions (GSES), with its extensive experience in PV training, design and inspections, is regularly involved in discussions over practical methods that installers can use to implement the latest standards and guidelines. This article describes the key changes to the standard. Please note that not all changes are included here, so GSES recommends that installers read the standard for themselves to ensure they are aware of all current requirements. 

Heavy-duty conduit within buildings

When the previous version of the AS/NZS 5033 standard was released in 2012, one of the key changes that shocked the industry was the requirement to use heavy-duty (HD) conduit to protect all DC wiring in a building. This requirement was introduced with an aim to reduce the risk of short circuit by providing additional mechanical protection.

The latest version of the standard has reduced the scope of this requirement, providing a more practical method of achieving the desired protection. The areas requiring HD conduit are now limited to those that are not clearly visible, specifically, ceiling spaces, wall cavities and under floors. In other areas of a building, cabling is more visible and therefore there is a lower risk of damage. Nonetheless, DC PV cables within a building, but not within these cavities, need to be protected with medium-duty (MD) conduit. While fewer areas will now require HD conduit, the change may not have a significant impact on PV installations in the domestic market. Cabling is often run within cavities in order to hide ‘ugly’ conduit - this leaves only a short length at the inverter that can be in MD conduit. To avoid changing between different types of conduit, such as MD, HD and UV-resistant conduit, some installers choose to use UV-resistant HD conduit at all times (Figure 1). Although using only UV-resistant HD conduit increases the cost of materials, it increases the durability of the system and may reduce the installation time. The revised HD conduit requirements will have a significant impact when PV systems are installed on sheds and commercial buildings, where cavities are not used to run DC cabling. In these installations, it is now possible for the installation to be completed without HD conduit. In addition, non-domestic buildings are permitted to be exempt from using HD conduit where the installation method otherwise achieves the objective of minimising short-circuit risk. An example of this may be the use of cable trays. However, it will be difficult to demonstrate adequate protection - so, a safer alternative would be to adhere to the same requirements as domestic installations.

For more information, see AS/NZS 5033:2014 4.3.6.3.2.

Figure 1: UV-resistant HD conduit - a good option for achieving compliant conduit throughout the PV installation.

Bonding cabling requirements

Since the release of AS/NZS 5033:2012, earth cables for bonding the array have been required to be 4 mm². This led to installers running 4 mm² earthing cables, independently, all the way from the array to the main switchboard. However, the 2014 release of AS/NZS 5033 has brought to light that the 4 mm² requirement was to ensure mechanical durability of the earth cable at the array and therefore the 4 mm² minimum is not necessary at the AC side of the inverter. It further specifies that the earthing cable from the array frame can be connected to the AC earth conductor at the inverter. However, in doing so, installers need to ensure that the earthing system will not be interrupted if the inverter is removed and that the cable is of sufficient size according to the system rating and type.

For more information, see AS/NZS 5033:2014 4.4.2.2.

AC and DC segregations clearly defined

Although AS 3000:2007 covers segregation of circuits, it does not directly refer to segregation of AC and DC. With AS/NZS 5033:2014, additional requirements have been introduced, specifically for AC and DC segregation. It is not only clear that AC and DC need to be segregated, but insulation barriers have also been clearly specified as the means of segregation. Insulation barriers between AC and DC must be equivalent to double insulation and IP4X. The only exception to this is when cabling is outside enclosures, where 50 mm separation can be used. Within 50 mm, an insulation barrier will be required.

A simple way to abide by these requirements is to install AC and DC in separate enclosures and separate conduit (Figure 2). Installing AC and DC in the same enclosure, with a compliant insulation barrier, is difficult to achieve. The IP4X rating requires the barrier to prevent penetration of objects with a 1 mm diameter or greater. In addition to this, AC and DC switchgear cannot share the same mounting rail, unless it is constructed from a non-conductive material. It will be difficult for barriers installed within enclosures to follow these requirements, unless purpose-made, compliant enclosures are used.

For more information, see AS/NZS 5033:2014 4.4.4.3.

Figure 2: AC and DC installed in separate conduit and enclosures. This is the most effective way to achieve compliant insulation barriers between AC and DC circuits.

Restricted access

Another significant addition to AS/NZS 5033 in 2012 was the voltage rating for domestic systems limited to 600 V and restricted access for non-domestic systems greater than 600 V. In many instances, this has resulted in installation of large cages around the inverter, isolators and cable runs (Figure 3). However, the 2014 version of the standard provides clarification that reduces the need for installing these cages. It now states that, if HD conduit is used on all accessible cabling, up to and including the inverter terminals, and the DC isolators and protection devices are in enclosures - only accessible with a tool - then there is no need for additional barriers. This will save installers a lot of work, especially if they are already using HD conduit and installing isolators within enclosures with lockable flaps. However, if a lockable room is used for providing restricted access then these precautions are not necessary.

For more information, see AS/NZS 5033:2014 1.4.61 and 3.1.

Figure 3: Cage installed by Solar Powered Homes to achieve restricted access. Cages like this may no longer be necessary.

Matching parallel strings

In addition to matching modules connected to the same maximum power point tracker (MPPT), AS/NZS 5033:2014 now requires that strings connected in parallel have a maximum variance in open circuit voltage of 5%. Although this may seem minor, not adhering to this can result in circulating currents between strings, even when the system is isolated. This could lead to a potential hazard if the circuit is disconnected without adequate protection (such as a load-breaking DC isolator). A difference in voltage between strings with similar modules can be caused by the variance in manufacturing tolerance, where power ratings of each module can vary up to ±3%. Modules deteriorating over time can then compound the difference. Therefore, installers upgrading old systems with new parallel strings need to pay particular attention to this requirement.

For more information, see AS/NZS 5033:2014 2.1.6.

DC-conditioning units and microinverters

As previously stated, one of the key drivers of updates to the standard is the introduction of new products to the industry. In line with this, AS/NZS 5033:2014 has included specific requirements for DC-conditioning units (also known as power optimisers) and microinverters (Figure 4). However, please note that power limits and installation methods have been set for these product-specific requirements, so it is important that they are read carefully before using these products.

For more information, see AS/NZS 5033:2014 2.1.5 and 4.3.12.

Figure 4: Left: Enphase microinverter. Right: SolarEdge power optimiser (a DC-conditioning unit). These types of products are now covered by AS/NZS 5033:2014.

One of the main benefits of these new products is that individual modules can be orientated in different directions, owing to the ability of these products to track the maximum power point (MPP) of each module independently. The previous standard only considered the scenario of a string of modules connected to a single MPPT and therefore did not allow for the flexibility of these new products. With AS/NZS 5033:2014, systems that incorporate devices that track the MPP of each module, such as DC-conditioning units and microinverters, are exempt from the requirement for all modules in a string to be in the same orientation within ±5°. This is particularly useful for installing on roofs with small areas facing different directions.

For more information, see AS/NZS 5033:2014 2.1.6.

Another point the previous version of AS/NZS 5033 did not address was whether a load-breaking DC isolator was required between DC-conditioning units and the inverter. AS/NZS 5033:2014 now specifies that load-breaking DC isolators are required as normal; however, the isolator’s rating may be matched to the inverter’s maximum input ratings, as long as the DC-conditioning units will not exceed these ratings under normal and first fault conditions. As for microinverter systems, the previous standard already specified that load-breaking DC isolators are not required, but in AS/NZS 5033:2014 certain criteria must now be met by the microinverters for this to apply.

For more information, see AS/NZS 5033:2014 2.1.5 and 4.3.12.

As DC-conditioning units and microinverters have unique electrical characteristics, it has been unclear how they should affect the labelling and signage displayed. However, AS/NZS 5033:2014 has now specified labelling requirements that are appropriate for these products. For DC-conditioning units, the voltage and current displayed on the fire emergency information signs are to be equal to the maximum input ratings of the inverter, consistent with sizing the load-breaking DC isolator. For microinverter systems, displaying these ratings is generally not necessary as the voltage is usually the same as for other AC electrical systems (240 VAC). To allow for this, AS/NZS 5033:2014 has specified a fire emergency information sign for microinverters that does not include system ratings. Furthermore, as microinverters have a simple shutdown procedure, the method of isolating the system has also been incorporated into the fire emergency information sign and therefore a separate sign for the system shutdown procedure is not necessary.

For more information, see AS/NZS 5033:2014 5.4.1.

Signage

Uncertainty around fire emergency information signs has not been limited to DC-conditioning units and microinverter systems. Even for standard PV systems, the conditions used for calculating the displayed system ratings have varied. To remove inconsistency, AS/NZS 5033:2014 specifically states that the displayed values shall represent the PV array maximum voltage (at minimum temperature) and the short-circuit current at standard test conditions (STC) (provided by the module manufacturer). This means that measurements taken during commissioning are not to be displayed on these signs. It also further specifies that, where multiple arrays are installed, the voltage shall be the highest value present and the current shall be the sum of all array currents. These clarifications will help to provide consistency in the industry and more reliable information for emergency workers.

Another requirement introduced in 2012 was the warning regarding DC isolators not de-energising the PV array and array cabling. GSES has observed many PV systems installed since this update that have not included this warning, sometimes owing to the installer not being aware of the requirement or using up old-stock labelling kits. In AS/NZS 5033:2014, shutdown procedures have now been given their own clause and the required warning needs to be black writing on a yellow background. An example shutdown procedure has also been displayed in the standard. These changes to the standard may assist in the uptake of this requirement, including the new colouring. Installers need to ensure that the labelling kits they use are updated to meet AS/NZS 5033:2014.

Although installing the correct labelling and signage is important, where they are displayed is also vital. AS/NZS 5033:2014 has included several adjustments to the labelling and signage requirements that help ensure they are installed in practical and visible locations. For example, the labelling of conduit has been simplified from being required at each end and each change in direction, to being required at every 2 metres, consistent with the cabling labels. Furthermore, the labelling needs to be visible. This means that, if conduit is fixed to a wall, the solar labelling needs to be facing out. Installers should review AS/NZS 5033:2014 5 Marking and Documentation, to confirm they are installing labels in appropriate locations.

For more information, see AS/NZS 5033:2014 5.

Keeping on top of changes

To assist PV installers in keeping on top of changes in the industry, like these necessary standards updates, the Clean Energy Council has put in place a continuous professional development (CPD) program. GSES also provides professional development days at locations around Australia, which give installers the opportunity to achieve the annual requirement of 100 CPD points in a single day. Topics covered in recent GSES professional development days include commissioning, maintenance and fault finding; responding to solar tenders: technical content; and PV module power conditioning and control devices.

*Dan Atkins has worked with GSES as a Project Engineer and Photovoltaics (PV) Systems Inspections Manager since 2011. He has completed a Bachelor of Engineering in Renewable Energy at the University of New South Wales. As Inspections Manager, Dan is responsible for the oversight of PV installation audits around Australia, including technical review of inspection outcomes and the management and training of PV inspectors. He has invaluable experience in assessing Australian PV standards and has provided technical consultancy services to regulatory authorities.