Q&A: New Wiring Rules and switchboards

DaRa Switchboards

Friday, 14 September, 2018


Q&A: New Wiring Rules and switchboards

The six-month transition period for the new Wiring Rules Standard (AS/NZS 3000:2018) ends in January 2019. This article provides answers to questions on key changes related to switchboards.

Q: Can you drill a weep hole in an IP rated electrical enclosure to manage condensation issues?
A: This is not an acceptable method to manage condensation as it destroys the IP rating of the enclosure. Condensation issues are now to be managed by using suitably IP rated breathing/pressure equalisation valves to assist with changes in humidity and drainage of moisture.

Q: Can you install an IP2X electrical equipment/enclosure outside a building?
A: Yes, but only if the enclosure is installed under the eave, specifically within the 30-degree area covered by the eave (image 1). Electrical equipment/enclosures installed in the shaded area must be at least IP33 rated with the exception of meter panels that are rated to IP23.

Q: If you are adding final sub circuits to an existing switchboard do you need to consider upgrading all the sub circuits with RCD protection?
A: No. However, you will have to ensure the compliance to the new edition of the standard if you are carrying out alterations. Refer to clause 2.6.3.2.5 to ensure the additional protection by RCDs is considered.

Q: Can I run the actives from the main switchboard to a distribution board and run the neutral from another distribution board?
 A: No. All conductors of a sub main or a final sub circuit must be connected on one switchboard.

Q: If the installation is supplied with multiple supplies do I need to have main switches for each supply at the main switchboard?
A: You are not required to have main switches for each supply at the main switchboard as long as the main switches for alternative or supplementary supplies are located at any switchboard within the installation, provided these main switches are installed in accordance with AS/NZS 3010 or AS/NZS 4777.1.

Q: Do you need to have the supply conductors of a switchboard rated above 800 amps separated using insulation or barriers?
A: No. An IP2X enclosure with bare busbars is acceptable. Refer to clause 2.5.5.1 (3).

Q: What sub circuits need to be installed with RCDs for domestic and residential installations?
A: Irrespective of the type (lighting, socket outlets, fixed equipment, etc) and load current ratings (10 A, 32 A, 1 phase, 3 phase etc), ALL final sub circuits must be RCD protected.

Q: Do you need to install RCDs for all sub circuits in non-domestic/non-residential installations?
A: No. You are only required to install RCDs for final sub circuits of lighting, socket outlets, direct connected handheld electrical equipment and direct connected electrical equipment that represents an increased risk of electric shock up to and including 32 A. This is up from 20 A, and therefore will have an impact on your switchboard circuit designs, which may not have previously been designed with RCDs. Risk assessment will need to be performed on all fixed equipment to determine if those circuits require RCD protection. In the absence of such an assessment, all fixed equipment must be protected by RCDs. Refer to clause 2.6.3.2.3.3.

Q: What are the changes in the new standard that would impact the switch room, electrical cupboard and switchboard sizing to comply with accessibility and emergency exit requirements?
A: The changes include the following requirements:

  1. The distance from all faces of a closed switchboard must be, as a minimum, 1 metre from all faces of the switchboard. In a domestic installation this can be reduced to 0.6 metres. Therefore, even if the switchboard is constructed using lift off type doors, the switch room walls must be, as a minimum, 1 metre from all faces of the switchboard to comply with this requirement.
  2. Unimpeded space of at least 0.6 metres around the switchboards with switchboard doors in any position and switchgear fully racked out position.
  3. Where switchboards are located opposite each other, the clearance of 0.6 metres must be measured with all doors in the open position.
  4. If the nominal capacity of the switchboard is more than 800 A (ie, a high current switchboard) and/or the length of the switchboard is more than 3 metres, the switch room must have 2 exits spaced well apart. You may have only 1 exit if there is at least 3 metres of clear space from the switchboard (door open and equipment racked out).
  5. Doors of enclosures dedicated to switchboards that open into a passage or narrow access way must be capable of being secured in the open position to prevent workers being inadvertently pushed towards the switchboard.
  6. Openings or doorways must be at least 0.9 metres wide by 2.2 metres high.

Q: Do I need to de-rate the cables that go inside the ceilings, walls and under floors?

A: Yes. You need to consider that the cables are completely surrounded by insulation (if the length is more than 400 mm) and de-rate the cables as per AS/NZS 3008.1.
Wiring systems in domestic installations must be installed on the assumption that thermal insulation in ceilings, walls and under floors, if not currently installed, will be installed in the future. This may lead to using the next cable size up for lighting and power circuits.

Q: Where do we need to use arc fault detection (AFDDs) devices?
A: These devices are used to detect arc faults in sub circuit wiring and not in switchboards. It is recommended to use AFDDs in premises with sleeping accommodation, premises that store materials which pose a fire risk and locations where combustible construction material is stored. Use of AFDDs is not mandatory; however, the use of such devices is considered good practice.

Q: Can you install a solar inverter within 3 metres of a pool?
A: No. Equipment related to a generating system, including engine driven generator sets, standalone power systems, grid connected inverter systems and battery systems must be installed further than 3 metres from baths, showers and other fixed containers.

Q: What is the new switchboard standard?
A: The AS/NZS 61439 series published in 2016 is the new switchboard standard. The old standard, AS/NZS 3439 series, is still valid until 2021. AS/NZS 3000:2018 now provides appendix K which references the new switchboard standard.

Q: As per the new switchboard standards do you need to verify the short circuit withstand strength of every switchboard?
A: No. Verification of the short circuit strength is only required for switchboard assemblies that exceed the short circuit current of 10 kA rms or 17 kA peak.

Q: What are the routine verifications a switchboard manufacturer should undertake as per the new switchboard standard?
A: Verification will comprise the following categories. Refer to clauses 11.2 to 11.8 of AS/NZS 61439.1:2016 for more details:

  1. Degree of protection of enclosures.
  2. Clearances and creepage distances.
  3. Protection against electric shock and integrity of protective circuits.
  4. Incorporation of built-in components.
  5. Internal electrical circuits and connections.
  6. Terminals for external conductors.
  7. Mechanical operation.
  8. Performance (see clauses 11.9 and 11.10 of AS/NZS 61439.1:2016).
  9. Dielectric properties, wiring, operational performance and function.

Please refer to the new publication to learn about the other changes. You could also get advice from organisations such as Master Electricians, NECA and NESMA if you are a member. It may be worth becoming a member of such organisations to get up-to-date information and assistance to navigate through the transition period and achieve compliance to the new edition of wiring rules. Your trusted electrical inspector could also guide you through the changes and compliance. The new standard can be purchased through SAI Global https://infostore.saiglobal.com/en-au/Standards/ASNZS-3000-2018-1974289/.

Image credit: ©iStockphoto.com/Minerva Studio

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