Blog Details
The ten (10) most frequently asked questions on AS/NZS3000:2018 Wiring Rules

Question #10

When performing minor work on a switchboard e.g. replacing a circuit breaker with an RCBO, is it a requirement to bring the whole of the switchboard up to the new standard?

Answer:

No, the only requirements are:

  • New circuit added to a switchboard are required to fitted with an RCD in domestic and as required in non-domestic/non-residential installations.
  • All the circuit protection devices are replaced on a switchboard then all the circuits required to be RCD protected shall be RCD protected.
  • When the whole of the switchboard is replaced, then all the circuits required to be RCD protected shall be RCD protected.
  • Please refer to clause 2.6.3.2.5 and 2.6.3.2.5 (b) of AS/NZS 3000:2018 (Wiring Rules)

 

Question #9

When carrying out repairs to a switchboard is it deemed that we (the electrician) have then taken “ownership” of this board as we are the last electricians to work on the switchboard, leaving us with the obligation to bring the switchboard up to the current AS/NZS3000:2018 standard?

Answer:

No, 1.9.3.2 Repairs

Repairs to existing electrical installations or parts thereof may be affected using methods, fixtures and fittings that were acceptable when that part of the electrical installation was originally installed or with methods, fixtures and fittings currently available as direct replacement, provided that the methods satisfy the fundamental safety principles of Part 1 of this Standard.

Appendix I of AS/NZS 3000:2018 provides guidance on the ratings of overload protective devices where alterations or repairs involve the use of existing imperial conductors.

 

Question #8

When carrying out alterations to a switchboard, where a 20-amp MCB was installed on a 2.5mm2 power circuit, a 16-amp MCB installed on a 1.5mm2 or a 10-amp on 1mm2 lighting circuit, where there is very limited or no information on how the cabling has been previously installed. Are we OK to replace these with the same rating RCBO?

Answer:

Yes, ensure you state “repair of circuit protection device by installation of an RCBO of equivalent size in the same location” on your Certificate of Electrical Safety.

 

Question #7

Clause 2.6.3.2.3 3 (d) requires an RCD to be fitted to the final sub circuit if the is an increased risk of electric shock. When determining what an increased risk of electric shock is, what guidelines do I use?

Answer:

When determining what type of electrical equipment or appliance that is permanently connected to supply will cause an increased risk to the user, the following steps are recommended:

 

  1. only final sub circuits up to and including 32 A are required to be protected with additional protection of an RCD.
  2. is the electrical equipment deemed to be class1 (exposed conductive parts – steel housing etc) then install an RCD on the final sub circuit.
  3. are there any external influences that can contribute to an increased risk of electric shock, such as;
  • in an area where mechanical damage may occur – mechanical workshop where cars are stored or repaired.
  • Outside, exposed to the elements where water, rain, vegetation, animals, condensation excessive temperature may have a negative effect on the electrical equipment.
  • Internal/external, exposed to excessive dust build up, water, corrosive fumes, steam or oil in the immediate vicinity or even subject to excessive vibration under the normal conditions of use.

If yes to any of the above, then install an RCD on the final sub circuit.

  1. does the type of electrical installation provide the increased risk of electric shock, is it a:
  • mechanical workshop
  • Engine repair centre
  • Steel fabrication workshop
  • Manufacturing production line
  • Brewery
  • Butcher shop
  • etc

If yes to any of the above, then install an RCD on the final sub circuit.

  1. are any particular industrial activities performed that may cause an increased risk of  an electric shock, such as:
  • Drilling
  • Welding
  • Steel cutting
  • Steel fabrication

If yes to any of the above, then install an RCD on the final sub circuit.

 

Question # 6

Do I need to provide the 1m clearance from the end of the open door of the switchboard?

Answer:

No, clearance from the end of a switchboard doors in non-domestic and non-residential is are as per clause 2.10.2.2 where an unimpeded space is required of at least 0.6 m around switchboards with switchgear doors in any position and with switchgear in a fully racked-out position.

Exception for domestic switchboards

In a domestic electrical installation this distance may be reduced to 0.6 m from the face of the switchboard.

 

Question number # 5

Do I need to provide an RCD on a car hoist in a mechanical workshop?

 

Answer:

Yes, an RCD is required on the final subcircuit as the steel hoist with the motor attached is deemed to represent an increased risk of electric shock to the user. This applies to a final subcircuit supplying the hoist up to and including 32 Amps.

 

Question number # 4

Do I need to provide an RCD on a Hot water unit or a stove in a domestic installation?

Answer:

Yes, an RCD is required on all final subcircuits in a domestic installation, there is no limit on amperage of the protection device (In) and no exceptions.

 

Question number # 3

Are 10ma RCD’s required on all final subcircuits within a kindergarten, day-care centre or a school up to and including year 8?

Answer:

No, this is a “New Zealand” only requirement and does not apply in Australia. Suggestion mark (highlight) any hard copies of the Wiring Rules that are in your possession to indicate the NZ only clauses.

 

Question number # 2

When installing an RCD on a final subcircuit for a 3-phase load that does not have a requirement for a neutral what type of RCD do I need to install?

Answer:

RCD’s come in several different types as well as different pole configurations. There is no such thing as a 3 phase RCD, they are either single pole, two pole three pole or four pole.

The RCD uses a core balance principle of operation and providing all poles of the RCD have the same current flow in normal conditions of operation and when a fault occurs an out of balance is detected greater than the required trip current the RCD will operate perfectly without a neutral conductor.

With reference to the Type of RCD being either Type1, Type two etc, guidance is given in clause 2.6.2.2 of the Wiring Rules (AS/NZS 3000:2018)

 

Question number # 1

In the situation where I need to install an RCD on a final subcircuit that supplies a storage hot water unit with a boost element what type of RCD do I need to install?

Answer:

As the hot water unit is a resistive load, there is no requirement for other than a type 2 RCD. Refer clause 2.6.2.2 of the Wiring Rules (AS/NZS 3000:2018)

A hot water unit with a boost element only has one element at a time energised, either off peak or boost element. The final subcircuit supplying the hot water unit is users the common neutral principle, therefore if a RCBO is used the poles are to be linked ( clause 2.2.1.3 (b) – Wiring Rules)

The number of poles required is three. There is no such thing as a 3 phase RCD, they are either single pole, two pole three pole or four pole.

The RCD uses a core balance principle of operation and providing all poles of the RCD have the same current flow in normal conditions of operation and when a fault occurs an out of balance is detected greater than the required trip current the RCD will operate perfectly.

In this case only one active and the neutral is used at any onetime with the other active having zero current thus the RCD operates as required.

Information relating to Wiring Rules can be found in TKB, or email technical@neca.asn.au for further info.

Source: Roy Sands, Technical Manager, NECA Victoria, 05/03/19

 

 

2 comments to this Blog

Ray, 12:37 PM. Tuesday 2019 10th September

Please go to https://www.facebook.com/pg/electricianXchange.com.au/posts/ to see responses back to this

Anonymous, 9:20 PM. Monday 2019 9th September

Question number 1 in regards to booster element on hot water system and using an rcd. It specifies a 3 pole rcd. I’m yet to find one manufactured that’s rated for 20A. They also specify linking the poles. Are they wanting a loop off the booster supply or off the off peak supply as the bottom element does not need the booster supply as it will just continue to reheat 24/7 with the off peak rendering useless. \nStill just trying to get my head around how they physically see it being wired or if I’m just thinking too deep into it?

Leave a reply

I want to post anonymously.
Would you like to be notified of new comments to this Blog Thread?
Yes, email me as new comments are added