Wiring Rules 2018: Part 2, Section 5
Earthing has a crucial but often overlooked role in what makes an electrical installation very safe or extremely dangerous.
A close reading of Section 5, ‘Earthing arrangements and earthing conductors should, hopefully, dispel any misconceptions.
People see a main earth connection or an earth bonding cable connected to a pool fence or on a conductive building without any further protection and it is assumed to be somewhat benign. After all, it can (almost always) be touched without consequence.
Even in the industry some electricians don’t isolate before disconnecting an earth conductor or when temporarily separating two conductors where remaking a connection. In most cases they get away with it, but that is only because everything in the installation is sound.
However, if there is an unknown fault in the installation, disconnecting an earth conductor can be just as dangerous as disconnecting a neutral when the circuit active is energised and there is a load (no matter how small) on the circuit.
Correct earthing is paramount to ensure that circuit protection operates properly and quickly. It is crucial for the safety of an installation and the people using it – and that makes this section as important as all the others.
Also, although most installations are still connected to an MEN system connected grid, there are many instances in which alternative earthing systems are required. Think of certain mine sites, remote installations, stand-alone grids, micro-grids and other settings. Hence there is more information on these alternative earthing systems.
Changes listed in the ‘preface’ include:
- MEN system clarification and accessibility of connections;
- updated SELV and PELV requirements;
- expanded and clarified equipotential bonding for showers, bathrooms pools and spas;
- earthing of conductive materials in outbuildings;
- earthing for switchboard enclosures with unprotected consumer mains;
- earthing of conductive reinforcing in outbuildings with showers or baths; and
- earthing connection point and bonding of conductive pool structures and fittings within arm’s reach, with figures included.
Substantial changes from the 2007 edition in Part 2 Section 5 in page order include:
- A reworking of figures. (p269-270)
- Additional Note 5 under ‘other earthing systems’ to recognise additional installation systems, with other notes renumbered from (a) to (d) to 1 to 4. (p271)
- Sentence added under ‘MEN’, ‘general’, ‘exceptions’ after the note for the MEN or ME connection to be in an accessible position for disconnection and testing. (P281)
- Minor changes to Table 5.2 clarifying stainless and steel clad – with stainless steel being equally complying, and qualifying that the 20mm steel pipe must have a minimum 3mm wall thickness. (p283)
- Redrafted colour diagram is provided showing all the different earthing configurations that can be used. (Users should remember that earthing conductors should be installed such that the earth connection to various remaining earthing conductor connections is not accidentally disconnected if one earthing connection point is disconnected. (p292)
- New terms are introduced under ‘particular methods of earthing’, ‘outbuildings’, for ‘individual outbuildings’ and ‘combined outbuildings’ to clarify that individual outbuildings can have an MEN instead of an earth from the source of supply and likewise for combined outbuildings. But in the combined outbuildings only one incoming supply can have an MEN connection and all the others must have their earth conductors from that MEN connection. This has also required splitting the original (a) into (a) and (b) with considerable change in test and the original (b) becoming (c). Figures 5.4 and 5.5 have been added to explain. (p293-295)
- Under ‘unprotected consumer mains’ figures 5.6 (A), (B) and (C) are added. Also (but not shown *) a second sentence and note are added immediately under the heading with further detail here and with references to the figures throughout. The original notes are now also headed ‘exception’ but the intent of these has not changed. (p296-300)
- Under ‘arrangement’, ‘general’ note (f) is changed from general access floors requiring additional bonding to grid-connected inverters now requiring bonding. There is no other change. (p304)
- Requirement for bonding under ‘showers and bathrooms’ for combined outbuildings is further detailed in two new paragraphs. The ending of Note 3 has is changed to ‘sufficient’ from the previous ‘satisfactory where bonding is required at more than one location’. Note 4 is modified to clarify that this is not a requirement in existing buildings, and also with more emphasis placed on doing it wherever practicable. (p307)
- Order of headings under ‘swimming pools and spas’ is substantially changed and considerably modified. Due to this, all cross references have been rehomed. A new figure 5.9 ‘examples of bonding arrangements’ has been added. The new order of headings is:
- ‘Bonding arrangement’; the wording in (a) and (c) has been changed but (a) and (d) remain as before. There are no changes in intent. The new figure 5.9 is also referenced.
- ‘Conductive pool structures’: two new paragraphs and an exception are added to further clarify the requirements and Note 2 is changed to reflect other changes.
- ‘Pool equipotential conductor connection point’: is changed from ‘equipotential conductor connection point’ and the opening paragraph substantially reworded, with minor changes also to (a) and (c).
- ‘Electrical equipment’, no change apart from an example added under (b). (p309)
- ‘Conductive fixtures and fittings’: the opening paragraph is considerably expanded to reflect the changes under the ‘swimming pools and spas’ heading, previous (a) and (b) are deleted and or incorporated in new paragraphs 1 and 2, and new exceptions 1 and 2. (p309-310)