18th Edition Updates- RCDs and Definitions

by Editor on September 17, 2017

What’s coming in the 18th Edition?RCDs and new Definitions.

The first update in a series covering some of the proposed changes and additions that are likely to be included in the 18th Edition Regs.


It won’t be such a surprise when you sit the new 18th Edition if you’ve an idea of what’s in the pipeline!

Some significant changes changes will include:

  • New Definitions
  • The increased use of RCDs
  • Supplementary main earthing
  • Special location changes
  • New Part 8 for Energy Efficiency
  • Protection against fire- AFDDs
  • Protection against overvoltage
  • Embedded Heating Cables
  • Restructuring of Inspection and Testing Part 6

New Definitions

In Part 2 the Definitions have been modified – the word “Departure” could now be a definition.
There is mention of phrase “Desk Study”, whatever that means?!

The word “Discrimination” will probably be replaced by “Selectivity”!
So instead of “discriminating” between different devices, we could now be using “selectivity”.

  • The new definition says:  Selectivity is the ability of a protective device to operate in preference to another protective device in series.

Increased use of RCDs

All Sockets

It was always going to come! RCDs to socket outlets. 411.3.3 – Amended Reg:

  • Wherever a socket outlet (up to 32A) is located, it must be protected by an RCD.
  • There will no longer be an option for labelling or carrying out a risk assessment as was previously the case in commercial installations.

RCDs on Domestic Lighting Circuits

411.3.4 – New Reg:

  • All household lighting circuits shall be protected by 30mA RCD.
  • This is probably already the case in many homes due to the 50mm depth Regulation where new split load RCD consumer units have been installed and for special locations. But now RCDs and RCBOs will cover all lighting circuits.

More 18th Edition updates to follow soon!


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