Within older domestic installations that complied with earlier versions of the Wiring Regulations the main bonding and supplementary bonding should be in place. However, within a new installation due to the introduction of RCDs and new Wiring Regulations it is now possible to omit both main and supplementary bonding in a new installation.
Omission of Main and Supplementary Bonding
As per regulation 411.3.1.2 BS7671:2018 a main protective bonding conductor shall be connected to any extraneous-conductive part as previously described. However, any metallic pipes entering the building that have an insulating section at their point of entry (ie plastic) need not be connected to the main protective bonding.
The omission of supplementary bonding in bathrooms has been possible even before the introduction of the 18th Edition and providing that your bathroom complies with requirements of regulation 701.415.2 and all (points iv, v and vi) have been met.
(iv) If required, all main protective bonding is in place
(v) All final circuits are protected by a 30mA RCD
(vi) All extraneous-conductive parts within the location are effectively connected to the protective equipotential bonding.
Re point (vi) – This can be checked by measuring the resistance between any exposed-conductive parts and any extraneous-conductive parts and the maximum permitted value for this resistance if using RCDs is 1667 ohms (see regulation 415.2.2).
“For more information please visit our 18th Edition online course at the-Regs.co.uk and also our online Domestic Installer Training at partPtrained.co.uk“