With the 18th Edition of BS 7671 just around the corner, we take a look back at the last amendment to the 17th Edition of BS 7671 and the requirements for using RCDs in non-domestic environments.
The latest amendment to the IET’s Wiring Regulations reinforces the requirement for using residual current devices (RCDs) in non-domestic environments. It will make it harder for designers to omit the use of RCDs from installations, a practice which puts safety at risk, according to one of the electrical industry’s largest manufacturers.
Under Chapter 41 of ‘Amendment 3’ to BS 7671:2008, which came into effect on 1st July 2015, a documented risk assessment must now be undertaken in order for non-domestic socket outlets with a rated current below 20A to be installed, without an RCD to protect it.
Steve Marr, an expert in power distribution at Legrand UK, welcomes the new amendment. “Under the new legislation RCDs will become a much more regular fixture across non-domestic power distribution systems, making the workplace much safer. They can only be omitted if a documented risk assessment determines that RCD protection is not necessary.
“Amendment 3 placed the responsibility for the omission of RCD protection clearly on the installation’s designer. The designer must produce a risk assessment which determines that RCD protection was not necessary and justify their reasoning, possibly in a court of law, if someone is killed or injured as a result of RCD protection being omitted.
“If the risk assessment is performed by someone other than the electrical designer then the electrical installation designer must equally be prepared to justify his or her own decision to accept the finding of the risk assessment and omit the RCD protection to the socket outlet(s) from his or her design.”
Before Amendment 3, RCDs could be omitted if the socket outlet was used ‘under the supervision of skilled or instructed persons’. This ambiguous terminology has in the past been used as a loophole which allowed a number of installations to be carried out without RCDs, despite presenting some risk.
In one such example, RCDs were omitted throughout a school under the assumption that they were to be used ‘under the supervision of a person instructed by the head teacher’. As such, children were put at risk and exposed to socket outlets without residual current protection.
It is likely that the cost of RCDs and the potential for nuisance tripping has led to some organisations exploiting the loophole and omitting the protective devices under the pretence that the socket outlets were sufficiently supervised to pose ‘no risk’.
Steve continues: “Whilst ‘nuisance tripping’ can be a huge inconvenience, it often stems from having too much electrical equipment being supported by one RCD. However, in the vast majority of cases, it should not be necessary to omit RCD protection for a socket outlet.
“Good design should see socket outlets connected to an RCD that serves a sufficiently small number of other sockets or equipment, to ensure that earth leakage is kept within tolerance to avoid unwanted tripping of the RCD.”
Steve concludes: “In short, RCDs are there to save lives. Whilst some RCDs may trip on occasion, the potential consequences for not using them far outweigh the initial one-off cost of including them in an installation. The new amendment removes ambiguity and reinforces the requirement for inclusion of RCD protection. This will undoubtedly make the workplace a safer place.”
Legrand’s Electrak range of underfloor to workstation power and data distribution systems features a number of socket systems, floor boxes and grommets which are available with both built-in and modular RCD protection options.