Regulation 132.16

This article clarifies the requirements of BS 7671 for alterations and additions. It also highlights the importance of carrying out a pre-assessment of the existing electrical installation prior to...

Photo of Paul Collins
Paul Collins | Technical Director

Objective: ES 7671 is written with its main focus on new electrical installation work, and this frequently results in issues when trying to apply its requirements to existing installations such as when, for example, making additions and alterations to an existing installation. 

This article clarifies the requirements of BS 7671 for alterations and additions. It also highlights the importance of carrying out a pre-assessment of the existing electrical installation prior to starting such work. 

Introduction 

Regulation 132.16 contains a requirement that no addition or alteration shall be made to an existing installation unless it has been ascertained that: 

  • the rating and condition of any existing equipment, including that of the distributor, is adequate for the altered circumstances. 

  • the earthing and bonding arrangements of the installation, if necessary for the protective measure applied for the safety of the addition or alteration is adequate. 

This requirement is often interpreted as meaning that in order to carry out an addition or alteration, the existing circuit being modified must be made to conform to all applicable requirements of BS 7671 current at the time that the modification is made. This is not the case. Whilst any defects and non-compliances in the existing installation which may detrimentally affect the safety of the addition or alteration must be remedied are observed during the course of the work concerned with alterations or additions may remain uncorrected but must be recorded on the certification for the addition or alteration under 'Comments on the existing installation'. 

132.16 deconstructed 

The requirement 

Currently, regulation 132.16 states that: 

No addition or alteration, temporary or permanent, shall be made to an existing installation, unless it has been ascertained that the rating and the condition of any existing equipment, including that of the distributor, will be adequate for the altered circumstances. Furthermore, the earthing and bonding arrangements, if necessary for the protective measure applied for the safety of the addition or alteration, shall be adequate. 

Some history 

The UK wiring regulations have additions and alterations for many years. 

For example, the Eighth Edition; Regulations for the Electrical Equipment of Buildings, issued in 1924, contained the requirement, reproduced as Fig 1, calling for it to be ascertained that the existing electrical equipment of the electrical installation was suitable for the additional current demand caused by an alteration or addition. 

Up until the publication of the 17th Edition (BS 7671:2008), the requirements for additions and alterations continued to state specifically that it was necessary to determine that the existing equipment, including that of the distributor, 'which will have to carry any additional load' was adequate for the altered circumstances. Although no longer stated explicitly, the fundamental requirement for sufficient capacity to supply any additional demand safety remains the key issue when an addition or alteration is made to an existing installation. 

The existing installation being added to or altered. 

Any defects or omissions observed in the existing installation that would affect the safety of the addition and alteration; that is, those classified as immediately dangerous (Cl), potentially dangerous (C2) or requiring further investigation (FI) during periodic inspection and testing, must be corrected before a certificate is issued. To obtain this information it is recommended that a pre­ work assessment should be undertaken of those parts of the existing installation on which the addition or alteration is reliant for reasons of safety. In the case of any deficiencies attributed a Cl classification, measures should be taken to remove the immediate danger as soon as is possible. 

Assessing the suitability before starting the work is also highly advisable from a business point of view. If after starting work, for example, it becomes apparent that there is no bonding to an extraneous-conductive-part, when the customer is informed of the need for this additional work, they may disagree and argue that they have already agreed a price for the work. However, if you apply due diligence before starting, and advise on the lack of required bonding, an appropriate price can be agreed and work required can be suitably planned and documented. 

Any other defects and non-­compliances found in the existing installation during the pre-assessment or whilst undertaking the alterations or additions should be recorded on the certification covering the alteration or addition (644.1.2). There is no requirement to carry out remedial work on any such observed deficiencies. 

However, before an addition or alteration is carried out, the adequacy of the following must be determined in respect of any additional current demand resulting from the modifications: 

The current rating of the equipment of the supplier and distributor 

This would require a knowledge of the characteristics of the supply (132.2) and an assessment of the maximum demand, including any additional loading introduced by the modification (311.1). If the existing capacity is found to be insufficient, the distributor should be contacted to upgrade the supply arrangement before the addition or alteration is energised.

Text Box

The Energy Networks Association has published guidance on cut-out ratings for installations where it is intended to install electric vehicle charging equipment or heat pumps, which can be downloaded free of charge at energynetworks.org/ publications/cut-out-rating-guidance­to-electric-vehicles-or-heat-pumps­ installers 

The rating of any existing equipment in the final circuit(s) being modified and any distribution circuits supplying the final circuit(s).
This could include the current rating of distribution boards (536.4.202; 551.7.2), overcurrent protective devices and live conductors (Chapter 43). It could also include the earth fault loop impedance of the circuit(s) where knowledge of this is required for the protective measure(s) employed (643.7.3). 

The earthing arrangements

The adequacy of the main earthing of the existing installation and of the circuit protective conductors of the distribution and final circuits associated with the modification should be established (regulation group 543.1), noting that calculating the minimum cross-sectional area (csa) using the equation given in regulation 543.1.3 will generally result in a smaller acceptable csa than applying the selection criteria described in regulation 543.1.4.

The main protective bonding

It should be noted that any existing main protective bonding conductor does not have to conform to the requirements of the edition of ES 7671 current at the time of the modification in order to be adequate. Its adequacy should be verified in the same manner as would be applied during a periodic inspection; that is, it may be considered to be adequate where the conductor has a csa of not less than 6 mm2, it has been in place for a significant time, it shows no signs of thermal damage/ distress and it is effectively connected at both ends.

Requirements for the alteration or addition 

It is necessary to confirm that the electrical installation work of the addition or alteration complies with any relevant requirements of the current edition of BS 7671 and does not impair the safety of installation (641.5). 

On completion of the addition or alteration, an Electrical Installation Certificate (EIC) must be issued to the person ordering the work (644.l). Where the addition or alteration does not include the addition of one or more new circuits, or the replacement of a distribution board, a "Minor Electrical Installation Works Certificate" (MEIWC) may be issued instead of an EIG (644.4.201). 

Examples 

Best Practice Guide 4 - Electrical installation condition reporting: Classification Codes /01· domestic and similar electrical installations (BPG4) published by Electrical Safety First (ESF) includes a list of inadequacies observed during periodic inspection and testing for which the contributing organisations, including NICEIC, believe improvement is recommended (Code C3). BPG4 advises that this code indicates that whilst an observed inadequacy is not considered to be a source of immediate or potential danger, improvement would contribute to an enhancement of the safety of the electrical installation.

To paraphrase; such improvements are 'nice to have, but not essential for the safety of the electrical installation'. As such, it is not necessary to rectify any deficiency that warranted a:C3 classification code. This would include, for example: 

  • absence of additional protection by RCD for: 

  • AC circuits supplying luminaires in domestic household premises 

  • cables installed at a depth of less than 50 mm from a surface of a wall or partition where required for a particular type of cable installation 

  • absence of an Arc Fault Detection Device (AFDD) in: 

  • a Higher Risk Residential Building (HRRB) 

  • a House in Multiple Occupation (HMO) 

  • purpose-built student accommodation (halls of residence) 

  • care homes 

  • undersized csa of a main protective bonding conductor where the conductor has a csa of not less than 6mm2 and there is no evidence of thermal damage. Note: BPG4 recommends that this non-compliance doesnot require the allocation of any classification code. 

Summary 

Neither regulation 132.16 or regulation 641.5 requires that a circuit being altered or added to, or any other part of the installation which may have a bearing on the safety of any such alteration or addition, must be made fully compliant with the requirements of BS 7671 before an addition or alteration is made. 

Because the addition or alteration is being made to an existing installation, the requirements for periodic verification apply to any assessment of its suitability for modification. If there are no observed instances of damage, deterioration, defects or conditions that warrant being classified as immediately dangerous (Cl), potentially dangerous (C2) or requiring further investigation (FI), the existing installation may be considered to be in a satisfactory condition for continued service and so suitable for modification. 

It is often suggested that regulation 132.16 requires an installation to be fully compliant with the requirements of the current edition of BS 7671 before additions or alterations may be made to it. This misinterpretation can result in unnecessary cost when even the most minor additions or alterations are carried out and, in some cases, this may mean that additions or alterations that might improve the safety of the installation are not carried out. Moreover, such a misinterpretation may also mean that additions and alterations are carried out by persons that are not electrically competent. 

As such, it is likely that this is having a detrimental effect on electrical safety.