A helpful and crisp guide to install a new electrical consumer unit in your property

There exist list of factors for which you may have to replace your existing electrical consumer unit or CU. An existing unit may not comply with the BS 7671 requirements (an example that is relevant here includes absence of RCD protection). The existing consumer unit may also have no spare capacity to add further circuits. You could even be recommended to upgrade and replace the existing unit after a periodic inspection. So what are the basic considerations to replace an existing consumer unit especially the domestic ones? Let us try exploring the answer in the following sections.


Few things to consider and the potential pitfalls

Right from the beginning it is important to keep the clients aware of the developments. From an electrician’s perspective one should hold discussions with clients to make sure they are fully aware about what is involved and what in going on revolving the matter. Consumer unit replacement is a big and serious task and so it must be planned smartly. If the task is not properly planned in advance it can lead an electrical contractor to an array of troubles. However most of these issues are possible to avoid when have the accurate information and the correct checks done right from the early stages of the job. Moreover the right checks and information prove helpful designing as well as installing the new unit smoothly in course of time. Here are few considerations to take into account to make the overall task of consumer unit replacement easy and smooth.

  • Consider discrimination between any sub mains
  • Supply isolations or existence of a disconnecting switch on the supply side of a consumer unit (In case the switch is not there then there must be an arrangement made with the DNO or Distribution Network Operator)
  • Different types of CU configuration must be broadly discussed with a client (The options include high integrity, RCBO and dual RCD, etc.)
  • It is also important to run an assessment of the existing installation beforehand to make sure replacement of the CU can be carried out smoothly

Comply with the regulations

It is sad but true that a large number of unit installers do not fully appreciate all the regulations related to consumer unit replacement. A common approach this category of installers follows is executing the work while firmly believing mentioning the defects on the EIC or Electrical Installation Certificate is sufficient. A little technical input here may prove helpful for many; those defects can only be mentioned or recorded in the comments part of the existing installation section provided those defects do not invoke any of the following classification codes – C1, C2 and F1.

Installers must comply with the BS 7671 guidelines as well as the Electricity at Work Regulations of 1989. These regulations include the following –

  • Regulation 12 is meant for cutting of the electric supply and isolation of a circuit.
  • Regulation 13 includes taking precautions to work on equipments that are made dead.
  • Regulation 14 covers working on or near live electrical conductors explains an electrician who quotes reasonably for changing consumer units in London. 

The BS 7671 requirements

Consumer unit replacement falls under the category of new work and is considered as making an alteration to an existing electric system. As a result that task has to be designed, erected and even verified as per the guidelines mentioned in the Regulation 110.1.2 (VI) of the BS 7671. As per the Regulation 610.4 it is also important to ensure the existing installation is not impaired in the process. Regulation 132.16 mentions requirements of addition and alterations which in other words confirms the existing range of equipments has to be sufficient to carry out the alteration and this includes the distributor’s equipments as well. Even the bonding and earthing have to be proper and sufficient to support the installation.      

The Regulation 415.1 deals with design to ensure additional protection. Additional protection is ensured by 30mA RCD and unwanted tripping of the RCD also has to be considered as per the directives included in the Section 314, Division of Installation. In addition to everything mentioned above one also has to go by the manufacturer’s instructions as per the Regulations 134.1.1 and 510.3 respectively. Identification notices complying with Section 514 has to be fitted on completion of the work followed by issuance of an EIC which is as per the requirements if Sections 631 and 632. This EIC issuance is mentioned in Regulation 631.1 and lastly the work has to be notified to the local authority. However an electrician who deals with new electrical consumer unit over the years in London says this notification is only valid for properties located in England and Wales.

Best practices followed in the industry

Considering all these legal obligations and requirements mentioned above it is pretty easy for anyone to go wrong or commit a mistake somewhere down the down. In order to avoid mistakes the industry follows its best practices. Let us explore those practices in the section below.

Before replacing a consumer unit it is important to encourage a customer to carry out an EICR or Electrical Installation Condition Report on the given property. A fresh EICR helps an electrical contractor identify the requirements of Regulation 132.16. In the long run it helps complying with all the necessary regulations involved with new consumer unit installation easily. This also helps testing competence of the existing bonding and earthing arrangements. Even suitability of the equipments and the materials supplied by the DNO can be checked out in one go. One of the most important aspects in this context is ensuring polarity of the incoming supply.

Any defect or fault is easy to get highlighted during this phase of the task. Thus remedial work can be carried out smoothly without much disruption of hindrance of the project completion. According to experts working at the widely trusted Electric Works London most importantly in this approach a contractor does not find himself in the dock at the end of the day to clear out the faults that were not included in the original contract right from the start. 

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