The complete guide to commercial and industrial EICRs in the UK. Legal requirements, three-phase testing, larger installations, documentation standards, costs, inspection frequency, and common findings — everything you need to deliver professional commercial inspections.
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Written and reviewed by Andrew Moore, founder of Elec-Mate, against BS 7671:2018+A4:2026, IET Guidance Note 3 and the IET On-Site Guide.
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01 · Certificates
A commercial EICR (Electrical Installation Condition Report) is a detailed inspection and testing report on the electrical installation of a commercial or industrial premises. It assesses the condition and safety of the fixed wiring, distribution equipment, and earthing and bonding arrangements against the requirements of BS 7671 (the IET Wiring Regulations), recording any defects, deterioration, or non-compliances as coded observations.
While the EICR format is the same for domestic and commercial installations (the BS 7671 form is universal), commercial EICRs differ significantly in scope, complexity, and the expertise required. Commercial installations typically involve three-phase supplies, multiple distribution boards, sub-main cables, diverse earthing arrangements, and specialist equipment that requires specific knowledge to inspect and test safely.
The purpose of a commercial EICR is to determine whether the electrical installation is in a satisfactory condition for continued service, to identify any defects that could pose a danger to persons or property, and to recommend remedial work and a date for the next inspection. The report provides the legal evidence that the duty holder (employer, landlord, or building manager) needs to demonstrate compliance with their obligations under health and safety legislation.
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02 · Certificates
The legal framework for commercial electrical inspection is more extensive than for domestic premises, reflecting the higher risk associated with commercial and industrial installations and the employer's duty of care to employees and visitors.
Section 2 places a general duty on employers to ensure, so far as is reasonably practicable, the health, safety, and welfare at work of all employees. This includes the maintenance of plant and systems of work (including electrical installations) in a condition that is safe and without risks to health. Section 3 extends this duty to non-employees (visitors, contractors, members of the public) who may be affected by the employer's undertaking. A periodic EICR is the accepted method of demonstrating compliance with these duties in respect of the electrical installation.
Regulation 4(2) requires that every electrical system shall be maintained so as to prevent, so far as is reasonably practicable, such danger. The HSE Memorandum of Guidance on the Electricity at Work Regulations (HSR25) states that regular inspection and testing is an essential part of any preventive maintenance programme. Regulation 16 requires that adequate records are kept — the EICR and schedule of test results constitute these records. These regulations apply to all workplaces, not just those with employees, and carry criminal penalties for non-compliance.
The "responsible person" (usually the employer or building manager) must carry out a fire risk assessment that considers all potential sources of ignition, including electrical faults. An unsatisfactory electrical installation is a significant fire risk, and the fire risk assessment should reference the most recent EICR. Fire and rescue authorities can request to see the EICR during fire safety inspections, and the absence of a current EICR can result in enforcement action.
Commercial property insurance policies typically require the policyholder to maintain the electrical installation in good condition and to have periodic inspection and testing carried out by a competent person. Failure to maintain a current EICR may invalidate the insurance cover, leaving the business exposed in the event of a fire or electrical injury claim. Insurers may also specify a maximum interval between inspections that is shorter than the BS 7671 recommendation.
03 · Certificates
Planning a commercial EICR requires careful consideration of the scope of inspection, the extent of testing, the access arrangements, and the impact on business operations. Unlike a domestic EICR where the entire installation can typically be inspected in one visit, commercial EICRs may take multiple days and require careful coordination with building management.
The scope must be clearly defined before work begins. What is included in the inspection? The fixed wiring and distribution equipment are always included. But does the scope extend to emergency lighting, fire alarm circuits, external installations, temporary installations, or tenant fit-out installations? These boundaries must be agreed with the client in writing to avoid disputes about what was and was not inspected.
04 · Certificates
Three-phase installations are standard in commercial and industrial premises and require testing procedures that go beyond the single-phase testing familiar from domestic work. The additional tests, the higher voltage levels, and the larger fault currents involved make three-phase testing more demanding and more hazardous than single-phase work.
Phase rotation must be verified at every three-phase distribution board using a phase rotation meter. The standard rotation in the UK is L1-L2-L3 (clockwise). Incorrect phase rotation causes three-phase motors to run in reverse, which can damage equipment and pose a safety hazard. Phase rotation must also be checked when paralleling supplies or connecting standby generators. The test is quick but critical — it should be the first test performed on any three-phase board.
PFC must be measured at every distribution board in the installation. In three-phase installations, both phase-to-earth and phase-to-phase fault currents must be measured, because the highest PFC may occur between phases rather than between a phase and earth. The measured PFC must not exceed the rated breaking capacity of the protective devices installed in the board. PFC values in commercial installations can be very high (10 kA, 16 kA, or more at the intake), so accurate measurement is essential for verifying that protective device ratings are adequate.
Earth fault loop impedance must be tested on circuits supplied from each phase. Values can differ between phases depending on the cable route, the position of the circuit within the distribution board, and the characteristics of the supply. The schedule of test results must identify which phase supplies each circuit and record the Zs value accordingly. In TN-S and TN-C-S earthing arrangements common in commercial premises, the external earth fault loop impedance (Ze) at the intake provides the baseline, with the circuit impedance (R1+R2) added to give the total Zs for each circuit.
Insulation resistance testing on three-phase installations requires testing between all live conductors and earth (L1-E, L2-E, L3-E, N-E) and between all live conductors (L1-L2, L2-L3, L3-L1, L1-N, L2-N, L3-N). This is significantly more testing than a single-phase installation. The minimum acceptable value remains 1 M-ohm for circuits rated at 500 V or below, tested at 500 V DC. Each phase and the neutral must be tested individually to identify the specific conductor with degraded insulation if a low reading is obtained.
05 · Certificates
Commercial installations range from a small shop with one distribution board to a multi-storey office building or factory with dozens of boards, sub-main cables, and a hierarchical distribution structure. Inspecting larger installations requires a systematic approach to ensure every part of the installation is assessed.
The structure of a typical larger commercial installation includes a main intake (the point of supply from the DNO), the main switchboard or panel board, sub-main cables feeding distribution boards on each floor or in each area, and final circuits from each distribution board to the points of use. Each level of this hierarchy must be inspected and tested: the intake and main switchboard, each sub-main cable, each distribution board, and a representative sample (or all) of the final circuits.
For very large installations, a 100% inspection and test of every circuit may not be practical or necessary. BS 7671 and GN3 allow for sampling, provided the sample size is sufficient to provide confidence in the condition of the installation as a whole. The sampling strategy must be documented on the EICR, explaining what percentage of circuits was tested and the rationale for the sample. If the sample reveals significant defects, the sample size must be increased to determine the extent of the problem.
The EICR for a larger installation may cover multiple pages of schedule of test results, with separate schedules for each distribution board. Observation codes must be applied consistently across the entire installation, and the overall assessment (satisfactory or unsatisfactory) must reflect the worst findings across all parts of the installation.
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06 · Certificates
Commercial EICR documentation must be thorough, accurate, and professionally presented. The report will be reviewed by building managers, facilities teams, insurers, enforcement officers, and potentially legal professionals in the event of an incident. Sloppy documentation undermines the credibility of the inspection and the inspector.
The overall assessment — satisfactory or unsatisfactory — must be clearly stated. An installation is assessed as unsatisfactory if any C1 (danger present) or C2 (potentially dangerous) observations are recorded. The observation codes must be applied correctly and consistently, as incorrect coding can lead to legal challenges and professional liability issues.
07 · Certificates
Commercial EICR costs are determined by the size of the installation (number of distribution boards and circuits), the complexity of the installation (three-phase, specialist equipment, diverse earthing), the access arrangements (normal hours vs out-of-hours working), and the location (London and South East rates are higher than other regions).
These intervals are guidelines, not absolute rules. The inspector should set the "next inspection recommended before" date based on the specific condition of the installation, its environment, and the nature of the business. An installation in good condition in a clean office environment may safely go to the maximum interval. An installation showing signs of deterioration in a harsh industrial environment should be inspected more frequently.
08 · Certificates
Certain defects and non-compliances appear repeatedly on commercial EICRs. Being aware of these common findings helps inspectors know what to look for and helps building managers understand the typical issues that arise.
Missing or inadequate main equipotential bonding to metallic service pipes (gas, water, oil) is one of the most common C2 observations on commercial EICRs. Bonding conductors may have been removed during plumbing alterations or were never installed. BS 7671 Regulation 411.3.1.2 requires main bonding conductors to extraneous-conductive-parts including metallic service pipes, structural steelwork, and lightning protection systems.
Older commercial installations often lack RCD protection on socket outlet circuits, which is required by BS 7671 Regulation 411.3.3 for socket outlets rated up to 32 A. This is typically coded C3 (improvement recommended) rather than C2 because the installation may have been compliant with the regulations in force at the time of installation. However, the inspector should consider whether the absence of RCD protection represents a genuine risk in the specific circumstances.
Distribution boards with missing, illegible, or inaccurate circuit charts are extremely common in commercial premises. Circuits may have been added, removed, or repurposed without updating the chart. This makes safe isolation difficult and increases the risk of the wrong circuit being disconnected. BS 7671 Regulation 514.9.1 requires every distribution board to have a durable chart identifying each circuit.
Commercial distribution boards are frequently overcrowded with additional circuits squeezed in, cables dressed poorly, and neutral bars overloaded. Overcrowding can lead to overheating, difficulty in identifying circuits, and challenges with safe isolation. The original design spare capacity has been consumed by additions over the years, and what should be a tidy, well-organised board has become a mess of cables and connections.
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