Fixed Wire Testing: What It Is, How Often and How It Is Planned
Updated: Oct 9
Fixed wire testing is the inspection and testing of a building's permanent electrical installation: the distribution boards, cables, sockets, lighting circuits and hardwired equipment. It is the commercial name for an EICR (Electrical Installation Condition Report), and it is how a business shows it is meeting its legal duty to keep its electrical systems safe. PAT testing, by contrast, covers the plug-in equipment.
What is fixed wire testing for?
The duty comes from the Electricity at Work Regulations 1989. Regulation 4(2) says that, as may be necessary to prevent danger, all systems shall be maintained so as to prevent such danger, so far as is reasonably practicable. That duty falls on employers and the self-employed, and on employees for matters within their control.
The law does not name a test or a frequency. HSE's position is that installations should be tested often enough that there is little chance of deterioration leading to danger. Fixed wire testing, recorded on an EICR against BS 7671, is the accepted way of showing you have done that. Without a current report, a business has very little evidence to point to after an incident.
How often does a commercial property need an EICR?
There is no single legal interval. The commonly recommended maximum intervals come from Table 3.2 of the IET's Guidance Note 3, which sets initial frequencies by type of premises, and the IET is careful to say these are recommendations, not legal requirements. As summarised in Aviva's risk guidance for business customers, they are:
Industrial premises: every 3 years
Offices: every 5 years
Shops: every 5 years
Commercial premises generally: every 5 years or on change of occupancy
Educational premises: every 5 years
After the first inspection, the interval is set by the electrician who carries out the testing, based on the type of installation, how it is used, how well it is maintained and the conditions it works in. A busy commercial kitchen, a workshop with dust and vibration or a building with an ageing installation will often get a shorter interval than the table suggests. Our post on how long an EICR lasts covers domestic and rented intervals alongside these.
Guidance Note 3 also recommends routine checks between formal inspections, typically once a year for offices, shops and industrial premises, and every 6 months for educational premises. These are visual checks and RCD test-button checks, looking for damage, overheating and obstructed switchgear. They do not need an electrician, but whoever does them must be able to use the installation safely and recognise a defect.
What happens during commercial electrical testing?
A commercial EICR follows the same pattern as a domestic one, on a bigger scale. We book it through our fixed wire testing service, and a typical visit covers:
A walk-round and records check. The inspector looks at the age and likely condition of the installation, any work done since the last report, how the building is used and whether circuit charts and drawings exist.
Visual inspection. Distribution boards, cable containment, accessories, emergency switching, labelling and signs of heat damage.
Dead tests. With circuits isolated: continuity of protective conductors, insulation resistance and polarity.
Live tests. Earth fault loop impedance, prospective fault current and RCD operation.
The report. Observations coded C1, C2, C3 or FI, an overall result and the next inspection date, with full schedules of results for every board tested.
If the building has escape lighting, its circuits are inspected as part of the installation, but emergency lighting testing has its own routine of monthly function tests and an annual full discharge test.
Sampling: 100% or a percentage?
On larger installations, Guidance Note 3 allows a sample to be tested once there is a reliable baseline. Its suggested minimums include 100% of the main switchgear externally, at least 25% of final circuit distribution boards (and representative), and between 10% and 100% of final circuit accessories, increased if faults are found.
Two cautions. First, Aviva's risk guidance for business customers recommends a full 100% test where there are no or limited records, and suggests testing all accessible sockets because that is where people interact with the system. Second, the same guidance warns that contractors quoting on a 10% sample are offering a reduced service that may not be enough for compliance. When you compare quotes, compare the sample size, not just the price. Checkatrade gives a typical UK range of £30 to £50 per circuit plus VAT for commercial EICRs (figures last updated September 2024), so the circuit count tells you a lot about whether a quote is realistic.
How testing is planned around trading hours
Dead testing means switching circuits off, which is the part businesses worry about. Good planning keeps the disruption small:
Board by board. Circuits are isolated one distribution board or one circuit at a time, so most of the building stays live.
Critical loads first. Servers, refrigeration, alarms, lifts and tills are identified before the day and either tested at quiet times or kept on while other circuits are tested.
Out-of-hours visits. Offices are often easier in the evening or at a weekend; shops before opening; industrial units around shift patterns or shutdowns.
Staff notice. Staff need to know which areas will lose power and when, and IT should shut down equipment properly before its circuit goes off.
Where isolation really is impractical (continuous processes, some healthcare settings), the guidance allows a planned regime of continuous monitoring and maintenance instead, with proper records.
Fixed wire testing questions, answered
Is fixed wire testing the same as PAT testing?
No. Fixed wire testing covers the permanent installation up to and including the socket. PAT testing covers equipment that plugs into it. A business normally needs both, on their own schedules.
Who is responsible if we rent our premises?
It depends on the lease. Often the landlord is responsible for the installation and the tenant for its day-to-day use and their own equipment, but many commercial leases pass the testing duty to the tenant. Check the repairing clauses, and agree in writing who books and pays for the EICR.
What happens if the report is unsatisfactory?
Any C1 or C2 observation makes the report unsatisfactory. C1s need immediate action, usually on the day; C2s need urgent repair. Once the work is done, the electrician issues certification for it; our guide to electrical certificates explains which one you will get. If the report shows the installation has reached the end of its life, it should say so with reasons, and a planned rewiring of the worst areas can be phased around the business.
Arranging fixed wire testing
Whether you need an electrician in Stafford, Telford or Wolverhampton, we test shops, offices, workshops and industrial units across Shropshire and Staffordshire from our base in Shifnal, and plan each visit around how the building is used. Send us the number of distribution boards and your opening hours through our contact page and we will put together a quote.
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