What it is
Three-phase installations need the right test equipment and careful planning of isolations. Testing can form part of a full EICR, or be targeted at specific distribution, sub-mains or equipment supplies following alterations. We agree the scope in writing first so it's clear what will and won't be covered.
What's included
- Scope agreed in writing
- Testing of three-phase distribution and circuits within scope
- Report or certificate appropriate to the work
Not included
- Areas outside the agreed scope
- Remedial work
Who needs it
- Commercial and industrial premises with three-phase supplies
- Sites adding machinery or extending distribution
What you'll receive
EICR, Electrical Installation Certificate or Minor Works Certificate, depending on the work.
How often
As part of periodic inspection or after alterations.
What the rules say
Each point is labelled so you can tell what's law, what's a British Standard, and what's good practice or comes from your lease, licence or insurer.
- Legal requirementGreat Britain
Workplace systems must be maintained to prevent danger
The Electricity at Work Regulations 1989 require electrical systems at work to be maintained, so far as reasonably practicable, to prevent danger. They don't set a fixed inspection interval: how often depends on the type of installation, its use and condition.
Sources: Electricity at Work Regulations (opens external site): Electricity at Work Regulations 1989, regulation 4; HSE maintenance guidance (opens external site): Electrical safety: maintenance
- Technical standardUK (BS 7671)
What makes a report unsatisfactory
C1 (danger present) and C2 (potentially dangerous) make the overall result unsatisfactory. On reports issued to BS 7671 Amendment 4 (2026), C3 (improvement recommended) and FI (further investigation advised) don't affect the overall result. Older reports used 'further investigation required without delay', and an FI made them unsatisfactory.
Sources: IET model EICR form (opens external site): BS 7671:2018+A4:2026 model Electrical Installation Condition Report form; IET Wiring Matters (opens external site): Further investigation (Wiring Matters, issue 110, July 2026); IET (current BS 7671) (opens external site): Ensure you are up to date with BS 7671
- Lease, licence or insurerVaries
Your insurer or lease may set an interval
Commercial leases, insurers and some licensing bodies may require periodic EICRs at a set interval. Check your documents: these are contractual duties, not general law.
Before your appointment
- Agree shutdown times for plant and machinery fed from the boards being tested.
- Share drawings and schedules for the supply and sub-mains.
If something's found
- Anything dangerous is reported to you straight away, with options to make it safe.
- Further work is quoted before we do it, so nothing is added to your bill without your agreement.
- Completed work is certified, and notified to building control where the law requires it.
What affects the price
- Number of boards and sub-mains
- Size of the supply
- Shutdown planning and out-of-hours working
Read more
- Commercial electrical compliance: a practical checklist
The inspections and records most commercial premises need, which are law, which are British Standards, and which come from your lease or insurer.