The Friday deadline, the 10% sample and the IT manager
You are asked to carry out an EICR on a 1970s six-storey office building with 12 distribution boards and about 300 final circuits. There are no previous certificates and no drawings. The client wants the report by Friday because the insurer is asking, and your fee is based on a 10% sample of circuits plus inspection of every distribution board. On the first board - a 30-way TP&N board serving floor 2 - you find a socket circuit with a cracked accessory exposing basic insulation at a spur, no RCD on any socket circuit, two spare ways with no blanks, and a 32 A MCB feeding a 4 mm² submain to a comms room with no protective device at the far end. The IT manager says nothing can be switched off during business hours.
1. How do you adjust the sample, and why?
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10% sampling is a starting point, not a rule. Sampling is only defensible while the sample is representative and unremarkable. The moment it uncovers defects, the statistical basis collapses - the sample has told you the population is not uniform.
- Extend to 100% of socket circuits across all 12 boards: a cracked accessory and a no-RCD pattern are design/age issues, not one-offs.
- Extend to every board of similar age and construction, not a percentage of boards, since you have already found missing blanks and no RCD in the first one you opened.
- Record the increased extent and the reason in the report. The fee was based on a smaller extent, so agree the additional work in writing before doing it - but do not sign a report based on a sample you now know is unrepresentative.
- The insurer's Friday deadline does not change the technical decision. If the extent cannot be completed in time, issue a report that clearly states what was and was not covered - an incomplete report is defensible; a false 'satisfactory' is not.
2. Classify the four findings and explain the reasoning behind each.
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- Cracked accessory with exposed basic insulation - C2. Basic insulation is not a live part, but it is not designed to be touched and gives no protection against contact or moisture; it will deteriorate. It would be C1 only if live parts themselves became accessible.
- No RCD on socket circuits - C3 for the installation as found (it met the standard of the day), with a recommendation. C2 where sockets are used for portable equipment outdoors or in other higher-risk locations.
- Two spare ways with no blanks on a live TP&N board - C2 where the opening gives access to live parts (the degree of protection is not maintained); C3 if the ways are internally screened and nothing live is reachable. Open the board and look before you code it.
- The 32 A MCB feeding 4 mm² - check before coding. 4 mm² thermoplastic clipped direct has a tabulated capacity of about 37 A, so the 32 A device protects it and there is no non-compliance; a protective device at the far end is not a requirement. If the cable runs through thermal insulation or is bundled, capacity can fall to around 27 A and the 32 A device no longer protects it - that is a C2 (overload protection not effective). Do not code a defect that the design and installation method do not support.
3. How do you handle the IT manager's instruction, and can you issue a satisfactory report?
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The instruction is a constraint on the extent, not a technical finding.
- Record it as an agreed limitation, specifically: 'No circuits de-energised during the visit; dead testing and RCD operation not carried out on circuits serving the comms room.'
- The consequence: insulation resistance, continuity, Zs and RCD operation for those circuits are unverified. A circuit you could not test cannot be declared satisfactory.
- The overall report will be Unsatisfactory in any case because of the C2s found, but even without them an EICR with significant limitations must state clearly that it covers only the extent described and must not be read as a clean bill of health.
- Offer a practical route: out-of-hours shutdown windows or a rolling programme of isolations, so the dead testing can be completed and the limitation removed at a follow-up visit.
- The C1/C2 items require immediate written notification to the person responsible, recommending isolation of the affected circuit now - not on Friday.