Periodic Inspection of a 1992 Apartment Block
Periodic inspection of the common areas of a 1992 five-storey apartment block in Nicosia. The intake is TN-C-S, 400/230 V, 100 A. Each flat has its own board with a 30 mA RCBO; the landlord's lighting and lobby socket circuits are on a small board with no RCD. Findings: IR on the landlord's lighting circuit 0.42 MΩ line-neutral, 200 MΩ line-PE and 180 MΩ neutral-PE; a landing light fed from a flat's board line but with its neutral from the landlord board; a 32 A ring final with a 2.5 mm² unfused spur, 9 m long and run through thermal insulation, supplying two double sockets; a lobby socket with a cracked plate and a missing shutter, leaving a 4 mm gap to live parts; main earthing conductor 10 mm²; water bond 4 mm² with a corroded clamp. Ze is 0.22 Ω and the prospective fault current at the intake is 1.9 kA. No SPD is fitted.
1. Classify each finding and state the overall assessment.
Read the worked answer
- Lobby socket with cracked plate, missing shutter and a 4 mm gap to live parts: C1 - danger present. Isolate, disconnect or make safe immediately.
- IR 0.42 MΩ line-neutral with high L-PE and N-PE: C2 - below the 1 MΩ minimum. The low L-N value suggests a line-neutral fault, damaged cable or connected load; retest with loads removed and investigate if it remains low.
- Borrowed neutral: C2 - isolating the flat board leaves the landing light neutral connected to the landlord board. The 'isolated' neutral can be live and there is a parallel neutral current; shock risk and a trap for the next contractor.
- 32 A ring with a 2.5 mm² unfused spur, 9 m in thermal insulation, feeding two double sockets: C2 - a spur may supply one socket or one FCU; two double sockets is non-compliant, and the insulated cable may not carry 32 A, so the spur is not adequately protected.
- Main earthing conductor 10 mm²: acceptable for a 100 A TN-C-S supply; record, no code.
- Water bond 4 mm² with a corroded clamp: C2 - below the 10 mm² main bonding requirement for PME and the connection is unreliable.
- No RCD on lobby sockets: C2 - 30 mA additional protection is required for socket outlets up to 32 A.
- No SPD: C3 - improvement recommended, subject to a risk assessment.
Overall: unsatisfactory.
2. Describe the further investigation and the order in which the remedial work should be done.
Read the worked answer
Make the C1 safe first: isolate the lobby socket circuit, disconnect or replace the socket, label it, and tell the landlord in writing. Then plan the C2s:
- IR: isolate and disconnect loads, test L-N, L-PE and N-PE at 500 V DC. If it is still 0.42 MΩ, split the circuit and test sections to locate the fault; repair or replace the cable and retest.
- Borrowed neutral: trace line and neutral and rewire the landing light so both come from the same board. Isolate both boards while working, verify with a voltage indicator, and retest.
- Spur: fit a 13 A FCU at the origin (making it a fused spur) or remove one socket and return the other to the ring. Check the cable's derated capacity in insulation and protect at 20 A or lower if necessary; verify Zs and RCD.
- Bonding: replace the 4 mm² with 10 mm² and fit a proper clamp to clean metal; test continuity to the MET.
- Add 30 mA RCD protection to the lobby sockets and recommend an SPD.
Re-inspect and retest after the remedials, and record the results against each observation.
3. What report should be issued, and what must the client be told about the C1 and the borrowed neutral?
Read the worked answer
Issue an EICR with the extent and limitations agreed in writing (common areas only, flats excluded), a schedule of inspections, and a schedule of circuit details and test results. Record the C1/C2/C3 codes and the overall assessment 'unsatisfactory'. Give the report to the duty holder or landlord and keep a copy.
The C1 must be notified immediately and the circuit left isolated until repaired - do not reconnect it to 'keep the lobby working'. Explain that the borrowed neutral is a danger to any electrician isolating the flat and must be corrected before the next inspection; label both boards. Recommend a re-inspection date, typically five years or on change of tenancy for common areas, and state that the C2 items must be remedied before the next EICR. If the landlord refuses to make the C1 safe, escalate to the local electrical inspectorate. Do not describe the installation as compliant just because Ze and prospective fault current are acceptable.