Progress Payment Pressure and Concealed Nonconforming Work
You are the licensed electrical supervisor for a 6,000 m² mixed-use building in Isfahan. During a site visit you find that the contractor has installed 2.5 mm² Cu on twelve 20 A dedicated socket circuits because 4 mm² cable was unavailable; the measured load on each circuit is 13 A. The contractor has also routed a new 400 V submain through a service shaft without firestopping at two floor penetrations, and has asked you to approve a progress payment covering that work. The client is pressuring you to sign the payment certificate before as-built drawings and test sheets are submitted, because the bank deadline is tomorrow. The contractor says the 2.5 mm² is 'protected by the 20 A breaker' and offers to provide a letter from the cable supplier. You must decide what to do and what to put in writing.
1. Is 2.5 mm² Cu on a 20 A dedicated socket circuit acceptable on the basis of the measured 13 A load?
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Not automatically. A 2.5 mm² PVC Cu conductor in conduit may have a base ampacity of about 24 A, but after applying the actual ambient temperature, grouping, and installation method it can fall below 20 A. The measured 13 A load does not prove protection: socket circuits can be overloaded, and the breaker must protect the cable for the design current and fault conditions. The contractor's supplier letter is not a substitute for a derating calculation. Require the designer to confirm the corrected ampacity of 2.5 mm² in the installed route and the voltage drop over the circuit length. If the corrected ampacity is below 20 A, either replace with 4 mm² or reduce the breaker to 16 A and confirm that the circuit design, socket rating, and volt drop remain acceptable.
2. How should you handle the missing firestopping at the two floor penetrations?
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Firestopping of floor penetrations is a life-safety requirement and cannot be treated as a minor finish item. The submain must not be concealed or certified without approved firestop details, correct annular space, and inspection records. Issue a written non-conformance, require the contractor to stop closing the shaft, and exclude that portion from any payment recommendation until it is remediated and photographed. The electrical supervisor's signature certifies that the work is inspectable and compliant, not merely that cable continuity exists. If the penetration is already concealed, require opening and inspection, then approved firestopping and reinstatement.
3. What should you do about the client's demand to sign the progress certificate before as-built drawings and test sheets are submitted?
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Do not sign a certificate that misrepresents the work. Write to the client and contractor listing the nonconformities, the outstanding as-built drawings, test sheets, load calculations, and firestop records, and state that payment can be recommended only for verified compliant work. A progress certificate is a professional representation, not a favour to meet a bank deadline. Keep copies of the letters, site instructions, and photographs. If pressure continues, escalate through your employer or the professional engineering disciplinary process. Signing for noncompliant concealed work creates personal liability and may expose you to disciplinary action; the correct response is to certify only what you have inspected and to record the exceptions clearly.