Commercial electrical faults rarely announce themselves cleanly. The symptom you see — RCD tripping at 2pm, fluorescents flickering on a Monday, freezer defrost cycling that throws the breaker — is downstream of a cause that needs systematic diagnosis. Millar Electrics applies the same diagnostic methods used in industrial maintenance: thermal imaging, insulation resistance, three-phase analysis, leakage logging, and elimination by isolation. The output is a written incident report with the cause identified, the rectification documented, and recommended preventative actions for the building's maintenance plan.
Common commercial faults we diagnose
Nuisance RCD trips on grouped RCDs from accumulated leakage; switchboard hot terminations identified on thermal imaging; three-phase imbalance causing neutral overheating; harmonics on lighting circuits causing nuisance tripping on Type AC RCDs; sub-main faults reading good on visual but failing under load; ground-loop currents in comms cabinets; degraded TPS cable in old industrial fit-outs; capacitor-bank failure in power-factor correction units. Each has a characteristic test signature once you know what to look for.
Diagnostic methods
Thermal imaging under load (FLIR-based) for switchboard and sub-board hot-spotting. Insulation resistance testing (megger) on isolated circuits to find degraded TPS or moisture-ingressed cabling. Earth fault loop impedance testing for fault-clearing time. Three-phase clamp-on analysis for balance and harmonics. RCD trip-time and trip-current testing under load. Leakage loggers connected over 24–72 hours for intermittent faults. We work the diagnostic ladder rather than guessing.
Reports and records
Every fault visit ends with a written incident report: time on site, work performed, parts used, test readings, photographs, and recommended preventative actions. Suitable for building managers, insurer audits, and owners corporation files. For prescribed work we lodge a Certificate of Electrical Safety with Energy Safe Victoria. Recurring fault-finding clients move onto maintenance contracts where we work the preventative side rather than reacting to incidents.
Standards we work to
Repair and rectification work is installed to AS/NZS 3000 (the Wiring Rules). Verification testing follows AS/NZS 3017 — insulation resistance, earth fault loop impedance, RCD trip-time and trip-current under load, polarity and continuity. Safe-work procedures while diagnosing energised commercial switchboards follow AS/NZS 4836, including isolation, lock-out, and live-work permits where unavoidable. Thermographic inspection follows the severity bands and reporting conventions described in our Thermographic Inspection service.