Electrical Installation and Maintenance
Electrical Installation and Maintenance tests correct selection, testing before energisation and planned upkeep of motors and panels.
Core rules
- Follow IS 732 for wiring installation and the IE Rules/CEA safety regulations for clearance, protection and inspection.
- Before energising: insulation resistance test (typically at least 1 MΩ at 500 V DC for LV), earth continuity, polarity, RCD trip test and visual check.
- MCB rating must protect the cable, not just the appliance; check cable current-carrying capacity after derating for conduit, grouping and temperature.
- Preventive maintenance includes terminal tightening, cleaning, bearing lubrication, insulation resistance checks, contactor inspection and thermal scanning.
- Record test results and keep a single-line diagram and cable schedule up to date.
Worked example
A 3 kW, 230 V water heater at pf 0.85 draws I = 3000/(230 × 0.85) = 15.3 A. A 20 A MCB is chosen. A 2.5 mm² copper PVC cable in conduit may be rated around 20 A after derating, which leaves little margin; a 4 mm² cable is safer. The earth conductor for a 4 mm² phase conductor is also 4 mm². The insulation test is done with the heater isolated and the megger connected between phase/neutral bunched and earth.
Traps
Do not select an MCB larger than the cable rating; do not megger a circuit with sensitive electronics connected; do not skip the polarity and earth-continuity checks; and do not assume a new installation needs no retest after modification.