Estimation, Costing and Maintenance of Panels
This domain tests quantity take-off, priced bills of material, and the maintenance regime that keeps a panel reliable after handover.
Estimating the panel
- Work from approved drawings: single-line diagram, panel layout, bill of materials and wiring schedule.
- Take off quantities item by item: enclosure, MCCB/MPCB, contactor, overload relay, timers, relays, terminal blocks, busbar in kg, wire in metres, glands, lugs, ferrules, labels, earthing strip.
- Add wastage, typically 5–10% for wire and small consumables.
- Build the price: material + labour (per point or per panel) + fabrication + testing + transport + overheads (10–15%) + profit + GST at the applicable rate.
- Prepare rate analysis for each item so the quotation can be defended, and put assumptions in writing.
Maintenance
- Preventive: scheduled insulation-resistance tests, torque checks on busbars and terminals, dust cleaning, contact inspection, relay setting verification, battery health checks.
- Predictive: thermographic scanning of joints under load, vibration checks, power-quality logging.
- Breakdown: fault-find from the schematic, record root cause, replace with approved spares, retest before return to service.
- Keep an asset register, maintenance log and spare-parts list; track MTBF and MTTR to justify replacements.
Worked example
A panel bill of material has materials ₹48,000, labour ₹6,000, testing ₹1,500 and transport ₹500 - subtotal ₹56,000. Overheads at 10% add ₹5,600, giving ₹61,600; profit at 12% on cost adds ₹7,392, giving ₹68,992; GST at 18% adds ₹12,419, so the quoted price is about ₹81,411. Missing the wastage on 120 m of wire is the kind of small slip that eats the margin.
Traps
- Forgetting GST, transport, testing or overheads in the quotation.
- Measuring wire from the layout instead of the wiring schedule.
- Maintenance logs that record only 'checked and OK' with no readings.
- Fitting a replacement contactor of lower utilisation category or wrong coil voltage.