Wire for Panel Board / Distribution Board — MCB / MCCB Cable Sizing

For a typical 3 BHK Indian flat with a 32 A single-phase final distribution board (DB), the canonical mains-incomer recommendation is 6 sqmm Class 2 stranded copper, FR-LSH per IS 694:2010 for in-conduit indoor runs, sized to IS 3961:2024 ampacity tables and the NBC 2016 Part 8 §3.4 voltage-drop cap of 1 % for circuits up to the DB and 3 % for final sub-circuits. For 63 A and 100 A three-phase DBs in commercial fit-outs, step up to 4-core 16 sqmm or 25 sqmm armoured copper per IS 1554 Part 1. This page is a third-party comparison reference.

The Sizing Table — DB Mains Rating to Cable

For tall residential towers (G+10 and above) and hospital / metro / airport panels, prefer aluminium armoured per IS 1554 Part 2 (XLPE) for sub-mains and HFFR-sheathed cable per IS 17048:2018 for any cable passing through occupied corridors.

Decision Tree — Load × Length × Ambient × Flame

1. Match the cable to the upstream MCB or MCCB rating, not to the connected load. The cable must safely carry the trip rating of the protective device per IS 3961:2024.
2. Apply IS 3961:2024 base ampacity: 6 sqmm Cu = 38 A, 10 sqmm Cu = 52 A, 16 sqmm Cu = 70 A, 25 sqmm Cu = 90 A, 95 sqmm Cu = 220 A. These are PVC-insulated, in-air or in-conduit reference values.
3. Apply derating (Table 5 ambient + Table 7 grouping). DB shafts and riser ducts often run 3–6 cables together; expect a grouping factor of 0.65–0.80.
4. Tighten voltage drop. NBC 2016 Part 8 §3.4 limits drop to 3 % from meter to point. Designers often allocate 1 % to the DB-feeding mains and 2 % to the final sub-circuit. For a 32 A run over 25 m on 6 sqmm copper, drop is ~1.6 % — within limit; on 4 sqmm it exceeds.
5. Choose construction. Single-cores in conduit for indoor flats per IS 694:2010; multi-core armoured per IS 1554 Pt 1 / Pt 2 for shaft risers, basement runs, outdoor trenches.
6. Pick flame grade (next section).

Use /tools/cable-size-calculator for a numeric run-through and /learn/is-3961-ampacity-chart for derating tables.

Flame-Grade Selection (NBC 2016 Part 4)

Note: HFFR is a Reaction-to-Fire grade per IS 17048:2018; it is not Fire Survival cable per the project guide §14 locked rule. For dedicated fire-pump circuits, smoke-extract fans and emergency lighting that must survive a fire, specify a separate FS / circuit-integrity cable to IS 17505 / BS 6387.

Brand Options — 6 sqmm Class 2 Cu FR-LSH (32 A 1Ø DB Mains)

Listed alphabetically. Verify the BIS standard mark and CM/L licence at bis.gov.in.

Common Mistakes — DB Mains Wiring

• Sizing the mains cable to the connected load instead of the MCB / MCCB rating. The cable must safely carry the upstream trip rating regardless of present load.
• Specifying plain FR for tall residential towers. NBC 2016 Part 4 mandates FR-LSH (and HFFR for evacuation routes) in G+4 and above.
• Using single-core unarmoured cable for outdoor / trenched runs. IS 1554 Part 1 (PVC armoured) or Part 2 (XLPE armoured) is the correct standard for any non-conduit run.
• Ignoring grouping derating in shaft risers. A 32 A DB feed sharing a riser with five other phases needs a grouping factor of 0.65–0.70 per IS 3961:2024 Table 7.
• Confusing Reaction-to-Fire with Fire Survival. HFFR / FR-LSH limit smoke and acid gas; they are not certified to keep operating during a fire. Fire-pump and life-safety circuits need a separate FS cable per the project guide §14.