Which wire size for which circuit? A home-wiring guide
1.0, 1.5, 2.5, 4 or 6 sq mm — the usual wire sizes for lights, sockets, ACs and geysers in Indian homes, and why FRLS and HRFR wires are worth it.
Wire size is the one decision in a house you can’t easily undo once the walls are plastered. Here are the sizes most electricians around Siliguri use for a typical home — a starting point to discuss with your electrician, not a substitute for one.
The usual sizes
| Circuit | Copper wire | Typical MCB |
|---|---|---|
| Lights and fans | 1.0 – 1.5 sq mm | 6 A – 10 A, B curve |
| 6 A sockets | 1.5 – 2.5 sq mm | 10 A – 16 A, C curve |
| 16 A power sockets (kitchen, iron, fridge) | 2.5 sq mm | 16 A – 20 A, C curve |
| Split AC, geyser | 4 sq mm | 20 A – 25 A, C curve |
| Main / sub-main to a floor | 6 – 10 sq mm | per load |
Longer runs, bunched wires in one conduit, and hot roof spaces all reduce how much current a wire can carry safely — when in doubt, go one size up. The extra cost is small next to rewiring.
Earth wire
Run a proper earth conductor with every circuit — usually the same size as the phase wire for small circuits. Green or green-yellow by convention.
Colours
Keep to the standard colours so the next electrician can work safely: red / yellow / blue for phases, black for neutral, green for earth.
FRLS, HRFR and why they matter
- FRLS — Flame Retardant, Low Smoke. If a fire starts, it gives off far less smoke, which is what usually stops people getting out.
- HRFR — Heat Resistant, Flame Retardant. Handles higher conductor temperatures before the insulation softens.
For homes, flats and offices, either is a worthwhile step up from plain PVC wire.
Buying tip
House wire comes in 90 m coils (and 180 m project packs in some ranges). Count your runs per size before ordering — a photo of the electrician’s list on WhatsApp is enough for us to quote Havells, Polycab and other ranges side by side.
Quick answers
Which wire is used for lights and fans?
1.0 or 1.5 sq mm copper wire is the usual choice for lighting and fan circuits in homes, protected by a 6 A or 10 A MCB.
What size wire for a 1.5 ton AC?
Most electricians run a dedicated 4 sq mm copper circuit for split ACs, protected by a 20 A or 25 A C-curve MCB, especially on longer runs.
What is the difference between FRLS and HRFR wire?
FRLS (Flame Retardant, Low Smoke) wire gives off less smoke if it burns, which matters for escape in a fire. HRFR (Heat Resistant, Flame Retardant) wire tolerates higher temperatures. Both are better than plain PVC wire for homes.