House Wiring Guide: Wire Sizes, Conduits, MCBs & Safety Basics

Good wiring starts with a list of everything the building will run — today and in the next ten years. Lights, fans and sockets are the easy part; the real drivers are air conditioners, geysers, induction cooktops, ovens, washing machines, water pumps, EV chargers, inverters and rooftop solar.

From that list the electrician works out the connected load, applies a realistic diversity factor (not everything runs at once), and decides the supply type — single-phase for most smaller homes, three-phase for larger homes, multiple ACs or commercial spaces. The load assessment then drives the size of the incoming cable, the main switch, the number of circuits and the DB size. Planning spare capacity now is far cheaper than rewiring later.

The short answer: lighting circuits typically use 1.5 sq mm copper wire, general sockets 2.5 sq mm, and heavy appliances like ACs and geysers 4 sq mm on their own dedicated circuit. The main feed from the meter to the DB is sized from the total load, usually 6–16 sq mm for homes.

These are common starting points for copper wiring in Indian homes over normal run lengths. Long runs, many circuits bunched in one conduit, high ambient temperatures or a large AC can all call for the next size up — the final choice should always be matched to the MCB rating and the actual load.

For most homes and offices, FRLS (Flame Retardant Low Smoke) copper wire is the sensible minimum, and ZHFR / LSZH (Zero Halogen Flame Retardant) is the better choice for escape routes, basements, hospitals, schools and densely occupied buildings.

All three are PVC or polymer-insulated building wires, but they behave very differently in a fire. The biggest danger in a building fire is often the smoke and toxic gas, not the flame — which is why low-smoke and halogen-free insulation matters. Always use copper conductors for building wiring and buy from a reputable manufacturer with the ISI mark on the coil.

Concealed wiring — PVC conduits chased into walls and laid in slabs before plastering — is the standard for new construction because it looks clean and protects the wire. Surface wiring in PVC conduit or casing-capping is the practical option for renovations, rented spaces, warehouses and anywhere walls can't be cut.

For concealed work, use good-quality rigid PVC conduit of a size that leaves room to pull wires out later, and never fill a conduit so tightly that it can't be rewired. Keep draw wires in empty conduits, avoid sharp bends, and keep power wiring in separate conduits from data, TV and CCTV cables to avoid interference.

The rule of thumb is to divide the building into several smaller circuits instead of a few big ones, and to give every heavy appliance its own circuit and MCB. That way a fault in one room doesn't black out the whole house, and each wire is protected by a breaker sized for it.

An MCB protects the wire from overload and short circuit; an RCCB protects people from electric shock and earth-leakage fires. A safe installation needs both.

Each outgoing circuit gets an MCB rated for its wire size — B-curve for lighting and general sockets, C-curve for motors, pumps and ACs with high starting current. A 30 mA RCCB (or RCBO on individual circuits) is the standard for personal protection on socket, kitchen and bathroom circuits, and a double-pole or four-pole main switch or isolator lets the whole installation be switched off safely for maintenance.

Every socket, metal switch plate, appliance body and DB must be connected to a proper earth — without it, MCBs and RCCBs cannot do their job. Run a green-yellow earth wire with every circuit, bond metal water pipes and structural steel where required, and provide at least two independent earth pits.

Chemical (maintenance-free) earthing is a good choice for new homes and dry soil. Earth resistance should be tested at installation and then at least once a year.

In India, wiring practice is guided by IS 732 (the code of practice for electrical wiring installations), with IS 3043 covering earthing, and the Central Electricity Authority (Measures relating to Safety and Electric Supply) Regulations setting the legal safety requirements. The National Building Code also covers electrical installations in buildings.

In practice, compliance means ISI-marked wires, switches and breakers; correct wire sizes and breaker ratings; colour-coded conductors (red/yellow/blue or brown for phase, black or blue for neutral, green-yellow for earth); RCCB protection; proper earthing; and insulation-resistance and earth-resistance testing before the supply is switched on.

A well-run job follows a clear sequence, and most problems come from skipping a step.

Electrons plans and installs new wiring for homes, flats, shops and offices across Zirakpur, Panchkula, Chandigarh and Mohali. We start with a site visit and load assessment, lay out circuits and the DB around how you'll actually use the space, install with ISI-marked materials, test every circuit before handover, and offer AMC and 24/7 emergency call-outs afterwards. Whether it's a new build or a renovation in the Tricity, we plan for both safety and the load you'll add in the years ahead.