How to Choose Wires and Cables for Home & Office

How to Choose the Right Wires and Cables: A Practical Guide

Wire and cable selection seems simple until you’re standing in front of a supplier
catalog full of gauges, insulation types, and core counts. Getting it wrong isn’t just
inefficient — undersized wiring is a genuine fire hazard.

Quick answer: Choose cable size (in sq mm) based on the connected electrical load
and run length, choose insulation type (PVC, XLPE, FR, FRLS) based on the installation environment and fire-safety requirements, and always size for a safety margin above your calculated load.

Understanding Wire Gauge (Cross-Sectional Area)

Wires are sized by their cross-sectional area in square millimeters (sq mm) — common
residential sizes range from 1.0 sq mm (light circuits) to 4 sq mm or more (AC points,
high-load sockets). Undersized wire for a given load causes excessive heat build-up,
insulation degradation, and fire risk over time; this is one of the most common wiring
mistakes in both new construction and DIY renovations.

Types of Insulation and What They Mean

• PVC (Polyvinyl Chloride) — the standard, cost-effective insulation for general indoor wiring.
• FR (Flame Retardant) — resists flame propagation, reducing fire spread risk.
• FRLS (Flame Retardant Low Smoke) — additionally limits toxic smoke emission during fire, important for enclosed spaces like offices, hospitals, and multistorey residential buildings.
• XLPE (Cross-Linked Polyethylene) — higher temperature tolerance and better electrical properties, commonly used for industrial and higher-voltage power cables.

Single Core vs Multi-Core Cables

Single-core wires are standard for internal domestic and office wiring pulled through
conduit. Multi-core (armoured) cables — where several insulated conductors are combined under one outer sheath, often with steel wire armouring — are used for underground runs, outdoor installations, and connections between panels where physical
protection is needed.

A Quick Sizing Rule of Thumb

While a qualified electrician should always confirm final sizing based on load calculations and run length (voltage drop increases with cable length), a general guide many
electricians reference:

• Lighting circuits: 1.0–1.5 sq mm
• Socket/plug circuits: 2.5 sq mm
• AC and geyser points: 4–6 sq mm
• Main distribution feeders: sized individually based on total connected load

FAQs

Q: What size wire do I need for an AC point? 

• Most residential AC points use 4 sq mm wire, though this depends on the AC’s load and the length of the run — always confirm with a qualified electrician.

Q: What’s the difference between FR and FRLS cable? 

• FR cable resists flame spread; FRLS additionally reduces smoke and toxic gas emission during a fire, making it the preferred choice for enclosed and high-occupancy buildings.

Q: Is armoured cable necessary for indoor wiring?

•  Not usually — armoured cable is primarily used for underground runs, outdoor installations, and situations needing extra physical protection; standard indoor wiring typically uses unarmoured cable through conduit.