The Right Wire for Your Air Conditioner: Why It Matters
India adds millions of new air conditioner units every year. With summer temperatures exceeding 45°C in parts of the country and affordable inverter ACs now within reach for middle-income households, the AC market is booming. What is not growing fast enough is the quality of wiring behind these ACs.
An undersized wire running to a 1.5-ton AC will overheat. Slowly, over months, the insulation degrades at the terminal. The connection loosens. A spark occurs. A fire starts inside your wall, where you cannot see it until the smoke is already filling your rooms. This is not a rare scenario: undersized AC wiring is one of the leading causes of residential electrical fires in India.
This guide from Kundan Cab gives you the definitive wire sizing guide for every common AC type, plus MCB sizing, circuit rules, and installation best practices.
Wire Size for Each AC Capacity: Complete Reference Table
AC Capacity Typical Current Draw Recommended Wire MCB Rating Circuit Type 0.75 ton Window AC 5–7 A 1.5 sq mm FR copper 10A or 15A Can share 5A circuit if lightly loaded 1.0 ton Split AC 7–9 A 2.5 sq mm FR copper 15A or 16A Dedicated circuit strongly recommended 1.5 ton Split AC ★ 10–12 A 2.5 sq mm FR copper 16A or 20A Dedicated circuit — mandatory 2.0 ton Split AC 14–16 A 4.0 sq mm FR copper 20A or 25A Dedicated circuit — mandatory 3.0 ton Cassette AC 18–22 A 4.0–6.0 sq mm FR copper 25A or 32A Dedicated circuit with RCCB 5.0 ton Tower AC 22–28 A 6.0 sq mm FR copper 32A Dedicated circuit, 3-phase if available 10+ ton Central AC 40+ A 10–16 sq mm (IS 1554) 50A+ Three-phase industrial grade
The 1.5-ton split AC is by far the most common AC type in Indian homes. Always use 2.5 sq mm ISI-certified FR copper wire on a dedicated 16A/20A circuit.
Why You Must Use a Dedicated Circuit for Every AC
A dedicated circuit means the AC is the only load on that circuit breaker. No fans, no sockets, no lights. This is important because:
- Startup surge current: An AC's compressor draws 3–6 times its running current at startup (called inrush current). Sharing a circuit means other loads experience a voltage dip at every AC startup.
- Continuous load rating: Circuit breakers and wire are rated for continuous loads at 80% of nominal ampacity. A 1.5-ton AC at 12A on a shared 15A circuit leaves almost no headroom.
- Heat accumulation: Shared circuits carry higher average currents, accelerating insulation aging at connections.
Expert Rule of Thumb
One AC unit = one dedicated circuit = one MCB/breaker. Never share an AC circuit with any other load. This is not just best practice — it is required by the Indian Electricity Rules, 2005 for circuits above 3,000W.
Circuit Length and Voltage Drop — Why It Matters
Standard 2.5 sq mm wire is sized for AC loads up to approximately 30 metres of circuit run (one-way). If your AC circuit is longer, say, a 35-metre run from a main panel to a bedroom on the opposite side of a large floor plate, consider these options :
1. Upgrade to 4 sq mm wire: Reduces voltage drop by ~40% over the same length; the most reliable solution
2. Reposition the MCB sub-panel: Shorten the circuit run by placing the distribution board closer to the AC zones
3. Use a voltage stabiliser: Protects the AC from low voltage, but does NOT protect the wire; always address the wire first
What Wire Does Kundan Cab Recommend for AC Use?
For 1.5-ton split ACs, Kundan Cab HomeGuard 2.5 sq mm FR Wire (IS 694:2010) on a dedicated 16A/20A MCB circuit. For 2-ton ACs — Kundan Cab HomeGuard 4 sq mm FR Wire on a dedicated 25A circuit. Both are available at https://www.kundancab.in/products/homeguard-wires/fr and through authorized dealers across India.
FAQs
1. Can I use 1.5 sq mm wire for a 1.5-ton AC?
No. A 1.5-ton split AC draws 10–12 A continuously. 1.5 sq mm wire is rated for 13–16 A in conduit, leaving almost no thermal headroom. Using 1.5 sq mm for a 1.5-ton AC is a safety violation and a fire risk. Always use 2.5 sq mm on a dedicated circuit.
2. What MCB should I use for a 1.5-ton split AC?
A 16A or 20A single-pole MCB (Type C curve for motor loads) is correct for a 1.5-ton AC on a dedicated 2.5 sq mm circuit. Pair it with a 25A RCCB on the incoming supply for additional earth-fault protection.
3. Can a 2.5 sq mm wire handle a 2-ton AC?
It is marginal. A 2-ton AC draws 14–16 A, and 2.5 sq mm wire in a conduit is rated for 18–20 A. The wire will not burn immediately, but it will run hot, degrade faster, and is not recommended for 2-ton units. Use 4 sq mm for peace of mind and code compliance.
