Worked example — general guidance only
An AC rated at 6A would typically call for around a 10A MCB and 1.5 sq mm copper wire — always have this confirmed by a licensed electrician for your specific installation.
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MCB rating & wire gauge guidance
Recommended MCB
10 A
Recommended wire
1.5 sq mm
⚠ General planning guidance only — not a substitute for a licensed electrician. Wire run length, ambient temperature, conduit fill and local electrical code (IS 732) all affect the correct final specification for your installation.
How this is calculated
Design current. We take the AC's nameplate rated current and add 25% headroom, since compressor motors draw a brief starting surge above their running current.
MCB rating. The next standard MCB size at or above the design current (from 6A, 10A, 16A, 20A, 25A, 32A, 40A…) is recommended.
Wire gauge. We match the MCB rating to a copper wire cross-section commonly used in Indian residential wiring practice for that current range — a starting reference, not a calculation of your specific run's voltage drop or heat dissipation.
Typical MCB & wire gauge by AC tonnage — general reference
For browsing only, not a specification — always size a real installation from the AC's own nameplate current using the calculator above, then have it confirmed by a licensed electrician.
| Tonnage | Typical rated current | Recommended MCB | Recommended wire |
|---|---|---|---|
| 0.8 Ton | ~4.05A | 6A | 1.5 sq mm |
| 1 Ton | ~5.07A | 10A | 1.5 sq mm |
| 1.5 Ton | ~7.6A | 10A | 1.5 sq mm |
| 2 Ton | ~10.14A | 16A | 2.5 sq mm |
Rated current is estimated from a 3-star unit's typical full-load draw at each tonnage — your specific model's nameplate current may differ. This is general planning guidance; always have the final MCB and wire specification confirmed by a licensed electrician for your actual installation.
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Frequently asked questions
Is this a substitute for a licensed electrician?
No. This is general planning guidance to help you understand roughly what to expect before an installation — the final MCB and wire specification must be confirmed by a licensed electrician, accounting for your specific wire run length, ambient temperature, conduit fill and local electrical code.
Why does the calculator add 25% headroom to the rated current?
AC compressors draw a brief surge current on startup well above their steady running current, and continuous-duty loads like ACs are conventionally derated for safety margin — a 25% headroom over nameplate rated current is a common starting point for sizing.
Why is a dedicated circuit recommended for an AC?
Sharing a circuit with other high-load appliances increases the risk of nuisance tripping or overheating. A dedicated MCB and wire run sized for the AC alone is standard practice for split and window AC installations in India.
What standard governs residential AC wiring in India?
IS 732 (Code of Practice for Electrical Wiring Installations) is the relevant Indian Standard, alongside your local electricity board's wiring rules. A licensed electrician will apply these correctly for your specific site.
What happens if the MCB is undersized for the AC?
An undersized MCB will trip repeatedly, especially on the compressor's startup surge — a nuisance, but the safe failure mode. It will not by itself cause a fire; it protects the circuit by cutting power before the wiring is overloaded.
What happens if the wire gauge is undersized?
This is the genuinely dangerous scenario: an undersized wire can overheat under sustained AC load even if the MCB doesn't trip, which is a real fire risk. This is exactly why wire sizing should be confirmed by a licensed electrician, not estimated from a table alone.
Can I run two ACs off the same circuit?
Not recommended. Standard practice in India is one dedicated MCB and wire run per AC unit, sized for that unit alone — sharing a circuit between two ACs risks nuisance tripping at best and overloading at worst.
Does the reference table below apply to window ACs the same way?
The same current-to-MCB-to-wire logic applies, but window ACs are typically lower tonnage and often run off a standard 15A/16A domestic socket circuit rather than a dedicated line — check your specific unit's nameplate current against the table regardless of AC type.
My AC's actual nameplate current is different from the reference table — which do I use?
Always use your own unit's actual nameplate current, not the table's tonnage-based estimate — the table is a general planning reference for browsing, while the calculator above and your electrician should work from your specific AC's real rated current.