Which MCB for 1.5 Ton AC, 1 Ton and 2 Ton?

MCB for a 1.5 ton AC: the short answer

For a 1.5 ton AC, electricians commonly fit a 16A or 20A MCB on a circuit that feeds nothing else. For a 1 ton AC, 16A is typical. For a 2 ton AC, 20A or 25A. The MCB’s job is to protect the cable from overload and short circuit, so the exact rating follows the cable laid to the AC point and the current the AC draws.

Tonnage is the AC’s cooling capacity, not its electrical rating. Two 1.5 ton ACs can draw quite different currents depending on the model, the star rating and whether the compressor is inverter or fixed-speed. That is why the AC’s own installation manual, which lists the recommended breaker, is the final word.

We manufacture MCBs, and the switches and sockets that go on AC points, at our works in Marol, Andheri East, Mumbai. This guide gives the typical ratings, the reasons behind them and the MRPs of the parts we make. The installation itself is a job for a licensed electrician.

Which MCB for 1 ton, 1.5 ton and 2 ton ACs?

The MCB commonly fitted for a home AC is 16A for a 1 ton unit, 16A or 20A for a 1.5 ton unit, and 20A or 25A for a 2 ton unit, each on a dedicated circuit, whether the AC is a split or a window model, with the breaker in the AC’s installation manual overriding these typical figures.

1 ton: 16A covers most small units, 1.5 ton: 16A–20A the most common home AC, and 2 ton: 20A–25A larger living-room units. One AC, one MCB applies to all three.

Where your AC’s manual gives a different figure, follow the manual. Where it gives a range, the electrician picks within it to match the cable.

Which MCB for 1.5 ton AC: 16A or 20A?

A 1.5 ton AC takes a 16A MCB when it plugs into a 16A socket and the manual allows it, and a 20A MCB when the manual asks for more or the unit is wired to a 20A or 32A DP switch, since the socket or switch on the wall must be rated at least as high as the MCB.

That last rule is the one people miss. A 16A MCB pairs with a 16A socket. A 20A MCB pairs with a 20A switch or a 32A DP switch, with the AC wired in rather than plugged. A 20A MCB feeding a 16A socket leaves the socket as the weak point.

So the question to put to your electrician is not “16 or 20?” alone, but “which MCB, which cable and which wall point, together?” The manual answers the first; the cable already in the wall often decides the rest.

Which MCB for a 1 ton AC?

A 1 ton AC typically takes a 16A MCB on its own circuit, with a 16A socket on the wall, because its running current is well inside 16A while the rating still leaves margin for the compressor’s start-up surge and matches the cable commonly run to a 16A point in an Indian home.

In our range that point is a VIYONA 401 single pole 10 kA MCB in the board (₹145 MRP for 6–32A) and a 16A socket such as the VIZA V263 (₹160) on the wall, switched by a 20A switch such as the KEMPS K147 (₹120).

Small rooms tempt people to run a 1 ton unit off the nearest 6A socket with an adaptor. The plug will not fit a 6A socket for a reason: 6A vs 16A socket explains why.

Which MCB for a 2 ton AC?

A 2 ton AC typically takes a 20A or 25A MCB on a dedicated circuit, often double pole, and is usually wired to a 32A DP switch with an indicator rather than plugged into a socket, because its higher current and longer summer running hours need heavier cable and a wall point rated above the MCB.

A DP MCB 6–32A from our VIYONA range is ₹350 MRP. On the wall, the VIZA V1250 32A DP switch with indicator is ₹330, and the KEMPS Peony 32AX DP switch with indicator is ₹360 in white (K116) and ₹392 in grey (K516). A 32A switch on a 20A or 25A circuit keeps the switch well above the MCB.

Large units are also where an old cable is most likely to be undersized. A 2 ton AC replacing a 1 ton one is a reason to have the run checked, not just the breaker.

How much current does an AC draw?

An AC draws its rated input power divided by the supply voltage, so at 230 V a unit with a 1,500 W input draws about 6.5 A and one with 2,300 W about 10 A while running, which is why the MCB, rated for the cable and the start-up surge, sits well above the running figure.

The MCB is rated above that running current for two reasons. A fixed-speed compressor draws a much higher current for a moment as it starts, and an MCB rated too close to the running current would trip at every start. And the MCB protects the cable, so it is matched to the cable’s capacity rather than to the AC’s bare running figure. The nameplate input watts, not the tonnage, is the number to read.

B curve or C curve MCB for an AC?

Where an MCB’s curve is marked, a C curve is commonly used on AC circuits, because a C-curve breaker’s instant trip fires at roughly 5 to 10 times its rating and rides through a compressor’s start-up surge, while a B curve, at 3 to 5 times, can trip at every start of a fixed-speed unit.

The curve is printed as a letter before the rating: B16, C16, C20. Under IS/IEC 60898-1, B commonly suits lighting and heaters, C circuits with motors and compressors. The curve changes how the breaker handles a brief surge; it does not change the rating or the cable.

Our catalogue does not state a trip curve for our MCBs, so we do not claim one. Check the face of whichever breaker you buy, and let your electrician decide whether it suits the AC circuit. If an AC breaker trips at every start, our guide to an MCB tripping again and again explains how the curve, the compressor and the rating each play a part.

Inverter vs non-inverter AC: does the MCB change?

The MCB for an inverter AC is usually the same rating as for a non-inverter AC of the same tonnage, because the rating is set by the cable and the maximum load, but an inverter AC ramps its compressor up gradually and avoids the sharp start-up surge, so it is far less likely to trip the breaker at start.

An inverter unit gives more margin against nuisance tripping; a fixed-speed unit needs the margin the rating and curve provide. If an AC trips its MCB every time the compressor starts, do not simply fit a bigger MCB. That can mean the MCB is undersized, but it can also mean a failing compressor or a wiring fault. An electrician checks which.

Whether either kind also needs a stabilizer depends on your supply; see stabilizer for AC and fridge.

Single pole or double pole MCB for an AC?

Many electricians fit a double pole MCB for each AC, because it breaks both phase and neutral and fully isolates the circuit when it is off, which is safer for a technician servicing the outdoor unit, though a single pole MCB, which breaks the phase only, is also used on AC circuits in Indian homes.

We make the 10 kA MCB in single pole and double pole from 6A to 32A, which covers the 16A, 20A and 25A ratings used on AC circuits, with a 10 kA breaking capacity, to IS/IEC 60898-1. The KEMPS TinyTrip modular MCBs add a cut-off beside the AC point, never in place of the board MCB.

Do I need a separate MCB for each AC?

Yes, each AC needs its own MCB on its own circuit, because two ACs on one circuit add their running currents and their start-up surges together, which overloads the cable on a hot afternoon and means one unit’s fault or surge trips the other, so every AC point gets a dedicated circuit from the distribution board.

A 2BHK with an AC in each bedroom and one in the living room has 3 AC circuits, each with its own MCB, plus an incomer sized for all of them running together on a summer evening. That is the load your main MCB and sanctioned load must cover. Our worked example in how to design a modern electrical layout puts ten outgoing MCBs, including those three, on a 12 way board.

Plan the board with spare ways for ACs added later. Our SPN white line MCB box runs from 2–4 way (₹380) to 16–18 way (₹950).

A double pole MCB for each AC takes two ways, so recount the board in our MCB box size list before you buy.

Which socket for a 1.5 ton AC?

A 1.5 ton AC plugs into a 16A socket on a 16A circuit, never a 6A socket, and on a 20A circuit it is usually wired directly to a 20A switch or a 32A DP switch with no plug at all, because the wall point must always be rated at least as high as the MCB feeding it.

For a 16A socket: the VIZA V263 or VIZA V1266, both porcelain base. For a 20A switch: the KEMPS 20AX one-way switch (K147) or the VIZA 20A one-way switch (V1246). For a 32A DP switch: the VIZA V1250. The switch and socket ratings table lists every rating we make.

The AC point itself commonly sits about 7 ft from the floor near the indoor unit; our switch board height guide covers every other point in the room.

Wire size for an AC circuit

The cable from the board to the AC point is sized by the electrician for the AC’s current and the length of the run, and the MCB is then chosen to protect that cable. That order matters: cable first, MCB second. An MCB chosen first and a cable fitted to whatever was on hand is how circuits overheat.

We do not give a cable size here, because cable size is set by the length of the run, how the cable is laid and the AC’s current, and it is fixed by the electrician under the wiring rules. What you can do is ask the question: which cable, which MCB, and why.

Signs your AC MCB is wrong

Three signs point to a mismatch. Trips at start-up: the MCB may be undersized, the curve too sensitive, or the compressor struggling. Trips on hot afternoons: the circuit may be shared with other loads. Warm switch or socket: the point or its connection is overloaded or loose, and needs attention now.

We keep trip diagnosis in one place so the advice never disagrees: MCB tripping again and again sorts trips by pattern, and switch getting hot or socket sparking covers heat at the wall. In each case, an electrician checks the AC’s current, the cable and the MCB together rather than swapping one part.