What size wire for a 3 ton AC in Pakistan — and for a 4 ton?

PILONE CABLES TECHNICAL TEAM

3 ton: 6 mm² copper on a 25 A MCB. 4 ton: 10 mm² on a 32 A MCB.

A 3 ton air conditioner typically draws 3000–3600 W, about 14–16 A on Pakistan's 220 V supply; a 4 ton draws about 18–22 A. On a 4 ton you can stay at 6 mm² only where the cable is clipped in open air on a short run — once it goes into conduit, take 10 mm². Read the rating plate on your own unit first: the current printed there, not the tonnage, is what the circuit is sized to.

What a 3 ton AC draws, and what a 4 ton draws

These are the two largest sizes commonly wired as a single-phase point in a Pakistani house — a 3 ton for a hall or a large drawing room, a 4 ton for a shop floor or a ducted room. Both sit well above the 1.5 ton point most homes wire, and neither belongs on the same circuit as anything else.

Circuit sheet for a single-phase 220 V fixed-speed unit. Power figures are typical for these tonnages — take the real number from your unit's rating plate. Current capacity and voltage drop per BS 7671, installation reference method C (clipped direct), 30°C ambient; conductor data per IEC 60228. Verify sizing with a licensed electrician for your installation.
Parameter	3 ton	4 ton
Typical power	3000–3600 W	4000–4800 W
Running current at 220 V	14–16 A	18–22 A
Start surge, fixed speed	2–3 × running	2–3 × running
MCB rating	25 A	32 A
MCB curve	C	C
Live and neutral	6 mm²	10 mm²
Earth	6 mm²	10 mm²
Isolator at the unit	Double pole, at or above the MCB	Double pole, at or above the MCB

The arithmetic is plain: 3600 W ÷ 220 V = 16.4 A, and 4800 W ÷ 220 V = 21.8 A. The breaker goes above that figure, and the cable goes above the breaker.

Why 6mm² for a 3 ton, and not 4mm²

A 3 ton air conditioner on a 220 V single-phase supply draws about 14–16 A while it runs, so the point takes 6 mm² copper on a 25 A MCB: 6 mm² carries 46 A clipped direct in open air at 30°C and 41 A when three conductors are loaded, which leaves the circuit standing above the breaker even after it is derated for conduit and a Lahore summer. 4 mm² clears the running load on paper, but 11 A is the whole of its headroom over the breaker, and conduit and a Lahore summer spend that headroom long before they spend the 21 A that 6 mm² starts with.

Margin is the two-core current capacity less the 25 A MCB this point runs on. Copper conductors, PVC insulated. Current capacity and voltage drop per BS 7671, installation reference method C (clipped direct), 30°C ambient; stranding and conductor data per IEC 60228. Trade codes are imperial-diameter shop names, not IEC areas — they do not coincide exactly. Verify sizing with a licensed electrician for your installation.
Size	2 core	3 core	Voltage drop	Class 2 strands	Trade code	Margin
2.5 mm²	27 A	24 A	18 mV/A/m	7/0.67	7/.029	+2 A
4 mm²	36 A	32 A	11 mV/A/m	7/0.85	7/.036	+11 A
6 mm²	46 A	41 A	7.3 mV/A/m	7/1.04	7/.044	+21 A
10 mm²	63 A	57 A	4.4 mV/A/m	7/1.35	7/.052	+38 A

Take 6 mm² for a 3 ton point in any normal installation — 46 A against a 25 A breaker, 21 A of margin to spend on conduit, grouping and heat.
Take 10 mm² on a 4 ton, or on a 3 ton where the run is long and enclosed — 63 A against a 32 A breaker.
2.5 mm² is not a candidate here. 27 A against a 25 A breaker is 2 A of headroom, and it is gone the moment the cable enters a conduit. It is in the table to show where the ladder starts, not as an option.

Nobody can give you the exact derated figure without seeing the installation, which is why the sensible move at this load is to buy the margin rather than the calculation. If you ask for it at the shop by the trade code, 6 mm² is the coil marked 7/.044.

4 ton AC wire size in mm

A 4 ton unit at 18–22 A needs a 32 A breaker, and a 32 A breaker needs a cable that stays above 32 A after derating. 6 mm² starts at 46 A and 10 mm² starts at 63 A. Clipped direct on a short run, 6 mm² holds. In conduit, bunched, or on a long run to an outdoor unit on the roof, 10 mm² is the size that still has margin when the summer is at its worst.

Check the supply on the rating plate before you buy either. Most 3 ton units sold here are single-phase 220 V, but a fair number of 4 ton and ducted units are three-phase 400 V. A three-phase unit splits the same power across three lines, so the current in each line is much lower and the cable is sized differently — use the three-phase cable size guide for that one, not this table.

How far the point can be from the distribution board

At this load, heat decides the size and length decides whether you go one size up again. The cable's own drop is its voltage drop figure multiplied by the current and the one-way run length. A unit pulling 15 A on 6 mm² over a 30 m run drops 7.3 × 15 × 30 ÷ 1000 = 3.29 V, comfortably inside the 6.6 V budget. Put the same load on 4 mm² and it becomes 11 × 15 × 30 ÷ 1000 = 4.95 V — still inside the budget, which is exactly why voltage drop is the wrong reason to pick 6 mm² here. Heat is the reason.

Cable's own voltage drop in volts, one-way run from the distribution board to the AC point, at 15 A for a 3 ton and 21 A for a 4 ton. Budget is 3% of 220 V = 6.6 V. Voltage drop figures per BS 7671 for PVC-insulated copper. This drop adds to any sag already on the supply, so treat the budget as a ceiling, not a target.
Run	4 mm² at 15 A	6 mm² at 15 A	6 mm² at 21 A	10 mm² at 21 A
10 m	1.65 V	1.10 V	1.53 V	0.92 V
15 m	2.48 V	1.64 V	2.30 V	1.39 V
20 m	3.30 V	2.19 V	3.07 V	1.85 V
25 m	4.13 V	2.74 V	3.83 V	2.31 V
30 m	4.95 V	3.29 V	4.60 V	2.77 V
40 m	6.60 V	4.38 V	6.13 V	3.70 V

Read the far right of the table and the limits fall out: 6 mm² carrying 15 A runs to about 60 m before it spends the whole 6.6 V, and at 21 A it runs to about 43 m. 10 mm² at 21 A reaches roughly 71 m. Measure the real route — up the wall, along the slab, out to the outdoor unit — not the straight line, and check it against the voltage drop calculator.

Wiring the circuit

The point gets its own way out of the distribution board. At 14–22 A there is nothing to share a circuit with.
Add the load to the board before you add the circuit. Two of these units in one house is another 32 A the main has to carry.
Run the earth in the same size as the live and neutral — a single 3 core cable gives you all three in one pull.
Fit a double-pole isolator within reach of the outdoor unit so the machine can be worked on dead.
Terminate on the full conductor. At 6 and 10 mm² a strand left out of the terminal is the most common cause of a hot connection.

Current capacity depends on how the cable is installed. Derate for conduit, grouping, and ambient temperature above 30°C. At this load a wrong size does not trip a breaker, it cooks a termination. Have a licensed electrician confirm the size for your load and run length — or start with the cable size calculator.

The cable for this job

Two-core standard cable with black outer sheath, cut back to show red and black insulated stranded copper conductors

6MM² · 2 CORE · 450/750 V · CU CLASS 2

6mm 2 Core Standard Cable

Stranded copper, 7/1.04 class 2, PVC insulated and sheathed, 450/750 V, drawn on the Pilone line in Lahore. Rated 46 A clipped direct at 30°C — the size this point takes. The trade calls this coil 7/.044.

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Also made in 6mm²: 6mm 3 core standard cable, 6mm 4 core cable, 6mm 3 core flexible cable. The 3 core carries live, neutral and earth in one pull, which is what an AC point wants. For a 4 ton in conduit, step up to the 10mm 3 core cable.

Frequently asked

What size wire is needed for a 4 ton AC in mm?

10 mm² copper for the live and neutral, on a 32 A MCB, wherever the cable runs in conduit or bunched with other circuits. A 4 ton unit draws roughly 18–22 A at 220 V, and 10 mm² carries 63 A clipped direct against 46 A for 6 mm². On a short run clipped in open air, 6 mm² on a 25 A MCB still holds.

Is 4mm wire enough for a 3 ton AC?

Not for the fixed wiring. 4 mm² carries 36 A clipped direct at 30°C, which is only 11 A above a 25 A breaker, and that margin goes quickly once the cable sits in conduit through a Lahore summer. 6 mm² carries 46 A and keeps the headroom. 4 mm² belongs on a 1.5 or 2 ton point.

What MCB size for a 3 ton AC?

25 A, on a C curve. The unit runs at about 14–16 A, so a 20 A device sits too close to the load and a fixed-speed compressor's start will trip it. A C-curve device rides a bigger inrush before it opens than a B-curve device of the same rating.

Does a 3 ton AC need a three-phase supply?

Most 3 ton units sold in Pakistan are single-phase 220 V and wire like any other AC point. Some larger 4 ton and ducted units are three-phase 400 V — the rating plate says which. A three-phase unit splits the same power across three lines, so each line carries far less current; size that circuit with the three-phase cable size guide.

What size earth wire for a 3 ton AC point?

Run the earth in the same size as the live and neutral. On a 3 ton point that means 6 mm², and the simplest way to get it is one 3 core 6 mm² cable carrying live, neutral and earth in a single run. Do not borrow an earth from another circuit or from a water pipe.

6mm and 10mm cable for the AC point, at the factory rate

We draw the copper in Lahore and sell it at the day's rate — no dealer margin. Tell us the length and your city: Punjab in 1–2 days, rest of Pakistan in 2–4.

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