2 ton AC wire size — and where 4mm stops being enough

PILONE CABLES TECHNICAL TEAM

4 mm² copper on its own 25 A type C MCB, 3-core, up to about a 25 m run. 6 mm² beyond that.

A 2 ton unit draws 2000–2400 W, which is 9–11 A on Pakistan's 220 V supply. This is the tonnage where 4 mm² starts to run out of room: it clears a 25 A breaker by 11 A on paper, but only by about 2 A once the cable is derated for conduit and summer heat. That margin, not the running current, is what decides 4 against 6.

The circuit sheet for a 2 ton AC

Read the rating plate on the outdoor unit first — it carries the real maximum current for your model. Failing that: 2000 W ÷ 220 V = 9.1 A and 2400 W ÷ 220 V = 10.9 A, with a start surge on top — as a rule of thumb two to three times the running current, though the LRA on the plate is the number to size against.

Circuit sheet for one 2 ton unit on a 220 V single-phase supply. Copper, PVC, BS 7671 reference method C (clipped direct), 30°C ambient; conductor data per IEC 60228. Check your own rating plate first. Verify sizing with a licensed electrician for your installation.
Parameter	Value
Appliance	2 ton split or window air conditioner
Power, typical	2000–2400 W
Running current at 220 V	9.1–10.9 A
Start surge	LRA on the plate — rule of thumb, 2–3× running
Breaker rating	25 A MCB
Breaker curve	Type C
Live and neutral, to 25 m	4 mm² copper
Live and neutral, past 25 m	6 mm² copper
Earth (CPC)	Same size — the third core
Cable make-up	3 core, 450/750 V PVC

Where 4mm² stops being enough

For a 2 ton air conditioner in Pakistan, 4 mm² copper on a dedicated 25 A type C MCB is the size up to about a 25 metre run: the unit draws 9–11 A at 220 V and 4 mm² is rated 36 A clipped direct at 30°C, which clears the breaker by 11 A on paper and by about 2 A once the cable is derated for conduit and summer heat. Past 25 metres, or where the run is enclosed and hot, take 6 mm² — it keeps about 9.5 A of margin on the same assumptions.

So on a 2 ton unit the argument is 4 against 6, and it is decided by margin over a 25 A breaker rather than by the running current — every size in this table carries 11 A without noticing. On a 1.5 ton unit the same argument sits one rung down, at 2.5 against 4.

Margin is the two-core capacity less the 25 A MCB rating, before derating; derated margin applies a worked correction of 0.75 for a warm enclosed run. Read the two-core column for a single-phase AC point even on a 3 core cable — live and neutral are the only loaded conductors. Copper, PVC. Current capacity and voltage drop per BS 7671, reference method C (clipped direct), 30°C ambient; conductor and stranding data per IEC 60228. Verify sizing with a licensed electrician for your installation.
Size	2 loaded cores	3 loaded cores	Voltage drop	Class 2 strands	Margin on 25 A	Derated margin
2.5 mm²	27 A	24 A	18 mV/A/m	7/0.67	+2 A	−4.8 A
4 mm²	36 A	32 A	11 mV/A/m	7/0.85	+11 A	+2.0 A
6 mm²	46 A	41 A	7.3 mV/A/m	7/1.04	+21 A	+9.5 A
10 mm²	63 A	57 A	4.4 mV/A/m	7/1.35	+38 A	+22.3 A

The derated column is where the answer lives. Suppose the factors for conduit in a wall and a hot roof space multiply out to 0.75: 2.5 mm² falls to 27 × 0.75 = 20.3 A, under the breaker meant to protect it; 4 mm² falls to 36 × 0.75 = 27 A and holds by 2 A; 6 mm² falls to 46 × 0.75 = 34.5 A and keeps 9.5 A. Two amps is a working margin only if you know the route is cool and open. Take the exact factors for your method and ambient from BS 7671.

The 4mm to 6mm crossover, by run length

A 2 ton unit pulls roughly a third more current than a 1.5 ton, and voltage drop scales straight with current — so the same cable reaches about a third less far.

Volts lost in the cable at 10.9 A, the top of the running band at 220 V. Figure = mV/A/m × 10.9 A × run ÷ 1000. Run is one way, along the route the cable takes. Voltage drop per BS 7671, reference method C, 30°C, copper, PVC. Verify sizing with a licensed electrician for your installation.
Run	2.5 mm²	4 mm²	6 mm²	10 mm²
10 m	1.96 V	1.20 V	0.80 V	0.48 V
15 m	2.94 V	1.80 V	1.19 V	0.72 V
20 m	3.92 V	2.40 V	1.59 V	0.96 V
25 m	4.91 V	3.00 V	1.99 V	1.20 V
30 m	5.89 V	3.60 V	2.39 V	1.44 V
40 m	7.85 V	4.80 V	3.18 V	1.92 V

Hold the installation to 3% of 220 V — 6.6 V — and give the AC final circuit half of it, 3.3 V, because the submain from the meter to the board has already spent the rest. On that budget 4 mm² runs 3.3 ÷ 0.120 = 27 m and 6 mm² runs 41 m. So: 4 mm² up to about 25 metres, 6 mm² beyond it — and earlier than that if the run is in conduit through a hot roof, bunched with other circuits, or a second AC point is planned on the same route. A ground-floor board feeding a second-floor outdoor unit is usually already past the line. Check your figure in the voltage drop calculator; the same sum for the smaller unit is in the 1.5 ton AC wire size guide.

2 ton AC ke liye wire size kya honi chahiye?

4 mm² copper (trade mein 7/.036), apne alag 25 A MCB par, agar board se AC point tak 25 meter tak ka faasla hai. Us se zyada lambai par, ya jab wire garam chhat ke andar conduit mein ja raha ho, to 6 mm² (7/.044) lein. 3-core lein taake earth bhi usi size ka ho.

2.5 mm² (7/.029) is unit ke liye kaafi nahi. Derating ke baad uski capacity 25 A breaker se neeche chali jati hai.

Wiring the circuit

The AC point gets a dedicated 25 A type C circuit from the board. At this load, hardwire it through a double-pole isolator beside the outdoor unit rather than running it on a plug and socket.
Pull 3 core so the earth is the same size as the live, and land the outdoor unit's chassis on it.
Measure the route the cable takes, not the room, and decide 4 or 6 mm² from that figure before you buy.
Total the load on the board first. Two 2 ton units on one house draw 18–22 A running between them, and that is a submain and main-switch question before it is a cable question.

Current capacity depends on how the cable is installed. Derate for conduit, grouping, and ambient temperature above 30°C. 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

4MM² · 2 CORE · 450/750 V · CU CLASS 2

4mm 2 Core Standard Cable

Class 2 stranded copper, 7/0.85, PVC insulated and sheathed, 450/750 V, drawn on the Pilone line in Lahore. Rated 36 A clipped direct at 30°C.

Factory-direct price

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This is the price of the wire, not the air conditioner. Cable tracks the daily copper rate, so we quote per metre and per coil on WhatsApp — send the length and your city for the exact figure.

For an AC point take the 3 core version, so the earth matches: 4mm 3 core standard cable. Past 25 m, or on an enclosed hot route, step up to 6mm 3 core standard cable — also made as 6mm 2 core cable and 6mm 3 core flexible cable.

Frequently asked

What is the 2 ton AC wire size in mm?

4 mm² live, 4 mm² neutral and 4 mm² earth on a dedicated 25 A type C MCB, for runs up to about 25 m in a cool, accessible route. Past that, or where the cable is in conduit through a hot roof space, go to 6 mm². The unit draws 9–11 A at 220 V; the size is set by the breaker it has to clear, not by that running current.

Should I use 6mm cable for a 2 ton AC?

Yes on a long or hot run. 4 mm² is rated 36 A and clears a 25 A breaker by 11 A on paper, but at a combined derating of 0.75 that becomes 36 × 0.75 = 27 A — only 2 A of margin. 6 mm² becomes 46 × 0.75 = 34.5 A and keeps 9.5 A. On voltage drop, 4 mm² runs 27 m against a 3.3 V budget and 6 mm² runs 41 m.

What MCB for a 2 ton AC, and which curve?

25 A, type C, on a circuit of its own. The running current is 9–11 A and the compressor start puts a brief surge on top — as a rule of thumb two to three times that, with the plate's LRA as the real figure. A type C curve rides the inrush; a type B on this circuit will nuisance-trip at switch-on.

Can two 2 ton ACs share one circuit?

No. Each unit needs its own run from the distribution board and its own 25 A MCB. Two of them together draw 18–22 A running and start on top of each other, which is a submain question, not a final-circuit one.

Is a commercial 2 ton AC wired the same way?

Not always. Commercial units are sometimes three-phase on 400 V, which changes both the cable and the protection — and on a three-phase circuit you read the three-loaded-conductor column, where 4 mm² is 32 A rather than 36 A. Check the nameplate on your specific unit.

4mm and 6mm wire at the factory rate

We draw the copper in Lahore and sell it at the day's rate — no dealer margin. Send the metres and your city and we will price both sizes so you can see the difference: Punjab in 1–2 days, rest of Pakistan in 2–4.

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