What size wire for a 1.5 ton AC in Pakistan — 2.5mm or 4mm?

The whole circuit sheet, not just the wire

Start at the rating plate on the outdoor unit: it gives the maximum current for your exact model, and no chart beats it. Where the plate is unreadable, these are the working figures. The arithmetic: 1500 W ÷ 220 V = 6.8 A, 1800 W ÷ 220 V = 8.2 A, so the running current sits in the 6.8–8.2 A band. On top of it comes the compressor start surge, which the breaker curve has to ride out — as a rule of thumb two to three times the running current, though the number to size against is the LRA printed on the plate.

That is the sheet an electrician wants before he opens the wall. The rest of this page is the working behind those rows.

The best wire for 1.5 ton AC points — and the one exception

For a 1.5 ton air conditioner in Pakistan, 4 mm² copper on a dedicated 20 A type C MCB is the size that holds in every normal installation: the unit draws 6.8–8.2 A at 220 V, 4 mm² is rated 36 A clipped direct at 30°C, and it keeps a working margin over the breaker once it is derated for conduit, grouping and summer ambient. 2.5 mm², rated 27 A on the same basis, is acceptable only where all four of these are true at once: the run is under 20 metres, the cable is clipped or in surface trunking rather than buried conduit, it is not bundled with other loaded circuits, and the breaker is 16 A rather than 20 A.

The 1.5 ton AC cable size in mm, then, is 4 mm² live, 4 mm² neutral, 4 mm² earth. This is the ladder that decision is read off.

Ask three shops and you get three answers, because each one is quietly assuming a different installation — the conditions above are what the disagreement is really about.

• Take 4 mm² if any one of these is true: the cable runs in conduit or is chased into the wall; the run is over 20 m; it shares a conduit with other loaded circuits; the breaker is 20 A; the unit is fixed-speed.
• 2.5 mm² is defensible only when none of those is true — a short surface run, on its own, on a 16 A breaker.
• Never 1.5 mm². At 19.5 A it sits below a 20 A breaker before any derating at all. The cable would fail before the protection did.
• Aluminium is the wrong metal here. We sell aluminium cable and it earns its place on service drops and long feeders, at sizes well above this one. At 4 mm², on the small terminals inside an AC isolator, copper is what belongs.

Where the 2.5-vs-4 argument is actually settled

Every figure above is a 30°C, clipped-direct number, and nobody installs like that. Take a real job: master bedroom in Lahore, 18 m from the distribution board, cable in conduit chased into the wall, fixed-speed 1.5 ton.

Running current is 1800 ÷ 220 = 8.2 A, and both sizes carry that on paper. The question is what they carry after correction. Conduit in a wall runs hotter than open air, and a Lahore roof space in June is nowhere near 30°C, so both figures come down. Suppose the correction factors for your method and ambient multiply out to 0.75: 2.5 mm² becomes 27 × 0.75 = 20.3 A against a 20 A breaker — the margin is gone. 4 mm² becomes 36 × 0.75 = 27 A, still 7 A clear.

Take the exact correction factors for your method and ambient from BS 7671, or have your electrician do it. The point is not the 0.75 — it is that the derated number, never the table number, is what the breaker has to sit under. Most sizing charts skip that step, and it is the whole argument.

How far the AC can be from the distribution board

Heat decides the size on short runs, length decides it on long ones. Voltage drop is the cable's own loss: millivolts per amp per metre, times the current, times the one-way run.

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 2.5 mm² runs 3.3 ÷ 0.148 = 22 m, 4 mm² runs 3.3 ÷ 0.090 = 37 m, 6 mm² runs 55 m. So 2.5 mm² is out of budget at about the length an ordinary house run reaches, while 4 mm² still has room at the far corner of a double-storey plot. Check your own length in the voltage drop calculator; on a 2 ton unit the same sum bites far earlier, as the 2 ton AC wire size guide shows.

1.5 ton AC ke liye kitne mm ka wire chahiye?

4 mm² copper wire, apne alag 20 A MCB par. Trade mein isko 7/.036 kehte hain. AC 220 volt par takreeban 8 amp kheenchta hai, magar compressor start hote waqt current aam qaida ke tor par do se teen guna ho jata hai — asal figure plate par likha LRA hai, aur isi liye wire running current se bara liya jata hai. 3-core lein, taake earth bhi 4 mm² ho.

Dukaan par aksar 7/.029 (jo 2.5–3 mm² ke naam se bikta hai) diya jata hai. Woh sirf tab chalta hai jab run 20 meter se kam ho, wire deewar ke andar conduit mein na ho, aur breaker 16 A ho. Warna garmi aur conduit ke baad uska margin khatam ho jata hai.

What happens when the supply drops to 190 V

Same unit, same 18 m run, peak hours, supply sagging. The watts do not change, so the current rises: 1800 ÷ 190 = 9.5 A instead of 8.2 A. The cable's own drop then stacks on top of the sag at the unit's terminals — 18 × 9.5 × 18 ÷ 1000 = 3.08 V on 2.5 mm², and 11 × 9.5 × 18 ÷ 1000 = 1.88 V on 4 mm². The compressor sees about 187 V one way, 188 V the other.

Read those two numbers honestly: going up a size buys 1.2 V. Cable size is not the defence against a sagging supply — a stabilizer is. Take 4 mm² for the derating margin and the run length, not because thicker copper will fix the voltage on your street.

Wiring the AC point

• Take the run from the board, not from a nearby socket. A type B breaker on this circuit will nuisance-trip on the compressor inrush and the householder will blame the cable.
• Terminate at a double-pole isolator beside the condenser, so a technician can kill the unit without walking to the board. A plug joint on a hardwired split is a weak point that gets warm.
• Measure the route, not the room: down the wall, along the chase, out through the sleeve, up to the outdoor unit, plus a metre at each end.
• On the second or third AC point it is the main switch and the incoming submain, not the AC cable, that become the limit. Total the load before you add the way.

7/29, 7/36: what the trade codes mean in mm²

Half the confusion here is that the shop and the standard speak different languages. Ask for a size in mm² and you get quoted a strand code: seven strands of 0.036 inch is 7/.036. The codes are imperial and do not land exactly on the IEC nominal areas, which is why one wire has two names.

Ask for 7/.036 and you get what this guide calls 4 mm². Ask for 7/.029 and you get the 2.5–3 mm² wire most shops reach for when a customer says "AC ka wire" — the one that runs out of margin first on a 20 A breaker in conduit. 4mm wire for an AC point is the size we draw most of, made as 4mm 3 core standard cable and 4mm 3 core flexible cable.

How many metres of wire for one AC point

A split install is two cable purchases, and most sizing guides price only one. Measure both before you ask for a rate.

Cable is sold by the coil in Pakistan and coil lengths differ between makers, so ask for the coil length with the rate — it decides whether one AC point costs you part of a coil or all of it. Total your runs, add a metre at each end, and send that figure with your city; we quote against your metres, not a guess. The interconnecting run has its own rules, set out in the split AC interconnecting cable guide.

The cable for this job

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 is 4 mm² too: 4mm 3 core standard cable for a fixed run in conduit, or 4mm 3 core flexible cable where the tail bends around the condenser. The 2 core sizes — 4mm 2 core cable price, 4mm 2 core flexible cable — suit circuits with the earth run separately.

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