What size wire for LED lights — and why LEDs do not make it thinner
PILONE CABLES TECHNICAL TEAM
1.5 mm² copper — the wire shops sell as 3/.029 — on a 6–10 A lighting MCB. Two cores plus earth for one-way switching, three plus earth for two-way.
An LED fixture is 5–20 W, which is 0.02–0.09 A at 220 V. That is the lightest load in a house and it is not what the cable is sized on. A lighting circuit is sized on the breaker protecting it, on the switch wiring it has to carry, and on what somebody will hang off it in ten years' time.
The lamp does not size the cable
A light point in a Pakistani house is wired in 1.5 mm² copper (3/.029) on a 6–10 A lighting MCB whether the fitting is a 12 W LED downlight or a 60 W filament lamp, because the conductor is chosen for the circuit and its protection rather than for the fitting on the end of it. The arithmetic makes the case on its own: twenty-four 12 W downlights total 288 W, which is 288 ÷ 220 = 1.31 A on a cable rated 19.5 A clipped direct at 30°C. The same twenty-four points in 60 W lamps would have drawn 6.5 A. Both sit comfortably inside 1.5 mm², so switching to LED changes the running current by a factor of five and changes the correct cable by nothing.
One lighting circuit on a 220 V single-phase supply. Voltage drop = mV/A/m × current × one-way run ÷ 1000. Current capacity and voltage drop per BS 7671, reference method C (clipped direct), 30°C ambient, two loaded conductors; conductor and stranding data per IEC 60228. Derate for conduit, grouping and ambient above 30°C. Verify sizing with a licensed electrician for your installation.
Parameter
Value
Fixture
LED bulb, panel, downlight or strip driver
Power, typical
5–20 W each
Current at 220 V
0.02–0.09 A each
Circuit cable
1.5 mm² copper (3/.029)
Capacity of that cable
19.5 A
Voltage drop figure
29 mV/A/m
Breaker
6–10 A lighting MCB
Cores, one-way switching
2 plus earth
Cores, two-way switching
3 plus earth
24 downlights at 12 W
288 W — 1.31 A
Drop on that circuit over 25 m
0.95 V
What actually decides a lighting circuit
Voltage drop is not the limit here and neither is heat. Twenty-four downlights 25 m from the board lose 29 × 1.31 × 25 ÷ 1000 = 0.95 V, well inside any sensible budget. Three other things do the deciding, and none of them is the lamp.
The switch wiring. One-way switching takes a live and a neutral plus earth. Two-way switching — the stair light, the bedroom light with a switch at the door and one at the bed — needs three cores plus earth between the two switch positions. Get the core count wrong and the wall is opened twice.
The breaker, not the cable, when a bank of drivers trips at switch-on. Every LED driver takes a very short, high inrush as its capacitors charge, and a large bank of them can trip a sensitive breaker at the moment the switch is closed while running happily afterwards. That is a breaker-curve question for your electrician; a thicker cable does not change it.
What the circuit becomes later. Lighting circuits get extended — a fan point added here, an outdoor light there. 1.5 mm² leaves that headroom; a conductor chosen to suit 288 W does not. How many points one circuit should carry is worked through in the ceiling fan wire size guide, and total quantities per house size in the 5 marla house wiring guide.
Current capacity depends on how the cable is installed. Derate for conduit, grouping, and ambient temperature above 30°C, and take the correction factors for your own method from BS 7671. Have a licensed electrician confirm the size for the whole circuit, not a single fitting — or start with the cable size calculator.
Solid copper conductor, PVC insulated, 450/750 V, drawn on the Pilone line in Lahore. Rated 19.5 A clipped direct at 30°C — the wire light points are pulled in.
1.5 mm² copper, jise dukaan par 3/.029 kehte hain, 6 se 10 A ke lighting MCB par. Ek LED sirf 5–20 W leti hai, yani 0.09 amp tak, magar wire poore circuit ke hisab se chuna jata hai, bulb ke hisab se nahi. Two-way switch ke liye teen core plus earth chahiye.
LEDs use far less power — can I use a thinner wire than before?
No. Twenty-four 12 W downlights draw 1.31 A where the same points in 60 W lamps drew 6.5 A, and 1.5 mm² is the right conductor for both. The cable is chosen to sit above the breaker protecting the circuit and to leave room for points added later, neither of which changes when the lamps do.
Why does the MCB trip the moment a bank of LED lights is switched on?
Because of inrush, not overload. Each driver draws a very short, high current as its capacitors charge, and many drivers switching together can trip a sensitive breaker at that instant while the circuit runs normally afterwards. The fix is the breaker's rating and curve, chosen by your electrician. A thicker cable changes nothing.
How many cores do I need for a two-way light switch?
Three plus earth between the two switch positions, so both switches can pass the live either way. One-way switching needs two plus earth. Deciding this before the conduit goes in is worth more than any argument about conductor size, because the core count is what forces the wall open a second time.
1.5mm cable for the lighting circuit, at the factory rate
We draw the copper in Lahore and sell it at the day's rate — no dealer margin. Tell us the metres and your city: Punjab in 1–2 days, rest of Pakistan in 2–4.
