Which Size Earth Wire Does Each Circuit in Your Home Need?
Earth wire size in a home follows one common rule: in each circuit the earth wire matches the phase wire it runs with, 1.5 sq mm with 1.5, 2.5 with 2.5. Below we explain why it must not be thinner, the earth wire for an AC, what green wire means, how the main earthing conductor to the pit differs, the mistakes electricians find, and the sockets, plug tops and copper wire we supply from Mumbai.
Key takeaways
- Circuit earth — same size as the phase in each run: 1.5 sq mm for lights, 2.5 sq mm for sockets, 4 sq mm where the AC circuit uses 4.
- Why — the earth carries the full fault current until the MCB trips; thinner means a slower trip and a live metal body.
- AC — matches the AC circuit’s wire, commonly 2.5 or 4 sq mm; run it to the outdoor unit.
- Main earthing conductor — board to pit, sized by the electrician under IS 3043; heavier than circuit wire.
- ⚠ Never use neutral as earth, or a water pipe as the earth path.
Earth wire size: the short answer
Earth wire size for the circuits in a home follows a simple common practice: the earth wire in each run is the same size as the phase and neutral wires it travels with, so a 1.5 sq mm lighting circuit has a 1.5 sq mm earth and a 2.5 sq mm socket circuit a 2.5 sq mm earth, up to sizes well beyond any home circuit.
The main earthing conductor, the one that joins the distribution board’s earth bar to the earth electrode in the ground, is a different matter. It is sized by the electrician for the whole installation and the electrode, under IS 3043 and IS 732, and is commonly heavier than any circuit wire.
This guide covers both, explains why an earth wire must not be thinner than the phase, the size for an AC, what green wire means, and the common mistakes. How the electrode itself is built is in our types of earthing guide, and how to test it in how to check earthing. We make the sockets, plug tops and MCBs at the far end of the earth wire, at our works in Mumbai.
What size earth wire is used in house wiring?
In house wiring, the earth wire in each circuit is commonly the same size as that circuit’s phase wire: 1.5 sq mm for lighting and fan circuits, 2.5 sq mm for socket circuits, and 4 sq mm or more where an AC or geyser circuit uses 4 sq mm, with the electrician confirming each run.
Common practice: phase wire and matching earth wire by circuit (sq mm)
General practice, not a design: the earth equals the phase size in each run. Bars to scale with 6 sq mm. Your electrician sizes every circuit under IS 732.
The rule electricians are taught, from the protective conductor tables used under IS 732, is that for phase conductors up to 16 sq mm the earth conductor is the same size as the phase. Every circuit in a home sits inside that range, so in practice: same size as the phase.
Some installers run one earth wire of a single size to several points. That can be acceptable where it is at least as large as the largest phase it protects, but matching each run is simpler and easier to check later.
| Circuit | Phase wire | Earth wire | Typical MCB |
|---|---|---|---|
| Lights and fans | 1.5 sq mm | 1.5 sq mm | 6A to 10A |
| Socket circuit | 2.5 sq mm | 2.5 sq mm | 16A |
| AC on 16A | 2.5 sq mm | 2.5 sq mm | 16A |
| AC or geyser on 20A | 4 sq mm | 4 sq mm | 20A |
| Board to earth pit | Not applicable | Sized under IS 3043 | Not applicable |
Why should the earth wire be as thick as the phase?
The earth wire should be as thick as the phase because during a fault it carries the full fault current, the same current that flows in the phase, until the MCB trips; a thinner earth wire has higher resistance, which slows the trip, lets the appliance body sit at a dangerous voltage, and can overheat the earth wire itself.
What happens in a fault: the phase touches a metal body, current rushes down the earth wire, the MCB sees the surge and trips fast. The lower the resistance of that path, the bigger the surge and the faster the trip.
A thin or long earth wire limits the fault current. The MCB may then take longer to trip, or may not trip at all, while the metal body stays live. That is when a touch becomes a shock.
An RCCB adds a second layer, because it trips on a small leakage whatever the earth wire’s size. But it still needs a connected earth to see most leaks quickly. We do not make RCCBs; our guide to RCCB vs ELCB covers what they do.
An earth wire that is too thin, loose or missing gives no warning in daily use. Everything works, right up until a fault.
Each run’s earth is the same size as its phase wire.
The earth carries the full fault current until the MCB trips.
Run it to the outdoor unit’s terminal, sized to the AC circuit.
Never a thinner earth, a neutral link or a water pipe.
What size earth wire for an AC?
The earth wire for an AC is the same size as the phase and neutral wires on the AC’s circuit: commonly 2.5 sq mm for an AC on a 16A MCB and 4 sq mm on a 20A MCB, read from our catalogue’s in-conduit ratings of 18 A and 24 A, with the electrician confirming for the run length and the AC manual.
So the AC question is really two: which MCB the AC’s circuit needs, then which wire carries that MCB as laid. Our MCB for 1, 1.5 and 2 ton AC guide answers the first, and which wire for AC the second. The earth simply matches the phase.
An AC has a metal body on both the indoor and outdoor units, and the outdoor unit sits in the rain. Its earth matters more than most, and should run all the way to the outdoor unit’s earth terminal, not stop at the wall point.
The same applies to a geyser, a washing machine and a fridge: metal bodies near water. Our guide to a washing machine giving shock shows what a missing earth feels like.
When a new AC is fitted on an old point, ask the installer to confirm there is an earth wire at the point and that it is connected at the board.
What is the green wire size in house wiring?
The green wire in house wiring is the earth wire, and its size is not fixed by its colour: it is chosen to match the phase wire of the circuit, so a green 1.5 sq mm wire runs with lighting circuits and a green 2.5 sq mm wire with socket circuits, while newer wiring uses green-and-yellow instead.
Colours seen in Indian homes: Older: green earth Newer: green-and-yellow. Whichever is used, it should be used only for earth, never as a phase or neutral.
Our VIYONA copper wire comes in five standard colours: black, red, blue, yellow and green, in every size from 0.75 to 6 sq mm. So a green earth can always be matched to the phase it protects.
MRP of a 45 m coil of VIYONA wire, any colour including green (₹)
MRPs from our current catalogue, 45 m coils. Bars to scale with ₹5,085 as the full bar. Every size comes in green.
Which colour does what, phase, neutral and earth, is set out in our phase, neutral and earth guide.
What size is the main earthing wire to the earth pit?
The main earthing conductor from the distribution board to the earth pit is sized by the electrician for the installation’s fault current and the type of electrode, under IS 3043, and is commonly a heavier copper or galvanised iron wire or strip than any circuit wire, because every circuit’s fault current passes through it.
This run is not a DIY job. It sets how well the whole house is earthed. Size, material and the joint at the electrode all count, and the joint should sit in an inspection chamber where it can be checked.
Common faults at this end: a corroded joint at the pit, a conductor cut during building work, and an earth bar in the board that is loose. Each can leave every socket in the house without a working earth, while lights and fans carry on as normal.
Electrode sizes, plate, pipe and rod, are drawn in our types of earthing guide. We do not make electrodes or earthing material; we make the 3 pin sockets and plug tops the earth reaches.
Ask your electrician to note the main earthing conductor’s size and material, and the earth resistance reading, in writing after the job.
Can the earth wire be thinner than the phase wire?
In home circuits the earth wire should not be thinner than the phase wire it protects, because it must carry the same fault current long enough for the MCB to trip; a thinner earth is a common cost-cutting shortcut that leaves the circuit working normally but poorly protected.
The temptation is understandable: the earth carries no current in normal use, so it looks like spare copper. It is not spare. It is the path for the fault.
Three shortcuts to refuse: Thinner earth to save cost One earth for the whole floor Earth taken from a water pipe.
Water pipes are now often plastic, and a metal pipe can be cut or replaced without anyone thinking about the earth. Use a dedicated earth conductor back to the board.
Never use the neutral as an earth, and never join neutral and earth at a socket. It can put the metal body of an appliance at the neutral’s voltage, which is not always near zero.
Does every socket need an earth wire?
Every 3 pin socket needs an earth wire connected to its earth terminal, because the third pin exists to join the appliance’s metal body to the house earth; a 3 pin socket without an earth behind it looks the same on the wall but offers none of the protection the pin promises.
Points where the earth matters most: AC Geyser Washing machine Fridge Iron Kitchen sockets.
Our guide to the 2 pin vs 3 pin plug explains why heavy appliances carry the third pin, and 6A vs 16A socket covers which socket each needs.
Our 3 pin sockets include the VIYONA 119 6A 3 pin socket at ₹40 MRP and the KEMPS K193 6AX and 16AX universal socket with shutter at ₹205 MRP. Each has an earth terminal; the earth wire and its connection are the electrician’s job.
A plug-in socket tester or a meter test by an electrician shows whether a socket’s earth is connected. A line tester cannot.
Common earth wire mistakes in homes
The commonest earth wire mistakes in Indian homes are earth wires missing from some points, earth wires smaller than the phase, loose screws at the earth terminal, neutral and earth swapped or joined, and old installations where the earth runs only to the board and not to the sockets.
What an electrician checks: Earth at every 3 pin point Size matches phase Tight terminals No neutral-earth link Pit joint sound.
Symptoms that point to an earth problem: a tingle from a metal appliance, an RCCB that trips in the rain, and a tester that glows where it should not. Our how to check earthing guide sets out what you can check safely and what needs a meter.
A home with no earth at old sockets is one of the signs listed in our when to rewire a house guide. Adding earth during a rewire is far cheaper than adding it later.
Any tingle from an appliance: switch off at the MCB, unplug it and call a licensed electrician before using it again.
What we make for the earth end of a circuit
We make the parts at the earth end of a circuit, 3 pin sockets, plug tops, MCBs and MCB boxes, at our works in Marol, Andheri East, Mumbai, and supply VIYONA copper wire in green and four other colours, made for us by a partner to IS 694; we do not make earth electrodes, earthing compound or RCCBs.
From our catalogue: VIYONA 243: 6A plug ₹68 VIYONA 244: 16A plug ₹110 VIYONA 411: DP MCB ₹350.
VIYONA 244 is a 16A 3 pin plug top at ₹110 MRP, with the earth pin that joins an appliance to the earth wire. Our VIYONA electrical wire page lists every size and colour.
MCBs in our VIYONA 10 kA range are made to IS/IEC 60898-1 under BIS licence, from a works certified to ISO 9001:2015.
Wiring a new home? Ask for an earth wire to every 3 pin point, sized to its circuit, and a written earth resistance reading at handover.
FAQs
What size earth wire is needed for a house?
What size earth wire for a 1.5 ton AC?
Can the earth wire be smaller than the phase wire?
Is 1.5 sq mm earth wire enough?
Which colour is the earth wire in India?
Can the neutral wire be used as earth?
Why buyers choose Vinayak Electricals
- 3 pin sockets, 6A and 16A plug tops, MCBs and MCB boxes made in-house at our works in Marol, Andheri East, Mumbai.
- VIYONA copper wire in green and four other colours, 0.75 to 6 sq mm, made for us to IS 694 under ISI licence.
- MCBs in our VIYONA 10 kA range to IS/IEC 60898-1 under BIS licence CM/L-2544151.
- We say plainly what we do not make: earth electrodes, earthing compound and RCCBs.
- ISO 9001:2015 certified; making electrical accessories since 1995.
- Published MRPs; sold through 500+ dealers with delivery across India.
Copper wire in every size, green included
See sizes, colours and MRPs for our VIYONA copper wire, then order through a dealer or call us.
View VIYONA wire
