Thailand's Wire Colour Code (TIS 11-2553) Which Wire Is Live, Neutral & Ground
You open a wall box and find brown, blue, grey, black and green-yellow wires — which ones are live, and which is the ground? This page lays out wire colours under Thailand's current standard TIS 11-2553 (aligned to the international IEC 60227), for both single-phase and three-phase systems, with a side-by-side table against the old TIS 11-2531 code and a warning about the colours whose meaning changed — so you can read the wiring in your home more safely.
Under Thailand's current cable standard TIS 11-2553 (aligned to IEC 60227): a brown wire is the Line (L, live), light blue is the Neutral (N), and green-yellow is the Ground (สายดิน, G). In a three-phase system the three live conductors are brown, black and grey (L1/L2/L3), while neutral stays blue and ground stays green-yellow. The catch: older homes wired to the previous standard (TIS 11-2531) used white/grey for neutral, and dark blue used to be a LIVE phase — the opposite of today's light-blue neutral. So with old or mixed wiring, never trust colour alone: confirm with a voltage tester and have a licensed electrician do the connections.
What Are the Brown, Blue and Green-Yellow Wires?
How Do Single-Phase and Three-Phase Colours Differ?
The only difference is how many live wires there are — neutral (blue) and ground (green-yellow) are the same colour in both. Single-phase has one live wire (usually brown); three-phase has three live wires coloured brown, black and grey for phases 1/2/3 respectively. See the table:
| Conductor | Symbol | Colour (TIS 11-2553) |
|---|---|---|
| Live (single-phase) | L | Brown (typical) |
| Lives (three-phase) | L1 · L2 · L3 | Brown · Black · Grey |
| Neutral | N | Light blue |
| Ground / Earth | G / PE | Green-yellow (or green / bare) |
Note for single-phase: the standard is strict only that neutral must be blue and ground must be green / green-yellow. The live wire “may be any colour other than neutral and ground,” so in practice you may see brown, black or grey live wires (some single-core THW wiring uses black for socket circuits and white for lighting circuits as the live). The colours you must never repurpose are blue (neutral) and green-yellow (ground).
How Does TIS 11-2553 Differ From the Old TIS 11-2531?
The old TIS 11-2531 used black, red and dark blue for the three live phases, white or grey for neutral and green for ground. It was replaced by TIS 11-2553 to match the globally used IEC 60227. The biggest change is the neutral colour (white/grey → light blue) and the meaning of blue:
| Function | Old (11-2531) | New (11-2553) |
|---|---|---|
| Live (3φ) | Black · Red · Dark blue | Brown · Black · Grey |
| Neutral (N) | White or grey | Light blue |
| Ground (G) | Green | Green-yellow |
⚠️ The most dangerous point: in the old standard dark blue was a LIVE phase, but in the new one light blue is neutral, and old neutrals were often white/black. So in an older home a wire that looks “bluish” may be live, and a black wire may be neutral — never guess from colour alone.
What Goes Wrong If Wires Are Connected to the Wrong Colour?
Wire colours are not decoration — they are a safety system that lets the next person wire correctly. Getting them wrong causes real problems:
Swapping live and neutral (L↔N): the appliance may still run, but the switch then breaks the neutral instead of the live, leaving the device/lamp holder energised even when switched off — a shock risk during maintenance.
Reusing the green-yellow wire for anything else: the ground colour must be reserved for ground only. Using it as a live or neutral makes the next technician assume it is safe to touch — potentially fatal.
No ground wire (green-yellow) at all: if current leaks to an appliance's metal body there is no safe path to earth, so the casing stays live waiting for someone to touch it — which is why water heaters and washing machines must always have a ground wire (for how a leak also inflates the bill, see the electrical-leakage page).
How to Read Home Wiring — Can You Trust the Colours Alone?
Sizing questions like “which wire number carries how many amps” are a separate topic from colour — for conductor/main-wire sizing see the meter & main-wire size page, and for connecting the ground wire correctly see the dedicated grounding page.
About the Author
Compiled by the CapSolar team under Frank Lee (Founder). CapSolar is a commercial & industrial solar EPC/PPA provider in Thailand that distils electrical standards and safety guidance from official sources (TISI / EIT / the utilities). This article is general information — real wiring and connection work should be done by a licensed electrician.
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