The answer in two lines
The earth (grounding) wire is green and yellow together, the international identification of the protective conductor (PE) per IEC 60445. Per IEC 60364-5-54 (as presented in Schneider Electric's guide), its size equals the phase wire up to 16 mm², then 16 mm² or half the size above that. When the earth wire is separate from the phase wires, the minimum is 2.5 mm² if mechanically protected and 4 mm² if not. Final work should be done by a qualified electrician or engineer.
Want to know the size and colour of the earth wire, how to connect it, and whether it can be thinner than the live wire? It matters because the earth conductor carries fault current away from your body when something fails. In this guide from Tawredaat (توريدات), an electrical and finishing materials store in Cairo and Giza (FAQ here), we explain the colour and size and what the sources say, without inventing numbers.
What colour is the earth wire, and must it be green and yellow?
The protective conductor (PE) is identified by the colours green and yellow together. The international standard IEC 60445 (identification of conductors and terminals) has a clause dedicated to the "Protective conductor" under bi-colour combinations, per the table of contents shown in VDE Verlag's preview. Secondary sources such as Industrial Monitor Direct list PE as green/yellow, and Wikipedia says most jurisdictions now require the protective conductor to have green/yellow insulation. Note: the standard's own text is paid and we did not read it in full.
- ✔ Use green and yellow for the earth conductor only, never for any other function.
- ⚠ Do not place a wire of another colour as earth, because the next technician will take it for something else. If only another colour is available, let the technician decide the solution and the correct marking.
- ⚠ Our product pages do not state the insulation colour (see the last section), so ask our team or check the coil before buying.
Earth wire size: must it match the phase wire?
Per the simplified method in IEC 60364-5-54 (as presented in Schneider Electric's Electrical Installation Guide), for the same metal (copper to copper):
| Phase conductor size (S) | Minimum earth conductor size |
|---|---|
| Up to 16 mm² | Same as S |
| Over 16 and up to 35 mm² | 16 mm² |
| Over 35 mm² | Half of S |
In a flat the common sizes (1.5, 2.5, 4, 6 and 10 mm²) are all under 16 mm², so the simplified rule says: the same size.
| Phase wire size | Minimum earth wire by the simplified rule |
|---|---|
| 1.5 mm² | 1.5 mm² |
| 2.5 mm² | 2.5 mm² |
| 4 mm² | 4 mm² |
| 6 mm² | 6 mm² |
| 10 mm² | 10 mm² |
What about the 2.5 and 4 mm² minimums?
The same guide says that when the earth wire is separate from the phase wires (not inside the same cable), the minimum is 2.5 mm² if mechanically protected and 4 mm² if not. So a 1.5 mm² lighting circuit may need a separate earth larger than 1.5 mm², depending on the case. Whether it counts as "mechanically protected" is the installing engineer's decision, not the customer's.
Can the earth wire be smaller than the rule?
The guide also mentions an engineering calculation method that depends on fault current, breaker clearing time and insulation type; that is an engineer's job. We do not offer a smaller figure because we could not fully verify the formula from the source. The safe approach is to follow this table as a minimum and leave any reduction to an engineer. Never pick the earth size by guessing.
Before choosing the size, remember that the phase wire size itself comes from the load and the breaker; see our apartment breaker guide.
How do you connect the earth wire properly? The basics
IEC 60364-5-54 (title: earthing arrangements, protective conductors and protective bonding conductors in buildings) is the general reference. Details vary with the building and its earthing system, and we do not write detailed steps or earth resistance values without a source. The practical basics:
- ✔ Every outlet and appliance with an earth terminal takes the green-yellow earth wire, per the product's instruction sheet.
- ✔ The earth wire must run continuously to the distribution board and the earth bar of the system, with no break in between.
- ✔ Use the same metal (copper) and the size from the table above; a flexible (fine-stranded) wire is easier to pull through conduit.
- ✔ Make sure each connection is tight and holding, with no extra bare copper.
- ⚠ Do not cut off the earth pin of a plug, and do not connect earth to the live wire or the neutral.
- ⚠ Never open anything while the power is on. Switch off the main breaker and leave installation and testing to a qualified electrician or engineer.
- ⚠ An earth wire alone is not enough without a sound earthing system and a residual current device. See our RCCB guide.
Common mistakes with the earth wire
- ⚠ No earth wire at all: many appliances need one, so ask the engineer before closing the walls.
- ⚠ Using green-yellow for anything but earth: it creates a hazard for any technician after you.
- ⚠ Connecting earth to the neutral: wrong, and it makes the appliances unsafe.
- ⚠ Joining wires by wrapping tape instead of a proper terminal: the joint loosens over time.
Earth wire available at Tawredaat
These products are active and in stock now, described only from each product page: Elsewedy Cables fine-stranded copper earth/grounding wire, 100 m coil. The pages do not state the insulation colour or a standard number, so ask our team if green-yellow matters to you.
| Size | Product |
|---|---|
| 2.5 mm² |
Elsewedy fine-stranded copper earth wire 2.5 mm², 100 m coil tawredaat.com/products/fine-stranded-copper-wire-100-m-2-5-mm-earth |
| 4 mm² |
Elsewedy fine-stranded copper earth wire 4 mm², 100 m coil tawredaat.com/products/fine-stranded-copper-wire-100-m-4-mm-earth |
| 6 mm² |
Elsewedy fine-stranded copper earth wire 6 mm², 100 m coil tawredaat.com/products/fine-stranded-copper-wire-100-m-6-mm-earth |
| 10 mm² |
Elsewedy fine-stranded copper earth wire 10 mm², 100 m coil tawredaat.com/products/fine-stranded-copper-wire-100-m-10-mm-earth |
A 1.5 mm² earth wire is not among the products listed here, so ask our team. See also the wires and cables collection (tawredaat.com/collections/power-wires).
Frequently asked questions
What colour is the earth wire?
Green and yellow together, the identification of the protective conductor PE in the international standard IEC 60445.
Must the earth wire be the same size as the live wire?
Up to 16 mm², yes, per the simplified method in IEC 60364-5-54 (Schneider Electric). Above that it differs. A separate earth wire has a 2.5 or 4 mm² minimum.
Can I use 1.5 mm² as earth?
If the earth is separate, the minimum is 2.5 mm² mechanically protected or 4 mm² unprotected per the same guide. The engineer decides.
Which sizes do you stock?
2.5, 4, 6 and 10 mm², 100 m coils from Elsewedy.
Can I connect the earth myself?
Final connection should be done by a qualified electrician or engineer, and never with the power on.
Do you deliver?
Tawredaat delivers in Cairo and Giza only.
Ready to choose your earth wire?
See wires at Tawredaat, with delivery in Cairo and Giza.
About Tawredaat: Tawredaat (توريدات) is an Egyptian supplier of electrical and finishing materials, serving homeowners, companies and contractors in Cairo and Giza. Questions? See our FAQ.
English summary: The earth (protective) conductor is green and yellow together (IEC 60445). Per the simplified method of IEC 60364-5-54 as presented by Schneider Electric's guide, it equals the phase conductor up to 16 mm2, then 16 mm2 up to 35 mm2 and half above that; a separate earth conductor is at least 2.5 mm2 if mechanically protected or 4 mm2 if not. We give no detailed wiring steps or earth resistance values; installation should be done by a qualified electrician or engineer.
Sources
- Schneider Electric Electrical Installation Guide, Sizing of protective earthing conductor (simplified method based on IEC 60364-5-54: phase conductor up to 16 mm2 gives a protective conductor equal to it, from over 16 up to 35 mm2 gives 16 mm2, over 35 mm2 gives half; the guide also gives the minimum 2.5 mm2 if mechanically protected or 4 mm2 if not, when the protective conductor is separate from the phase conductors) — electrical-installation.org/enwiki/Sizing_of_protective_earthing_conductor
- Schneider Electric Electrical Installation Guide, Conductor sizing (repeats the 2.5 mm2 / 4 mm2 minimums for a separate protective conductor and the rule that the protective conductor generally equals the phase conductor up to 16 mm2) — electrical-installation.org/enwiki/Conductor_sizing
- iTeh Standards catalogue, IEC 60364-5-54 (title: Electrical installations of buildings, Part 5-54, Earthing arrangements, protective conductors and protective bonding conductors; scope clause 541.1) — standards.iteh.ai/catalog/standards/iec/8b936659-704a-418d-86f1-0937624a2edd/iec-60364-5-54
- IEC webstore, IEC 60445:2021 (identification of equipment terminals, conductor terminations and conductors; gives general rules for using colours to identify conductors; the paid text was not read by us) — webstore.iec.ch/publication/66712
- VDE Verlag preview of IEC 60445 ed. 7 (the table of contents lists clause 6.3 Use of bi-colour combinations and 6.3.2 Protective conductor; the body text is not in the free preview) — vde-verlag.de/iec-normen/preview-pdf/info_iec60445{ed7.0}b.pdf
- Industrial Monitor Direct, European control panel cable colour codes (IEC 60445 reference; lists the protective earth conductor as green/yellow; secondary source) — industrialmonitordirect.com/blogs/knowledgebase/european-control-panel-cable-colour-codes-iec-60445-reference
- Wikipedia, Electrical wiring (states most jurisdictions now require the protective earth conductor to be insulated, with green/yellow insulation) — en.wikipedia.org/wiki/Electrical_wiring
- Tawredaat product pages (brand Elsewedy Cables, fine stranded copper earth/grounding wire, 100 m coil, sizes 2.5, 4, 6 and 10 mm2; the pages do not state the insulation colour or a standard number) — tawredaat.com/collections/power-wires
