Installation wires: conductor types and identification
For installation wires, green-and-yellow identifies a protective conductor and blue identifies neutral. Brown, black and grey are common line-conductor colours. Other colours can serve different purposes depending on the circuit and identification system. The actual function of an existing conductor must still be established: colour alone is not sufficient.
This page covers individual insulated conductors, such as H07V-K. It explains the main colours, solid and fine-stranded construction, and the importance of suitable selection and termination. Our installation-cable page covers multicore cables and their markings in more detail.
What is an installation wire?
The conductor is the electrically conducting material, such as copper. Together with its insulation, it forms a core. An individual insulated wire has no additional common sheath like that of a multicore sheathed cable.
These wires are used in suitable protected wiring systems and for appropriate equipment, distribution-board or control wiring. The product construction and manufacturer's instructions determine the permitted use. An individual insulated wire cannot simply be substituted everywhere a sheathed cable is specified.
Match conductor and terminal
What do the colours mean?
The table explains basic principles for present-day low-voltage installations in the Austrian and European context. Special installations, machinery and other countries can have additional or different requirements.
| Colour | Typical function or context | Important distinction |
|---|---|---|
| Green-and-yellow | Protective conductor, PE | The combined colour identification is reserved for protective functions, not ordinary line, switched-line or control use. |
| Blue | Neutral conductor, N | Can carry current in normal operation. Colour is not proof that the conductor is dead. |
| Brown | Often line or an appropriately identified switched line | Does not automatically identify L1 or a push-button function. |
| Black | Often line or an appropriately identified switched line | Consider the diagram, identification and actual circuit. |
| Grey | A common present-day line-conductor colour | Do not assume an old grey conductor has the same function as a modern one. |
| Orange or violet | Additional identification within particular control or switching systems | No universal assignment to a push-button, lamp, alarm or particular voltage. |
For example, a switched line is needed between a switch and a luminaire. Brown or black may serve this function within the applicable requirements. Colour alone does not establish whether a particular wire is permanently supplied, switched or part of another control arrangement.
Exceptions concerning blue conductors in German examples must not automatically be applied to Austria or Switzerland. This overview does not give general permission to use blue as a line conductor. The requirements applicable to the actual installation govern its use.
Protective and neutral conductors do different jobs
The protective conductor, PE, forms part of the protection against electric shock. It is not intended to carry normal load current. The protective current path must work under fault conditions; green-and-yellow insulation alone does not prove that it is connected correctly.
The neutral conductor, N, is part of the operating circuit and may carry current. A blue conductor is therefore not automatically dead or safe to touch. PE and N must not be interchanged or joined at a connection point at someone's discretion.
A PEN combines protective and neutral functions. Its use depends on specific requirements for the supply arrangement, construction and identification. An old installation with few cores cannot be assessed or altered simply by renaming a colour or adding a bridge.
What are “lamp wires” and “push-button wires”?
The informal term “lamp wire” commonly refers to a switched line supplying a luminaire. It does not identify a separate standardised wire type. Whether and when it is live depends on the circuit.
A “push-button wire” has a function within a control circuit, such as a connection to an impulse relay or another controller. The term specifies neither a colour nor a voltage. Push-buttons can operate in different control systems.
For orange and violet wires, the identification system is especially important. Machinery and control panels can have their own conventions. These colours cannot simply be read as fixed rules for building wiring.
Single-core, solid or fine-stranded?
These terms describe different properties. Single-core means that a wire or cable has one core. Solid means that its conductor consists of one wire. A fine-stranded conductor contains many thin wires forming one conductor.
A single-core wire can therefore contain a fine-stranded conductor. Several strands do not make it a multicore cable. The distinction also affects termination: a terminal must accept the actual conductor construction and size.
In H07V-U, -U identifies a solid circular conductor. H07V-K has a fine-stranded conductor for appropriate fixed wiring applications. Its flexibility does not make it a universal choice for continuously moving equipment connections.
One conductor can contain many strands
Reading H07V-K 1.5 mm²
| Element | Meaning in this example |
|---|---|
| H | Harmonised construction |
| 07 | Rated voltage U₀/U of 450/750 V |
| V | PVC core insulation |
| -K | Fine-stranded conductor for appropriate fixed wiring applications |
| 1.5 mm² | Nominal conductor cross-section, not the outside diameter of the insulated wire |
| Colour description, such as blue | Colour of the supplied wire; its use must suit the identification system |
U₀ is the rated voltage between conductor and earth; U is the rated voltage between conductors. Product data also specify installation conditions, temperatures and bending limits. A voltage marking alone does not establish suitability for every environment.
H07V-K is an individual insulated wire. Grouping several such wires together does not provide a common sheath or replace the selection of a suitable connecting cable.
Terminals and ferrules must suit the conductor
Not every terminal accepts every conductor type. Some are designed for solid conductors; others also accept stranded or fine-stranded construction. Conductor type, size, material and any required preparation must suit the actual terminal.
There is no universal rule that ferrules are always required or always better. Some terminals are intended to accept fine-stranded conductors without ferrules. Other connections require appropriate preparation. The permitted conductor range with a ferrule may differ from that for an untreated conductor.
Stripping length, insertion method and any tightening torque come from the product instructions. A familiar value from another connector is not a general setting. Preparation must not damage insulation or conductors, or remove individual strands.
Historical colours: no safe conversion chart
Older installations can contain earlier colour systems and later alterations. Different identification schemes may even coexist within one installation. A chart that equates an old colour with a new colour is therefore not a safe connection guide.
It would be particularly misleading to treat an old grey conductor automatically as a modern grey line conductor, or an old blue wire as neutral without verification. Single-colour green or yellow is not equivalent to present-day combined green-and-yellow identification either.
The blanket statement that protective conductors did not exist in older installations is incorrect. Depending on the installation, there may be a separate protective conductor, a combined PEN or inadequate protective provision. The actual arrangement must be assessed.
Alterations therefore involve more than colour matching. A competent electrical professional must establish conductor functions, the protective arrangement and its condition, and carry out the required verification. New coloured marking alone does not repair an unsuitable or faulty installation.
Colour does not determine current-carrying capacity
A blue wire and a black wire with the same construction and cross-section do not have different current ratings merely because of their colour. Relevant factors include conductor material, insulation, installation method, ambient temperature, grouping and the number of loaded conductors.
Thermal insulation or closely grouped loaded circuits can restrict heat loss. A neutral carrying unbalanced or harmonic currents is not automatically unloaded. Tabulated ratings must be used with their stated assumptions and appropriate corrections.
Selection also includes length, voltage drop, termination conditions and coordination with overcurrent protection. The description “1.5 mm²” alone does not establish a suitable protective-device rating. Our installation-cable page explains these factors further.
Common mistakes and useful checks
- Assigning unidentified conductors by colour alone, or joining old and new wires simply by matching colours.
- Using green-and-yellow to make up a missing switched line or neutral.
- Inserting a fine-stranded conductor into an unsuitable terminal.
- Treating a ferrule as an automatic improvement regardless of the connection instructions.
- Assuming that conductor size, colour or neat appearance proves that the complete circuit is safe.
Appropriate verification includes positive identification, undamaged insulation, suitable terminations and the electrical tests required for the actual work. Visual inspection alone proves neither protective-conductor continuity nor the complete effectiveness of the protective measures.
Work on fixed electrical installations requires the relevant competence. A safe de-energised condition must be established and verified before conductors are touched. Our five safety rules explain the principle; they do not replace training or assessment of the actual installation.
Short answers to common questions
Does a blue wire mean that it is safe to touch?
No. Neutral may carry current, and colour does not prove the function of an unidentified wire. The absence of voltage must be verified by an appropriate safe procedure before work.
What colour is a lamp or push-button wire?
There is no universal colour. Its function comes from the circuit and identification system. Orange or violet does not prove that a control voltage is harmless.
Can H07V-K be used as a moving equipment cord?
Not merely because it is fine-stranded and easy to bend. This construction is intended for appropriate fixed wiring. A moving connection requires suitable cable construction and product approval for that application.
Does every fine-stranded conductor need a ferrule?
No. Follow the terminal and application instructions. Some terminals accept fine-stranded conductors without ferrules. A ferrule must neither exceed the permitted connection range nor prevent full insertion.
Related topics
Connect conductor type, terminal and verification
Core count and conductor construction answer different questions. One insulated core may contain a solid wire or multiple strands. Suitability for a terminal follows its actual instructions, not the word flexible alone.
A ferrule is not a universal solution for every terminal. Type, dimensions, occupancy and preparation remain important. Physical fit does not establish an approved durable connection.
After connection, consider the whole condition: identified function, suitable joint, intact insulation and necessary tests. Correct colour alone does not prove the correct path.