Approved Wire Connections in Junction Boxes and Panel Entry Methods

Short Answer

According to HD 60364 standards regarding connection methods: "The connection, tapping, and termination of conductors and cables must be performed using crimping, welding, soldering, or clamps (screw, bolt, etc.) in accordance with the applicable instructions approved in the prescribed manner." There are four approved methods; twisting is not one of them. A "twist" as described in some contexts is merely the preparation of conductors before welding or soldering, rather than a standalone connection method. Spring-loaded (screwless) terminals are not explicitly named in the standard text—they are a type of clamp according to manufacturer terminology and fall under the "etc." category.

In practice, three options are used within junction boxes: spring-loaded terminals for solid and flexible copper conductors (up to 4 mm², or up to 6 mm² in lever-operated series), crimp sleeves for high-load lines and for connecting conductors of different cross-sections, and split-chamber terminals or bi-metallic sleeves for connecting copper to aluminium. Connections must remain accessible for inspection and maintenance (HD 60364-4-41/5-52 principles)—junction boxes must not be plastered over.

Requirements of HD 60364 and relevant standards

Requirement	Reference	Practical application in the junction box
Connection methods: crimping, welding, soldering, or clamps (screw, bolt, etc.)	HD 60364	Terminals, sleeves, welding, soldering. Twisting is not a valid connection method.
Conductor slack to allow for reconnection	HD 60364	Specific slack length is not defined by the standard; in practice, 10–15 cm of each conductor is left.
Connection points must be accessible for inspection and maintenance	HD 60364-5-52	The junction box must have a cover and be located in an accessible place, not hidden behind tiles or wallpaper. HD 60364-5-52 excludes connections made by welding, soldering, or crimping from the accessibility requirement; HD 60364 does not make such an exception.
Conductors and cables must not be subject to mechanical tension at the connection points	HD 60364-5-52	The cable must be secured before the junction box, with conductor slack provided inside.
The insulation of the connection must be equivalent to the insulation of the continuous conductor	HD 60364-5-52	Terminals within a housing, sleeves with heat-shrink tubing, or insulated connectors.
Connections must be made in junction or tapping boxes, in insulated terminal housings, or in equipment enclosures	HD 60364-5-52	Connections made "in-chase" or within a partition void without a proper box are not permitted.
Copper and aluminium must not be connected directly	HD 60364 / EN standards	Use split-chamber terminals with contact paste, bi-metallic sleeves, or clamps with an intermediate plate.

Connection methods: which to choose

The four methods defined by standard practice effectively provide six implementation options: clamps can be spring-loaded or screw-type, and insulated connectors (IEC) represent a distinct product category.

Method	Suitable conductors	Advantages	Limitations
Spring-loaded terminal (tool-free, lever-actuated)	Copper according to series specifications: e.g., WAGO 221-41x – 0.2–4 mm² solid and 0.14–4 mm² flexible, 2273 – 0.5–2.5 mm² solid only, 221-61x – 0.5–6 mm²	Tool-free, reusable, transparent housing allows visual inspection of the conductor	Current rating per terminal datasheet: 24 A (2273), 32 A (221/222 for 4 mm²), 41 A (221-61x); aluminium – only in series specifically approved by the manufacturer using contact paste
Crimp sleeve (GML, GML-P)	Copper 1.5–240 mm²; multiple conductors of different cross-sections can be combined in one sleeve	Permanent connection, current capacity is limited only by the conductors; suitable for service entrances and group circuits	Requires a crimping tool with the correct die for the cross-section; non-reusable – must be cut to change
Welding	Copper conductors (using carbon or graphite electrodes with DC welding)	Monolithic contact	Requires a welding machine and electrode; rarely used in residential wiring
Soldering	Copper conductors	Tools are widely available	Time-consuming, solder joint quality is difficult to verify visually; rarely used in residential wiring
Screw terminal (block, split-bolt connector)	Copper and aluminium, branch connections from a main line	Reusable, designed for large cross-sections	Flexible conductors must use ferrules (e.g., H07V-K with ferrule), otherwise the screw will sever the strands; torque must be checked
Connector cap (twist-on wire connector)	Copper, total cross-section based on cap marking (ranges vary by manufacturer: e.g., 1–13 mm² or up to 16 mm² and more)	Fast and inexpensive	Copper conductors only, primarily single-core; not specifically listed as a standard method in HD 60364

Typical Applications

Copper to copper, single cross-section

For solid conductors such as NYM-J 1.5–2.5 mm², use a spring-loaded terminal for the required number of conductors or a crimp sleeve (e.g., 4–6 mm²) for two or three conductors. The terminal is easier to use and reusable; the sleeve is used where the line current exceeds the terminal's rated capacity (e.g., 24–32 A per datasheet) and where the junction box will remain closed for years.

Conductors of different cross-sections

Spring-loaded terminals are designed to accept conductors of different cross-sections in different ports. For crimp sleeves, the sleeve size is selected so that the sum of the conductor cross-sections does not exceed the sleeve's capacity: for example, 2.5 + 1.5 + 1.5 mm² = 5.5 mm², so a 6 mm² sleeve is selected (this is a practical rule; manufacturers provide specific selection tables). Do not use conductors of different cross-sections under a single screw in a terminal block, as the screw will clamp the thicker conductor, leaving the thinner one loose.

Copper to aluminium

Direct contact is not permitted: the pair forms a galvanic cell, causing the aluminium to oxidise and the connection to overheat. Acceptable methods include terminals with separate ports and contact paste (only in series specifically approved for aluminium), aluminium-copper crimp sleeves (bi-metallic), or branch connectors with an intermediate plate.

Flexible conductor (e.g., H07V-K, H05VV-F) with solid conductor

Flexible conductors cannot be inserted into plain spring terminals (such as WAGO 2273 or similar); a lever-operated connector is required. When using screw terminals, flexible conductors must be fitted with a ferrule (e.g., DIN 46228); otherwise, the screw may sever the individual wire strands. Alternatively, a crimp sleeve can be used to connect flexible and solid conductors without a ferrule.

Which enclosure to choose

• Outdoor under cover, basements, or garages – surface-mounted IP54/IP55 boxes equipped with cable glands from the same category.

The number of entries should be selected based on the number of cables plus one spare. Using a single box for two circuits (e.g., lighting and sockets) is permissible provided there is sufficient volume: conductors with a 10–15 cm slack should be able to be laid without force, and the cover must close without pressing against the wires.

How to route multiple cables into a single distribution board

The same logic applies as with junction boxes, though the volumes are larger. The procedure is as follows:

1. Connect neutral and protective conductors to the respective busbars. Each conductor must be placed into its own slot on the N or PE busbar; two conductors may only be placed under a single busbar screw if the manufacturer explicitly permits it (e.g., specified in the technical data as "2 × 2.5 mm²"). In accordance with HD 60364-5-52, the number of connected conductors must be considered when selecting connection devices.
2. Maintain sufficient conductor length within the enclosure – the length should reach the furthest terminal plus an additional 10–15 cm. Arrange conductors along the enclosure walls and secure them with cable ties, ensuring they are not overtightened.

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Frequently Asked Questions

What are the approved methods for connecting wires in a junction box according to HD 60364?

Crimping, welding, soldering, and clamps (screw, bolt, etc.) must comply with the HD 60364 series. Connections must be accessible for inspection and maintenance, must not be subject to tensile stress, and must have insulation equivalent to that of the conductors.

Is twisting wires in a junction box permitted under HD 60364?

As a standalone connection, no; twisting is not listed as an approved method. Twisting is only permissible as a preparation step for conductors before welding, soldering, or using a connector cap.

How to connect multiple cables to a single distribution board?

Each cable must enter via its own gland or entry point, secured to the enclosure. The N and PE conductors should be connected to the respective busbars (one conductor per terminal), and phase conductors to the MCBs of their respective groups. Flexible conductors must be terminated using ferrules (e.g., H07V-K). Do not bundle multiple lines under a single screw; use a cross-module or busbar system instead.

Is it permissible to clamp two identical conductors under a single terminal?

Only if the terminal is specifically designed for this purpose and specified by the manufacturer (e.g., "2 × 2.5 mm²"). Some MCBs and busbars allow two rigid conductors of the same cross-section—always verify this in the specific product's technical datasheet. Never attempt to clamp conductors of different cross-sections or a combination of rigid and flexible conductors under a single screw.

How to connect H07V-K conductors of different cross-sections?

Use a crimp sleeve based on the total combined cross-section or a lever-operated terminal where each conductor sits in its own dedicated port. For screw terminals, each conductor must be fitted with an individual ferrule, or both conductors may be fitted with a twin ferrule (e.g., H07V-K(2)) if the cross-sections are identical.

When are ferrules required for board wiring?

While HD 60364 does not explicitly mandate ferrules for every connection, it is a standard requirement of professional practice and terminal manufacturers: multi-strand flexible conductors (such as H07V-K or H05VV-F) must be terminated with ferrules before being inserted into a screw terminal. For rigid single-strand conductors (such as H07V-U or NYM-J), ferrules are not required. For spring-loaded lever terminals, flexible conductors can be inserted without a ferrule.