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close this bookHandling and Connection of Cables and Lines for Fixed Laying - Course: Basic skills and knowledge of electrical engineering. Trainees' handbook of lessons (Institut für Berufliche Entwicklung, 17 p.)
close this folder3. Connection of Cables and Lines for Fixed Laying to Electrical Equipment
View the document(introduction...)
View the document3.1. Making Screw Joints
View the document3.2. Criteria for Clamped Joints in Electrical Installations
View the document3.3. Pressed Joints
View the document3.4. Making Wire-wrap Joints
View the document3.5. Making Soldered Joints

3.1. Making Screw Joints

- Before the lines are fed into and connected in the electrical equipment, it is recommended to strip (remove) the insulation as per section 2 hereof.

- For the stripping length, the arrangement of the connections in the equipment is important.

- The connecting lines are to be fed into the connection area of the electrical equipment with their entire sheathing.

- The sheathing of the line must project into the equipment approximately 3 mm.

- When feeding-in lines into equipment with screw joints (e.g. moisture-proof equipment), correct assembly of the screw joint is of utmost importance.

Feeding-in the line with the sheathing prevents the conductor insulation from being worn through by sharp edges of the equipment and, consequently, eliminates possible sources of faults!

Figure 9 Arrangement of the elements when assembling a gland screw joint

1 sealing ring, 2 pressure ring, 3 plug

- The conductor insulation must end 1 mm before the point of clamping.

Figure 10 Connection of a conductor to a terminal

1 terminal, 2 conductor

Clamping of the conductor insulation might be detrimental to the function of the connection!

Conductors stripped too much may result in short circuits!

When are lugs to be bent for clamped connections?

- One conductor only is to be connected to terminals of installation switches, sockets and electrical equipment

- Points of connection and joints must not be covered by other conductors.

- Conductors are to be connected only in the direction of rotation of the clamping screw.

Figure 11 Connection of 4 conductors to one terminal with distributor plate

1 direction of rotation of the screw, 2 distributor plate

- Aluminium conductors are slightly to be greased with acidless grease (anti-corrosive grease) before they are clamped.

- If Cu and Al conductors are to be jointly clamped to one joint, it is to be made sure that the two conductors are not in direct contact.

Figure 12 Connection of a Cu conductor and Al conductor to one terminal

1 Cu conductor, 2 Al conductor, 3 terminal

- The clamped conductor must be supported by the whole contact area of the point of connection or joint.

- If several conductors are connected to one connection bolt, it is to be made sure that a washer is inserted between the conductors and a lock washer at least after every three conductors.

Figure 13 Connection to a connection bolt

1 cable eye, 2 conductor with lug, 3 connection bolt, 4 washer, 5 lock washer

- For connections of protective conductors or middle conductors one conductor per point of connection is admissible only.

- Series connection of the protective conductor from built-in unit to built-in unit is admissible only if the protective conductor is looped.

Figure 14 Looping of a line over a terminal

Looped lines are admissible only within one assembly (e.g. from lamp to lamp within one luminous band).

- When connecting a cable eye and a lug to a connection bolt, the cable eye and lug must be separately connected. (See also Figure 15)

- When connecting conductors to cap screws without clamping saddle or distributor plate, no more than three conductors, which may differ by up to two cross-sectional steps, must be connected with one washer each to be inserted between the conductors.

Figure 15 Connection to a connection strap with cap screw without clamping saddle

1 pressure elements (cap screw, lock washer, washer), 2 conductor, 3 washer, 4 connection strap

- When connecting conductors to cap screw with clamping saddle, one conductor only must be connected per saddle side. (The conductors may differ by one cross-sectional step.)

Figure 16 Connection to cap screw terminals with clamping saddle

- When connecting conductors to cap screws with distributor plate, one conductor only must be connected per distributor plate. (The conductors must have the same cross section).

Figure 17 Connection with cap screw and distributor plate

- Conductors to be connected to connection bolts or screws with no connection facilities must have at least the following cross sections:


Minimum cross section

M 3 to M6



M 8



M 10



M 12



M 16



Washers used for connection of conductors to screws or bolts must cover at least two thirds of the conductor!

Screw slots must not be damaged by wrong-size or defective screwdrivers!