Elektro Tipp: Still a "hot" topic: If terminals get too hot - Safe connection of conductors To Know more details click here: http://hensel.in

1. Regards,
Felix G. Hensel
Managing Director of
Gustav Hensel GmbH & Co. KG
Collection
of
new
ideas
in
the
Electrotechnical
Industry
A bad terminal connection can cause damage...
The ELEKTRO
Customer information for electricians 1/2014
30th Volume, 125th Edition
For example, a bad connection within
the PE-link can lead to absence of the
required residual current for switching off
the protective device and thus personal
safety is no longer guaranteed.
This edition of Elektro Tipp shows how
screw-type terminals can be safely
connected to.
The safety of every electrical installation,
including the devices installed in it,
depends on terminals used millions
of times for connecting cables and
conductors.
Concerning many connections the
electrician makes every day, it is often
difficult to consciously be aware of the
functional inter-connection between
terminals, the conductors to be
connected and one’s own actions.
Still a “hot” topic:
If terminals get too hot
Safe connection of conductors
Dear reader,
Proximity to electricity is an integral
part of our daily lives and has the
potential to profoundly affect us in
many ways.
Electrical faults have been identified
as one of the common causes for
fires in buildings. Most of these
faults have been traced to loose
terminations which go undetected
till the damage is done.
With more than 80 years of
experience, we are in a good
situation to caution our readers
against common pitfalls and tips
to ensure that you have a safe and
reliable installation.
Please do not hesitate to reach out
to your local HENSEL specialist if
you need more information.
Here,
the clamping units
are scorched!
The whole distribution
board could have been
burnt!

2. What are the characteristics of a safe terminal connection?
An bad terminal connection can cause damage!
Mechanical tensions in the terminal
These occur, for example, due to a lack
of strain relief or not sufficient wiring
spaces, particularly for conductors with
a large cross-sectional area.
Wrong torque
If there is an excessively high torque,
the terminal lacks the properties of the
spring needed to produce an optimal
contact pressure.
An unsuitable terminal for the
conductor
Terminals are established for certain
specific types of conductor and cross-
sections. Connection of different types
of conductors and cross-sections at
the same clamping unit is usually not
permissible.
Examples of bad terminal connections:
How does a terminal connection become bad and what are the possible consequences?
Clamping units become bad when the conductor is no longer ensuring safe current transfer.
The contact begins to char and becomes a potential fire risk.
A faulty terminal usually represents a high fire risk. If there is an imperfect PE conductor
connection (PE) then personal safety is no longer ensured in the case of a fault!
Terminals with screw connections
Conductors are mechanically and
electrically connected together using a
clamping screw. Selecting the correct
terminal and torque determines the level
of safety of the terminal connection.
In the following, Elektro-Tipp is only
concerned with “screw-type terminals”.
Terminal 10 mm2
wired, re-wire and take
a photograph
Different terminal
technologies
The probable consequences:
Terminals with screw-less connections
Plug-in terminals automatically ensure
that the contact is made by the
regulating force of the spring on the
conductor and will therefore not be
considered any further here.

3. What are the characteristics of a safe terminal connection?
Three factors determine the safety of a connection:
1. Selecting a suitable terminal
Selecting the correct terminal according to the type of
conductor and cross-section. Solid, stranded or flexible
conductors have a different contact behaviour. The
connectable nominal cross-section can be taken from the
marking on the terminals.
Aluminium conductors place special demands on a terminal
and on pre-treatment of the conductors.
Summary:
A terminal connection is safe if all three
factors mentioned are observed
3.
Permanent contact pressure through an optimal torque and spring effect
2. Adequate wiring space and strain relief for the cable
The terminal connection must relieve all strain and pressure
on the conductor, for example, by means of a cable gland
or cable strain relief device. The conductor must be inserted
into the terminal in such a way that no external mechanical
effects can act upon the terminal connection. This applies for
all conductors, particularly for solid conductors with a large
cross-section.
An adequately
large wiring
space allows
the conductor
to be connected
pressure-relieved.
Ensuring the correct contact force is a basic requirement
for terminals: It is generated through simple operation of the
clamping screw. The contact is safe if a good connection and
safe current transfer to a defined location is guaranteed with
the prescribed power (optimal torque).
The amount of torque required depends on the terminal
construction and size.
Only the correct
torque guarantees
reliable terminal
connections!
The spring tension of the contact is set by using the
prescribed torque. In this way, the required contact pressure
is generated and the specified spring deflection is achieved.
An excessively high torque destroys the spring effect.
If the torque is too low the contact pressure is not sufficient
enough, and this can result in a loose connection or the
contacts becoming charred.
Connecting term
inals for copper conductors (Cu)
Hint: The connection of different types of conductors and/or different cross-sections at one clamping unit is not permitted.
f1 = flexible with end ferrule
Type of term
inal
Fixed in cable junction
boxes
Clamping
units
per pole
Rated
connecting
capacity
mm
2 and
types of
conductors
Conduc-
tors to be
connected
per pole
Tightening
torque
Current
carrying
capacity
Rated
cross
section of
term
inal
DKL 04
D 9025, D 9125, D 9225,
D 9245, D 9045, DP 9025
DP 9221, DP 9222
DE 9325, DE 9326
DE 9345, DE 9346
KD 5025, KD 5045
KF 5025, KF 5045
KF 9025, KF 9045,
DN 2035, KF WP 2025,
KF WP 2045, KF WP 3025
KF WP 3045
1
6 sol
4 sol
2.5 sol
1.5 sol
1-2
1-3
1-4
1-6
1.2 Nm
–
6 mm
2
KKL 06
K 9065,
KD 5065
KF 5065, KF 9065
KF WP 3065
1
10 sol
6 sol
4 sol
2.5 sol
1-2
1-3
1-4
1-4
1.5 Nm
–
10 mm
2
KLS
10
K 9105, K 8105
KD 5105
KF 5105, KF 9105
KF WP 2105,
KF WP 3105
2
16 s
10 sol
6 sol
4 sol
2.5 sol, f1
1-2
1-4
1-4
1-4
2-6
2 Nm
63 A
16 mm
2
KLS
25
K 9255, K 8255, K 9502
KD 5255
KF 5255, KF 9255
2
35 s, f1
25 s, f1
16 s, f1
10 sol, f1
6 sol
1-2
1-4
1-4
1-6
1-6
3 Nm
102 A
35 mm
2
KLS
50
K 9504
2
50 s
35 s
25 s
16 s
1-4
1-4
1-4
1-6
12 Nm
150 A
50 mm
2
S 51
K 7055, K 9355, K 9505,
KF 9355, KF 9505,
KF 5355, KF 5505,
KD 5355, KD 4355
2
50 s
35 s
25 s
16 s
1-4
1-4
1-4
1-6
12 Nm
150 A
50 mm
2
K 7004
4
70 s
50 s
35 s
25 s
16 s
1-4
1-4
1-4
1-4
1-4
10 Nm
216 A
70 mm
2
1-4
10 Nm
216 A
70 mm
2
DK Cable Junction Boxes
Technical Details
Terminals
rent cross-sections at one clamping unit is not permitted.
g Rated
connecting
capacity
mm2 and
types of
Conduc-
tors to be
connected
per pole
Tightening
torque
Current
carrying
capacity
Rated
cross
section of
terminal
2
xes
Hensel provides information
about the torque in Nm for
all screw-type terminals
in its main catalogue.
The spring
effect
Drehmoment
in der Klemmschraube
Strom
Leiter
Stromschiene
Zugkraft im Bügel
„Zugbügel“
Tightening torque in
the screw-type terminal
Current
transfer
Conductor
Busbar
Traction force in
clamping unit

4. Sunguvachathram
-
Walajabad
Road
4th
km
behind
Samsung/Flextronics
Sriperumbudur
-
631
604
∙
Kanchipuram
Dist,
Tamil
Nadu
Phone:
+91-44-3727
0202
Fax:
+91-44-3727
0200
Email:
info@hensel-electric.in
∙
www.hensel.in
Hensel
Electric
India
Pvt
Ltd
Industrial
Electric
Power
Distribution
Systems
35
Kunnam
Village
Terminal connections, as well as
the whole electrical plant, must be
checked regularly.
Check regularly
Terminal connections must be checked
regularly, as well as the entire electrical
system.
In this way the electrician is also ensuring
the safety and reliable operation of the
electrical installations over the long-term.
Inspection intervals
Electrical installations must be checked at
regular intervals so that any defects can
be identified and eliminated. Depending
on the devices and terminals used, the
inspection intervals may be different.
Thus, terminals of aluminum conductors
need special expertise and different
checks than terminal connections of
copper conductors. (See also Elektro-
Tipp 2/2013 Professional Connection of
Aluminium Conductors) .
More information about
service intervals can be
found in the Installation
and Maintenance
Manual of the equip-
ment manufacturers.
Delivery in India via Hensel authorized
distributor network ­
spanning 130 cities and industrial centers.
Delivery in South East Asia via Hensel authorized distributor
network in all ASEAN countries.
Delivery in Middle East via Hensel authorized distributor ­
network
in all GCC countries.
Distribution boards
Combinable enclosure system
with door up to 250 A, IP 66
DK Cable junction boxes
1.5 to 240 mm
2
, IP 54-67
KV Small-type distribution
boards up to 63 A,
3 to 54 modules, IP 54- 65
Mi Distribution boards
up to 630 A, IP 54-65
Cable entry systems
Photovoltaik distributors
that meet the standards
Construction board panels
up to 630 A, IP 44-65
R. Rajesh
Managing Director
Hensel Electric India
Pvt Ltd
info@hensel-electric.in
www.hensel.in
Delivery only via electrical
wholesalers!
Collection
of
new
ideas
in
the
Electrotechnic
al
Industry
The ELEKTRO
Customer Information for Electro-technical Specialists
Felix G. Hensel
Managing partner of
Gustav Hensel GmbH Co. KG
Dear Reader,
The higher the price for copper rises,
the more people in the electrical com-
ponent business look for a possible
substitute for this increasingly expen-
sive raw material.
When it comes to cables, people are
turning to aluminum conductors with
larger cross-sections.
In this edition of Elektro Tipp we will
deal with the professional connection
of aluminum cables. It requires special
installation expertise and of course the
right cable junction boxes with termi-
nals for aluminum and copper con-
ductors.
Hensel has offered a complete range
of products for this very purpose for
years and they have proven very reli-
able and can also help produce relia-
ble connections with aluminum cables
when the instructions are followed.
We believe that we have once again
proven our skill in the connection of
cables and conductors and have
helped electricians to solve often ur-
gent problems with our range of prod-
ucts and services.
We look forward to working with you
in the future.
How can aluminum cables be
properly connected?
Most devices and terminals are
designed only for connecting
copper cables. Therefore special
requirements need to be adhered
to with aluminum conductors.
To save money, more and more
people are thinking about using
aluminum cables instead of cop-
per. It is especially true of wires
with larger cross sections.
Professional Connection
of Aluminum Conductors:
Special expertise is needed!
We can also
connect aluminum
conductors
in this terminal?
Why?
Do we have to note
something special?
2/2013
Practical working aid
for electricians in poster formate.
More detailed information on this theme
Proceed to download at www.hensel.in!
Three Factors Determine a Safe Terminal Connection
PASSION FOR POWER.
Gustav Hensel GmbH Co. KG · D-57368 Lennestadt · www.hensel-electric.de HEI, INDIA
Pole with one clamping unit Pole with two clamping units - only the same cross
section and cable type per clamping unit
Labelling with max. number and dia-
meter of conductors to be connected
per pole
Examples to tightening torques:
labelling of terminal, specifications in the Hensel main catalogue
1. The suitable terminal
Adequate large wiring area
n no mechanical stress of the
terminals
n additional strain relief
2. Adequate wiring
space
Too small wiring area
n Bending radius of the
conductors is too small
n Conductors standing
inclined to the
terminal
n the material of the conductor and its insulation
n the number and shape of the wires forming the con-
ductor (identical for each clamping unit)
n the cross-section of the conductor (identical for each
connection)
n the number of conductors to be connected with each
other (see terminal labeling)
Terminals for
incoming cables
Mi VE 120
4-pole
Mi VE 125
5-pole
Mi VE 240
4-pole
Mi VE 245
5-pole
Mi VE 302
2-polig
Mi VE 303
3-polig
Mi VE 304
4-polig
Rated connecting capacity 150 mm2
150 mm2
240 mm2
240 mm2
300 mm2
300 mm2
mm2
mm2
300 mm2
Current carrying capacity 250 A 250 A 400 A 400 A 630 A 630 A 630 A
Tightening torque 20 Nm 20 Nm 40 Nm 40 Nm 50 Nm 50 Nm 50 Nm
Clamping units per pole 2 4 2 4 2 4
2-5-pole, for copper and aluminium conductors, zum Einbau in Mi-Leergehäuse Größen 2 bis 8,
fixed on mounting plate 300 x 300 mm, with Befestigungsschrauben.
Terminals for incoming cables
Only the correct torque guarantees
reliable terminal connections!
3. The optimum torque

Tightening torque in
the screw-type terminal
Current
transfer
Conductor
Busbar
Traction force in
clamping unit
Nm
F
Elasticity
Effects with terminals with steel body
Overview of types and shape of conductors
Type Shape
rigid [r]
solid (sol) round conductor / solid sector shaped conductor /solid
stranded (s)
round conductor /
stranded
sector shaped conductor / stran-
ded
flexible (f)
Hint: Terminals without marking „r“ (rigid conductors only), „f“ (flexible conductors only), „s“ or „sol“ (solid conductors only) can be used to connect all types of conductors.