Power Cables and Wiring Harnesses

Design guidelines Power cables and wiring harnesses

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Power cables and wiring harnesses Revisions

Rev Date Description Responsible (company, dept, name, tel)

Changes to prior revision(s)

1 2007-11-28 Initial release Kristian Dristig, V3P, 26320, +46 31 3224577

1. All information updated.

Contents TURevisionsUT .........................................................................................................................................................................1 TUContentsUT...........................................................................................................................................................................1 TUIntroductionUT ......................................................................................................................................................................2 TUApplicationUT .......................................................................................................................................................................2

TUCompulsoryUT................................................................................................................................................................2 TUIntended readerUT .........................................................................................................................................................2

TUDefinitionsUT ........................................................................................................................................................................3 TUAcronymsUT .........................................................................................................................................................................6 TUComponent design rules UT ..................................................................................................................................................6

TUGeneralUT ......................................................................................................................................................................6 TUConnectorsUT ................................................................................................................................................................6 TUSplices UT .......................................................................................................................................................................7 TUHosesUT.........................................................................................................................................................................8 TUTapeUT...........................................................................................................................................................................9 TUBack shells and manifoldsUT .......................................................................................................................................10 TUTerminalsUT .................................................................................................................................................................11 TUWires and cablesUT .....................................................................................................................................................12 TUPass-throughUT ...........................................................................................................................................................13

TUClamping and routing design rulesUT ................................................................................................................................14 TUAim of clampingUT .......................................................................................................................................................14 TUClamping at the same vibration reference UT...............................................................................................................14 TUClamping at breakoutsUT.............................................................................................................................................16 TUSplit clamping UT ..........................................................................................................................................................17 TUClamping distance to an electrically connected component UT....................................................................................17 TUBoxes and cabinetsUT .................................................................................................................................................17 TUPower cable routingUT .................................................................................................................................................18 TUCoding for connectorsUT..............................................................................................................................................19 TUTemperatureUT ............................................................................................................................................................19 TUChemicalUT ..................................................................................................................................................................20 TUDrainingUT ...................................................................................................................................................................20

TUInstallation and assembly issues UT ...................................................................................................................................21 TURouting and clamping the wiring harness UT................................................................................................................21 TUClamping for connectors or components UT.................................................................................................................26 TURouting and clamping inside cab/bodyUT....................................................................................................................26 TURouting and clamping power cablesUT........................................................................................................................26 TUConsequences of improper installationUT ...................................................................................................................27


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Introduction This document contains design guidelines for power cables and wiring harnesses. In this document, the term wiring harness (W/H) is used to cover both power cables and wiring harnesses.

The purpose of this guideline is to support design engineers when designing wiring harnesses. It may also serve as an introduction to new employees or be used at design reviews to help validate the design. This document can also be used as a reference when it comes to requirement specification in industrialisation projects.

The electrical system in a vehicle or construction equipment consists of electrical control units (ECU), sensors, switches, actuators, etc., which communicate and are supplied via a network consisting of a wiring harness. The wiring harnesses may consist of single wires, twisted wires, screened wires, splices, terminals, single wire seals, grommets, shrink hose, back shells, different kind of hoses, different kind of tape, fasteners, cable channels, connectors (to components or inline), etc. High power consumers are supplied by cables with a greater cross-section, those are called power cables.

The document mainly consists of the following parts.

Component design rules which describes the components, basic design rules for when a certain component should be used and how it should be used together with all important aspects that should be considered when doing the design.

Clamping and routing design rules which covers rules for clamping and routing in different situations/locations, which is of major importance when doing a wiring harness design.

Installation and assembly issues which describes basic installation and assembly rules and good practice. Also, consequences of improper installation are given to explain why appropriate installations are necessary. This section supports the design engineer with an extended view on W/H installation issues, which is good to have in mind when designing wiring harnesses.

If the wiring harness components and installation requirements are not fulfilled, possible consequences are power shortage, short circuits and network failures leading to malfunction of the electrical systems in the vehicle or construction equipment. This can cause safety related and functional failures. Therefore, it is of highest importance that the design and installation of wiring harnesses is made thoroughly and with outmost care.

Application

Compulsory GIB-T has decided that these guidelines are mandatory for new designs (i.e. for industrialisation projects started after the official release of this document) within the Volvo Group. The guidelines are only applicable to 12 and 24 V systems and cover general wiring harness and power cable installations.

Requirements are expressed with shall, are mandatory, etc., and items with more room for interpretation are expressed with should, are recommended, etc. The requirements are valid until otherwise is stated and shall be fulfilled to ensure high quality and compliance within the Volvo Group.

If the need for a more detailed description is foreseen, specific technical regulations or other kinds of documents shall be issued. In such case, the priority of this guideline will be changed. If deviations are made from this guideline, every single case needs to be validated and reported to the affected quality function/responsible and affected industrialisation project.

The pictures in this document are examples of correct and incorrect installations; the intension is to show examples, not to have valid and up-to-date pictures of the products.

Intended reader The intended readers of this guideline are design engineers working with wiring harnesses. However, also others working with wiring harnesses or related areas are expected to benefit from reading this document (e.g. geometrical responsible, technical project managers, etc.).


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Definitions Abrasive surfaces: Items capable of causing damage to the routed commodity in a rubbing condition during vehicle/machine operation (e.g. sharp edges, bolt threads, braided hoses, corrugated hoses, etc.).

Back shell: Plastic part between a connector and hose.

Body: The body of Volvo buses.

Cable: Two or more wires in a twisted or parallel configuration (multi core) or a screened wire. Also, a single wire intended for power distribution; normally, with a conductor area of 16 mm or more.

Cable harness: See wiring harness

Cable tie: A plastic self-sizing strap, capable of bundling or fastening specified loads during vehicle operation.

Conductor: A strand or combination of strands not insulated from each other, suitable for carrying an electrical current.

Connector: A device that connect the wires/cables in the W/H to another W/H or electrical component. Refers to a complete connector including connector housing complete with assembled wire terminals, wire seals, blind plugs, facial seals and/or other associated components.

Crimp: A mechanical joint of two or more wires or a wire to a terminal with the intention to conduct electricity through the crimp to the connected parts with as low loss as possible. A crimp usually consists of a barrel (could be a stand alone barrel for wire to wire crimping or a terminal barrel that is a part of the terminal for wire to terminal crimping) where the wire/wires are placed inside of the barrel and then by outer compression force forced together to a functional union. When more then one wire is crimped to a single terminal it is called a doubling.

Fretting corrosion: Micro chafe between pin and socket terminal which in the long term creates oxides between the conductors causing poor conduction.

Grommet: A part used to seal/secure from unwished transfer of certain chemicals/material between different environmental zones but letting the wiring harness and/or power cables pass.

Heat shield: Reducer of heat radiation to lead away and protect surrounding environment and components.

High heat sources: Exhaust pipe, servo pipes, compressor pipes, and other surrounding components whose surface temperature exceeds 100 C.

Housing: Connector without terminals, seals, secondary locking, etc. The housing is the part of the connector which holds everything together. The housing can sometimes also include the coding etc. Housing is sometimes named insulator.

Insulation: Material having good dielectric properties used to separate close electrical components, such as wire conductors.

Manifold: Plastic part between hoses.

Multicore cable: More than one wire (individually insulated) moulded together or bundled together in a tight hose. The wires inside a multicore cable can be twisted in different combinations. A multicore cable can also be called jacketed cable (a jacketed cable can be a single wire combination or more, mostly for mechanical and environmental support).


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P-clamp: A fastener that has the profile shape of the letter P. P-clamps can be made of different materials and configurations (e.g. covered with rubber/silicon/Teflon) and exists in several different dimensions and designs (e.g. with different holes, self-locking, etc.).

Plastic conduit: Corrugated or smooth wall tubing used to protect hoses, wiring harnesses, power cables, tubing, pipes, etc.

Screen: A conducting layer placed around a wire or cable to limit the penetration or escape of electric or electromagnetic fields. The screen can be connected in different ways depending on electrical system architecture design. Screens are sometimes called shields. Usually the screened cables are jacketed cables with one or more wires inside of the screen (different set-ups).

Single Wire Seal: Usually a soft elastic part that is threaded over a wire close to the terminal to secure the connector cavity from water intrusion (or other substances). It is very common that the single wire seal is crimped or fastened to the terminal or kept at place by a secondary locking part. The single wire seal can also be a gel placed in the connector cavities before inserting the wires and in some cases the single wire seal is replaced by a family seal that can be incorporated in the connector housing design. Needed in wet environments, i.e. for all connectors on the engine, chassis, etc.

Strand: A single continuous length of conductive material. Usually, Automotive wires are made of a combination of several strands due to mechanical properties.

Terminal: A metallic component applied (usually crimped) to a wire, aimed for connection to a mating part and further distribution of electric current. Terminals are designed to fit into each other and are on one side called pin/tab and on the other side socket/receptacle. Terminals can be a part of a connector and can also be designed to fit a bolt or a screw (ring terminals).

Wire: A single conductor covered with insulation, normally with a cross-section less than 16 mm. A wire is not aimed for high power distribution.

Wiring harness (W/H): Wires and/or cables bundled together for connecting contact points on one or more electrical components. Sometimes a single wire can be called wiring harness if secondary operations are needed to construct the part (e.g. tape, terminal, or conduit added).


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Figure 1. Wiring harness and power cables overview (example).

A Ring terminal I Cable box (plastic in this case)

B Power cable J Inline connector

C P-clamp (with screw) K Rubber cap (protection)

D Pass-through (with grommet inside) L Tie strap

E Back shell M Tie strap with anchorage (fastener)

F Bracket N Manifold

G Connector O Corrugated hose

H Heat shield (for a sensor in this case)


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Acronyms ADR European Agreement concerning the international carriage of Dangerous goods by Road

BA/BU Business Area or Business Unit

DFA Design For Assembly

EATS Engine After Treatment System

ECU Electrical Control Unit

GIB-T Group Issue Board Technology

START A database of available components. Note that the database includes both approved and not approved parts and is not all-embracing.

SWS Single Wire Seal

W/H Wiring Harness

Component design rules

General Several component families exist:

Connectors Splices Hoses Tape Back shells and manifolds Terminals Wires and cables Pass-through

In the following sections, general information and design rules on each component family are given. This includes different types of components, when and how to use them, and important aspects to consider.

When manufacturing wiring harnesses, the supplier/manufacturer is to fulfil the requirements in valid wiring harness manufacturing standards as well as valid related technical regulations. This ensures the quality of delivered components and the W/H.

Connectors

Description There are two different kinds of connectors:

Connector to connect an apparatus (electrically connected component): The general design rule is to use tab terminals in the wiring harness (the dead/non-supplying part has the pins).

Inline connection: This is used to connect one W/H to another or to cut the W/H for process assembly reasons. This requires both a pin and socket connector. The general design rule is to use socket terminals in the wiring harness (the dead/non-supplying part has the pins).

Connector usage Many criteria have to be taken into account when choosing the type of connector. See the connector collection in HTUSTARTUTH for guidance. Whenever a new connector is to be chosen, either for an apparatus or for an inline connection, the connector shall be reviewed and approved by the local connector competence team member.


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Splices

Description A splice is an electrical and mechanical connection between two or more wires done by ultrasonic welding or mechanical crimping with a crimping joint, or other electrical or mechanical conductor.

Ultrasonic: Welding by friction generated by high-frequency (20-40 kHz in automotive wire applications) vibrations and compression force.

Crimping joint: Small tube or barrel of metal that can be sealed or unsealed. It is the same as a splice, but crimping by compression force is used instead of ultrasonic welding.

Usage and design The following points are important to consider when planning using a splice.

A splice is used to split a wire into several wires, or to change the wire cross-section due to mechanical issues, without using any connectors.

The number of wires should not exceed ten wires in total in a splice. Each splice will introduce a resistance, which will increase the total resistance of the W/H. The total

resistance of a circuit must be checked, especially for CAN buses.

A splice can be used to counteract capillary effects within a wire. In some applications, fluids can penetrate the insulation along the strands inside the plastic. In this case, a splice with one cable in each end is used to stop the flow of liquid. This technique is, for example, used in cables for fuel injectors. (Note: Does only apply to mechanical splices.)

A splice can also be used to change from a heat-resistant cable to an ordinary cable once the cable is far enough from the heat source. This is primarily done to reduce costs and must be studied for each individual case.

Splices are one of the wiring harness most sensitive parts. Clearly stated requirements must be distributed and followed by the wiring harness supplier together with proper follow up done by the affected quality department at Volvo and supplier.

When connecting wires to a splice, consider the following points regarding the dimensioning of the wires:

1. Be cautious regarding the cross-section of the wires. Each wire, on both sides of the splice, must be dimensioned to accept maximal current.

2. Any wire with a cross-section area inferior to the third of the biggest one should not be used. Example: A 0.35 mm wire shall not be used in a splice where there is a 1.5 mm wire. In this case 0.5 mm is the minimal cross-section area.

3. The diameter of an ultrasonic splice should not be larger than 16 mm (equal to the sum of all wires).

4. When choosing the shrink hose for a certain splice, the number of wires and/or the total cross-section on each side of the splice must be compatible with the chosen shrink hose shrinkage level. E.g. if a certain shrink hose has the property of being able to shrink four times of its original size (un-shrinked) be sure that the total diameter of each side of the splice does not differ more than four times, so that the shrink hose fixates properly on both sides. This must be checked in the component specification for the certain shrink hose.

Protection of splices Splices must be protected against mechanical damage and corrosion. The minimal requirement is to add shrink hose or any other appropriate protection. Several types of tubing exist and their specification shall be based on e.g. temperature environment and wire gauge combination. Extra adhesive inserted into the tube/splice could also be used to seal the splice from moisture. For powertrain harnesses the usage of shrink hose with adhesive is mandatory to preserve tightness.

A splice with standard shrink hose or equal is not water-tight. If the splice is located in the chassis or in a place where


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water can stagnate (water-sensitive areas) specific moisture-proof shrink hose must be used.

Only approved shrink hoses are allowed.

Placement of splices Regarding the placement of splices, the following points apply.

If ultrasonic welded splices are used, the splices can easily be damaged if they are bent. Therefore, splices in the W/H may only be located where the W/H is straight; placing a splice in a bend or curve of the W/H is not allowed.

For engine environment, a splice shall not be positioned on a clamping point for mechanical reasons. Even if a moisture-proof shrink hose is used, the splice must never be located at the lowest point in a W/H

outside the cab/body. The risk is water stagnating around the splice in the hose; a splice is moisture-proof not water-proof.

Never put the splice in wheel housing or in areas with high exposure of water. The minimum distance between two splices shall be 50 mm (free wires). The recommended minimum distance between a splice and a bundle end is 250 mm.

Hoses

Description A hose is a protection added around the wires in a W/H bundle. There are different types of hoses depending on the kind of protection required, for example protection against impact, abrasion, chafing, or temperature.

Hoses are divided into two main categories:

Corrugated hoses Soft hoses

Corrugated hoses There are different types of corrugated hoses. They can be made of different materials with different properties and be slotted or closed. Alternatives include:

Slotted, i.e. open, with different designs: o overlapping o self locking o etc.

Closed, which is the only type approved at Volvo Powertrain and for ADR applications o All the above consisting of different materials:

Corrugated hoses made of PA (Poly Amid) are: mainly used in the chassis to protect from impact, abrasion, and chafing. mandatory for ADR installations (i.e. for any W/H at the rear of the cab and

rearwards on dangerous goods trucks).

Corrugated hoses made of PP are: a bit softer than PA and therefore has a slightly smaller bending radius. at the time of writing, somewhat cheaper than PA. used in the engine compartment and other hot areas, where the ADR demands are

not applicable.


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Usage

The diameter of the hose shall be adapted to the total size of the wires and cables inside, i.e. leave as small space as possible inside the hose. Movement of wires inside the hose can damage the wires and lead to electrical failures. However, it should be taken into consideration that for closed corrugated hoses there must be enough space to thread wires with terminals and single wire seals mounted.

When manifolds are used, the size and type of the manifold should be set to be compatible with the profile and diameter of the corrugated hose. Information is available in the HTUSTARTUTH database or from the local component responsible.

Soft hoses There are different types of soft hoses. They can be made of different materials with different properties and be slotted, closed, like a spiral, etc. Examples of different kind of materials are PVC plastic, spiral plastic, PUR, Teflon, and weaved hoses, such as glass fibre reinforcement.

Usage

Soft hoses are used instead of corrugated hoses inside the cab/body when there is a need for protection of cables. Corrugated hoses are only used in special cases inside the cab. Soft hoses are also used when corrugated hoses can not be used because of:

Lack of space Extensive bending Difficulty in routing the W/H The connector is not designed for corrugated hose connection Mount ability in W/H assembly

Before replacing a corrugated hose by a soft hose, it needs to be checked if any manifold/backshell between the hose and the equipment or connector is required and existing.

Specific applications for soft hoses

Soft hoses or spiral plastic hoses are sometimes added around the wires inside a corrugated hose, on short length and in a specific place, to protect wires from abrasion in some severe application, e.g. high vibration and not enough clamping points. It can also be used as protection for a single wire or very few wires inside a corrugated hose at locations with high vibrations.

Tape

Description Tape, or adhesive tape, is a continuous and flexible strip of cloth, metal, paper, or plastic and usually available in various widths. Tape exists in a wide range of materials and designs, many developed for specific areas and applications.

Usage Adhesive tape (e.g. electrical tape) is used to insulate and protect electrical wires from e.g. chafing, rubbing, noise, and heat. Tape could be used as an alternative to soft hoses. The usage needs to be checked in each individual case and agreed upon with the concerned W/H supplier. Tape is also used to mark wiring harnesses and power cables for where p-clamps or other fasteners should be mounted in production. Different colours of tape can also distinguish several branches of wiring harnesses, not to be mounted in the wrong way. Tape is also used to keep the wiring harness bundles together (spot and/or spare tape).

All tapes used must be approved by the concerned design engineering department because of the risk of non-compatibility with other components. Some tape materials and adhesives can have a negative influence on the wire-insulation materials used. The tape also needs to have the same temperature class as the wires it encapsulates.


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Back shells and manifolds

Description A manifold is a moulded plastic part used to make the holding/intersection between different hoses. A back shell is a similar component, but bonding a connector and a hose. The purpose of the back shell is the same as the manifold but also to secure that the tension forces go through the back shell and the connector housing instead of the wires and terminals. A safe routing of the harness should be ensured at the rear of a connector, when there is a risk of chafing between the W/H and other components. The usage of manifolds and back shells contributes to this and also gives a good protection of the wires and can improve the tightness of a connector. Instead of manifolds and back shells, e.g. shrink hose or tape could be used. If using shrink hose or tape instead of back shell it is under no circumstances allowed to fixate the shrink hose or tape directly to the wires; it must always be secured to the connector housing so that tension forces are not applied to free wires and by that the terminals.

For severe applications, manifolds and back shells shall be used. For engine applications where the space always is narrow and the environment severe, and for truck applications which need to comply with the ADR regulations, the usage of manifolds and back shells together with a safe routing is mandatory to preserve quality.

As a recommendation, the minimum distance between two manifolds or between a manifold and connector should be 50 mm (if not the manifolds are designed to be connected together). At shorter lengths, there is a big risk that the manifold opens due to mechanical stress.

Back shells Depending on the wiring harness routing, different kinds of back shells are available:

Straight outlet, i.e. 0 or 180 90 outlet In some cases other outlet angles are available, e.g. 45

Straight or 90 back shells should be preferred (as much as possible) rather than specific angle components since they need to be specifically developed and tooled in most cases. The local component responsible should be consulted as to which back shells are available.

The backshell choice depends on the following:

The connector, and which back shells are available If single wires or multicore cable is being used The hose

o The number of wires it should contain o Tape o Splice or no splice o Corrugated or soft hose o Slotted hose or not o Diameter of the hose o Profile (depending on hose supplier)

Wiring harness routing Manifolds between hoses To make a link between three hoses, two kinds of manifolds exist:

Y-shape T-shape

To connect more than three hoses, other types may be available from the supplier. Because of the many different sizes of hoses available, many variations of manifolds exist. It is also possible to adjust the diameter size of a manifold with an adaptor. A lot of different dimensions etc. of manifolds are listed in the HTUSTARTUTH database.


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Terminals

Usage A terminal is used to connect power cables or single wires to bolts or connectors.

Crimping on cable terminals To ensure a good crimping with correct electrical and mechanical properties, it is important to have a cable of adequate size and the right type of cable terminal. Especially for multi-cable crimping, the choice of cable terminal is not easy and should be made in cooperation with the W/H maker. Multi wire crimping (doubling) for connector terminals is not allowed in engine and chassis wiring harnesses (not applicable to cables). All combinations shall be reviewed by the W/H maker.

The crimping is one of the most critical parts of a W/H. Crimping should be done according to demands stated from the terminal manufacturer. The supplier of the W/H should also provide crimp analysis material to the BA/BUs quality department, e.g. microcut analysis and pull tests. This should be studied and approved by the affected quality instance.

Ring terminals A ring terminal can be placed in a very exposed location and therefore the following important rules need to be considered for the design.

Choose the most appropriate angle: Crimping makes the crimping zone sensitive. Stress between the terminal and the cable due to installation problems must be avoided not to break the terminal or the wire. Bending the cable close to the crimping of the terminal is not allowed. To avoid mechanical stress, many terminals with different bending angle exist; choose the most appropriate angle. Take special concern with battery cables since they are very stiff.

Choose the right hole diameter o Too big: risk not having enough contact surfaces to carry the current o Too small: risk damaging the threads on the stud

All ring terminals in wet areas must have the crimps covered by a shrink hose with adhesive. For engine applications all terminals are considered to live in a wet area and they should thereby have the crimps covered by shrink hose with adhesive. An exception from this rule is the injector wiring harness (is located under the valve cover). If there are any other situations where exceptions must be made, this must be documented according to the designing BA/BUs documentation routines, e.g. in a technical regulation.

Choose a ring terminal which is approved by the Volvo Group. Problem of tightness When a wire is crimped to a terminal, e.g. ring terminal that is located outside the cab/body, the other end of the wire is not allowed to go to a connector of an apparatus. This is due to the fact that a terminal is not water-tight. The consequence can be water penetrating the wire and creating damage both to the wire itself or the connected component. This is called capillary effect and can be avoided with a barrel splice with a wall or the use of capillary stopping wires.

Single Wire Seal, SWS, is to be used for all connectors in wet areas or other specific applications when connecting a stud on the chassis directly to an ECU, actuator, sensor, or likewise. However, in some connectors the SWS function is carried out with the sealing incorporated to the housing implying no need for separate SWS (i.e. family seal). Single wire seals do not function as supposed with multi wire crimping (doublings).

Multi-cable crimping is not allowed on the chassis since it is not possible to ensure tightness in the multi-crimping area. The only exception is to route power from one stud to another, where no risk of migrating water in a system exists.


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Wires and cables

Description An electrical wire/cable allows carrying current from one point to another, e.g. from an electrical source to an electrical device. It is made of a conductor (metallic strands carrying the current) and covered by insulation. The metallic strands can be very thin, which leads to the consequence that they can easily be damaged if not handled in an appropriate way. Depending on the size of the cross-section, it is called wire or cable.

Which wire to use Wires and cables must be used in a temperature environment inferior to their temperature class. If the maximum ambient temperature is above the temperature class of a certain wire, the wire must be routed in a cooler area, if possible, or replaced by a wire with an appropriate temperature class. The temperature all along the routed wires must be considered.

The choice of wire size shall be based on the following:

Maximum current to be carried Maximum ambient temperature Vibrations Terminals available for connected components Wire length If the wire is a part of a supply, it should be dimensioned to be able to blow the fuse Mechanical issues Wire derating curves What kind of wires that are routed together in the same bundle

The tier2/subsupplier sets up a derating curve from calculations or measurements for the supplied wires. It gives the admissible current for each wire size according to ambient temperature and cross-section. See diagram 1 for an example of how such a derating curve can look like.

Diagram 1. Example of a derating curve for wires.


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All wires outside the cab/body shall be 0.75 mm2 or greater due to mechanical stress. Wires used inside the cab/body could be 0.35 mm2 or less if included inside a multi-core cable.

Except for the above stated general rules, the local electrical distribution system department should be involved in the process of determining the wire and cable areas.

Pass-through A pass-through is a passage between two or more different environmental or vehicle zones. It is for example often used to secure the passage between a wet area and a dry area, allowing the cable to continue between the different zones without any harmful leakage. A pass-through can have many different configurations/designs due to its geometrical and environmental positioning and application.

If one of the zones around the pass-through is a wet zone, the choice of sealing parts is crucial. To seal several wires in a pass-through, a grommet can be used. The grommet must seal both around the wires and against the inner plastic or metal surface of the pass-through.

Other crucial aspects to consider when designing a pass-through solution are the following.

Mountability: It must be possible to mount the cables through the pass-through in a way that is efficient for production. The pass-through should also be designed so that it can fit into its environment and be installed in an easy and secure way. Often, also connectors need to be mounted through the pass-through. Design for assembly, DFA, is very central for this type of component.

Partitioning: Is the use of a pass-through the best solution or should an inline connector be used instead? When choosing an interface between different zones, one must consider many different aspects such as architecture, mount ability, after market (spare parts), service, logistics (smaller parts and if they can be used in different applications), and variant management.

Material: The materials chosen for the pass-through must be compatible with the surrounding environment and the relevant application/installation. The application/installation often has certain demands such as smoothness of the material, strength, and heat resistance.

Environment: The environment can be very demanding in terms of heat, vibrations, dust and dirt, moisture, and chemicals. These things should be taken into account when choosing design and material.

Life cycle aspect: A design, whether it is of a complete wiring harness or of a subcomponent, should be done with the life cycle as reference. An engine wiring harness should be designed for the life time of an engine and so the pass-through must also be able to withstand the same amount of time in its environment.

Figure 2. Pass-through to cab. Figure 3. Pass-through from cab to outside cab and

inline connectors to different wiring harnesses.


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Clamping and routing design rules This section covers general clamping and routing rules for different situations, which need to be considered in the design. The main target is to secure the lifetime of the W/H at an appropriate cost level.

Note: This section is not applicable to Volvo Bus transportation clamping.

Aim of clamping It is important to clamp the W/H in such a way that it can not be damaged or damage surrounding components:

The maximum distance between two fixation points is 400 mm, but o 300 mm for vehicle EATS applications (fixated on vehicle parts). o 150 mm for engine, transmission, and EATS applications (fixated on mufflers etc.).

W/H or power cables, routed beside or close to the power train shall have a clearance of 30 mm minimum. W/H or power cables, routed along or through abrasive surfaces, shall be prevented to touch these surfaces,

e.g. sharp edges, bolt threads, and rough edges. This can be achieved by securing with additional clamping or any other protective device (cable channels etc.), so that the W/H is not damaged. If corrugated hose is used as protection it is also important to consider the effect it could have on the surrounding components, due to its rough surface (together with vibrations).

For engine and transmission, P-clamps shall be used in the largest possible extent, due to durability and serviceability. For other applications, P-clamps could be used if suitable.

For engine applications, cable ties with anchor should preferably not be used due to that they can easily come off in such a vibrating environment. In a service perspective cable ties constitute a risk in the clamping strategy, due to that they are not "forcibly" put back once cut.

Critical clamping locations that are specified on the W/H (e.g. by tape marking) must agree with intended placement in the vehicle.

Clamping at the same vibration reference In order to avoid fretting corrosion and damaged conductor strands, connectors and W/H must be fixed at the same vibration reference. This applies to both sides of inline connectors. Clamping the W/H on two different assembly parts with different vibration levels, e.g. on the gearbox on one side and on the frame on the other side, is not allowed. This means that the part of the wiring harness that handles the vibrations should be a fastener, not a back shell, manifold, terminal, etc. The fastener fixation should be fixated to the cover of the bundle (e.g. a corrugated hose or soft hose) not the free wires. For illustration, see the following examples.

1. A connector with fixation device included in the housing: three fixing points, same vibration reference.

Figure 4. Harness bundles fixated on both sides of an inline connector,

and the connector is equipped with a built in fixation (e.g. anchor).

2. A connector without fixation device included in the housing: two fixing points + tie wrap, same vibration reference.

Figure 5. Harness bundles fixated on both sides of an inline connector,

and the connector is fixated to the same vibration reference with a tie strap.


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3. Incorrect design: The W/H is fixed on one side on the gearbox and on the other side on the frame. Not the same vibration level. Specific testing is required to validate such a design.

Figure 6. Illustration of how the wiring harness branch that comes out of the inline connector misses fixation to the same

vibration reference as the connector, before going to the frame (different vibration reference than the gearbox).

Figure 7. Example of a correct and an incorrect clamping for a wiring harness bundle between two different vibration references.


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Clamping at breakouts Note: This section is not applicable to Volvo Powertrain.

At a breakout from the wiring harness main branch (see figure 8), fit a cable tie at the break point A to keep the main branch bundle together. If the distance to the next fixation point is > 300 mm or if there is relative movement (comparing the main branch and outlet branch), fit a tie strap on the outlet branch, see point B. Also, be sure to fit a tie strap and/or fastener where the outlet branch is gathered together after the breakout, see point C.

Figure 8. How to properly strap/fixate the different bundles at an outlet point.

If the breakout is to a component with relative movement, e.g. frame/cab, frame/engine or frame/transmission, it is important that the free part of the W/H has sufficient length to allow free movement (see figure 9). If this is not achieved, there is a great risk of the W/H being damaged or the W/H damaging surrounding components.

Figure 9. Illustration of sufficient over length for a wiring harness

bundle routed between two different vibration references.

Due to the high risk of chafing when relative movement occurs, it is important to use fasteners in such a way that this is prevented.


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Split clamping Electrical cables and W/H that are protected with corrugated hoses should not be bundled together with other rubber or plastic hoses. This is because it is difficult to tighten the clamp with appropriate force. If the clamp is tightened too hard, the corrugated hose is deformed and the cables and wires can be damaged. If it is not tightened enough, chafing due to relative movement can occur. Split clamping positions shall be used. Electrical cables and wiring harness are not to be clamped together with fuel or hydraulic lines. If not possible to avoid, use an appropriate spacer (not recommended).

Clamping distance to an electrically connected component The maximal length between the rear of a connector and the first clamping point must be considered carefully. If the first clamping point is too far from the connector, terminals in the connector will receive a lot of stress due to relative movement between the W/H and the component. This can cause fretting corrosion, possible micro cuts, and damage conductor/strands causing unwanted electrical properties.

The distance between a connector and the first clamping point is to be maximum 100 mm. Avoid stretching the W/H, since the length of the cables then will be longer than the clamping distance. (It is the rear of the terminal in the connector that has to be considered, not the rear of the back shell or connector housing fixed to the connector. See figure 10.)

Figure 10. How to measure the correct distance for clamping

the wiring harness connected to a component.

It is important that the first clamping point is in the same mode of vibration (no relative movement) as the connected component.

The component owner (i.e. the responsible designer/department) of the connected component should early in a project be involved to integrate fixation points in the component design. This must be driven and communicated to the affected component responsible by e.g. the local W/H and packaging engineers.

Boxes and cabinets At the entrance of a cabinet, box and such like, where the W/H must pass through a hole, it must be clamped in a fashion that prevents water from following the W/H through the hole. It is recommended that the W/H point slightly downward at the outside of the cabinet box. This rule also applies to all connectors; the end of the hose needs to be considered so that condensed water does not stagnate at the contact.


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Figure 11. The entrance of a wiring harness branch into a cabinet (component).

Power cable routing Power cables that are routed along or through abrasive surfaces must not come in contact with these surfaces, e.g. sharp edges, rough edges, bolt threads, or braided hoses. If frame routing is used, routing through cross members is prohibited. Fasteners must ensure that no contact with the frame is possible and that the cables are secured from chafing on sharp edges. Also, power cables shall not support any other mechanical loads than their own.

Figure 12. Illustration of proper clearance between power cables and component housing.

Power cables routed beside or close to powertrain parts, e.g. gearbox and engine, shall have a clearance of minimum 30 mm. Power cables should always be routed on top of brackets. In such case where mounting underneath is necessary or sharp edges exist in brackets, a rubber washer must be used to protect the cable from chafing on the bracket.


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Figure 13. Illustration of the use of a rubber washer for fixation of power cables.

Signal and power cables which run in parallel with one another should be separated by an appropriately high clearance or a grounded shield plate should be used.

Coding for connectors There are different ways of coding, such as:

Colour Mechanical Text marking Wiring harness length differentiation (reach ability) for the connection

If there are several identical connectors coding is required. At least one of the coding techniques is mandatory to be used to avoid inversion. It is important that the coding is clear, to obtain a correct assembly. In situations where inversion leads to a serious consequence, e.g. damaged machine or safety risks, the use of both colour/text and mechanical coding is recommended.

Figure 14. Example of several connectors of the same kind with different coding

(length differentiation) since they are located in the same geometrical area.

Temperature As far as possible, avoid locating W/H components in hot areas. This may damage the components, accelerate the aging, and lead to the use of unnecessary expensive material for components and specific plating for terminals. To be able to avoid placement of wiring harness components in hot areas, it is important to participate early in industrialisation projects to communicate the W/H needs (e.g. pig tails, placement of component connector, etc.) to other component owners.

Each component has a temperature class, i.e. the maximum temperature for operation, which shall be considered as


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a requirement for installation. Information about temperature classes can be found in HTUSTARTUTH.

The use of a heat shield could be an alternative. Choose appropriate material and test the solution. The heat shield should in as high extent as possible be placed at the source of the heat, not at the surrounding heat sensitive affected parts (see figures 15, 16, and 17).

Figure 15. Example of a heat shield. Figure 16. Example of a connector and a heat shield.

Figure 17. Example of a wiring harness, connector, and heat shield.

Chemical W/H and associated components shall not be located where fluid can reach them (e.g. petrol leakage, oil leakage, or Ad-blue). This may cause chemical damage to plastics (insulation, hoses, etc.) or connectors, or require expensive specific chemical-resistant plastic housings and sealing systems. This must be secured by stating this as early as possible in the industrialisation project so that the electrically connected components are designed (e.g. the placement of the component connector) in the best way possible to avoid situations like stated above. In some cases it is impossible to avoid situations like this. In those cases be sure to specify the correct type of material for the wiring harness and belonging protection devices.

The W/H designed for routing within the battery box area needs a corrugated hose as mechanical protection. This must be made out of special plastic (e.g. PP), since this type of hose is more resistive to the gas that usually is present in the battery box. It also gives an extra protection in case of battery acid leakage.

Draining A recommendation is to drain slotted corrugated hoses at the lowest point. There will always be moisture and condensed water that will stagnate at the lowest point inside the hose. The solution illustrated in figure 18 should be preferred, i.e. a Y- or T-shaped manifold with an empty piece of corrugated hose clamped in a downward position. Make sure the draining is clamped in the lowest point.


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Figure 18. Example of a proper design of drainage of a slotted corrugated hose. Note the tie strap at the lowest point.

Installation and assembly issues Routing is part of W/H design; a good concept ensures that the routing will be operator independent and that the process repeatability will be under control, avoiding unexpected interferences. This section covers basic installation rules, good practice, and motivation for proper installation. If there exists a certain demand for assembly, this must be communicated to the affected production and after market for the affected BA/BU by the responsible wiring harness design department.

Routing and clamping the wiring harness

Clamping with cable ties When using cable ties to clamp a wiring harness with earlier made bundles, it is highly recommended to replace the earlier clamp by a new one that clamps the entire bundle. This is due to difficulties in reaching the correct clamping force on the cable ties, which causes a risk of either relative movement or deformed hoses. When relative movement occurs, the inner cable ties can break. Tightening must be realised face to the operator, i.e. no blind operation during assembly. See figures 19-22 for illustration.

Figure 19. Improper clamping of added wiring harness bundles. The original tie strap should be replaced by a new one embracing all of the wiring harness bundles.


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Figure 20. A number of wiring harness bundles fixated together and three bundles (corrugated hoses) not yet fixated.

Figure 21. Improper clamping with cable ties. Note that the strap

does not embrace all of the wiring harness bundles.

Figure 22. Correct multi bundle clamping. Note that the original cable ties are completely replaced by new ones embracing all of the wiring harness bundles.

Clamping force Clamping force is individual to each installation situation; several subjective aspects set the force. Generally, no relative movement is allowed between the components in the clamped bundle and the force shall not exceed a level that harms the single wires inside the hose.

Figure 23. The left illustration shows a properly tightened wiring

harness bundle and the illustration to the right shows an improperly tightened wiring harness bundle since the tightening force is too small.


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After tightening of the clamp is performed, no sharp edges caused by excessive tightening force are allowed on the corrugated hose. If the deformation of the hose is too big, there is a serious risk of damaging the single wires inside the hose.

Figure 24. A tie strap with anchorage fastened to a wiring harness bundle (corrugated hose)

with proper tightening force.

Figure 25. A tie strap with anchorage fastened to a wiring harness bundle (corrugated hose)

with too large tightening force.

Clamping over length chassis wiring harness bundles Over length in the wiring harness may occur due to optimisation of the amount of part numbers related to the amount of variant combinations. Excess cable must fold back on itself only once and be placed in the frame, in a location where the excess will be able to be used, or in a solid point due to e.g. vibrations. Do not wind in a coil.

Figure 26. Proper clamping of over length.

Bending To avoid damaging wires or corrugated hoses when bending, the diameter of the loop needs to be considered. Generally, the minimum bend diameter of corrugated hoses is to be two times the diameter of the hose (see figure 27).

Figure 27. Illustration of how to measure a wiring harness bundle

loop correctly to not exceed the maximum bend radius.

D = 2 x d (e.g. NW10 d = 13 mm D = 26mm) where d is the outer diameter of the corrugated hose.

When clamping a manifold breakout to a corrugated hose, it is important not to make the loop too short before the first clamping point is made. The minimum bend diameter needs to be considered, see figure 28.


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Figure 28. Illustration of the difference between a proper loop of a wiring

harness bundle outlet and a loop with too small bending radius.

Normally, the type of manifold is adapted to its installation, but situations like the ones previously illustrated can occur due to optimisation of the amount of part numbers related to the amount of variant combinations.

Supports and brackets When the W/H is to be assembled on a bracket it is normally assembled on the upper part of the bracket so that the bracket acts as a support, see figures 29 and 30. Bracket type and installation may vary. The wiring harness shall not support any other mechanical loads than its own.

Figure 29. Example of a wiring harness bundle supported by brackets.

Figure 30. Example of a wiring harness bundle supported by a bracket.

Multifunction brackets As far as possible promote multifunction brackets or cable channels which reduce assembly time while improving routing repeatability and quality.


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Figure 31. Example of a multifunction bracket.

When required, brackets are expected to:

Belong to a standard parts assortment (i.e. BA/BU common assortment) Avoid sharp edge that could damage the W/H Be mounted with standard assembly equipment (use standard screws) Include rotation-proofing device (see figure 32) Allow for proper tightening operation (see figures 33 and 34) Support ties preparation before W/H mounting (see figure 35)

Figure 32. A bracket design that prohibits twisting/turning of the bracket.

Figure 33. Illustration of how the holes for a tie strap should be dimensioned. See also figure 34.

Figure 34. Illustration of how the tie strap should look when assembled. See also figure 33.

Figure 35. Illustration of how a tie strap with anchorage has been pre-assembled to help

the wiring harness fixation/assembly.


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Clamping for connectors or components Make sure the corrugated hoses are fixed to the connectors, back shells, and manifolds in a correct way (according to Volvo and sub supplier specifications). Terminals must not be bent before, during, or after the W/H installation. Broken or tightly stretched cables or hoses are not allowed.

When clamping to a component (with or without a corrugated hose) and the first clamping point is on the component, the clamping should be done on the cable protection and it is important not to make the loop too short before the first clamping is made (see figures 36 and 37). For each unique wire/cable bundle refer to the wire/cable/hose supplier specification, for the minimum bending radius. As a general recommendation for bundles, the diameter should be minimum two times the diameter of the bundle.

Figure 36. Illustration of how the wiring harness branch coming out of an inline connector

should be fixated (left) and the same fixation with a too small bending radius (right).

Figure 37. Example of how the wiring harness branch coming out of a component connector should be fixated (left) and the same fixation

with a too small bending radius (right).

Routing and clamping inside cab/body Connectors that are not in use and over length W/H must be clamped or taped with assembly tape, cable ties, or equal to prevent noise and chafe. Over length W/H should be kept to a minimum, but shall be properly secured and properly protected, if needed, not to be harmed by or harm surrounding components. Fixate and/or apply noise-reducing devices (e.g. textile tape, foam, and shields) to avoid rattling noises. The connectors should, if they are used for aftermarket options, be easy to access for later usage. Roof wiring harness and floor wiring harness may be taped to facilitate the installation.

When clamping the W/H, it is important that it is not in contact or can come in contact (due to movement and/or vibration) with sharp edges and that it is clamped in a fixed position. If this is neglected, the W/H may be damaged and functionality might be lost, or the W/H may be an object for short circuit or thermal stress. Secure that edges in a pass-through do not chafe on the wiring and that grommets are correctly mounted and water-tight. If there is a risk that the bundle can move and chafe against surrounding components, this must be secured by using proper fasteners/fixations.

It is strongly prohibited to remove pre-assembled cable ties without replacing them by new ones. All pre-defined clamping points shall be used as well as the pre-assembled cable clips and cable channels mounted on the wiring harness. W/H and power cables should be routed in such a way that they do not interfere with later assembly of the interior. When assembling or pre-assembling panels high focus shall be put on not damaging the wiring harness by e.g. fixing points for panels.

Routing and clamping power cables If any damage on power cables or cable terminals is found before, during, or after the assembly process, it is not allowed to repair the cable. A new part must be installed. If the second insulation is visible, the power cable shall be scrapped and replaced.


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Figure 38. Illustration of two power cables where the outer insulation has

been damaged (the white PEX is visible through the PVC insulation).

Assembly and re-assembly of screws to cable terminals are specified to a torque, which must be met. It is strongly prohibited to diverge from this specification. Routing, clamping, and clipping on purchased components (e.g. engine/transmission, and battery box) shall not include removing or replacing bolts, nuts, or screws installed by the manufacturer. In such cases where this is unavoidable, the bolts, nuts, or screws are to be re-tightened with a torque according to the manufacturers specifications.

Generally, no relative movement is allowed between components in a clamped bundle or between clamping point and power cable.

Consequences of improper installation If the W/H installation is not performed properly, the following consequences may be the result.

Clamping general If the stated clamping requirements are not followed, the movement of the wiring harness protection, e.g. corrugated hoses, may cause chafe on the single wires inside the hose. Therefore, the type of wire and corrugated hose must be carefully selected and the clamping requirements met.

Unexpected movements of wiring harness can harm components in the surrounding areas, e.g. air-pipes. This may cause reduced conductibility or disrupt contact and may set other systems out of order.

Incautious handling Defects and dust on connectors and their sealing may affect the water protection and in the long term cause corrosion on terminals. Incorrectly applied force on the connectors when connecting may lead to destroyed terminals.

Abuse to the connectors (terminals), by incorrectly dimensioned test tools and probes might apply overstress to the spring force of the receptacles so that the fitting to the mating pin may be destroyed. This can lead to reduced conductibility or disrupt contact, which may cause malfunction, unplanned stops, and thermal stress.

Clamping to components If the stated requirements on clamping distance to component connections are not followed, micro movements between pin and socket, i.e. fretting, may occur. In the long term, this can create oxides and cause reduced conductibility or disrupt contact.

Power cables If the stated requirements are not followed on power cables, reduced conductibility or disrupted contact may be the consequence. This may lead to high power consumers not fulfilling their purpose, and may cause thermal stress and in worst case fire.

dte: Printed copies are uncontrolled. Print date: 2010-05-04

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Power Cables and Wiring Harnesses