Jake Green, Head of Technical Engagement with Scolmore Group, takes a look at some of the ways to avoid undue strain on cables, as well as delving deeper into the requirements of BS7671.

Wiring systems must be selected and erected to avoid during installation, use and maintenance, damage to the sheath or insulation of cables and their terminations (522.8.1). To ensure the requirements of this regulation are met, cables not installed in conduit or trunking are typically supported using a range of clips, saddles, band, glands and ties.

Requirements

All cables and conductors must be supported in such a way that the level of mechanical strain which naturally exists will not cause either the cable/conductor or the terminations to be compromised (522.8.5). Furthermore, all cable supports and enclosures shall not have sharp edges liable to damage the wiring system, and cable/conductors are not to be damaged by the means of fixing (522.8.11 & 522.8.12). It is important, therefore, that care is taken when selecting for use supports that are appropriate for the cable/conductors.

Types of support

There is a wide range of options available for the contractor when selecting cable supports. These include amongst other things:

• Cable ties
• Cable cleats
• Cable clips
• Cable tie accessories
• Cable glands

The type of fixing will depend on the nature of the surface to which the support is fixed. For example, cable ties would be suitable for fixing cables installed on basket tray or cable tray, whereas cable clips would be suitable for wooden surfaces. Similarly, the type of support will depend on the type of cable being installed. For example, cable cleats will be suitable for steel-wire armoured cables.

Guidance

The guidance issued within the On-Site Guide (OSG) published by the IET is helpful in deciding on the nature of cable support and the distances recommended between clips. Appendix D covers cables generally, specific applications such as caravans and the like, overhead wiring as well as conduit and trunking support.

Table D1 details spacings of supports for cables in accessible positions. Fig 1 gives an example of the recommended distance between clips for a cable having a diameter not exceeding 9mm based on Table D1. As the cable diameter increases the distance between clips is permitted to grow.

Image: Fig 1 Cable supports example – image courtesy of T.J. Bratley

Whilst the support distances are important, it remains the case that the purpose of cable supports is to ensure there is no undue strain on the cable or its terminations.

Similarly, when cables are bent it is important that there is no undue strain on the internal conductors caused when the bend is too tight (522.8.3). Fig 2 shows an example of the recommended bending radius for 1.5 mm² insulated and sheathed ‘twin and earth’ (Table D5 OSG).

Image: Fig 2 Bending radius example – image courtesy of T.J. Bratley 

Cable entry

Two issues must be addressed when cables enter an accessory: the risk of damage to the sheath/insulation at the point of entry, and any potential strain on connections.

Where a cable enters a metallic accessory box having no protection from sharp edges, there is a risk that the insulation surrounding conductors may become damaged leading to arc and shock risk. Where cables enter a metallic accessory box, it is important that protection is provided, such as with rubber grommets or similar.

Even where cables entering an accessory box or other metallic enclosure are protected from damage, terminations may still be impacted by strain as cables are left unsupported. In such circumstances it is necessary for suitable support to be provided and compression glands provided to ensure the electrical and mechanical strength of terminations (522.8.5 and Note).

Conclusion

All cables and conductors must be suitably supported to ensure that no undue strain exists on the cable or the terminations (522.8). Care should be taken to select appropriate support (clips, glands and the like) for cables and Unicrimp has a range of products to help the contractor in carrying out their duties.

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The post How to avoid placing undue strain on cables appeared first on Professional Electricians Wholesaler.

Jake Green, Head of Technical Engagement with Scolmore Group, considers the general requirements of Regulation 521.10.202.

After several tragedies, Regulation 521.11.201 (AMD 3 BS 7671: 2008) was introduced; its purpose being to limit the risk to firefighters from entanglement by cables when they entered or exited a premises.

This regulation has now been renumbered as 521.10.202 but remains essentially the same except for the removal of any reference to escape routes. It now reads: “Wiring systems shall be supported such that they will not be liable to premature collapse in the event of a fire.”

This requirement should not be confused with the recommendations of standards like BS5266-1 (emergency lighting) and BS5839-1 (fire detection and fire alarm systems), which recommend methods of cable support to maintain circuit integrity during a fire.

Escape routes and BS 7671

The original regulation referred to escape routes, and this generated a level of confusion: ‘How should escape route be defined?’

BS7671 defined escape routes differently to that used in other guides, regulations and legislation. For example:

• BS 7671 – ‘Path to follow for access to a safe area in the event of an emergency’.
• Building standards technical handbook – ‘…means a route by which a person may reach a place of safety…’.
• Approved Document B in England and Wales – ‘…that part which a person has to traverse before reaching either the safety of a final exit or the comparative safety of a protected escape route….’

The removal of ‘escape routes’ from the regulation now means that it applies to all areas of the installation.

Premature collapse

There is no specific definition of ‘premature collapse’ to be found in Part 2 of BS 7671. One dictionary definition of ‘premature’ is, ‘occurring or done before the usual or proper time; too early’.

Since the purpose of Regulation 521.10.202 is not to maintain the critical signal path, rather to limit the risk to firefighters; premature collapse should be considered in relation to that single purpose.

Electrical contractors, network installers and the like are not best able to judge how fires behave, the likely temperatures that will be attained, nor how firefighters will carry out their role within a premises that is on fire. It is important, therefore, that electrical contractors and other installers give due consideration to the support given to wiring systems to provide maximum reasonable application of Regulation 521.10.202.

Unicrimp, a Scolmore Group company, offers a comprehensive range of cable accessories within its Q-Fire fire-rated range that are designed to provide the necessary protection from premature collapse.

There is a great deal of responsibility placed on contractors to apply Regulation 521.10.202, not because they want to meet minimum expectations, rather because they want to protect firefighters who are working under extremely dangerous conditions.

An electrical contractor should consider, as a minimum, the following:

• Wall fixings:
• Careful consideration should be given to the mass of the wiring system that is to be supported (including the trunking, cable tray, etc. with the cables in situ).
• Will the structure of the building maintain sufficient fire resistance to permit cables to avoid the need for metallic supports? Will such supports be sufficient if firefighters damage ceilings when applying water?
• Cable clips – metallic clips are essential as indicated by Note 3 and 4 of Regulation 521.10.202.
• Brackets or internal clips for PVC trunking – to keep the lid or cables in place (see Note 3 of Regulation 521.10.202).

Conclusion

Electrical contractors should carefully consider their responsibilities when installing wiring systems. Under fire conditions, failure to make the right installation choices may lead to serious consequences.

For more information, click here

The post Considering the General Requirements of Regulation | Scolmore Group appeared first on Professional Electricians Wholesaler.

The EDA’s Product Knowledge Modules help businesses like yours create cross-selling and up-selling opportunities by building knowledge and confidence.

These training modules have won a Princess Royal Training Award in 2022 so you can be assured of their value.

Cables and Cable Management is one of 12 training courses in the programme. The EDA modules are completely flexible and can be studied in any order or combination. You choose only the training your team needs.

 E-learning option

All the EDA training modules are available in a digital format instead of a printed textbook. The digital learning option is a complete e-learning experience with videos and interactive content. The EDA team is happy to talk you through your options and can give you a demonstration of the new e-learning platform.

Cables and Cable Management training module covers:

• Wiring systems
• Telecommunications cables
• Optical fibre cables
• Special cables
• Substandard and counterfeit cables
• Cable fire performance
• Cable management systems
• Cable termination

City & Guilds accredited, this training programme harnesses decades of combined expertise from product experts at EDA manufacturers and allied trade associations to create an accessible and practical training opportunity for you and your team.

Test your knowledge

Have a go at this quiz sampled from the Cables and Cable Management module. Then check your answers below. If the results show that you need to boost your team’s know-how, talk to the EDA today.

Q1: What colour insulation is used to denote a protective earth conductor?

Q2: Name two types of metallic CMS.

Q3: How many bits per second (b/s) are there in one Mb/s?

Q4: To what do the following acronyms refer: LFH and LSF?

Q5: What colour ducting is used to denote a telecommunication installation in the

public highway?

Q6: What is the connection between a conductor and other equipment or

accessory called?

Scroll for answers

Q1: Green/yellow

Q2: Pre-galvenised (PG) zinc-coated steel, electroplating with zinc (EZ) or powder coated (PC).

Q3: 1,000,000

Q4: Low fire hazards (LFH) and low smoke and fume (LSF) cables

Q5: Grey

Q6: A termination

How did you do?

 Full marks: Well done!

3 – 5 out of 6: Not bad. Could the EDA training help you to fill in any gaps in your knowledge and help you progress in your career?

Less than 3: The EDA Product Knowledge Programme could be just what you need to boost sales.

Watch the video and download the course directory

There’s plenty of information online at www.eda.org.uk including video and downloadable Course Directory, giving you a summary of what’s covered in each of the 12 training modules. The EDA team is ready to help. Call 020 3141 7350 or email training@eda.org.uk

For more information, click here

The post EDA Insight: Cables and Cable Management quiz appeared first on Professional Electricians Wholesaler.

Jake Green, Technical Engagement Manager with Scolmore Group, considers the general requirements of Regulation 521.10.202.

After several tragedies, Regulation 521.11.201 (AMD 3 BS 7671: 2008) was introduced; its purpose being to limit the risk to firefighters from entanglement by cables when they entered or exited a premises.

This regulation has now been renumbered as 521.10.202 but remains essentially the same except for the removal of any reference to escape routes. It now reads: “Wiring systems shall be supported such that they will not be liable to premature collapse in the event of a fire.”

This requirement should not be confused with the recommendations of standards like BS5266-1 (emergency lighting) and BS5839-1 (fire detection and fire alarm systems), which recommend methods of cable support to maintain circuit integrity during a fire.

Escape routes and BS7671

The original regulation referred to escape routes, and this generated a level of confusion: ‘How should escape route be defined?’

BS7671 defined escape routes differently to that used in other guides, regulations, and legislation. For example:

• BS7671 – ‘Path to follow for access to a safe area in the event of an emergency’.
• Building standards technical handbook – …means a route by which a person may reach a place of safety…’.
• Approved Document B in England and Wales -…that part which a person has to traverse before reaching either the safety of a final exit or the comparative safety of a protected escape route….

The removal of ‘escape routes’ from the regulation now means that it applies to all areas of the installation.

Premature collapse

There is no specific definition of ‘premature collapse’ to be found in Part 2 of BS7671. One dictionary definition of ‘premature’ is, ‘occurring or done before the usual or proper time; too early’.

Since the purpose of Regulation 521.10.202 is not to maintain the critical signal path, rather to limit the risk to firefighters; premature collapse should be considered in relation to that single purpose.

Electrical contractors, network installers and the like are not best able to judge how fires behave, the likely temperatures that will be attained, nor how firefighters will carry out their role within a premises that is on fire. It is important, therefore, that electrical contractors and other installers give due consideration to the support given to wiring systems to provide maximum reasonable application of Regulation 521.10.202.

Scolmore group company Unicrimp offers a comprehensive range of cable accessories within its Q-Fire fire-rated range that are designed to provide the necessary protection from premature collapse.

There is a great deal of responsibility placed on contractors to apply Regulation 521.10.202, not because they want to meet minimum expectations, rather because they want to protect firefighters who are working under extremely dangerous conditions.

An electrical contractor should consider, as a minimum, the following:

• Wall fixings –
• Careful consideration should be given to the mass of the wiring system that is to be supported (including the trunking, cable tray, etc. with the cables in situ).
• Will the structure of the building maintain sufficient fire resistance to permit cables to avoid the need for metallic supports?
• Will such supports be sufficient if firefighters damage ceilings when applying water?
• Cable clips – metallic clips are essential as indicated by Note 3 and 4 of Regulation 521.10.202.
• Brackets or internal clips for PVC trunking – to keep the lid or cables in place (see Note 3 of Regulation 521.10.202).

Conclusion

Electrical contractors should carefully consider their responsibilities when installing wiring systems. Under fire conditions, failure to make the right installation choices may lead to serious consequences.

The complete Unicrimp fire range can be viewed here

The post Requirements of Regulation 521.10.202: premature collapse of wiring systems appeared first on Professional Electricians Wholesaler.