The Definitive Guide to Underground Cable Ducting

Fri 1st Oct 2021

INTRODUCTION

Ever wondered, what is underground cable ducting? Perhaps you’re curious about where it’s used or why there are so many types and colours of electric ducting. Or maybe you’re not sure about how to install cable ducting? Or what the law says about it? All of these questions will be answered in this article, tailor-made just for you!

Ducting can be a confusing topic, since many people associate the term with ventilation over utilities. And it’s definitely troublesome to find every answer you need in just one place. While that was previously the case, it isn’t anymore, because we did it! We gathered all the information we could find and compiled this article, to answer every single FAQ on underground cable ducting.

WHAT IS UNDERGROUND CABLE DUCTING?

What is Cable Ducting?

Cable ducting is a cabling protection system. Essentially, it’s a passageway for electricity/power/other types of cables to run through. Designed as durable and impact-resistant as possible, this makes sure that cables are protected from weather and any other external factor.

What is Underground Cable Ducting?

In the UK, underground electric cable ducting must comply with ENATS (Energy Network Association Technical Specification) 12-24 classes. It must also be manufactured according to BS EN 61386 (which superseded BS EN 50086). The local electricity provider should be able to advise which ducting class is required for your project.

Material & Class Types

Electric cable ducting is typically classified into three types – Class 1 for high voltage, Class 2 for low voltage and Class 3 for general-purpose applications. Apart from the colour coding (advise Laws & Regulations paragraph below) and the class types, underground ducting also comes in a range of different materials and designs. Ultimately, different types of utilities and installations require different types of ducting.

Plastic ducting is the most common these days, but even this comes in different types. Polyethylene and UPVC are usually the materials of choice for solid wall pipes. Their design suits various applications depending on the specification and project requirements. You should use Twinwall HDPE pipes in areas that require extra strength, such as beneath heavy concrete under roads or pavement. However, all pipe materials come in different compression strengths and SN ratings. So it’s always best to have a look at the manufacturer’s technical datasheet before installing.

WHY USE IT / IMPORTANCE

Organisation & Tidiness

For every building you see, they make use of utilities and services, delivered through pipework and cabling. There are millions of buildings and millions of miles of cables in the UK as well as in any other country worldwide. It would be practically impossible to leave all those cables on the ground. Therefore, burying cables can be a neat, tidy and organised cable routing solution, especially in dense areas.

Protection

Apart from aesthetic benefits, underground ducting protects water pipes, gas pipes and electric cables from damage. And more importantly, they protect people from their (potentially harmful) contents.

If left unprotected and above ground, cables and pipes are exposed to weather and environmental factors. That increases the risk of cables/pipes being crushed, broken, tampered with or compromised. This could also present a risk to the safety of people coming in contact with them. Exposure to a damaged electric cable could result in a harmful or even fatal electric shock. Burying below ground reduces many of these risks and simultaneously slows down the effects of weathering on the cable.

However, even when installed below the ground, pipes and cables can still be damaged by other factors, like root growth, or by individuals accidentally digging where they are placed. That’s where underground ducting comes in super handy. By running utility pipes and cable through ducting pipes, it provides an extra layer of protection and insulation against any type of damage or potentially harmful occurrence.

Saving Time & Money

Another essential benefit is that underground ducting saves time and money. When installed correctly, services like electricity, water, gas, internet and phone lines can all run smoothly without interruption. Additionally, any type of maintenance or repair work becomes easier. That increases general operational safety and reduces project costs considerably.

Leakage Prevention

Last but not least, another important reason for using underground cable ducting is that it’s a great way to ensure any substance leaking from cables doesn’t immediately affect water or other nearby sources. Both overground and underground cables can leak and ducting is a good solution to prevent any potential contamination.

DUCT INSTALLATION METHOD

Ever wondered how to install underground utilities ducting?

Installing ducting is relatively easy, but ensuring it’s safe, efficient and compliant requires some planning and insight. The main steps are:

how to install underground cable ducting

1) Choosing the right colour duct to match your utility

2) Choosing the right material while considering the conditions of your installation

3) Designing your installation route and making sure no other utilities run through it

iStep 4 – Turning off the utilities you are going to install before you start.

4) Digging a trench of the appropriate depth and width for your utility

5) Preparing a 50mm deep bed of sand or fine soil in the base of the trench, making it level with the access chamber/ catchpit interface

6) Installing the ducting efficiently, minimising bends and reducing waste wherever possible

7) Using draw cords and the pilot rope/wire to help run the pipes/cables through the ducting

iStep 9 – Checking the installation to ensure everything is connection and sealing is correct.

8) Turning utilities on again and inspecting whether there’s any visual leaks/connection issues.

9) Installing an appropriate marker table above the ducting at the recommended depth and filling in the hole.

Underground Cable Ducting Installation Process

Every manufacturer, however, has some additional steps or differentiators in this process according to their solutions’ requirements. To download the Installation Manual for the Furukawa Electric EFLEX Square Ducting System, please follow the link below:

EFLEX Square Installation Manual

For additional guidelines on Planning, Construction, Health & Safety and Site Conditions prior to installation, please advise: http://streetworks.org.uk/wp-content/uploads/2016/09/V2-New-Development-Sites-Issue-4-29-10-2013.pdf

LAWS & REGULATIONS

What does the law say about underground ducting?

Legislation for installing underground cables and utilities focuses on ensuring minimum installation depths for the relevant pipes and cables. Another legal requirement of underground ducting is to use the right ducting colour for the appropriate utility. Additionally, cables and pipes must be installed into ducts that are suitably-sized to accommodate their diameter. Before installation takes place, all cable ducts should be checked and cleared of obstructions. To ensure that the duct is suitable for the type of installed cable, UKPN (UK Power Networks) recommend:

Pulling a 3-metre sample of the LV-HV cable – identical to the one intended for final installation – through the full length of the duct to test the route
Examining the duct for any cracks or damage before proceeding to pull and install the complete cable length
If the sample cable shows deep scores or tears in the outer sheath exceeding half its thickness, the duct route must be repaired before installing the final cable

The usage or continuation of usage of any underground cable/pipe or attached equipment that does not comply with the current laws and regulations is illegal. The prosecution of anyone responsible is possible.

What are underground ducting colours codes and why are they important?

The reason each pipe is a different colour is purely for safety reasons, building regulations and to identify which ducting is protecting which type of cable.

The colour codes are useful during excavation or if any repairs are necessary in underground utilities networks. Particularly, they aim to reduce the chance of damaging underground services while also minimising the risks of anyone involved in this work. It’s important to know and adhere to the UK’s universal ducting cable colour codes.

There are minimum depth requirements for all underground utility ducting. Please consult Utility Ducting Depths image. (All depths indicated are from the top of the pipe to finished ground level.)

Additional Sources

For more information on the rules and regulations surrounding underground utilities, we suggest visiting the Street Works UK website. This Government site provides publications with specific guidance tailored to the location and intended use of underground cables. For example, guidelines around positioning underground utilities in new developments feature in Volume 2, while information regarding the management of third-party ducting feature in Volume 3.

Another useful and reliable source is the HSE Legislations website. HSE offers more information on excavation and underground services. This includes guidance on safe digging practices and using a cable locator to verify site plans against what’s actually in the ground. Professionals often recommend using plans as a starting point to locate underground cables, but warn against relying on them as definitive.

FREQUENTLY ASKED QUESTIONS

Is ducting the same as trunking?

Both cable ducting and trunking protect cables, keep them organised and conceal them from view. However, each one has a variety of uses and applications, with some key differences too.

First of all, Cable Ducting is for outdoor use and underground utility installations. On the other hand, installers mainly use Cable Trunking for indoor cable management. Additionally, the former consists of lengths or coils of pipe, whereas the latter is an enclosure, usually with a rectangular cross-section and a removable (or hinged) side.
Cable trunking is typically visible in office buildings, often appearing as a white plastic box running along walls and roofs. Its purpose is to cover electrical equipment, keeping it safe and tidy. You would never find trunking buried in the back garden. Or with power cables or utility pipes running through it. That is what underground ducting is for!

What are the HS Codes for Cable Ducting?

The HS Code for Trunking, Ducting and Cable Trays used in electrical circuits is 39259020. HS stands for the Harmonized Commodity Description and Coding System, and constitutes an international nomenclature for the classification of products. This code is commonly referred to as the Customs Tariff Number in many countries, where it is used for customs and tariff purposes.

Does Armoured (SWA) Cable need ducting?

There is no need for ducting when installing Steel Wire Armoured (SWA) Cable. You can bury it directly in the ground at a sufficient depth to prevent damage, with no additional protection needed.

However, you can apply a layer of sand or silted soil beneath the cable, then cover it with more sand or silted soil to protect the outer sheath from sharp stones.

FURUKAWA ELECTRIC CABLE DUCTING

E-Tech Components provide EFLEX Square – Furukawa Electric’s Underground Cable Ducting System, which enables the simplest and fastest installation of protected buried cable routes! EFLEX Square complies with ENATS 12/24 Class 1 Specification. Additionally, its units are stackable, which makes them ideal for underground multi-rack cable installations.

View our Cable Protection Solutions Here

FREE Technical Advisory Service
E-Tech Components UK Ltd maintains a free technical advisory service.
Contact us about any questions, enquiries or requests you may have: +44 (0) 1744 762 929