Meter Tail Regulations

Meter Tail Regulations

Please join our new Facebook group where you can continue the discussion and learning in a non-judgemental atmosphere! CLICK HERE – Electrical Assistance Facebook Group

If you’re in the process of installing a new consumer unit or conducting electrical inspections, it’s crucial to have a solid understanding of the meter tail regulations in effect. As of the current year, which is 2024, these regulations fall under the guidelines set out in the 18th edition of the wiring regulations, often referred to as BS7671.

Although there isn’t a specific document titled “meter tail regulations,” various sections within BS7671 pertain to the installation of cables, including the essential meter tails. Let’s break down the key sections of BS7671 that apply to meter tails:

Now, since this guide primarily aims to assist you with 18th edition electrical inspections (EICRs), our focus will mainly revolve around what you should be looking for during such assessments. However, it’s also vital to understand the considerations for installing meter tails in a new electrical setup.

For a comprehensive grasp of meter tail regulations, it’s advisable to cross-reference this information with our “Consumer Unit Regulations Guide 2024,” as it includes specific sections that relate to meter tails. This additional resource can provide further insights into this critical aspect of electrical installations and inspections.

Requirement for adequate support for Meter Tails/Cables

This is something which is far and away the most common issue with meter tails. They are often hung from the meter over to the consumer unit (or even fuse board on older installations).  This is often on the fashion of a large “lazy loop” as the thick cable does not bend too easily.

Adequate support for meter tails or cables is a fundamental requirement, and it’s worth noting that this is one of the most frequently encountered issues in the field of electrical installations. Meter tails are commonly observed to be hung in a rather haphazard manner, stretching from the meter to the consumer unit, or in older setups, the fuse board. This arrangement often takes the form of a large, somewhat sagging loop, resembling a “lazy loop.” The reason for this practice is the relative inflexibility of the thick cable, which doesn’t lend itself to easy bending.

To ensure the safe and effective functioning of the meter tails, it’s imperative to address this concern. Proper support and organization of these cables are vital not only for neatness but also to avoid potential hazards. Together with Adam, a local electrician in Warrington, let’s explore some key considerations for addressing this issue:

  1. Secure Fixtures: Install appropriate fixtures or cable clips that provide sturdy support for the meter tails. These fixtures should be designed to handle the weight and rigidity of the cables.
  2. Avoid Lazy Loops: As mentioned, the “lazy loop” configuration should be avoided. Instead, aim for a more direct and structured path from the meter to the consumer unit. This minimizes the risk of accidental damage and tripping hazards.
  3. Maintain Clearance: Ensure that the meter tails are routed to maintain adequate clearance from any obstructions or other wiring. This helps prevent overheating and potential damage.
  4. Proper Bending Radius: While meter tails may be less flexible than other cables, they still have a minimum bending radius that should not be exceeded. Be aware of this specification when planning the cable’s path.
  5. Compliance with Regulations: Always follow the regulations and guidelines outlined in the 18th edition wiring regulations (BS7671) regarding the installation of meter tails. These regulations exist to ensure safety and efficiency in electrical systems.

In summary, addressing the issue of adequate support for meter tails is essential for maintaining a safe and organized electrical installation. By avoiding lazy loops, using secure fixtures, maintaining clearance, and adhering to regulations, you can enhance the reliability and safety of the meter tail arrangement.

Meter Tail Regulations 2022 - Adequate Support Of Cables Against Strain
Adequate Support Of Cable? Hung as a loop from meter to consumer unit

I’ve personally encountered an instance that might leave you baffled – a tenant hanging an umbrella by the handle from the drooping meter tails! It’s a stark reminder of the casual approach that some people take towards electrical safety. Loose connections within main switches and electric meters are, without a doubt, a substantial source of fire risk. This underscores the critical importance of securing meter tails in a manner that places no undue strain on the terminations.

To achieve this, there are several methods to consider:

  1. Meter Tail Gland: A modern solution is to use a meter tail gland on the consumer unit. These are designed to provide a secure and strain-free connection for the meter tails, reducing the risk of loose terminations.
  2. Clips and Fixings: Alternatively, clips specifically designed for securing meter tails can be employed. In an 18th edition installation, it’s essential to use heat-resistant fixings for this purpose, ensuring they can withstand the demands of the electrical system.

When inspecting older installations, especially those where meter tails pass from an external cabinet through a wall cavity to the consumer unit, attention to detail is crucial. In most cases like this, the cable passing through the wall provides adequate support, assuming the length of the tails within the meter cabinet is not excessive.

However, a potential issue arises when the cable runs through thermal insulation, a situation frequently found in modern houses with cavity wall insulation. In such cases, a close inspection should be conducted (where feasible) to ensure there has been no thermal damage to the cable due to the installation method. Detecting and addressing such issues is vital for ensuring the safety and functionality of the electrical system.

So, the takeaway here is to always prioritize secure and strain-free connections for meter tails. Whether using modern meter tail glands, heat-resistant fixings, or diligent inspections, these efforts go a long way in mitigating fire risks and ensuring electrical safety.

Do Buried Meter Tails Need RCD protection?

It might sound peculiar, but indeed, meter tails buried in walls at a depth of less than 50mm from the surface require additional protection in the form of a 30mA RCD (Residual Current Device). This is a safety measure to prevent electrical hazards in such scenarios.

It’s essential to highlight that when cables are buried in walls containing metal parts, they must be RCD protected, regardless of the cable’s installation depth. This is a non-negotiable safety measure, as metal parts can conduct electricity and pose significant risks.

A common installation method for meter tails involves running them from an external meter cabinet through the wall cavity, and then into the consumer unit through the rear of the board. While this method may not align precisely with meter tail regulations specified in BS7671, it’s worth noting that this setup generally doesn’t present any apparent risks to the cable, especially when thermal insulation is accounted for (as mentioned in the previous section).

However, when it comes to cables buried less than 50mm beneath the wall surface, the situation changes. This is a scenario that’s not encountered very often, but there are specific cases where it arises. For instance, in older buildings converted into flats, where 16mm T&E cables are used as meter tails or submain cables. These cables may run throughout the building to supply individual flats.

In such cases, it’s challenging to trace the precise route of the cable through the building’s structure. Given the more significant nature of the submain cable, it’s advisable to seriously consider upgrading it. An ideal solution here is to use SWA (Steel Wire Armoured) cable, as it doesn’t require RCD protection in accordance with meter tail regulations.

Adding a 30mA RCD at the beginning of such a setup could lead to nuisance tripping issues and wouldn’t meet the requirement for the division of circuits to minimize inconvenience. Therefore, upgrading the cable to SWA provides a more effective and compliant solution.

Meter Tail Regulations – Identification Of Conductors

When delving into these regulations, it’s crucial to keep in mind the correct identification of conductors. This is vital for maintaining electrical safety and ensuring the system operates as intended.

On a single-phase supply, you’ll typically have two conductors: Live (L) and Neutral (N). However, when dealing with three-phase supplies, all three phases require distinct identification, along with the Neutral conductor. This differentiation is usually achieved through the colour of the conductor, a standard practice in electrical installations.

It’s worth noting that beyond the meter, there should be no unsheathed basic insulation. Exposed wires or cables pose a significant safety hazard, so this requirement is in place to mitigate risks.

In line with these considerations, some meter tails are now being manufactured with coloured sheathing. This design ensures that each conductor can be accurately identified, promoting safety and making it easier to work with the electrical system. When working with such meter tails, it’s essential to follow the manufacturer’s guidance and ensure that the colour coding is adhered to throughout the installation process. This helps maintain the integrity of the electrical system and minimizes the potential for errors during installation and maintenance.

Meter Tail Regulations 2024
Identification Of Conductors – Coloured Cables

The most common type of meter tails you’ll encounter is the plain grey sheathed variety. These cables, by their appearance, are indistinguishable from one another. However, it’s crucial to implement external identification measures to differentiate the conductors. This can be achieved in several ways:

  1. Lettering or Numbering: A simple and effective method is to label the conductors with letters or numbers. This external identification makes it easy to discern which conductor is which. For example, you might label them as L1, L2, L3 for the phases and N for Neutral.
  2. Colour Coding: While plain grey sheathed meter tails lack distinct colours, you can use color-coded tape or heat shrink sleeves to mark the conductors. This visual distinction simplifies identification and helps prevent errors.
  3. Conduit or Trunking: If the meter tails are enclosed within conduit or trunking, labelling or colour coding can be applied to the outside of these protective enclosures.
  4. Identification Sleeving: Using pre-printed identification sleeves is another effective method. These sleeves can be slipped over the cable ends, providing clear labels for each conductor.
  5. Terminal Blocks: For connections at the consumer unit or meter, you can use terminal blocks that come with clear labelling options. This ensures proper connection and identification of the conductors.
  6. Marking at Joints: When conducting splicing or connecting meter tails, clearly mark the conductors at these junction points to avoid any confusion.

External identification not only helps electricians during installation but also simplifies future maintenance and troubleshooting. It’s an essential practice for ensuring the accuracy, safety, and functionality of the electrical system, especially when dealing with meter tails that have plain grey sheathing.

Meter Tail Regulations for TT Installations

TT earthing arrangements have distinct requirements that go beyond those of Terra-Neutral (TN) systems. The primary difference lies in the need for additional safety measures due to the potential risks associated with TT systems.

In TN systems, the low loop impedance ensures that the main supply fuse or other main Overcurrent Protective Devices (OCPD) would disconnect if the meter tail were to accidentally contact the external enclosure of a metallic consumer unit or distribution board. This level of protection stems from the electrical characteristics of the TN system.

In the past, plastic (insulated) consumer units were exclusively used with TT earthing arrangements, as they mitigated the risk of live conductors coming into contact with the metallic enclosure. However, changes introduced in AMD3:2015 to the 17th edition of the wiring regulations mandated that all main switchgear in domestic properties must be of a non-combustible type, meaning metal enclosures.

The challenge with TT systems is that their loop impedance is generally much lower, which means they can’t be relied upon to disconnect the supply in the required time to prevent electrical hazards in the event of a live conductor coming loose and contacting the metal enclosure. As a result, specific regulations for meter tails in TT installations are more comprehensive compared to standard TN setups.

In TT installations, one critical requirement is ensuring the secure placement of the meter tails within the enclosure itself. This can be achieved through the use of a gland on the consumer unit body. Additionally, there are consumer units available with two hoop clamps positioned directly above the main switch. These clamps provide an added layer of protection to minimize the risk of accidental contact between the meter tails and the metal enclosure.

The goal of these regulations is to enhance safety in TT earthing arrangements and reduce the likelihood of electric shock or fire hazards associated with the use of metal consumer units in such systems.

Meter Tail Regulations for TT Installations
Regulations For TT Installations – Cable Glands

Indeed, when installing a metal consumer unit in a TT earthing arrangement system, it’s imperative to make sure that the meter tails have their full ‘double insulation’ – more accurately, the outer sheathing of the cable – extended all the way to the entry point of the main switch. This meticulous practice is essential to minimize the risk of any potential contact between live conductors and the metallic enclosure when used within a TT system.

The ‘double insulation’ concept, where both the conductor insulation and an additional outer sheathing protect the cables, adds an extra layer of safety. It reduces the chances of inadvertent contact or short circuits within the enclosure, which could otherwise lead to electrical hazards, such as electric shock, fires, or damage to equipment.

By ensuring that the meter tails maintain their full ‘double insulation’ up to the entry point of the main switch in a metal consumer unit, you greatly enhance the overall safety of the TT earthing arrangement system. This practice aligns with the regulatory requirements for TT systems and is a crucial step in preventing potential electrical issues and associated risks.

Meter Tail Regulations 2023 - Tails Gland
Gland on cable entry into distribution board

Choosing The Correct Size Cable

Sizing meter tails for domestic and small-scale three-phase installations involves relatively straightforward requirements. It’s important to ensure that the cable size is appropriate for the specific application to maintain safety and efficiency:

  • 16mm are fine for 60A, 63A & 80A main supply fuses (BS88/BS1361 Type2)
  • 25mm are required for 100A main supply fuses

When inspecting electrical installations with 16mm meter tails, it’s essential to be aware of certain considerations regarding the supply fuse and the cable size. Here are some crucial points to keep in mind:

  1. BS1361 Type2 Supply Fuse Holders: Newer BS1361 Type2 supply fuse holders often have “100A” written on a label, indicating the maximum-sized fuse that can be fitted. However, it’s important to note that the heads may contain lower-rated supply fuses, such as 80A, particularly in newer homes. Therefore, the labelled maximum does not necessarily reflect the actual rating.
  2. Avoid Disturbing the Main Fuse: When conducting inspections on installations with 16mm meter tails, it’s generally best practice not to disturb the main fuse, whether it is sealed or not. Checking the rating of the main fuse can be challenging without the appropriate documentation.
  3. Check for Separate Stickers: In some cases, there might be a separate sticker that indicates the actual rating of the fuse fitted, rather than the maximum rating of the fuse carrier. If such a sticker is present, it can provide the needed information.
  4. Consult the Distribution Network Owner (DNO): If information on the main fuse rating is not readily available, you may need to reach out to the DNO for clarification. However, even they might not always have detailed information, especially for older installations.
  5. Consider Future-Proofing: In new domestic installations, it’s advisable to fit 25mm meter tails. This is a proactive approach that considers the increasing demand for electrical power, especially with the rise of Electric Vehicles (EVs) and modern technologies. Many DNOs now specify 25mm as the minimum cable size for new connections to accommodate these growing current demands.

Ultimately, ensuring that meter tails are appropriately sized and that the main fuse rating aligns with the installation’s needs is essential for electrical safety and efficiency. When in doubt, consulting with a qualified electrician or the DNO can help you make informed decisions about meter tail sizing and main fuse ratings.

Rules on Max Length Of Meter Tails

Regulations regarding the maximum length of meter tails can vary and are often specified by the Distribution Network Operators (DNOs) rather than following the standards outlined in BS7671. It’s essential to be aware of these DNO-specific requirements, as they may differ from one area to another. Here are some important points to consider:

  1. Maximum Length of Meter Tails: Many DNOs stipulate that the maximum allowable length of meter tails should not exceed 3 metres without implementing another method of fault protection between the main service head and the consumer unit or distribution board. This requirement is in place to ensure that electricians don’t rely solely on the main service fuse (usually a BS1361 type 2) for fault protection.
  2. Methods of Fault Protection: To comply with the DNO’s regulations, one common solution is to install a “switch fuse” between the meter and the consumer unit. This switch fuse includes its own built-in fuse that provides additional fault protection for the meter tails if they are longer than 3 metres.
  3. Upfront DP MCB: In some cases, an upfront Double-Pole Miniature Circuit Breaker (DP MCB), often with a rating of 63A or 80A, is installed to provide protection to the tails after the switch fuse. However, this approach can sometimes lack selectivity, as a fault downstream may result in the upfront MCB tripping.
  4. Application in Flats/Apartments: These arrangements are commonly seen in flats and apartments where the incoming supply and meter are located much farther than the 3-metre limit set by the DNO. In such scenarios, a room dedicated to switchgear and meters on the ground floor is often utilized. The meter tails enter a switch fuse in this room before running up the building to serve each individual property.
  5. Different Cable Types: The cable used between the switch fuse and the property’s consumer unit is often something other than traditional meter tails. Steel Wire Armoured (SWA) submains or split concentric cables are commonly employed in these cases.
  6. Contacting the DNO: If you are unsure about the specific regulations of your local DNO or need to ensure compliance, it’s recommended to contact them directly. They can provide you with the necessary information and guidance to ensure that you do not extend the meter tails beyond their maximum allowable length, which is typically around 3 metres.

Adhering to the DNO’s requirements for meter tail length is essential to maintain electrical safety and regulatory compliance, particularly in situations where the standard 3-metre limit cannot be met due to the layout and location of the meter and consumer units.

Summary Of Regulations 2024

For a quick summary of the most important meter tail regulations, here’s a concise list of the key points:

Adequate Support: Ensure that meter tails are adequately supported to prevent strain on the connections

Sizing Based on Current Rating:

  • EICR: Use 16mm cable for up to 80A and 25mm cable for up to 100A.
  • New Installations: Typically, DNOs may require 25mm cables to accommodate modern demands, especially for Electric Vehicles (EVs).

TT Installations: Meter tails must have continuous sheathing all the way to the main switch. Special consideration should be given to preventing strain on connections, often achieved using hoop-type cable grips above the main switch.

Protection for Cables Buried Close to Walls: If any cables are buried less than 50mm from a finished wall surface, they must be provided with 30mA RCD protection. Note that this protection may not meet selectivity requirements between protective devices when used up-front.

Proper Conductor Identification: Conductors must be correctly identified to avoid confusion regarding polarity.

Maximum Length per DNO Regulations: Distribution Network Operators (DNOs) often specify that the maximum length of meter tails cannot exceed 3 metres without some form of consumer fault protection in between.

These regulations cover the fundamentals of meter tails, ensuring safety and compliance with industry standards and DNO requirements.

30 Responses

  1. I wonder if you could answer my question, whilst it appears that most meter tails seem to average around 3 metres long , is there a specific law that governs there length ?

    • Hello Keith, thanks for reading and posting the question.

      With regards the length of meter tails, this is actually not a regulation under BS7671 (The Wiring Regulations), however this is a requirement from the DNO (Distribution Network Owners).

      Some DNOs have differing requirements, however most require a maximum of 3M from their cutout.

      The reason behind this is that they don’t want to give fault protection to meter tails over this length with the main cutout fuse.

      You can have meter tails longer than this, however you need to have your own overcurrent protective device protecting the tails.

      Our local DNO, Northern Powergrid have this on their requirements for a new install on page 7 of this guide:

      Hope that helps?

      Regards, Electrical Assistance

  2. Is it permitted for meter tails to exit an external surface mounted meter box through the top, be secured to the wall and then passed through the wall higher up (assuming all is accomplished within the maximum distance for the tails)?

    • Hello David, thanks for posting the question.
      From what you describe, I don’t think this would be the correct way to achieve this. In the case of traditional “meter tails” being 6181Y cable, this cable is not suitable for mounting outdoors without additional mechanical protection (ie: capping, large trunking).

      Consideration must also be given to the fact that 6181Y cable is not suitable for mounting where it is subject to direct sunlight. Any amount of UV from sunlight will eventually damage the grey outer sheathing, causing it to go brittle and crack off.

      If you do need to run the tails surface mounted from the meter box, there are commercial products to resolve this issue, including exterior grade cable capping. Often seen on telephone poles covering the cable drops.

      This or some heavy duty trunking (50×100) or (100×100) leaving the meter box although you would have to ensure that any product used is suitable for use outside as exposure to weather can cause white trunking to go brittle and crack.

      Hope that helps?

      Kind regards

  3. Good morning,
    I will be having an additional single way consumer unit fitted to supply a EV charger.
    This unit will be fitted inside the fully enclosed porch approximately 300 mm above and slightly to the right of the meter box which is sunk in to the wall.
    Ideally I would prefer the meter tails to exit in to the cavity wall and then to be glanced in to the rear of the consumer unit.
    Although this would be more work it would give a cleaner finish without the tails being on display. There would technically be about 0.5M of tails in the cavity wall.
    The existing consumer unit tails also run in the cavity wall.
    I appreciate that the new regulations prefer tails not to go in to cavity’s, but would this be acceptable.
    Thank you for any advice you can give me.

    • Hello Martin

      Thanks for posting the question. From what you have described, I honestly cannot see any problem with running the tails within the cavity the short distance between the meter enclosure and the new EV charger consumer unit as you describe.
      One thing to be aware of is if there is cavity wall insulation, this can mean you need to use the next size meter tails up, as any cable ran through insulation experiences a “derating factor”. Using 25mm tails instead of the common 16mm on EV consumer units will suffice for such a short distance. Your installing electrician should be able to perform the necessary calculations.

      Hope that helps?


  4. Good Afternoon,

    Firstly this a really good & informative article, thanks for taking time to publish!

    A quick question.

    I have just carried out some electrical works in a property that has just had a new EVCP install. The installation is a TNC-S 3phase supply and the cut-out fuses are 100amp, all tails are 25mm, with all bonding up to date. The EVCP installer has used 16mm tails out of henley blocks to feed the new metal clad CU, which inside has a 40amp C curve 2pole Type A RCBO. The EV point is a tethered type 2 smart unit roughly 35m from the mains.

    Are the 16mm tails compliant, these are roughly 500mm long, no mechanical protection.

    The reason i ask, if we install a new EVCP and we have a 60 or 80amp fuse and need to upgrade this, the DNO WILL NOT upgrade the fuse to 100amp unless ALL tails are 25mm, this goes to say on any other fuse upgrade for any reason to 100amp! 100amp =25mm

    I notice that you say above: ” the common 16mm on EV consumer units will suffice for such a short distance”

    FYI – The EVCP was a freebie to my customer as they have just purchased there new EV car.

    I have asked half a dozen sparky’s today, we all say these should be 25mm, could you put help answer this please??

    Many thanks.

    • Hi Mr B, thanks for posting the in depth question and apologies for the delay in replying to this, it got missed in the many comments we receive.

      Whilst I can see the arguement from others that 100A should always be 25mm tails, bear in mind a situation like a feed being tapped from a busbar within a busbar chamber. As long as the load cannot effectively exceed the current carrying capacity of the cable used, either by the load being of a fixed design current, or an in-line OCPD, then you are allowed to omit overcurrent protection in these instances. The regulation in question is Regulation 433.3.1

      Would you tap from a busbar chamber to feed a small fixed load with a cable capable of carrying hundreds of amps continuously?

      In the instance you describe, the cable is protected against overload by the 40A RCBO in the EV charger CU. There is no possibility that the load can exceed this as the RCBO would trip. So from this point of view it would comply. Not only that, but the design current of a fixed load like the EV charger prevents any overload being placed on the 16mm tails.

      There is an article from the NICEIC which helps explain this, albeit using different examples:

      It should be noted, however, that where you mention the DNO, they have their own rules and regulations to follow, which do not always align with those within BS7671. They are quite within their rights to suggest that 25mm tails must be used throughout, in the first instance simply because the supply belongs to them and they can, but also from a practical point of view they cannot be sure that someone won’t come along and install another 40A circuit (or even more) alongside the existing EV circuit thus pushing the current draw above that which can be safely carried by 16mm tails.

      Quite frankly if it was me, I would have installed 25mm tails for sure, however the 16mm tails will be at no danger of “overloading” – just be sure that they are capable of carrying any short circuit fault current for the duration of time it takes the DNO OCPD to cut out.

      Hope that helps?

  5. Hi. would it be permissible to run 25mm tails straight through the back of the meter box, through a cavity wall and terminated into a 80a switch fuse? Then run 25mm swa to consumer unit. Basically meter box and switch fuse will be back to back on the cavity wall.

  6. Hi I am upgrading my single phase to a 3 phase to separate the power to a flat upstairs. My question is does overcurrent protective device go between the cut out and meter or between the meter and consumer box or both.

  7. If you extend the meter tails and so would be potentially altering the Ze of the consumer unit. Would you have to carry out a full installation test & certificate (new / altered installation)?

    • Hello Andy, thanks for posting the question

      I don’t think that a full inspection & test of the installation would be required, assuming that the additional length of the meter tails is not sufficient to require addition of a new overcurrent protective device being added up front.

      Obviously in this instance, where the meter tails would be over 3M and have some form of in-line fuse or circuit breaker, then you are effectively making the supply to the consumer unit a sub main and you should perform some tests to be certain that disconnection times will still be met by the final circuits.

      The best course of action would probably be to do an EIC, however just record the details of the specific works completed (IE: altering meter tails only) and that you complete the requisite tests of the incoming supply.

      If in any doubt, I’d suggest a quick call to your competent person scheme technical helpline to see what they advise, however I doubt they will suggest a full test unless you are altering the Ze by a large margin.

      Hope that helps?

  8. When I had extension constructed in 2011 my electrician said I needed another phase of supply due to the total load of electrical underfloor heating. We paid DNO to have a trench dug and new supply and 3 Phase meter fitted. Although the supply head has three 100A fuses only 2 sets of 25mm meter tails run from the meter and then to my 2 consumer units. If I now want to install a 3 phase ev charger, who can connect my meter to the currently unused 3rd phase? Is it my DNO or my supplier or my EV instsaller?

    • Hello Sean

      Thanks for getting in touch. The setup you have described, if there is currently no connection between the L3 of the incoming supply and the electric meter then this would generally be the responsibility of the supplier. The DNO won’t usually touch anything ‘after’ the service head

      Hope that helps?

  9. Hi, would it be acceptable in a new build to run meter tails around 4m in a ceiling to the consumer unit , these cables are around 50mm from the surface of the plaster board. if not what protection would be required to allow this? in way of plating or RCD protection.
    Thank you

    • Hi Nathan, thanks for posting the question.

      This is a bit of a difficult one to be honest. Most DNOs stipulate that the maximum length of meter tails without any further protection would be 3M. You could introduce a switched fuse to alleviate this problem which would allow you to use 4M no problem.

      The distance from the plaster board presents a bigger problem though. In terms of plating, I’ve seen the IET recommend 3mm steel plate which is earthed as protection. Obviously this is quite thick and may be difficult to install neatly depending on the area. For me, up front RCD protection is a no-no, simply because it would need to be 30mA to meet the buried cable requirements, however this would not provide any division of circuits as the up front RCD would cut out leaving the whole installation off.

      The best solution may be to use SWA cable. This does not need protecting when being buried less than 50mm from the wall surface due to the earthed armour protection. You would still need a switch fuse up front but now many are metal it would easily gland into the switch and also the consumer unit. Granted, it can be difficult to bend and run internally sometimes but it is a good option for extended meter tails.

      Finally, you could consider an alternative route. Once you have a switch fuse up front, within volt drop limits there is no further restriction placed on the length of the tails. Perhaps there may be another route that doesn’t involve burying the cable under the 50mm threshold, but it may be 10M long?

      Hope this has helped with some options, buried meter tails are always an awkward consideration, something we have come across multiple times and had to use various methods to get around. I still haven’t used 3mm steel plating yet though!

      Kind regards
      Electrical Assistance

      • Similar question about metre tails. I am having metre relocated outside and metre also moved. Dist board staying under the stairs so will be over 3 m away from the new outside box. So it is ok to have tails from metre to consumer unit over 5m long

        • Hi JB thanks for posting the comment

          It is OK to have meter tails which are more than 3M long (which yours will be), however they will need to have a switched fuse fitted between the meter and the dist board.

          You won’t be able to have 5M of meter tails without a form of overcurrent protection after the meter. 3M is the maximum whilst using the DNO fuse as protection.

          Hope that helps?

          Kind regards

  10. Hi, thank you very much for your time and answering my question , this has been very helpful and supported my understanding of the requirements.

    • No problem at all Nathan! I hope you managed to find an acceptable way to run the tails without causing too much inconvenience.

      Kind regards

  11. Hi,
    Is it acceptable to clip meter tails direct on to the surface of an internal garage wall. Approximate length 2m


    • Hi Sam, thanks for posting the question.

      Yes, clipping meter tails direct on an internal wall of a garage would be acceptable.
      Although you could just clip them direct, it may be worth (depending on the potential risk of mechanical damage within the garage) covering the meter tails in either trunking or with some form of capping to give them further protection.

      Hope that helps?

      Kind regards

      • Thanks very much for your reply. I thought it was acceptable to do this however I received a call from a customer today who I have just completed a rewire for (I should say he’s a retired electrician) and he was saying he was very concerned by the meter tails being clipped direct and not being in metal conduit or trunking and that he would have failed the install if he was signing it off. While I understand his point I didn’t think the way the cables had been installed contravened regulations.

  12. Hi,
    I want to install an ev charger and the installer has said that the tails need to be upgraded. Does the installer put in the tails and the energy supplier carry out the connection to the meter? I spoke to EDF and they said a private electrician should carry out the works. What is the correct procedure please?

    • Hello Rod, thank you for getting in touch with the question.

      This would very much depend on which meter tails required upgrading. There are effectively 2 sets of meter tails, those between the service head and the meter itself, and those between the meter and the consumer unit.

      The tails between the service head and the meter are the responsibility of your energy supplier and electricians are not allowed to alter/replace these.

      The tails between the meter and your consumer unit are your own responsibility, and you would need to get an electrician to upgrade these. However this is where it gets really awkward, as this requires the energy supplier to connect the new tails to the meter, but the energy supplier won’t touch your consumer unit. Quite frankly this always causes problems needing to co-ordinate the visit between the 2.

      Without seeing the installation myself it is difficult to advise any further I’m afraid. It may be possible to alter the CT settings for the car charger which would mean you could get away without altering the tails, although it would really depend on the current draw from the rest of the installation.

      Hope that helps?

      Kind regards

  13. Thanks for the great piece.
    I was wondering if you could help me with the double insulation aspect.
    Im working on some new builds where they have swa into the meter box, then swa out to the db.
    It’s gonna be very tight in the meter box. Are we allowed to use heat shrink, or maybe several layers of heat shrink on the striped back swa to meet the double insulation? Or is it even needed as you need a tool to open the meter box?

  14. Hi,
    I’m having some trouble convincing my energy supplier to attend and fit 25mm tails and an isolator switch for my upcoming EV charge point installation because they don’t know if the existing tails are 25mm or 16mm. They were changed a couple of years ago when I got Smart Meters.
    My question is how can I tell from the overall diameter of the cable?

    Many thanks.

    • Hi Jim, thanks for getting in touch and posting the question.

      I can give you some rough outer diameters, although there are small variations depending on the manufacturer of the cable.

      In the type we generally fit, 25mm are 12.5mm diameter, whilst 16mm are 10.5mm diameter. The difference isn’t big I’m afraid and it can be quite difficult to tell from the outer sheathing.

      Hope that helps you to get the tails sorted.
      Kind regards

Leave a Reply

Your email address will not be published. Required fields are marked *

Post comment