1.3: Condition Of Distributors Earthing Arrangement

Checking Supply Earthing Arrangement 18th Edition Electrical Inspections

EIC: 1.0 External Condition of Intake Equipment (Visual Inspection Only)
EICR: 1.0 External Condition of Intake Equipment (Visual Inspection Only)

1.3: Condition Of Distributors Earthing Arrangement

When undertaking 18th edition electrical inspections, whether part of an EIC (Electrical Installation Certificate) or an EICR (Electrical Installation Condition Report), the first section, 1.xx is full of visual inspections that must be completed on the incoming service equipment

Inspection 1.3 is a check of the condition of the distributors earthing arrangement. This test will only apply in instances where the incoming supply earthing arrangement is either:

  • TN-C-S – Terra-Neutral Combined-Separate. This earthing arrangement joins the incoming Neutral with the earthing terminal at the service head. This method is also often known as PME (Protective Multiple Earthing)
  • TNS – Terra-Neutral-Separate. This earthing arrangement has a separate conductor for the earth terminal, and this conductor runs from the transformer all the way back to the service head.

This inspection is visual only and will involve no dismantling of any of the supply intake equipment in order to check the “condition of earthing arrangement”

Have you been looking for a bit of a guide to checking the condition of the distributors earthing arrangement when completing electrical inspections? Want to be sure that you are compliant with 18th edition updates? Read on for the step by step guide….

Check Incoming Earthing Arrangement - TNS - TNCS - PME
Condition Of Distributors Earthing Arrangement – Supply Earthing Arrangement

Safety First! – ALWAYS Ensure These Items Before Starting

Specific risks which can be encountered inspecting the condition of the service cable include:

  • If the incoming service head is particularly damaged, or has any pieces of insulation missing then there is a risk of serious electric shock. A number of examples of fabric braided cables, or lead and paper sheathed incoming supplies where the cable has deteriorated do exist. Although you are not checking these specifically, the earthing arrangement is usually adjacent to the service head. By stating VISUAL INSPECTION only, it really does mean no need to touch.
  • Be aware that old metallic clamps used to earth the sheathing of TNS cables can work loose. DO NOT attempt to tighten these around the service cable. If the cable is in poor condition in any way, this could cause catastrophic damage to the service cable
  • If there is any doubt over damage, or the distributors earthing arrangement is verified visually to be in a particularly poor condition, you should always report your concerns to the DNO. This is simple and you only need to save 1 number to your phone (105)
  • This website is intended as a study/work aid to assist qualified/working electricians in order to keep current with changes in fields such as inspection & testing. It is also something of a repository for those studying in the field to gain general knowledge. It is in no way intended to be taken as DIY Electrical Advice and should never replace the services of a qualified & insured electrician.
  • electrical-assistance.co.uk assume no liability for any accident or injury, howsoever caused, whilst attempting electrical works. If you are working with electricity please ensure that you follow all local regulations in force in your particular area.

For further information on this please visit our regulations pages to learn more.

What Am I Checking For When I Inspect The Distributors Earthing Arrangment?

When checking the condition of the distributors earthing arrangement, you need to quickly be able to determine if there is any risk created by the incoming supply cables.

The most serious faults are of course, loose connections and damaged insulation/cable clamps. However there are some slightly less obvious signs of damage to the supply earthing arrangement which are worth keeping an eagle eye out for:

  • Loose TNS Clamp – As mentioned in the safety section, the metallic clamp holding the earthing conductor onto the sheath of the TNS supply cable can become loose. We have seen these so loose before that you can easily twist the clamp by hand. Obviously this cannot provide a good and reliable connection to earth. HOWEVER, do not attempt to tighten this yourself, over tightening can damage the service cable with disastrous results!
  • Incorrect TNS Clamp fitted – There have been numeruous examples of either BS951 clamps being fitted to the TNS sheath, or other poor quality clamps. In some instances these are actually fitted by the DNO (it’s their equipment!), although in modern cases these are usually replaced by a spring clamp. Be aware of ‘DIY TNS’ where the sheath of the service cable has been bodged cut and a BS951 clamp fitted to any armour wires/concentric cable within.
Condition Of Distributors Earthing Arrangement
Condition Of Distributors Earthing Arrangement
  • Weathering, Corrosion of Clamp – More of an issue with service heads located in basements and other damp areas, however be aware that corrosion can often affect the electrical soundness of old clamps.
  • Damage to Earthing Terminals on Service Heads – Although this sort of damage is quite rare, if the connection terminal for the Main Earthing Conductor (MEC) is on the service head, make sure that there is no obvious damage to the screw heads of the terminals (often bodged with poor fitting tools on modern heads with hex terminals). Check that the terminal has a sound connection to the MEC and that there is no evidence of cross-threading of any of the terminal screws.
  • General Physical Damage – Check the condition of any external ‘accessories’ that may be part of the distributors earthing arrangement. This could be terminal blocks, henley blocks, cable or anything else that forms part of the earthing system at the supply end. Check for damage of enclosures, undersized cables acting as intermediary MECs (between PME heads & henley blocks), and any signs of thermal damage in any way.
Checking Supply Earthing Arrangement 18th Edition Electrical Inspections
Additional Accessories (cable & Henley Block) which form part of Supply Earthing Arrangement

How Do I Record These Inspections?

If you are completing 18th edition inspection & testing, to be honest you are going to need something a little more robust than just a pen and paper!

With the cost of inspection schedule pads, test result pads & main EIC or EICR pads, it can soon add up to more costly than a modern software based approach anyway!

In the instance of EICRs, issues such as those with the supply earthing arrangement may not get reported to the DNO or actioned immediately (f they are not of immediate danger) and as such it is vital to leave some kind of evidence what the problem is.

Adding photos to an EICR also allows you to have a visual record, easily stored within the PDF file of that EICR. As such, you can easily revisit the exact issues and check the photos for yourself or to instruct a 3rd party.

This can be useful when preparing quotes for remedial works and the like. We use & recommend Tysoft Easycert Mobile for the best electronic certification. We are all about time saving for professional electricians here at electrical-assistance.co.uk and as such you need a solid and expandable certification software that you can depend on.

See more information about how we recommend you record these types of inspections here: Best 18th Edition Certification Software for 2020

Further Resources & Information on ‘Condition of Distributors Earthing Arrangement’

Here are some further resources relating to checking the condition of the ‘Supply Earthing Arrangement:

  • Northern Powergrid – Distribution Network Owner for much of the North of England. This includes Yorkshire, Humberside, and upto Newcastle, Sunderland, etc…
  • 105 Phone Number Scheme – A government scheme to enable people to be able to get in touch with their local DNO during power cuts, etc.. without having to remember different numbers. Useful to save to your phone in case you need to report any faults to the DNO

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