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Earth (CPC) Sleeving
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Staying Safe

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The purpose of my visit to you is to ensure your new accessories, products and circuits work, in all work undertaking in Chilcompton, Midsomer Norton, Paulton, Radstock or any surrounding area, your existing electrical installation continues to work as it should, but it is also my responsibility to ensure you remain safe during and after my visit to you. Your installation must remain viable and stable so as not to cause fire or electric shock. If you would like to find out more simply click on the green "Request Booking" button below to request a free, no obligation quote! You can also call Rich on 01761 325 007 or email


While I am working the safety of your family are a priority for, barriers will be erected where required and the power for any specific circuit we are working on will need to remain isolated (off), I hope to cause as little disruption to your day while I work, and where possible on the circuit being worked on will be isolated and off during the completion of your project. You can also check out and download my free 'Electrical Safety in the Home Guide' below - it's essentially a DIY EICR (Electrical Installation Condition Report).


If you'd like to read about the tests I will undertake on your new and existing installation during and after then please feel free to read the information below. I do appreciate that there will be some jargon you will not understand, and you do not need to, but I am here to ensure that your installation and new installation will be safe for your continued use - our electricians will be happy to go through any of this with you on request.  

Consumer Unit - Richard Speller checking the voltage of a single phase supply

During and after your installation your properties wiring and electrical system is checked to ensure everything is as it should be. All electricians, as part of the BS7671 wiring regulations, should provide your with at least one certificate on completion, below are the standard checks completed on the all of work we complete for you: 

Please note: if we do find a fault or issue and you don't want it fixed there is no obligation to have the problem fixed - I will not pressure you to have it fixed (this will ultimately add to the cost of your final bill). It just means you may have to find another company who will complete the work and who feels comfortable authorising and declaring an installation that is unsafe - when it is not. Profit will not come before our customers safety. 
1. The Visual Inspection 

This is usually completed on my initial visit to the property - simply checking that everything is where it should be and that it is safe, and that the work you want done can be completed safely and satisfactorily. Let's consider the following scenario; you've asked for new light fittings and some new switches added, if we find there is no Circuit Protective Conductors (CPC) present - common in some older installations - in light fittings that are not Class II insulated then we may not be able to complete the satisfactorily and therefore, unless you request it is fixed before we begin work, we won't be able to continue with the work - we do not want to be responsible for any life endangering situations, it is not within our ethos. We will not declare and sign off work that is unsafe.  

Presence of Earthing & the Arrangement 

There is an initial visual check to confirm the type of supply and earthing arrangement, the most common type of Earthing arrangement in the UK is TNC-S, with older properties perhaps owning their own earthing rod and in this case it would be TT.  You don't need to know this, but what we do need to confirm is the Earthing & Bonding arrangements are satisfactory and that the Earth Fault Loop Impedance meets the requirements of BS7671. Adequate Earthing & Bonding is fundamental to the safety of any electrical installation, all electricity needs a path back to earth and fault protection relies on a satisfactory earthing path - without it live parts could remain live and not be automatically disconnected (ADS). If a fault is found on the supply side then it can often lay at the door of the DNO (District Network Operator i.e. Western Power) and they will need to fix it, at no cost to you, before any work can begin, but you can be sure your installation is as safe as it can be. 

Adequacy of Earthing & Bonding Arrangements

As with the above, the Earth Fault Loop Impedance (also known as Ze - External Earth) is the impedance of the external earthing arrangement. It must be below a certain value so that the required disconnection times of your protective devices will be met (generally between 0.4s and 5s - this is dependent on the final circuit being served) - for a TNC-S Earthing Arrangement (most households in the UK) this needs to be below 0.35Ω. If it doesn't meet this value then the DNO must be informed and they will fix the issue at no extra cost to you - we have simply ensured that your home is safe for continued use. Your Ze will be measured and checked to ensure your installation is safe and protects "persons and livestock" (BS EN 61140). 

Presence of Main Protective Bonding Conductors 

Main Protective Bonding is the process of ensuring that everything is connected to the Main Earthing Terminal so that any extraneous parts will not remain live in the case of a fault. For example, most of us have gas and water pipes running into our homes and these pipes are mostly made of copper which is what your conductor cables are made of, copper is a great conductor (silver is the best... although imagine the cost implications)! Therefore, it is essential that these pipes are included into the electrical installation so as to prevent electric shock. All we will do is ensure that this bonding is present if the bonding is required.  

Circuit Details


An electrician needs understand the details of the circuit to be worked on and whether the existing circuit can handle the extra demand that is going to be placed upon it. We will be assessing the Installation Reference Method (how the conductors/cables are run within the circuit i.e. behind plasterboard or clipped direct), the size of the conductors which can impact on whether the circuit being worked on can handle the extra current, and what Protective Devices are present (for example, all sockets require a minimum of a 30mA RCD protection). 

The Test Results 

This happens once the circuit has been extended or altered, or newly created. For example, is their continuity within the Line (“LIVE”) and CPC (“EARTH”) conductors, if there isn’t it’s possible that a cable was snagged during the installation - successful continuity confirms that everything is connected and as it should be and during the installation everything went as expected - results can be calculated before the testing so that we’re sure the results are as expected. 


An insulation resistance test will then be conducted and again this ensures that at no stage along the conductor length are the live conductors touching which would result in a Short Circuit causing your RCD or other protective devices to trip. 


Polarity tests ensure that the Line and Neutral conductors are the correctly connected - for example if polarity is wrong unexpected parts of a lighting circuit can become live - for example the screw-fixing point of an Edison bulb. 


Maximum Zs (Earth Fault Loop Impedance) of the Final Circuit, including the Ze. This can be calculated and measured using a dedicated Multi Function Tester (MFT) and is measured at the furthest point of the circuit to ensure that the protective devices will disconnect in the desired time, as previously mentioned. The R1+R2 are measured, this is the Line and Circuit Protective Conductor. 


Finally, this RCD will be tested to ensure that they function properly and within the times they should - when tested it must disconnect within 300ms and the manual test button must be tested too (you should be testing this yourself, recommended to be every 3-6 months).

The Declaration 

I care about your safety, it is paramount. We also care about our reputation and want to ensure that we are protected as much as possible from accidents that may happen when DIY enthusiasts or unskilled persons attempt to alter circuits - of course there will always be people that are more than capable of electrical work, but we must ensure that it is clear within the certificate issued what work is ours and what isn’t. It's also ensure peace of mind for our customers whereby we ensure that the work we have designed, constructed and then inspected is safe and in accordance with the IET Wiring Regulations (BS 7671: 2018).

TNC-S Earthing Arrangment Speller's Sparks

Speller's Sparks LTD serves all surrounding areas, a radius of 10-15 miles of Chilcompton - watch my welcome video on my Home Page, which will introduce myself (Managing Director of Speller's Sparks) and show you the areas I work in. 

Follow the links below to see more information and get a little more personal with my local area: 

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