Watt & Co. Electrical - Electrician in Corsham covering Bath and West Wiltshire

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Single insulated cables and junction boxes

Poorly done joint found on a recent lighting re-wire. Single insulated cables outside of a junction box and just taped up buried in a wall.

By single insulated cables we mean cables that either have had their outer sheath removed or cables that only have one layer of insulation. Most commonly in domestic properties your electrician in Bath and West Wiltshire will use twin and earth cable. This is usually made up of two conductors the same size that have a coloured insulation (Line & Neutral), and a smaller uninsulated conductor (CPC) these are then protected by an outer sheath which is commonly grey. Hence the name double insulated cables.

So why is this a problem, what regulation does it break, how does it become a problem and how do we solve the problem? 

The outer layer of insulation is there to protect the coloured insulation against damage, a knock, rubbing or any movement can result in a problem, so without it, the cable is at greater risk of a fault or in some cases causing an electric shock. The regulation your registered electricians should be looking at here is REG 526.8 which states “the cores of sheathed cables from which the sheath has been removed must be enclosed”.

While this can be caused by stress on the cable or it being pulled too tight, more commonly than not, it is caused by poor workmanship at the initial installation where the installer has stripped back too much of the outer sheath. We find this all the time on new downlights where the joint box is too small.  

The problem can sometimes be a quick fix, simply re-terminating the cable connections and shorting the amount of single insulated cables inside the accessory or junction box will do, in other cases the cable has already been cut too short and this doesn't leave enough slack on the cable to re-terminate. When this is the case we have to fit a maintenance free joint. 

What do we mean when we say maintenance free? This is basically a joint that doesn't get affected by thermal cycling, doesn’t need to be tightened periodically, and can also not be accessible after installation. An example are Wagos. Wagos are by far the best option as they are not permanent and can be removed if need be and they can also me made maintenance free using dedicated Wago junction boxes. We use Wagos and Wago juncton boxes when we need to make a joint under the floor to extend the circuit and install new sockets. Wago junction boxes can also be used if you're having new kitchen electrics put in; Your electrician can install Wago junction boxes to protect you from electric shock if parts of your new kitchen aren't ready.

Older style junction boxes usually will have knockouts that don’t grip the sheath of the cable and utilise screw terminals that can easily be poorly used and not made tight enough, become loose due to thermal cycling and not grip the core of the cables correctly. Choc block connectors are an example and often will be found with electrical tape wrapped around them which is unacceptable.


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Take Care When Selecting an Electrician!!

Many Electricians in Bath and West Wiltshire are simply not interested in small electrical works. They want the choice jobs, and will drop you like a hot potato when a bigger, supposedly more lucrative, project comes in.

Others advertise as electricians having no qualifications.  They thrive on the basis that you don’t understand what they do and, as a result, overcharge for shoddy, and often dangerous, work.

I set up Watt & Co. Electrical in order to fill a gap in the domestic sector. I want to provide you with a quality service that provides you with exactly what you need from an electrician.

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