General

Circuit Breakers Perhaps the most common of all protective devices circuit-breakers are found in modern single-phase domestic consumer units and three-phase industrial / commercial distribution boards. The British Standard BS EN 60898 applies to these devices and they usually come in sizes of 2 A up to 125 A. Apart from its nominal rating (In) 10 A, 16 … Read more

I’m regularly asked… “With the City & Guilds 17th Edition qualification am I allowed to carry out work in domestic properties?” My reply… In order to carry out electrical work in domestic installations you will also need to comply with Part P and other relevant parts of the building regulations as well as the regulations in 17th … Read more

I know I probably need to get out more, but here’s ten reasons I like the 17th Edition of the Wiring Regulations ‘BS7671:2008+A3:2015’. Although it’s a non statutory document BS7671 provides guidance on ensuring the safety of all electrical installations here in the UK, assisting you to comply with the Electricity at Work Regulations. The … Read more

Looped Lighting Circuits – Electrical Installation 101. The most common method is the ‘loop in’ system. This is where cables loop in and out of each lighting point, which is usually a ceiling rose. The wiring may be a Twin and Earth PVC/PVC cable consisting of a Line, Neutral and CPC (in), a Line, Neutral … Read more

Automatic disconnection of supply (ADS) is the most widely used method for achieving protection against electric shock in an installation. It works by limiting the size and duration of any voltages between exposed-conductive parts / extraneous-conductive parts or Earth. This is achieved through a combination of factors that must be in place. Basic Protection: Provided … Read more

Voltage Drop Think of voltage drop as similar to a loss in pressure along a water pipe over a long distance. So just like with water in a pipe a conductor will lose ‘x’ amount of pressure measured in millivolts ‘mV’ for every Amp ‘design current’ that flows along it for each meter. This is … Read more

The purpose of performing a cable calculation is to ensure that a cable is not overloaded. This can produce an excessive amount of heat which in turn can damage the cable and the installation and may even cause a fire. So, here’s how that’s done… Firstly how much current is your appliance going to use? … Read more

Just a short one this week… Special Locations are locations or installations where there is an increased risk of receiving an electric shock. For this reason and according to BS7671 Part 7 Section 701 any location containing a bath or shower is deemed a ‘special location’. So that’s the whole of the bathroom! 701.32.2 to … Read more

This is more of an electrical general knowledge question rather than a Wiring Regulations one but they do pop up in the City & Guilds exam every so often. “A twin and CPC, PVC cable has a 2.5 mm line conductor with a resistance of 0.46 ohms and 2.5 mm neutral conductor with a resistance … Read more

Appendix 15 in BS7671 is probably the most useful practical description in the whole book. If you want to know what you can do and what goes where it’s all here. Ring Socket Circuits… Spread your sockets around evenly to avoid overloading any part of the ring. Don’t put immersion heaters, storage heaters on the … Read more