BS 7671: 18th Edition Wiring Regulations – Study when you want and pass your exam when you're ready…
Three 18th exam questions that cause problems… 1) What is the minimum dimension for a round diameter bonding ring network conductor when considering measures against electromagnetic disturbances? 25mm, 10mm, 8mm or 3mm It’s 8mm – take a look at 444.5.3 (ii) 2) Which one of the following external influences codes for ambient temperature is conventionally … Read more
Within older domestic installations that complied with earlier versions of the Wiring Regulations the main bonding and supplementary bonding should be in place. However, within a new installation due to the introduction of RCDs and new Wiring Regulations it is now possible to omit both main and supplementary bonding in a new installation. Omission of … Read more
For our 18th Edition online courses here at the-regs.co.uk and partPtrained.co.uk we currently have 28 City & Guilds exam venues and 7 EAL exam venues – “Covering the whole of the UK, from Exeter to Aberdeen and everywhere in-between!” Recently, I have noticed that some training centres are dropping City & Guilds altogether and switching … Read more
As current flows through a conductor due to it’s electrical resistance it produces heat. If the current in the conductor increases then the heat also continues to rise and eventually we could reach a temperature which will cause permanent damage to the cable or possibly even a fire within the installation. In order to prevent … Read more
Why on a TN-S earthing system is the maximum Ze given as 0.8 ohms by the supply authority when it’s often protected by a BS 88-3 100A fuse which has a maximum Zs of 0.38 ohms? This maximum value for Ze of 0.8 ohms for a TN-S earthing system is a value that is quoted … Read more
Within domestic installations there are numerous regulations within BS 7671:2018 concerning additional protection through the use of 30mA RCDs… 411.3.3: Gives us additional protection via a 30 mA RCD for ‘general’ sockets, both indoor and outdoors. 411.3.4: Again 30 mA RCD additional protection for all lighting circuits. 522.6.202: Cables buried in a wall less than … Read more
Within the 18th Edition as far as SPDs and protection against transient overvoltages are concerned there is no need to provide protection for single dwelling units (safe to assume they mean domestic, although there is no definition for a dwelling unit within Part 2 which I think is an oversight). There’s also a mention of … Read more
Why you shouldn’t spend too much time on the Appendices… At the back of the 18th Edition book ‘BS7671:2018’ we have 17 appendices containing additional or supplementary information to the rules and regulations within the book. If you look though you’ll see that Appendices 11 and 12 are empty. So in fact there’s just 15 … Read more
Calculating voltage drop… You won’t find this formula anywhere in BS7671:2018 as this is another example of where G&G / EAL assume some prior electrical theory knowledge, but the formula is… Voltage Drop = (mV/A/m) x Ib x L / 1000. (mV/A/m): To find the value for (mV/A/m) we need to look in the current … Read more
The 18th Edition exam is an assessment of your ability to use the Wiring Regulations BS7671 2018 out there in the big world. As such problems and questions may not always be worded exactly as you come across them in the book. The first step to answering a real life problem or any exam question … Read more