Revised version of the IET On-Site Guide reflects updates included in the latest 18th Edition of the IET Wiring Regulations to BS 7671:2018. The On-Site Guide (now with a blue cover) is intended to enable the competent electrician to undertake electrical installation work on small installations (up to 100 A 3-phase). It provides essential information in a convenient easy to use form, avoiding the need for detailed calculations.