BS EN IEC 62305 was revised in 2024. It is a full revision of the series rather than an amendment to the 2011 text, and two of the changes affect the output of a risk assessment rather than just its wording. If you are relying on an assessment written before the revision to justify the protection on a building, it is worth reading this.
Two changes matter here. The standard has introduced a single risk that combines loss of human life with loss caused by fire, where these were previously handled separately. And ground impact point density has replaced the older lightning strike density as the basis for estimating how many hazardous events a structure should expect.
The practical consequence is that the same building, assessed with the same inputs, can come out at a different protection class than it did under the previous edition. Not dramatically different in most cases, but enough to matter on a building that was previously borderline.
Part 1 tightened how surge currents due to lightning are specified for sizing surge protective devices on low voltage power and telecommunication systems. It also introduced the concept of types of loss with public relevance, and the idea of a frequency of damage that can impair the availability of internal systems. Annex D now points to the BS EN IEC 62561 series for lightning protection components.
Part 3 added minimum thicknesses for metal sheets and metal pipes used as part of an air termination system, set out in a table, where it is necessary to prevent puncture and hot spot problems. If you have a metal roof being used as a natural air termination, this is the change to check.
Part 4 gained several new informative annexes: on determining current sharing using modelling, on current sharing in photovoltaic installations specifically, on methods of testing system level behaviour, and on induced voltages in installations already protected by surge protective devices. The photovoltaic material is the one most likely to come up in practice, given how much roof mounted solar has been installed in the last few years.
If you are not sure which of those applies, send us the details and we will tell you. Call 01892 667258 or use the contact form.
