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The evolution and changes in the IET wiring regulations BS7671. The IET's wiring regulations are a constantly evolving body of work, and its latest iteration was launched in April 2026. It contains substantive changes in areas such as batteries, medical environments, and power over Ethernet. This article is written by Mark Kohl's, head of technical regulations at the IET. It both explains the background to the update and summarizes the key changes in the latest revision.
The latest iteration of the IET wiring regulations BS7671 was published in April 2026, bringing changes to the world of the electrical designer, installer, and maintainer of electrical installations. The IET wiring regulations BS7671 is the UK standard for low- voltage electrical installations. For most installations conventionally, BS7671 has requirements for new and amended installations on the consumer's side of the electricity meter. The picture gets a bit murky when you consider that some premises may not have an electricity meter. They may be off-grid, autonomous, and self-sufficient using and storing locally generated electricity. It also applies to bigger installations such as those in factories or hospitals where low- voltage electrical installations are supplied from private transformers rather than the public supply in the street.
Yes, it is another change and very soon after the last in 2024 and previous changes in 2022, 2020 and 2018. Changes in technology and the way people do things are ahead of where the standard is, meaning standards are struggling to keep up with the pace of change. This has been the case throughout the regulations history. And at the end of this article, there is a brief look at the history of and biggest changes in the IET wiring regulations.
BS7671 BS7671 is largely based on Senelch's harmonized documents. Senilech is the European Committee for electrottechnical standardization. AHD is a standard that has been agreed by Senate member countries. Senilech is a private organization made up of EU member states, EA countries and other members such as the UK. Senelch member countries are aligned on concepts such as protection against electric shock, voltages and frequency of electric current. We are familiar with products having a standard number with EN that is a circuit breaker to BEN60,898. A circuit breaker is a product and every time a product with that EN number comes out of the factory, the item is exactly the same as the last one. In electrical installations, for example, my house is different to your house, so we can't have an EN to cover all electrical installations. The UK therefore takes on the technical intent of an harmonized document in BS7671. It gets more complicated as Senate member countries have 3 years to implement the harmonized document in their national standard, removing any contradiction or duplication.
Many users of BS7671 voice their annoyance when BS7671 is updated. To many, it means buying another book and more guidance publications and perhaps retraining to update their qualifications. And I can see that. But what is the alternative? Let's say we decide in the UK to stop updating BS7671 and leave it stable for 10 years. We know exactly where we are, qualifications are stable, and no one needs to retrain. and more importantly buy any books. In that 10-year period, technology is still leaping ahead. Global manufacturers are creating products that align with changes in the installation standards of other countries, but not in the UK. Manufacturers would then need to make two types of products, one for the UK and one for the rest of the world. You could expect the UK version to be more expensive. Then, after 10 years, it's time to update the UK's national standard. we would find we are so far behind the world that the jump needed to upskill, retrain and reinvest in people, installations and infrastructure is prohibitively enormous.
One argument I hear regularly is from the point of view of those doing small electrical installation works in dwellings. They say I only add to existing circuits in kitchens or bathrooms. Why do I need to update? There are many facets to this but I keep coming back to competency and the law. The law in this case the electricity at work regulations 1989 is very clear. Regulation 16 states no person shall be engaged in any work activity where technical knowledge or experience is necessary to prevent danger or where appropriate injury unless he possesses such knowledge or experience or is under such degree of supervision as may be appropriate having regard to the nature of the work. where an installation has battery storage and this is used for example to keep a permanent supply to a freezer. How can a person be competent to work on a system when they are not up to date with current requirements? These are reasons as to why BS7671 is regularly updated. The days of the evergreen electrician are gone.
The main changes in BS7671 col 2018 plus a 4 col 20226 are largely related to technology. One area is stationary secondary batteries. Chapter 57 brings requirements for battery storage. Note the word secondary. This implies that the unit can be recharged while a primary battery is one that is procured fully charged and discarded once depleted. Battery storage technology is advancing at breakneck speed and over a few short years the available storage capacities have grown. Prices have dropped as take up of the technology increases. In electrical installations we will be somewhat familiar with solar photovoltaic or PV systems which can charge batteries during the day for the stored energy to be used overnight. For example, what we are seeing is batteries being installed where a PV system is not present. The batteries can be charged from a low electricity tariff overnight and appliances can be run from the stored energy far cheaper than using the supply from the utility company. In fact, it could be argued that the return on investment on the installation of stationary secondary batteries alone is quicker than a full PV/ battery system.
There are a lot of parameters to consider when designing a system that will incorporate a stationary secondary battery. The key consideration is how much power you want and how quickly you want it. Some battery systems can release lots of energy very quickly, charging a car for example, while others are designed to have a more relaxed approach to the release of the stored energy. Essentially, this is a discussion with the manufacturer once the designer has established the load profile. Connecting the battery, which is DC, to an AC system will require the use of power conversion equipment. Some batteries will have power conversion equipment already built into the unit. Energy flow is two-way, so the designer must ensure that birectional or hybrid inverters are used and that on existing installations, the relevant protective devices are birectional too. An example of birectional energy flow is vehicle to home or vehicle to grid. In addition to the electrical supply to the dwelling charging an electric vehicle, the battery of an EV can be used to charge the battery within the dwelling. Similarly, the energy stored in the battery of an EV can be exported to grid, ideally where a suitable export tariff is in place.
Consider that the cables connecting a battery/inverter to an electrical installation are protected by a residual current device, an RCD. There is therefore an electrical source on both sides of that RCD. Not all RCDs are suitable for this arrangement. If the RCD is in the open circuit position, the electrical source on what we'd conventionally term the load side can render the protective device inoperable. When choosing any protective device on a circuit where energy flow is birectional, the designer must establish that all relevant protective devices are suitable for the intended circumstances. This is extremely important on legacy systems. The location of stationary secondary batteries is extremely important. While the failure of batteries is proportionally very low, if a battery does fail, the resulting fire can be catastrophic. In dwellings, stationary secondary batteries should not be installed in escape routes, lofts or rooms where people sleep and fresh air ventilation to outdoors has to be provided for where stationary secondary batteries are installed in indoor locations.
The next area we are going to look at is medical locations. Section 710 medical locations has had a major revision. The scope of the section covers patient health care facilities such as hospitals, private clinics, medical and dental practices, health care centers, and dedicated medical rooms in the workplace to provide for the safety of patients and medical staff. It can also be used in veterinary clinics. The intention of section 710 is to provide safe installations in environments where people are more susceptible to the effects of electricity. When a patient is in an operating theater and a bodily intrusive procedure is being undertaken, for example, open heart surgery, the natural protection of the skin is not present. There may be fluids present and medical electrical equipment may be in use within the body. Our skin offers a natural defense to electricity up to a certain threshold, but beneath the skin, this level of protection is not there.
Knowledge of the intended use of a health care facility is paramount for a designer. Medical locations are classified by group that is group zero, one and two. Group zero is where the loss of supply is not a risk to safety of the patient. While group two is where discontinuity of the supply represents a risk of safety to the patient. In group two locations such as operating theaters, the loss of supply in that area poses a risk of safety to the patient. In these locations, a medical IT system is used. We're familiar with TN systems that is ter neutral where the neutral point of the supply is earth to terror French for earth. It means isolated from terror that is an unearthed system. A medical IT system utilizes a medical IT transformer with a medical insulation monitoring device. The concept is that the system operates without a connection to earth and is monitored by the insulation monitoring device. If an insulation fault occurs, the insulation monitoring device will see that the fault has effectively earthed the system and will sound an alarm to alert staff. This gives them time to remove or repair the fault. But should a second fault occur elsewhere on the system, automatic disconnection will occur. Elsewhere, a total loss of supply shall be prevented by the provision of two independent supplies and the provision of an uninterruptible power supply. The guidance is that this supply is located as near as possible to the equipment it supplies to avoid interference from external influences. The changes are significant and stem from an IEC standard IEC60364-7-710201 which was implemented in Senate countries in HD60364-7-710 col25.
The next area we are going to look at is power over Ethernet. Ethernet installations have been around for quite some time. These are the bunches of cables we see in data installations or those cables that connect computers to the network. As technology has evolved, it became apparent that the extra low voltage direct current used in Ethernet systems could be used to supply low wattage equipment such as LED lighting and power supplies for small appliances. Such systems are becoming commonplace and the selection of the power supply is very important. Section 716 is principally concerned with power supplies and cables using SELV which is safety extra low voltage and PELV or protection extra low voltage as the method for protection against electric shock. Conventionally, SELV and PELV require a voltage limitation of 50 volts AC volts alternating current and 120 volts DC volts direct current. However, section 716 is in part 7 special locations of BS7671 which supplements or modifies the general rules. In this case, section 716 limits SELV and PELV to 60VT ripple-free DC in dry locations and 15VT ripple-free DC in all other locations. The electrical connections for power over Ethernet are to comply with BSISO/IC11801-1 capable of supporting a continuous operating current of 750 milliamps per contact.
In conclusion, given that technology and products will continue to evolve, it should be no surprise that installation standards will be regularly amended, it is incredibly important for designers, installers, operators, and maintainers of electrical installations to be up to date with current requirements to protect themselves, their workers, their clients, and the public in general. While it is at times a more than irksome burden to reinvest in a business, the alternative is not a sustainable model. For those interested, here is an extra bit of background about the history of the IET wiring regulations, BS7671.
In 1871, the Society of Telegraph Engineers and of Electricians was established to deal with the seemingly endless breakout of fires across cities brought about by the implementation of this new black art known as electricity. Wealthy businesses could afford their own private fire service, but others relied on buckets of water handed along by willing volunteers. In 1882, the society issued the very first wiring rules. We refer to it now as the first edition. It wasn't a standalone publication, but part of a journal issued by the Society of Telegraph Engineers and of Electricians in September 1882. Subsequent editions were published as standalone publications. The constitution of the committee as cited in that first set of rules is quite astonishing. Notaries include Professor WG Adams F- FRS a pioneer in light and magnetism. Sir Charles T. Bright responsible for the first transatlantic telegraph cable in 1858. Sir William Thompson FRS first Baron Kelvin for his work on the coldest possible temperatures. He was rewarded by the naming of units for absolute temperatures in units of Kelvin. Over the intervening years, many changes were implemented as technology developed. The Society of Telegraph Engineers and of Electricians became the Institution of Electrical Engineers, the E, which in 2006 became the IET.
A relaxation to the regulations occurred in 1942 when it was clear that materials were in short supply, but this was terminated as of March 1st, 1946. A fascinating piece of work was carried out in 1944 and published as postwar building studies number 11 electrical installations published for the Ministry of Works by His Majesty's Stationary Office. Committees were commissioned to envisage the landscape of the UK postwar and prepare the populace given that there would be a shortage of money and materials. The work led to the development of the ring final circuit and the BS136313 amp plug and socket outlet system. The concept was that rather than having a separate circuit for each socket outlet of which three types were in use in dwellings, ratings of 5, 10, or 15 amps, which could require many circuits from many fuseways in the fuse box. A single circuit from the fuse box rated at 30 amps, would supply all socket outlets, each would be rated at 13 amps, requiring the plug to have its own fuse.
The next big change was in 1992. The 16th edition of the E wiring regulations was published in 1991. But in 1992, the E wiring regulations became a British standard BS7671. The history was that in 1973, the UK joined the European Economic Community often referred to as the common market or the EU as we now know it. One of the concepts was that traders could sell products across borders of European countries without hindrance. In 1992, the Mastri treaty was signed and member states agreed common economic provisions. BS7671 took a large slice of commonality with installation standards in European countries, aligning on products and concepts, meaning that products made in the UK could be sold and used in France, for example. E and BSI, the British Standards Institution, the UK's National Standards Body, came together to jointly manage and publish BS7671, the E wiring regulations. E had the historical gravitas experience and committees of experts, while BSI had access to international and European standardization.
This article was written by Mark Kohl's, head of technical regulations at the IET.
Here's a quick word about our sponsor, Vargo. Vargo is a global leader in electrical interconnection and open automation, supporting industrial and building engineers worldwide. With 75 years of innovation and 9,000 specialists, Vargo delivers safe, maintenance-free connectivity and scalable automation solutions built on open standards. From high performance terminal blocks that speed panel build to automation, energy management and smart buildings, Vargo enables resilient, efficient and future ready systems.