BS 7671 17th Edition: Amendment 3


In accordance with an amendment to the 17th Edition Wiring Regulations, newly fitted consumer units within domestic premises must:

  1. have their enclosure manufactured from non-combustible material, or
  2. be enclosed in a cabinet or enclosure constructed of non-combustible material and complying with Regulation 132.12.


British Standards doesn’t actually have a precise definition of a non-combustible material, but it’s generally accepted that ferrous metal (steel) best fits the bill. And Regulation 132.12, by the way, is about accessibility of electrical equipment.


What are the advantages of a metal consumer unit?


Sometimes, faults occur within a consumer unit, which lead to overheating, and then to combustion. A consumer unit with plastic casing will not withstand the heat of fire, and it will melt, allowing the fire to spread. There have been numerous injuries and deaths in British homes as a result of electrical fires, and many of these fires began in plastic consumer units.


Being non-combustible, a steel consumer unit will contain a fire for longer.


Consumer units are often sited in cupboards in the heart of the home, sharing their space with household hardware such as ironing boards and vacuum cleaners. Plastic consumer units are particularly vulnerable, and can suffer damage as people drag things in and out of the cupboard. Holes made for cable access can also weaken a plastic casing.


Metal consumer units are robust enough to withstand quite a bit of physical abuse!


What are the advantages of a plastic consumer unit?


Because metal is a very good conductor of electricity, a metal consumer unit is potentially very dangerous. In the event of an electrical fault, someone could be electrocuted just by touching the casing. To prevent conductivity, the consumer unit is painted, but if the paint is chipped, or if it melts through overheating, areas of metal will be exposed.


Plastic, on the other hand, is not a conductor of electricity. As long as it’s intact, a plastic casing will act as an insulator against electrical current.


And, of course, metal is more expensive than plastic.


Do I have to replace my plastic consumer unit with a metal one?


No, you don’t. But if you decide to invest in a new consumer unit, it will have to be one that’s made of metal. However, if the unit is housed within a metal enclosure, as specified in the second part of the regulation (“enclosed in a cabinet or enclosure constructed of non-combustible material”), you can buy a brand-new plastic consumer unit.


If you’re unsure about the condition of your consumer unit, or its suitability in your home, please don’t hesitate to phone us on 01603 559 311 or contact us here.