Why are consumer units now made of metal?

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Consumer units are now required by the regulations to have the construction of non-combustible materials

The BS7671 electrical regulations were changed in 2015, requiring that any consumer unit installed must be made of non-combustible material. Which meant that thousands of plastic consumer units sitting on shelves of retailers and wholesalers were now obsolete. Therefore a lot of angry people wondering if the change necessary?

There is mixed thought on metal consumer units as they have their pros and cons, which we'll look at in a minute. Over the years the requirement of materials of consumer units has been changed from metal to plastic and back to metal. The main reason for changes in the specifications is due to incidents occurring that prompted the committee to review current regulations.


Photo courtesy of Envriograf showing how consumer units made of plastic can quickly catch on fire.


So what are the main reasons metal consumer units are required by the BS7671:

  • Non-Combustible (Electricians are required by the regulations to fit consumer units out of non-combustible materials which is usually metal). It's not uncommon for overheating to occur inside consumer units when faulty connections arise. Over-loads occur or general faults with circuit breakers. All of which can lead to a plastic consumer unit melting and possibly catching fire to the surrounding area.
  • Robust - Being made of metal they are less likely to get broken, as often consumer units are installed by electricians in cupboards, and bulky items like hoovers are shoved in. Plastic consumer units are liable to have their casing damaged.
  • Electricians can terminate SWA glands without using an external enclosure, which is often the case with plastic consumer units.
  • Holes in the consumer unit for cable access, it's less likely to affect the structural integrity.

Looking at the above, metal seems like a great choice, but of course, with most pros, there are also cons:

  • The most prominent con would be being made of metal, they can conduct electricity. Meaning that someone would only need to touch the unit to be electrocuted. Although consumer units are painted to prevent conductivity. Overheating could melt the paint leading to exposed conductive areas, coupled with poor connections and any chipped paint on the outside of the unit could be hazardous.
  • Electricians with poor workmanship could leave sharp edges when making access holes that could lead to live parts touching on the metal of the enclosure, leading to the risk of electrocution.
  • Often more expensive than plastic consumer units.

Loose connection caused burning in this consumer unit, which could have quickly cause a fire.

So we can see some very obvious pros that outweigh the cons of metal consumer units. Here at EDB Electrical Services we can't help but agree with the choice of the committee. Especially seeing a photo like below you can look at the hazards of plastic consumer units. In the most recent update of the BS7671, non-combustible materials are still a requirement.

An interesting note is that plastic consumer units are still for sale. Often at much lower prices than the metal alternative on auction websites and private ads. We believe that if you are getting your consumer unit changed to take in mind a few things. First and foremost make sure you are using a fully qualified and insured electrician.

Secondly, if the price is much lower than the rest of your quotes, there is always the possibility that they may be planning to install a non-compliant consumer unit. Whilst this is hazardous and potentially costly if you come to sell your house and it comes up on a survey. Here at EDB Electrical Services we only install compliant, top quality products to ensure years of life for the user and the equipment.

Now that you have finished reading, consider reading some of the following:

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