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Do I need a consumer unit (fuseboard/fusebox) upgrade?

How do you tell if you need a new consumer unit?  Lets start at the beginning ... what is a consumer unit?

A consumer unit (often referred to as a fuseboard/fusebox) is a domestic electrical distribution board. They are generally installed close to your electricity meter and it’s a means of separating the electrical supply coming into your home into individual circuits.

The installation in your home is segregated into individual circuits for safety and convenience. It allows us to fit a protective device (circuit breaker, fuse, MCB) to each appropriately sized cable for each circuits design current.

As the wiring regulations have evolved (we are currently on amendment 2 of the 18th Edition of BS:7671 The Wiring Regulations), the requirements for safety have evolved too. As a general rule, we don’t apply the requirements retrospectively and regard installations as safe today if they were installed to the required standard at the time. There are some exceptions to this rule where it has been deemed that a genuine safety risk exists. Notable examples of this would be consumer units made of wood (for what I imagine are obvious reasons) and certain circuits without RCD protection.

Below are some pictures of common older style consumer units. Can you work out which of the following examples need to be replaced? Read on for our answers.

1.BS3036 semi enclosed rewirable fuse. Quite often this type have a wooden back box and no way to integrate RCD protection.

BS3036 semi enclosed rewirable fuse

2. This is one better than the previous. It has resettable circuit breakers (MCB) which is more convenient than fuse wire.

Fusebox with resettable circuit breakers (MCB)

3. An early resettable MCB board. 

An early resettable MCB board

4. A more modern MCB board. This one is a 3 phase unit but commonly this brand was also installed in residential projects. Its now very expensive to get retrofit components if adding RCD protection to circuits is required.

A more modern MCB board

5. RCD protected consumer unit. Plastic enclosure.

RCD protected consumer unit

6. Duel RCD Metal consumer unit 17th Edition. A much more modern consumer unit.

 Duel RCD Metal consumer unit 17th Edition

7. A modern consumer unit to 18th Edition BS:7671 This consumer unit has no SPD (Surge Protective Device).

A modern consumer unit to 18th Edition BS:7671

8. A recent installation including SPD installed by TVR. With the cover (and power) off.  

installation including SPD installed by TVR.

Did you work out which ones we would recommend replacing? Read on for more details.

Why do I need to replace my old consumer unit?

Generally, the reason we recommend changing a consumer unit is as the result of an inspection and test (EICR Electrical Installation Condition Report). We frequently conduct these for landlords but also home owners/home buyers. We grade defects according to The Electrical Safety First Best Practice Guide. Some items, like a wooden enclosure will cause a C2 grade defect (unsatisfactory, potentially unsafe) directly relating to the consumer unit. Other items like the lack of RCD protection to a room containing a bath or shower will also be graded C2. This doesn’t relate directly to the consumer unit but as we can’t add a protective RCD (residual current device) as a retrofit, we will advise the consumer unit is upgraded.

The other reason we may recommend an upgrade would be if you’re adding to your existing installation. Additions need to comply with the current version of BS:7671, which will almost certainly mean RCD protection as a minimum. It may mean a new circuit, and that might mean we need to add an SPD (Surge Protective Device) too. Sometimes with newer consumer units, its possible to retrofit these devices.

So, which ones should be replaced?

Consumer units number 1,2 and 3 above will need to be upgraded to achieve ‘Satisfactory’ on an EICR or to enable any addition (extra lights, sockets etc.). There are some workarounds, adding external RCD protection to individual circuits. We would recommend that is a poor way to proceed as the installation overall will be far safer and easier to use following an upgrade (try changing a fuse wire under your stairs in the dark!).

Consumer units 4 and 5 above may need to be upgraded. Sometimes we can’t acquire the internal components for old consumer units anymore. The only option is to replace the entire unit. Until recently, plastic consumer units were still being installed. It has now been deemed that metal (non-combustible) consumer units are significantly safer. They may still require upgrade if they are installed on the sole escape route from a property, below stairs or if they show any sign of heat damage.

Consumer units 6 and 7 above are unlikely to require upgrade. Some additions may require the addition of an SPD but this almost certainly wont involve a consumer unit upgrade.

Consumer unit 8 complies with all current standards. There are some rarer instances where AFDDs (Arc Fault Detecting Devices) may be required.

Please contact us for accurate pricing. To give some indication on cost to replace a consumer unit, for an average home this is now around £750. The cost has increased over recent years mainly due to the extra protective devices meaning materials cost is now higher. Usually, it takes around 1 working day to replace a consumer unit including testing all final circuits, and issuing certification. A consumer unit upgrade is a notifiable job under Part P of the building regulations.


Do you have any Consumer Unit/Fusebox stories to share? Please share them in the comments section below.

We hope you found this article useful and feel free to visit our CONTACTS page to get in touch.    

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