If you’ve got an old fuse box and you’re wondering whether it needs replacing, you’re asking exactly the right question. The answer isn’t always a straight yes or no, but there are clear situations where an upgrade is strongly recommended, and others where it becomes a legal and safety necessity.
To understand why, it helps to understand how consumer unit design has evolved over the past fifty years, because the gap between an old rewirable fuse board and a modern 18th Edition consumer unit is not just a matter of appearance. It represents half a century of learning about how electrical faults develop, how people interact with their electrical installation, and how the consequences of those faults can be minimised for all the different people who live in UK homes.
The Old Rewirable Fuse Box
The fuse boards fitted in UK homes through the 1950s, 1960s, and into the 1970s were simple devices. Each circuit was protected by a fuse carrier containing a length of thin wire sized to match the load it protected. If too much current flowed, the wire melted and broke the circuit.
This works, after a fashion. But the limitations are significant. Rewirable fuses are slow to operate under overload conditions. They offer no protection against earth faults or electric shock. If a live conductor touched earthed metalwork, or if a person received a shock, the fuse would only operate if the fault current was large enough to melt the wire. For many electric shock scenarios it simply wouldn’t respond in time. And when a fuse blew, it had to be rewired. Homeowners without the correct fuse wire to hand would sometimes bridge it with thicker wire or fold wire to make it fit, effectively removing all protection from that circuit entirely.
The 15th Edition: The First RCDs
The 15th Edition of the IEE Wiring Regulations, published in 1981, introduced residual current devices, then called earth leakage circuit breakers, as additional protection in specific situations. An RCD works on a fundamentally different principle to a fuse. Rather than responding to overcurrent, it monitors the balance of current on the live and neutral conductors. Any imbalance, even a very small one, indicates that current is taking an unintended path, possibly through a person, and the device trips within milliseconds.
The common solution of this era was to fit a single upstream RCD ahead of the existing circuit fuses. This gave a degree of shock protection across the whole installation, but it came with a significant drawback: any fault on any circuit, or cumulative earth leakage from any appliance across the whole board, would trip the single device and take out everything simultaneously.
The 16th Edition and the Split Load Board
The 16th Edition of the IEE Wiring Regulations was published in 1991 and formally adopted as British Standard BS 7671 in 1992. This gave rise to the split load consumer unit that remains the most common board type found in UK properties today.
A split load board divides the circuits into two groups, each protected by its own RCD. The two groups are typically arranged so that essential circuits, particularly the lighting, are split across both sides. If one RCD trips due to a fault, only half the circuits go off and there is a reasonable chance that lights are retained in at least part of the property, making it safer and easier to identify and address the problem.
This was a genuine improvement over the single upstream RCD. But by modern standards the split load board still has limitations. A single RCD protecting four, five, or six circuits means cumulative earth leakage from multiple appliances can cause nuisance tripping, and a fault on one circuit still takes out several others.
Part M of the Building Regulations: Designing for All Occupants
Alongside the technical evolution of the consumer unit, the Building Regulations introduced requirements that shaped how and where boards must be installed, with a particular focus on accessibility.
Part M of the Building Regulations, Approved Document M, covers access to and use of buildings. For new dwellings, consumer units must be mounted so that the operating switches are between 1,350mm and 1,450mm above finished floor level. This serves two distinct purposes.
First, it places the board within reach of a person seated in a wheelchair, ensuring that someone with a mobility impairment can reset a tripped device or isolate the supply without assistance.
Second, and equally important, it reflects the reality that consumer units are used in emergency situations by the whole range of people who live in UK homes. For elderly occupants, for people who are infirm, or for anyone with reduced mobility, having to navigate to a board mounted in an awkward or inaccessible location when the lights have gone off is a genuine safety risk, not simply an inconvenience. A fall in the dark trying to reach a consumer unit fitted at ceiling height is a real and preventable hazard.
This thinking also influences how modern boards are designed internally. Reducing the impact of a fault to the smallest possible area of the property keeps more of the home safe and lit for vulnerable occupants. A grandparent who loses all lighting across the entire property due to a single tripped RCD is at risk. That same person who loses the kitchen sockets but retains the hallway and bedroom lighting is in a considerably safer position.
The 17th Edition: Broader RCD Coverage and the End of Plastic Boards
The 17th Edition of BS 7671, published in 2008, significantly expanded the mandatory scope of RCD protection. Socket outlets up to 32A, bathroom circuits, outdoor circuits, and circuits to outbuildings all required 30mA RCD protection. This pushed the industry firmly toward more circuit-level protection rather than relying on shared RCDs covering everything.
The boards installed during the 17th Edition era, roughly 2008 to 2018, are the ones many UK homeowners have today. The most common configuration is a dual RCD or high-integrity board: a main switch, two RCDs each protecting a separate group of circuits, and individual MCBs for each circuit. Some higher-specification installations of this period used individual RCBOs per circuit, but this was not yet the standard approach.
The brands most commonly found on 17th Edition installations in UK homes include Wylex, which had been a dominant name in UK consumer units since the fuse board era and whose plastic split load boards were installed in enormous numbers through the 1990s and 2000s. MK Sentry was another widely installed brand from this period, as was Hager, which was establishing itself in the UK market with a reputation for quality components. Contactum boards were also commonly specified, particularly in new build developments. BG Electrical (British General) produced consumer units that were popular across the domestic market during this era.
It is worth noting that the brand of the board matters less than its specification and condition. A well-maintained Wylex board from 2010 with a proper dual RCD arrangement is not necessarily a problem. The same board with a failing RCD, signs of overheating, or inadequate protection for the circuits it serves is a different matter entirely. An EICR will assess the actual condition and suitability of whatever board is present rather than simply noting its age or manufacturer.
Amendment 3 to the 17th Edition, issued in 2015, introduced the requirement for consumer units in domestic premises to be housed in non-combustible enclosures. Plastic boards, including many of the Wylex and MK units that had been installed in such large numbers, had been identified as a fire risk when internal arcing or faults caused them to ignite. Steel enclosures became the standard from this point for all new installations and replacements. The major manufacturers responded quickly: Hager, Fusebox, Contactum, Lewden, and BG Electrical all introduced steel-enclosed ranges, and these became the default product from 2015 onwards.
Fusebox in particular grew significantly in market share during the transition to metal enclosures, gaining a strong reputation among electricians for competitive pricing and reliable components. Lewden, a long-established UK manufacturer, also became a popular choice for both domestic and light commercial installations. These brands, alongside Hager’s established range and Contactum’s continued presence in the new-build sector, make up the majority of metal-enclosed boards installed in UK properties since 2015. This is also directly relevant to location, which we’ll address below.
The 18th Edition: Individual Protection, AFDDs and Surge Protection
The 18th Edition of BS 7671, published in 2018 and effective from January 2019, together with Amendment 2:2022 and Amendment 3:2024, sets the standard for all new consumer unit installations today. The IET publishes BS 7671 and provides guidance on how its requirements apply in practice, and the 18th Edition represents the most comprehensive set of domestic electrical protection requirements the regulations have ever contained.
The defining feature is the move to individual RCBOs, Residual Current Breakers with Overcurrent, one per circuit. An RCBO combines MCB and RCD function in a single device. Every circuit has fully independent protection. A fault on one circuit trips only that circuit. Everything else in the property stays on. Lights stay on. The freezer keeps running. The occupant can read the clearly labelled board and identify exactly which circuit has tripped, without plunging the whole property into darkness.
For elderly or infirm occupants, for families with young children, and for anyone who relies on electrically powered medical equipment, this is a meaningful safety improvement that goes well beyond regulatory compliance.
The 18th Edition also introduced Arc Fault Detection Devices. An arcing fault occurs when electricity jumps across a gap in a damaged or deteriorated cable, generating intense heat without necessarily drawing enough current to trip an MCB or being detected by an RCD. Arcing faults are a significant cause of electrical fires. An AFDD monitors the waveform of the circuit current and detects the electrical signature of an arc, disconnecting the supply before the arc can ignite surrounding materials. Under BS 7671:2018+A2:2022, AFDDs are required in higher-risk premises including HMOs and care homes, and are recommended in dwellings generally. In a property with elderly or mobility-impaired occupants, the case for fitting AFDDs is a strong one.
Surge Protection Devices are also required on most new installations under the 18th Edition. An SPD absorbs transient voltage spikes arriving via the incoming supply, whether from lightning strikes on nearby power lines, switching events on the network, or other overvoltage events, and diverts the energy safely to earth before it can damage connected equipment. Modern homes are full of sensitive electronics, inverters, smart home devices, and networked equipment that is far more vulnerable to voltage spikes than the simple loads that older consumer units were designed to serve.
When Should You Upgrade?
Understanding this history makes the triggers for an upgrade much easier to grasp. Here are the situations where a consumer unit upgrade is either strongly recommended or required.
Your Board Has Rewirable Fuses
This is the clearest case. No RCD protection, slow to operate, and vulnerable to incorrect rewiring. If your property still has a rewirable fuse board, upgrading is a significant improvement to the safety of the installation.
There Is No RCD Protection, or Only a Single Upstream RCD
A board with no RCDs at all, or one with a single RCD sitting upstream of the fuses or MCBs covering the whole installation, provides inadequate protection by current standards. While this alone doesn’t trigger a mandatory upgrade, any new work being done, any circuits being added, or any C2 observations on an EICR relating to RCD protection will make the upgrade conversation very relevant.
Your EICR Has Identified C1 or C2 Observations on the Board
Where an EICR identifies C1 or C2 faults relating to the consumer unit itself, including faulty protective devices, accessible live parts, or inadequate earthing and bonding, remedial work is required. In many cases, particularly with older boards, a full consumer unit replacement is the most practical and cost-effective resolution.
You Are Adding New Circuits
Installing an EV charger, adding circuits to an outbuilding, rewiring a kitchen, or any other notifiable work requires the new circuits to comply with BS 7671 in its current form. If the existing board cannot accommodate new circuits with the correct protection, or has no spare ways, an upgrade is part of the work. The Health and Safety Executive is clear that electrical systems must be maintained to prevent danger and tacking non-compliant circuits onto an outdated board is not an acceptable approach.
You Are Selling or Letting the Property
Old boards are routinely flagged by surveyors, EICR inspectors, and buyers’ solicitors. For landlords, inadequate RCD protection on circuits is a common C2 observation that makes an EICR unsatisfactory and must be resolved before a property can be legally let.
The Location or Enclosure Is a Problem
This is an important reason that is often overlooked. Where a consumer unit is located can be as significant as its age or specification.
A plastic consumer unit positioned under the stairs is a particular concern. Under the stairs is typically a sole escape route from the property. If the consumer unit develops an internal fault and ignites, having a combustible plastic enclosure in that location dramatically increases the risk to occupants trying to escape. Under the 17th Edition Amendment 3:2015, new and replacement consumer units must be in non-combustible enclosures. Electrical Safety First specifically highlights the risk of plastic consumer units located under stairs or within escape routes. Where a plastic board is found in this position during an EICR, it is typically recorded as a C3, as Electrical Safety First’s Best Practice Guide 4 identifies, though the practical fire safety case for replacing it is compelling regardless of the code it attracts.
Other location problems include boards fitted at an inaccessible height, boards in damp or poorly ventilated locations, and boards in garage or outbuilding positions that are exposed to extremes of temperature. All of these can affect the reliability and safety of the protective devices over time, and all are valid reasons to consider upgrading and relocating.
The Board Shows Physical Signs of Deterioration
Scorch marks, discolouration, a burning smell, buzzing, crackling, or a board that feels warm to the touch are all serious warning signs indicating overheating or arcing. In most cases where physical damage is evident, replacement is safer and more practical than trying to repair individual components.
Is a Consumer Unit Upgrade Legally Compulsory?
There is no blanket legal requirement to replace an old consumer unit simply because it is old. However, what does trigger a mandatory requirement is an EICR that identifies C1 or C2 faults attributable to the board, new circuits being added that the existing board cannot accommodate compliantly, or a direct safety risk from the board’s condition or location.
Since 2016, all new or replacement consumer units in domestic premises must be in a non-combustible enclosure. This applies to replacements but does not retrospectively require every existing plastic board to be immediately changed. However, if your plastic board is being replaced for any reason, the replacement must be metal.
What Does the Upgrade Process Involve?
A consumer unit upgrade is a carefully executed job for a qualified electrician. The supply is isolated, the old board is disconnected and removed, the new board is mounted and all circuits are reconnected, and the installation is fully tested to BS 7671 before power is restored.
Testing covers continuity of protective conductors, insulation resistance, polarity, earth fault loop impedance, prospective fault current, and RCD trip times. An Electrical Installation Certificate is issued on completion. Because a consumer unit replacement is notifiable work under Part P of the Building Regulations, your electrician notifies building control on your behalf through their competent person scheme. As a NAPIT-registered contractor, Flodman Electrical handles self-certification and notification as part of every consumer unit installation. You receive both the EIC and the Building Regulations compliance documentation to keep for your records.
The job typically takes between four and seven hours for a standard domestic property. The power is off for most of that time, so it is worth planning for a full day without electricity.
Consumer Unit Upgrade or Full Rewire?
A consumer unit upgrade replaces the board and protective devices. The existing wiring stays in place. If the wiring itself is aged, damaged, or deteriorated, upgrading the board improves the level of protection but does not address the underlying condition of the cables.
A full or partial rewire replaces the cables. If your property has rubber-insulated wiring, aluminium wiring, or wiring that has been identified on an EICR as deteriorated or dangerous, a rewire addresses the root cause. In many older properties the most thorough solution is a rewire that includes a new consumer unit as part of the same project.
An EICR is the right starting point. It tells you the actual condition of the wiring and gives you a clear, evidenced basis for deciding what work is needed.
Talk to Flodman Electrical About Your Consumer Unit
Flodman Electrical are NAPIT-approved electricians based in Farnborough, covering Hampshire, Surrey, and Berkshire. If you are not sure what type of board you have or whether it needs replacing, we can carry out an assessment and give you an honest recommendation. If an upgrade is the right course of action, we will supply and install a fully compliant modern board, carry out all the necessary testing, and handle the Part P notification on your behalf.
Contact Flodman Electrical to discuss a consumer unit upgrade
Flodman Electrical Ltd, NAPIT Approved Contractor. Serving Farnborough, Hampshire, Surrey and Berkshire.
