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Most people only think about the consumer unit when something trips and will not reset, or when an electrician mentions it during a kitchen refit. Until then, it sits under the stairs or in a hallway cupboard, quietly doing its job. However, the consumer unit, still called the fuse box in many homes, is the part of the installation that decides how every circuit in the property is protected. Older fuse boxes used rewireable fuse wire (BS 3036) or cartridge fuses, while a modern consumer unit uses resettable devices.
A modern board is not simply a newer box. It brings together a main switch, circuit breakers, residual current protection, surge protection and, in some cases, arc fault detection. The way those devices are arranged affects safety, nuisance tripping and how easy future work will be.
At SND Electrical, we supply consumer units, MCBs, RCBOs and surge protection to electricians, landlords and homeowners planning upgrades. This guide explains what the parts do, what the current Wiring Regulations expect, and what actually matters when a fuse box upgrade is on the table.
For most UK homes having a board replaced today, we would start with a metal, RCBO-based consumer unit with a 100A main switch and a Type 2 surge protection device (SPD). Our Fusebox F3007MZ 7 way consumer unit and FuseBox F3011MZ 11 way consumer unit follow that layout: a 100A main switch, a Type 2 SPD that connects directly to the busbar, a steel enclosure and compliance with BS EN 61439-3. The F3015MZ, F3021MZ and F3031MZ versions cover larger homes.
Each circuit then gets its own Type A RCBO, such as the FuseBox Mini RCBO RTAM series (B curve, 30mA, 6A to 40A). Where budget matters more, a high integrity board with two RCDs and MCBs, like the Hager VML910CURKPP, is still a recognised approach. Either way, the board must be designed, installed, tested and certified by a competent, registered electrician.
The main switch isolates the whole installation on the consumer side of the meter. A 100A main switch is standard on our domestic Fusebox F3 boards. It does not replace the network operator's cut-out fuse, which belongs to the distribution network operator and must not be touched by anyone else.
A miniature circuit breaker (MCB) protects a circuit against overload and short circuit. MCBs to BS EN 60898-1 come in trip curves. Type B trips at 3 to 5 times its rated current and suits most domestic lighting and socket circuits. Type C trips at 5 to 10 times and suits loads with higher inrush, such as some motors and lighting banks. Our range includes the Fusebox MT06B series (Type B, 6kA, 6A to 50A) and Crabtree 6HS MCBs in Type B and Type C.
A residual current device (RCD) monitors the balance between line and neutral and disconnects when current leaks to earth, for example through a person. The 30mA rating is the standard for additional protection. An RCBO combines an MCB and an RCD in one device to BS EN 61009-1, so each circuit has its own overcurrent and earth leakage protection.
A surge protective device limits transient overvoltages caused by lightning activity on the network or switching events. Type 2 SPDs are the type normally fitted in consumer units. Type 1 devices are used where there is a lightning protection system or a higher risk at the origin of the supply.
An arc fault detection device (AFDD) to BS EN 62606 looks for the electrical signature of arcing, such as a damaged cable or a loose terminal, which an MCB or RCD may not detect. We stock combined units such as the FuseBox 30mA 2 pole AFDD RCBO in ratings from 6A to 40A.
A split load or dual RCD board places groups of circuits behind shared RCDs. It costs less, but a single earth fault can switch off several circuits at once, including lights. A high integrity board, like the Hager VML910CURKPP with two 100A Type A RCDs and eight MCBs, reduces that problem but still groups circuits together.
An RCBO board gives each circuit its own protection. If a faulty kettle trips the kitchen sockets, the lights, fridge freezer and heating stay on. It also makes fault finding easier, because the tripped device points straight to the circuit concerned. The trade-off is straightforward. RCBO boards cost more in devices, while dual RCD boards accept more disruption when something trips.
Device type matters too. BS 7671 restricts Type AC RCDs to fixed equipment known not to produce DC components, so Type A devices are the normal choice for homes full of electronics, LED drivers and induction hobs. The RCBOs we recommend for domestic boards, including the FuseBox RTAM series and the Crabtree Starbreaker Miniature RCBO from our Crabtree range, are Type A.
The current Wiring Regulations are BS 7671:2018+A4:2026. Amendment 4 was published on 15 April 2026, and the previous version was withdrawn on 15 October 2026. Its headline changes cover areas such as battery storage and Power over Ethernet, but several earlier rules shape every domestic consumer unit choice.
Your electrician will apply the full regulations to the specific property. This list simply explains why a board fitted ten years ago looks different to one fitted now.
In England, Approved Document P lists replacing a consumer unit as notifiable work. It must be carried out by an electrician registered with a competent person scheme, or notified to building control before work starts. Wales also treats consumer unit replacement as notifiable, while Scotland follows its own building standards.
A registered electrician will test the existing circuits, install the board, issue an Electrical Installation Certificate to BS 7671 and arrange the Building Regulations compliance certificate. Keep that paperwork. It matters when you sell, remortgage or let the property.
A new board can also reveal faults that an old fuse box ignored, such as a neutral to earth fault that makes an RCD trip. That is the protection doing its job, not a fault with the new unit. We cover notifiable and non-notifiable work in more detail in our guide to when to replace old sockets and switches and Part P basics.
An old board is not automatically dangerous, but these signs are worth an inspection by a qualified electrician:
Landlords in England must have the installation inspected and tested at least every five years. An EICR is also the sensible starting point for homeowners, because it shows whether the board needs replacing or the existing circuits need work first.
List every circuit: lighting per floor, sockets, kitchen, cooker, shower, immersion, smoke alarms and any outbuilding. Then add two or three spare ways for future work. Our consumer units run from compact garage units to the 44 way F2044MX with surge protection, and the Fusebox F3 range covers 7, 8, 11, 12, 15, 16, 21 and 31 way layouts.
A consumer unit is tested as an assembly under BS EN 61439-3. Mixing breakers from different manufacturers can take the board outside its tested configuration, so we always recommend devices from the same manufacturer as the enclosure. Browse our Fusebox range and circuit protection to keep the board and devices matched.
Mini RCBOs and standard height RCBOs need different space. The F3011MZ has room for both, according to its listing. Also check cable entry, tails clamp position and whether the board will be surface or flush fitted. Flush mounting frames such as the AFMF14, AFMF18 and AFMF24 are available for the F3 range.
Smaller sub-boards suit garages and garden rooms. The FuseBox F300GRAZ is a compact garage unit with a Type 2 SPD and B6/B16 MCBs. For damp or external locations, the FuseBox A65E06MWH is an IP65, 6 module unit designed for internal and external use. For EV charging, the FuseBox EV32ABDZ combines a main switch, a 32A Type A bi-directional RCBO and a Type 2 SPD.
Most of these come from treating the board as a box rather than a protection system. At SND, we match the enclosure, main switch, SPD and every RCBO or MCB as one specification.
Before ordering a consumer unit, confirm:
Broadly, yes. "Fuse box" usually describes older boards with rewireable or cartridge fuses, while a consumer unit uses resettable MCBs, RCDs and RCBOs. Most people use the two terms for the same thing.
In domestic premises, new consumer units must have a non-combustible enclosure, or be housed in a non-combustible cabinet. In practice, that means steel boards such as our Fusebox F3 range.
Under BS 7671, surge protection should be provided unless the owner declares that the risk of damage is tolerable and accepts it. Most new domestic boards therefore include a Type 2 SPD.
An RCBO board isolates a fault to one circuit, which reduces disruption and simplifies fault finding. A dual RCD board costs less but can switch off several circuits at once.
In England, consumer unit replacement is notifiable under Part P. Use a competent electrician registered with a competent person scheme, who can test, certify and notify the work.
The Fusebox F3007MZ, F3011MZ, F3015MZ, F3021MZ and F3031MZ include a 100A main switch and a Type 2 SPD. The FuseBox F300GRAZ garage unit and F2044MX 44 way board also include surge protection.
An MCB protects against overload and short circuit only. An RCBO adds 30mA earth leakage protection in the same device, so one unit protects the cable and the people using the circuit.
A consumer unit upgrade is one of the most important electrical improvements a home can have, but the badge on the front matters less than the specification inside. Metal enclosure, Type A RCBOs, surge protection, enough spare ways and matched devices make the real difference.
At SND Electrical, we look at the whole installation first. How many circuits are there? What is planned next? Is solar, battery storage or EV charging on the horizon? Answering those questions before ordering leads to a board that protects properly today and does not need changing again when the house does.