When to Upgrade Your Consumer Unit (Domestic and Commercial)

Plenty of properties in Halifax, Bradford and the rest of West Yorkshire are still running on consumer units that pre-date the current wiring regulations by two decades or more. Most days they sit there doing nothing dramatic. The day they fail, they fail badly. Here is how to tell when a board is asking to be replaced, and what an upgrade actually involves on a commercial or domestic property.

Signs the board is overdue an upgrade

There are five clear signals that come up on almost every survey we run. None of them are subtle once you know what to look for.

• Wire fuses or rewireable fuses. A porcelain or bakelite carrier with a strand of fuse wire inside is from a different era of safety thinking. If the board still has these, it predates current standards by decades.
• A plastic enclosure on a domestic board. Plastic consumer units have been non-compliant on new domestic installations since 2016. Existing boards can be left in, but they get flagged on every EICR.
• A single RCD covering the whole installation. A fault on the kettle takes out the freezer, the boiler control and the lights all at once. On a commercial setting it can take out the till system and the chillers in the same trip.
• Nuisance tripping that gets worse over time. An ageing RCD drifts on its trip threshold. By the time it is dropping the building once a fortnight, it is no longer doing its safety job reliably.
• No surge protection (SPD). Older boards do not have one. A nearby lightning strike or a grid spike will write off TVs, routers, fridges, HVAC controls, point-of-sale kit. A Type 2 SPD is now standard on a modern board.

Any one on its own is a conversation. Two or more, and the board is overdue.

BS 7671 18th Edition, what changed

The 18th Edition of BS 7671 (the UK wiring regulations) brought in several changes that matter for consumer units specifically. Boards in domestic settings now need a non-combustible enclosure, which in practice means a metal-clad unit. Surge protection became the default expectation rather than an optional extra. RCD protection was extended to nearly every circuit rather than just sockets and certain wet rooms.

Amendment 2 (2022) tightened arc-fault detection guidance and clarified the role of AFDDs on high-risk circuits like HMOs, care premises and high-occupancy commercial buildings. None of this means an older board is automatically dangerous tomorrow. It means that if a board is being upgraded anyway, the upgrade itself looks quite different to a board that was fitted in 2010.

RCBO vs RCD, the difference that matters

This is the single biggest practical difference between a modern board and an older one.

On the old design, one or two RCDs sat at the front of the board and protected groups of circuits. A fault anywhere in that group dropped the whole group. If you walked back into a half-dark unit and a freezer that had been off all day, that was usually the cause.

On a modern board, every circuit gets its own RCBO. An RCBO is an RCD and an MCB combined into one device. The fault drops only the circuit that has the problem. The kettle trips its own socket ring, the rest of the kitchen stays on, the freezer keeps running, and the fault can be isolated without standing in the dark.

On a commercial property, the saving is even more obvious. A fault on a single piece of plant no longer takes out the rest of the building. The till keeps running. The CCTV stays up. The cold storage stays cold.

What an upgrade actually looks like on the day

A standard domestic consumer unit upgrade takes two to four hours on site. A commercial board, depending on the number of circuits and the access, can run a full day. The job runs in the same order either way.

First, the supply is isolated at the meter (the supplier's cut-out fuse comes out, properly logged). The existing board comes off the wall. Every circuit is labelled before disconnection, so the new board goes back together without guesswork. The new metal-clad unit is fixed in position, usually exactly where the old one was, and the existing circuit cables are transferred across into the new RCBOs.

Then the testing starts. Earth loop impedance on every circuit. Insulation resistance on every circuit. Polarity. RCD operation. SPD function. Bonding to gas and water. The full set, on every circuit, before the supply goes back on. Anything that does not pass first time gets investigated and resolved before we close up.

In almost every case the supply is back on the same day. The customer gets the day before as a heads-up so they can plan around the couple of hours of no power.

Certification and notification

On completion the customer gets an Installation Certificate (or a Minor Works Certificate where the scope was smaller), the work is lodged with NAPIT, and the local authority building control is notified where it needs to be. That paperwork is what a landlord agent, an insurer, a solicitor or a mortgage lender will ask for. On commercial work it is what the FRA assessor and the buildings insurer expect to see.

What it costs

Most domestic consumer unit upgrades land in the £650 to £1,200 range, depending on the number of circuits and any minor remedials uncovered during testing. Commercial boards vary widely with the size and complexity, starting around £1,500 and running to several thousand on larger distribution boards. The price is fixed in writing before any work starts, after a free site visit.