Consumer Unit Upgrade with Full RCBO Protection
The job
This old consumer unit near Marazion lacked any RCD protection. Meaning that while it had MCBs, which protect the cable from overheating, melting, and catching fire, nothing was in place to protect the user of the electrical installation from electrocution. An RCD will isolate the supply in milliseconds upon detection of an imbalance between the incoming and outgoing current, significantly reducing the risk of fatal electric shocks. It is common in these modern times that each circuit has its own RCD protection with the use of an RCBO, which has individual RCD protection along with the overload protection of an MCB.
What I did
I replaced the old consumer unit with a new unit fitted with RCBOs throughout - one per circuit. Each RCBO combines a standard MCB (overload and short-circuit protection) with its own individual RCD (earth fault and shock protection), so a fault on any single circuit only trips that circuit rather than the whole board. The installation was tested, a certificate issued, and the work notified to building control through my NAPIT membership.
On the day
There's multiple reasons why you may upgrade your Consumer Unit. No RCD (Residual Current Device) protection Main switch RCD causing loss of all power Unsatisfactory EICR / Rental purposes No capacity for extra circuits If you have no RCD protection then there is nothing to protect the user of the installation from electrocution. So not only is it highly recommended to have RCD protection, the vast majority of the time it will be a requirement in rental properties.
About this type of work
When a consumer unit upgrade makes sense
There are several common reasons to replace a consumer unit, and they’re not all equal in urgency.
No RCD protection is the most pressing. MCBs protect the cable - they trip when there’s too much current, preventing overheating and fire. RCDs protect the person - they detect the tiny imbalance in current that occurs when electricity is passing through a human body and cut the supply in milliseconds. Without RCD protection, a fault that would be survivable with modern protection can be fatal. This is why it’s a requirement in rental properties and strongly recommended everywhere else.
A single RCD tripping the whole board is less of a safety issue but a significant practical one. Older boards often have one or two RCDs protecting groups of circuits. When a fault trips the RCD, everything on that section goes off - all the lights, all the sockets, or all the upstairs circuits. Without knowing what caused it, restoring power means working through the circuits one by one, often in the dark. RCBOs solve this by giving each circuit individual protection, so only the faulty circuit trips.
An unsatisfactory EICR will frequently flag consumer unit issues - missing RCD protection, an obsolete design, or a unit that’s showing signs of damage or deterioration. For rental properties in particular, an unsatisfactory EICR can prevent the property from being legally let until the issues are resolved.
The enclosure material sometimes comes up in EICRs - older plastic consumer units don’t meet current standards, which require metal enclosures for fire containment reasons. This wouldn’t on its own make an EICR unsatisfactory, but it’s worth noting when planning a future upgrade.
A consumer unit upgrade is notifiable work - it has to be certified and reported to building control. If the electrician is registered with a competent persons scheme like NAPIT (my membership number is 66376), they can self-certify and notify building control directly, which is simpler and faster than going through the local authority.