Upgrading your old system
When it comes to upgrading your old consumer unit or ‘fuse box’ there are a number things to think about.
The best place to start is to get a electrical installation condition report on your current installation. Any old wiring may no longer be compatible with the new units as they now have additional protection (RCD). A RCD is a device now required on all domestic circuits as per the 18th Edition BS7671 Wiring Regulations.
Now this is not to say your old installation is unsafe, as long as the regulations where met at the time of installation this is deemed as safe. However with the addition of RCD protection, these are far more sensitive and can protect you from such things as appliance faults as well as wiring faults.
selecting a consumer unit
Duel RCD (see picture i)
The most cost effective solution for a domestic premises is a Duel RCD Unit. This comes with two RCD switches, splitting the load of the house in half. So for example, you may three circuits protected by one RCD and three protected by another.
The down side to having only two RCD’s for all of your circuits, is if one of the circuits has a problem that trips the RCD, you will lose all power on that half of the unit until the problem is rectified.
RCBO’s (see picture ii)
The most efficient and recommended solution is to install RCBO’s. This unit is a regular circuit breaker (MCB) combined with an RCD. Which means each individual circuit has it’s own RCD protection. This is a far more convenient solution as if the circuit trips is does not affect any other circuit on the consumer unit.
The only down side to this is that the RCBO’s are more expensive than a standard circuit breaker.