The most common way of providing RCD protection is to install a new fuseboard or 'consumer unit' that includes one or more RCDs protecting the circuits fed by the fuse board. Often the RCDs will provide earth fault protection for up to 5 circuits. While this is safe, when earth fault conditions occur the RCD will trip and power will be lost to all those circuits. This can cause a lot of inconvenience, especially if a fridge or freezer is connected to one of the circuits, as any food inside the appliance could be spoiled. We fit fuseboards containing 'RCBO's. An 'RCBO' is a combined RCD and MCB and will provide overcurrent, short circuit and earth fault protection all in one switch. As each circuit will have a dedicated RCBO, 'nuisance tripping' of other circuits doesn't occur and the freezer doesn't defrost if other appliances in the home trip the RCD.
Another benefit of RCBOs is that in the event of an intermittent earth fault occurring, it would be obvious which circuit is faulty. With an RCD protecting several circuits, isolating the fault to an individual circuit may be difficult and more time consuming.
An update to the RCBO is now being manufactured by some companies. It is called an 'Arc Fault Detection Device'. Since the 18th edition of BS7671 (the electrical regulations), they have been required for new fuseboard/circuit installations. Unfortunately, they are, at the time of writing (June 2022) very expensive and not made by every fuseboard manufacturer. We always recommend that AFDDs be included in new fuseboards, however, due to their prohibitive cost, most customers prefer not to have them installed. We expect AFDDs to come down in price in the future. If a customer is not prepared to pay the excess for AFDDs, RCBOs may still be installed in a new fuseboard but a waiver, stating that "AFDDs were recommended but I chose to have cheaper RCBOs installed", must be signed.
