When is a fuse board upgrade necessary?

If you plan to have electrical work done in your home and the fuse board is out-of-date, it will usually need replacing with a modern consumer unit. In most cases additions or alterations to an electrical installation will require a 30mA RCD for additional protection – most older boards do not have this.

Upgrading from an old fuse board to a modern consumer unit is beneficial even if no other electrical work is planned. RCDs are life saving devices, and greatly reducing the risk of electric shocks.

RCD protection

An RCD, or Residual Current Device, switches off the electricity supply in the event of an earth fault. It offers a level of protection which ordinary fuses or circuits breakers cannot provide.

RCDs monitor the electric current flowing through the circuits it is used to protect. If it detects electricity flowing through an unintended path, such as through a person who has touched a live part, it will switch off immediately and greatly reduce the risk of death or serious injury. RCDs have been shown to be around 97% reliable and, when installed in a consumer unit, will protect all circuits and any appliances connected to those circuits.

Arc Electrical now install consumer units containing RCBOs and an SPD as standard, giving you peace of mind as you can be sure that your electrical installation is safe and protected by the most up-to-date methods. More information on the benefits of RCBOs and SPDs can be found below.

RCBOs

An RCBO, or Residual Current Operated Circuit-Breaker with Integral Overcurrent Protection is a device which performs both the functions of a regular circuit-breaker and an RCD. There are significant advantages of fitting an RCBO consumer unit over a dual RCD split load consumer unit.

Nuisance tripping

During the 17th Edition, between 2008 and 2018, split load, dual RCD consumer units were the standard. These units contained two RCDs, each protecting multiple circuits. At the time this was a cost effective way of providing RCD protection for all circuits in the installation that required it, however there were some disadvantages. Most notably an issue known as nuisance tripping.

Nuisance tripping can happen on any consumer unit where there is one RCD protecting multiple circuits. Modern appliances and plug-in power supplies, by their design, generate low levels of earth leakage current even when there is no fault present. This can be a problem when multiple appliances are connected across different circuits all protected by the same RCD, as their earth leakage currents can add up to exceed the trip threshold of the RCD.

Nuisance tripping is often intermittent and can be difficult to identify. It is also inconvenient as power is unnecessarily lost to several circuits at once, or in some cases all circuits in the house if a consumer unit has an RCD main switch.

The use of RCBOs alleviates these issues as each circuit essentially has it's own RCD protection, meaning an RCBO will only trip in the event of a genuine fault, and power will only be lost to that one circuit.

SPDs

An SPD, or Surge Protective Device, is used to protect the electrical installation and all equipment connected to it (such as TVs, computers and washing machines) from electrical power surges known as transient overvoltages.

Transient overvoltages are short surges of electricity caused by the sudden release of energy and can be either man-made or naturally occurring.

Man made surges are caused by switching of motors, transformers and some types of lighting. This has only become an issue in domestic premises in recent years as electric vehicle charge points, air/ground source heat pumps and speed-controlled washing machines have become more commonplace in households.

Natural transient overvoltages can occur due to direct lighting strikes on an overhead power or telephone line, causing the transient overvoltage to travel along the lines. This can cause significant damage an electrical installation and all associated equipment if no surge protection is in place.

As of the 18th Edition, the installation of an SPD is now a requirement for domestic premises, whether that is as part of a fuse board upgrade, new build or a property being rewired.

What is involved?

Before the fuse board is changed, preliminary inspection and testing is carried out on all circuits to ensure that no faults or examples of non-compliance are present. This includes, but is not limited to, the following:

• checking for damaged sockets, light fittings and accessories
• presence and/or suitability of main protective bonding (earth) to water and gas
• suitability of earthing conductor and meter tails
• testing end to end continuity of conductors on ring circuit(s)
• testing continuity of earth on all circuits
• insulation resistance testing on all circuits. Initially this would be checking for earth faults not detected by existing protective devices so that no nuisance tripping occurs when the new unit is fitted. Full insulation resistance tests will be carried out after the new unit is fitted
• Checking for grommets/correct sleeving in back boxes

Any faults or examples of non-compliance that arise during this procedure need to be addressed before any further work is carried out. Once any necessary remedial work is finished the new consumer unit can be fitted and a full series of testing can be carried out on all circuits.
Arc Electrical make every effort to ensure that the process goes as smoothly as possible – see our Customer Promise.

Upon completion of the work all appropriate certification and notification will be taken care of by us.