This is a question posed by many a householder, however of the reality is that it might not need to be changed. If the fuse board is damaged and there's a chance that people could touch "live" parts (risking an electric shock), then it does need to be changed.

The old fuse board will not meet the requirements of the BS7671 Wiring Regulations 17th Edition Ammendment 1 (2011). The fact that the installation does not meet the requirements doesn't mean it is illegal or indeed unsafe, however the new requirements are intended to make the installation "more" safe by reducing the chances of getting an electric shock.

In order for your domestic installation to meet the requirements of the "Regs" it must also meet the new RCD (Residual Current Device) requirements. RCDs cannot be fitted in older style fuse boards so if your installation needs to be brought up to date and made safer a new consumer unit will be needed.

There are numerous areas where RCDs are required, which should be rated at 30mA. These include;

• Any cable buried in a wall or partition at a depth of less than 50mm from the surface requires protecting by an RCD unless it is protected by earthed metalwork such as conduit or trunking.
• Any cable passing through a wall or partition that contains metal parts other than screws or nails.
• Any cable that is installed outside the 'cable safe zones' needs protecting with both earthed metalwork and an RCD.
• Every socket outlet rated 20A or less that is used by "ordinary persons" (i.e. home owners) intended for general use, require RCD protection.
• Mobile equipment used outdoors rated up to 32A.
• All circuits supplying power to a room that contains a bath or shower are required to be RCD protected.