parts enclosed to IP2X, even when the cover has been removed for servicing. Consumer units In the United Kingdom, BS 7671 defines a consumer unit as "A particular type of distribution board comprising a type tested coordinated assembly for the control and distribution of electrical energy, principally in domestic premises..." These installations usually have single-phase supplies at 230 V (nominal standard); historically, they were known as fuse boxes, as older consumer units used fuses until the advent of mini-circuit breakers (MCBs). A normal new domestic CU used as a main panel might have from 6 to 24 ways for devices (some of which might occupy two ways), and will be split into two or more sections (e.g. a non-RCD section for alarms etc., an RCD-protected section for socket outlets, and an RCD-protected section for lighting and other built-in appliances). Secondary CUs used for outbuildings usually have 1 to 4 ways plus an RCD. Recent (pre-17th edition wiring regulations) CUs would not normally have RCD protected sections for anything other than socket outlets, though some older CUs featured RCD incomers. Before 1990, RCDs (and split busbars) were not standard in CUs. Fuse boxes normally use cartridge or rewirable fuses with no other protective device, and basic 4-ways boxes are very common. Some older boxes are made of brown-black bakelite, sometimes with a wooden base. Although their design is historic, these were standard equipment for new installs as recently as the 1980s, so they are very common. Fuseholders in these boxes may not provide protection from accidental contact with live terminals. The popular 4-way fusebox normally had two lighting and two socket circuits, with heavy or sustained loads such as immersion heater and oven on a socket circuit. This arrangement is not recommended practice today, but it is common for existing installations. Larger boxes with more ways will have separate fuses for large loads such as immersion heater, oven and shower. Legacy fuseboxes A small number of pre-1950 fuseboxes are still in service. These should be treated with caution because exposed live parts are common on these boxes. The installations they supply will not meet modern standards for electrical safety. Another characteristic of very old installations is that there may be two fuses for each circuit; one on the live and one on the neutral. In rare instances, old ring circuits may be encountered with no fewer than 4 15 A fuses