Editing Ring circuit (section)

==Installation rules==
{{Unreferenced section|date=July 2021}}
Rules for ring circuits provide that the cable rating must be no less than two thirds of the rating of the protective device. This means that the risk of sustained [[Overcurrent|overloading]] of the cable can be considered minimal. In practice, however, it is extremely uncommon to encounter a ring with a protective device other than a 30&nbsp;A fuse, 30&nbsp;A breaker, or 32&nbsp;A breaker, and a cable size other than those mentioned above. Because the BS&nbsp;1363 plug contains a fuse not exceeding 13A, the load at any one point on the ring is limited.

The [[Institution of Engineering and Technology|IET]] Wiring Regulations ([[BS 7671]]) permit an unlimited number of 13A socket outlets (at any point unfused single or double, or any number fused) to be installed on a ring circuit, provided that the floor area served does not exceed 100&nbsp;m<sup>2</sup>. In practice, most small and medium houses have one ring circuit per storey, with larger premises having more.

An installation designer may determine if additional circuits are required for areas of high demand.  For example, it is common practice to put [[kitchen]]s on their own ring circuit or sometimes a ring circuit shared with a [[utility room]] to avoid putting a heavy load at one point on the main downstairs ring circuit. Since any load on a ring is fed by the ring conductors on either side of it, it is desirable to avoid a concentrated load placed very near the consumer unit, since the shorter conductors will have less [[Electrical resistance|resistance]] and carry a disproportionate share of the load.

Unfused spurs from a ring wired in the same cable as the ring are allowed to run one socket (single or double) or one fused connection unit (FCU). Before 1970 the use of two single sockets on one spur was allowed, but has since been disallowed because of their conversion to double sockets. Spurs may either start from a socket or be joined to the ring cable with a junction box or other approved method of joining cables. BS 1363 compliant triple and larger sockets are always fused at 13A and therefore can also be placed on a spur. Since 1970 it is  permitted to have more spurs than sockets on the ring, but it is considered poor practice by many [[electrician]]s{{who|date=May 2021}} to have too many unfused spurs in a new installation.

Where loads other than BS&nbsp;1363 sockets are connected to a ring circuit or it is desired to place more than one socket for low power equipment on a spur, a BS&nbsp;1363 fused connection unit (FCU) is used. In the case of fixed appliances this will be a switched fused connection unit (SFCU) to provide a point of isolation for the appliance, but in other cases such as feeding multiple lighting points (putting lighting on a ring though is generally considered bad practice in new installation but is often done when adding lights to an existing property) or multiple sockets, an unswitched one is often preferable.

Fixed appliances with a power rating of 3&nbsp;kW or more (for example, water heaters and some electric cookers) or with a non-trivial power demand for long periods (for example, immersion heaters) may be connected to a ring circuit, but it is strongly recommended that instead they are connected to their own dedicated circuit. However, there are plenty of older installations with such loads on a ring circuit.