A fused spur is a lower-rated branch circuit made from a higher-rated circuit, via a local fuse to protect the branch. This is done using a standard device called a fused connection unit, example here: BG fused connection unit . It often includes a double-pole switch to provide isolation if needed, and/or a power indicator, but it must contain a BS1362 cartridge fuse, the same type as used in our fused plugs. Most common fuses are 3 & 13A (also available 1, 2, 5, 7 & 10A).
For example, If you want a small supply for an outside light and there is a 32A circuit for socket outlets nearby, then you can install a fused connection unit with a 3A fuse to make a branch circuit for the light, instead of running a new lighting circuit all the way back to the panel. A fused connection unit can also used to connect a permanently installed appliance such as duct fan, instead of a plug and socket outlet. to stop people unplugging it to use the outlet. Here it's not technically a 'spur' but we have a habit of calling the fused connection unit itself a spur, or spur box.
Fused connection units were invented alongside fused plugs and the scheme of using socket outlet circuits of much higher rating than the plugs themselves. 32A circuits are popular, offering 7.4 kilowatts per circuit (compared to the 2.4kW of a 20A 120V outlet circuit), so a large number of typical appliances can be powered from one circuit. This is only possible due to the presence of fuses.
For example, If you want a small supply for an outside light and there is a 32A circuit for socket outlets nearby, then you can install a fused connection unit with a 3A fuse to make a branch circuit for the light, instead of running a new lighting circuit all the way back to the panel. A fused connection unit can also used to connect a permanently installed appliance such as duct fan, instead of a plug and socket outlet. to stop people unplugging it to use the outlet. Here it's not technically a 'spur' but we have a habit of calling the fused connection unit itself a spur, or spur box.
Fused connection units were invented alongside fused plugs and the scheme of using socket outlet circuits of much higher rating than the plugs themselves. 32A circuits are popular, offering 7.4 kilowatts per circuit (compared to the 2.4kW of a 20A 120V outlet circuit), so a large number of typical appliances can be powered from one circuit. This is only possible due to the presence of fuses.
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