fused spur from junction box??? | DIY Doctor UK DIY Forums Sep 30, 2008Once you use a fused spur unit you can then supply as many sockets as you want from that in the same way as you can plug in an extension with 6 sockets as the total is limited to 13 amp. One big problem with ring mains is insuring they remain rings, most likely you can come off the junction boxes but you must test to ensure they are rings first. Adding a spur to a ring circuit from a junction box A spur comes off the ring circuit via a junction box, or more usually via an existing socket - which ever is easier. See also Adding a spur to a ring circuit from a socket. To install a spur from a junction box, you require a 30amp junction box. Locate the cable of the ring main as close to the new socket as possible.