I want to install two spurs to my electrical ring main. I intend to install a 30amp 4 way junction box on the ring main. Can I run two spurs from this junction box as there are four connections? Ring main in, ring main out and two spurs. I will be grateful for any help given.
Electrical junction box wiring
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No, you should only take one spur from a ring final at any given connection point, whether it be an existing accessory or a junction box. If you can find some way of breaking into the ring rather than spurring from it, that would be preferable, second to taking a spur directly from the back of an existing accessory. A good electrician will try to avoid the use of JBs if at all possible, and they certainly shouldn't be installed under the floor or in another inaccessible location if the connection is made via screw terminal.
EDIT: I think I should clarify some terminology here. You mention you are installing 'spurs' - do you mean an electrical accessory containing a fuse and, possibly, a switch? If so, you're probably taking about a Fused Connection Unit, FCU for short.
A spur is a length of cable taken from a point on the ring to an electrical accessory, the said length of cable not directly forming part of the ring circuit.
EDIT: I think I should clarify some terminology here. You mention you are installing 'spurs' - do you mean an electrical accessory containing a fuse and, possibly, a switch? If so, you're probably taking about a Fused Connection Unit, FCU for short.
A spur is a length of cable taken from a point on the ring to an electrical accessory, the said length of cable not directly forming part of the ring circuit.
Thanks for this. I intend to run the spurs to terminate in 13amp switched sockets. One for a dishwasher and one for a double switched socket for general use of worktop kitchen appliances. Toaster, food mixer iron etc.
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It would be better to extend the ring - so instead of two spurs you split the current ring, connect one leg to the first socket, a new bit of cable between the two new sockets, and the other leg to the second socket. If you need to extend the existing cable you could do it with crimp connections, rather than junction boxes since I'm assuming you would be intending to do this under a floor or whatever?
When you submit you plans to Building Control for approval, what will you say about how you intend to comply with Part P of the Building Regulations?
That is quite a load for a connection taken through a junction box. A screw in the junction box becomes loose and reduces pressure on the copper wires and you will get a hot spot there. ( Screws do loosen over time as copper softens. happens quicker if the copper gets warm due to heavy currents).
Take the time and effort to do the job properly by extending the ring.
Screws in the terminals of sockets can also become loose over time but
[1] the problem is often obvious
[2] the resultant damage is much easier to repair than having to get to a junction box ( floor boards taken up maybe ? )
They do NOT comply with BS7671 for use as a non accessible joint.
what doesnt?
Maintenence free junction boxes installed in a location which is not accessible for maintenence, I&T.
The "maintainance free" connectors that depend on the pressure exerted by a spring cannot sensibly be considered as maintainance free unless they are install in an inert atmosphere as they are NOT gas tight metal to metal joints ( gas as in corrosive gases and vapours in the atmosphere )
copied from
http://www.ami.ac.uk/courses/topics/0100_gls/glossary/glossg.htm
Atmospheric conditions under floor boards can give rise to corrosion on metal in contact with air. Hence soldered joints should be heat shrink sealed to exclude the atmosphere from the joint.
Damp air being the most likely in domestic use leading to green "rust" on the copper. There are other air borne materials that create a dark brown, almost black coating on the copper.
While the following informative site is coming from the automobile point of view the principles of gas tight joints apply to all electrical connections.
http://www.sw-em.com/gastight.htm
copied from
http://www.ami.ac.uk/courses/topics/0100_gls/glossary/glossg.htm
Atmospheric conditions under floor boards can give rise to corrosion on metal in contact with air. Hence soldered joints should be heat shrink sealed to exclude the atmosphere from the joint.
Damp air being the most likely in domestic use leading to green "rust" on the copper. There are other air borne materials that create a dark brown, almost black coating on the copper.
While the following informative site is coming from the automobile point of view the principles of gas tight joints apply to all electrical connections.
http://www.sw-em.com/gastight.htm
how come i read from a link on here that they are.
Hager would like to have you believe that they are, and possibly other manufacturers too, but there's the key word - manufacturers.
It's up to you to interpret the regs, as it's been discussed to death here before if you care to try and dig up the old topics, but I think you have to be pretty imaginative to interpret them in such a way as to consider maintenance free JBs to be suitable for used in inaccessible locations.
Maybe someone was wrong. Can you provide a link to where it was written?
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