Hi Question , People on here and other forums always say do not use junction boxes if possible. I am going to wire up a loft area and the best way for me will be to have a couple of junction boxes along with some 13A double sockets . Now it seems to me that there is usually no restriction as to how many sockets I can have ( they will all be fed from a 16A RCBO ) , but my question , is a socket not a junction box ! , if so , then there is plenty of junction boxes in houses etc , and a 45A junction box has thicker connectors than a 13A socket ! , or am I not on this planet ! . regards Crankshaft
Although they are best avoided - for obvious reasons - if you use 'maintenance-free' JBs (there's a preferred brand on here but I forget which it is) you should be fine. These have spring connectors instead of screw-down, and also grip more tightly if the cable is pulled. Virtually no chance of them becoming loose. Screw terminals can loosen over time for all sorts of reasons - the ductility of the copper wire, movement when peeps move cables around when in the loft, and even from the AC 'hum' in the cables, I understand. It is pretty common to find less-than-tight JB screw terminals when redoing work - scary, as they can then overheat.
I must say I have never had a problem with old fashioned junction box screws coming loose but these are deemed not to be maintenance free. My observation on using maintenance free junction boxes is that it is possible for example to push in the live and neutral satisfactorily and not get the earth in fully, particularly when the earth (now called CPC) is of lesser diameter than the other wires, such as 2.5 T & E. I am just DIY and these maintenance free junction boxes are intended for use by professional electricians. If any amateurs ignore the Part P regulations IMHO they should at least obtain and use test equipment necessary to do the two dead tests (continuity and insulation tests) and the two live tests (loop impedance and RCD tests.) This assumes your installation does not have an earth rod (TT). If you do any of this incorrectly and have a fire then your insurance company may not pay out. It all depends on your level of skill and confidence and outlook on life.
In a properley designed system,there should be no need for joint boxes,screwed type or any other.However there are occasions when it is unavoidable,there are literally thousands of JB's in houses throughout the country,most cause no problems however if not correctly tightened or fitted they can cause issues.The regs state that JB's should not be used in inaccessible locations for example under floors or above ceilings nor should they be buried in walls! However there was some argument a while ago regarding the use of JB's under floors if there was access to it via a loose board,some said it was acceptable some said it wasn't.The maintainance free connectors are made by several companies and several types,Wago and Ideal are the 2 makes I use,avoid cheap stuff off Ebay,there are fakes.Then you have a choice of pushfit or lever connectors,pushfit as the name implies simply push onto a stripped cable,these can only be used on solid core,for example modern 2.5 T&E where each core is made up of one strand of copper.For multistrand or flexible cables then lever connectors are used,these have a tab or lever which is pulled back releasing the clamp,the cable is inserted and the lever pushed back clamping the cable securely.As with any joint it must be made in an appropriate enclosure.
No that's not true. A junction box is perfectly okay if you can see it or easily access it. The problem is junction boxes used in inaccessible places, like under floorboards, where they will be hidden. So if you are planning on using them in a loft that's not a problem. As for treating sockets as a junction box then no they aren't by definition but they are jointing two or more wires in the same terminal, the difference being they are easily seen and accessed. All as philthespark eloquently said.
I was not going to fix them were you could not get at them ( but I must have been able to get at them if I put them in ! ) the point I was trying to make was that people say try not to have junction boxes in the design of a circuit whether or not you can access them , but has I have said , each socket is a junction box in nature ( whether it is called it or not ) and you can fit has many as you like as long has the circuit is protected from overload , so I don't see why they say don't use junction boxes which usually have ( 45A ) a thicker joint that a socket . PS : I was not saying treat or use a socket as a junction box ! .
I understand what you are saying and, yes, a socket has a termination point that can also be used as a junction. The issue that you have probably picked up with junction boxes is when a new installation, or section of new wiring, is being installed there should be absolutely no need for any interim junction points on the wiring. The way that installations should be designed is so that the ends of the cables are present only at each accessory (switch, pendant, socket, FCU, etc etc). This means that faults can be found without having to rip down ceilings, chop holes in walls, pull up carpets and floorboards, etc. A junction box is often needded when one is adding in to an existing circuit and this is often unavoidable. These days, the MF junction box is the better way to do it. Multi-way junction boxes used to be the standard way to wire lighting circuits for houses. Like this Or a much worse bodged version like this
Never mind the wiring mess , what about were the pipe is laid , I bet a lot of thought went into that installation
I had a 6mm T&E cable here wrapped around a 22mm gas pipe,not one wrap, but several wraps, no logical reason as to why, I ended up removing & replacing cable properly.
No worries crankshaft I knew what you meant. Its not that you shouldn't have jb's mate. On a new installation it would be poor design to have to use one but quite often they can come in useful to save on cable. It's swings and roundabouts really. Its not bad practice or anything as long as installed well they are as good as any other part of the installation.
One problem with using JBs, is quite simply that the more joints there are in a cable, the greater the chance of one of those joints failing. Yes there are joints at sockets, FCUs, etc. but those joints will be there anyway and they are usually visible and easily accessible for periodic inspection. Just to add to what Devil's Advocate said, traffic, train lines and even aircraft can also cause vibration, loosening screw terminals or even causing cables to chafe on sharp edges.
Yes quite agree with you , but not to long ago I went to a friends house to change a double socket , for a double socket + usb , it was a spur from the lower ring main and boy did I struggle with it , there was 3 x 2.5mm2 cables going into each L -N -E , now a junction box just under the floorboards would of made that so much easier for me ( there was a access to get under the floor right next to were the socket was ) , there was not a lot of loose to pull it out very far also , as in most socket back boxes .
if were going to regs don't forget Minor works cert for all of this. . .no? If I had to do it I would be expected to, these regs are for everyone
13A sockets are designed to accept up to three 2.5mm2 cables or two 4mm2. The secret to easy wiring is to ensure the wires are all the same length going in to each terminal and the stripped copper conductors are all cut the same length and straight. Then you should be able to push them in to the socket terminal quite comfortably. Some sockets can be a pig if someone else has cut the wires on the short side. Wires that are all different lengths work against you. I have found the rule in this situation is to put the shortest in first.
There is usually not a lot of room at the rear of a 25mm back box when you shove the socket back in ! .