Radial vs Ring

Discussion in 'Electricians' Talk' started by Hans_25, May 20, 2019.

  1. robertpstubbs

    robertpstubbs Screwfix Select

    Can't the length of the circuit be reduced by using joints (accessible or permanent)?
    RorR.jpg
     
    Last edited: May 22, 2019
  2. gas monkey

    gas monkey Well-Known Member

    Sparks will be having badys
     
  3. robertpstubbs

    robertpstubbs Screwfix Select

    Personally I would prefer to wire 1 x 4mm2 wire into a socket terminal rather than 2 x 2.5mm2 wires.
     
  4. Hans_25

    Hans_25 Screwfix Select

    That's a really good point and I had wondered, if using a 4mm radial, whether that approach to wiring would be a "good" idea. Would be a lot easier at the sockets as only 1 cable to terminate, uses less cable and keeps the overall length down but of course adds in the cost of WAGOs or similar.

    Thoughts on this approach?
     
  5. Coloumb

    Coloumb Screwfix Select

    It's often used in offices as a distribution system with a central power rail track running down the middle of the room for desk to connect to. It's not something that is done in a domestic environment. Tbh I don't really "get" the point to this thread, if the spark doing the work for you want's it done with rings then your going to have a hard to convince him otherwise, specifically as technically tou will be working for him. Personally I would just let him get on with his job.
     
  6. Hans_25

    Hans_25 Screwfix Select

    Yes I will be following my Spark, just interested in the pros and cons of radial vs ring, which I think are laid out in this thread. I am intrigued to understand why a certain approach would be followed over other approaches.
     
  7. robertpstubbs

    robertpstubbs Screwfix Select

  8. mcooper2406

    mcooper2406 Active Member

    Just a laymen here with a bit of electrical experience in the past but would the method above not increase resistance due to the multiple junction boxes that would need to be used?

    Or is that a bit of a misconception?
     
  9. robertpstubbs

    robertpstubbs Screwfix Select

    Would the joints in JBs be worse than those in socket terminals?
     
  10. Hans_25

    Hans_25 Screwfix Select

    I would think a connection via a wago block would be a lot better than a screw-down compression fitting in a socket.
     
  11. unphased

    unphased Screwfix Select

    There are other aspects to the use of rings that are worth consideration. One is that rings are open to misuse, that is, they can be added to without proper application of rules, such as spurs off spurs, and can be broken by unscrupulous meddlers. All conductors in a ring circuit must be continuous for it to behave as a parallel circuit, if one or more conductors are not continuous it may not be apparent to the user, as an open ring will still allow sockets to function if one leg is still attached. A broken conductor presents safety compromises, too as the current carrying capacity of a broken ring is reduced. The electricity finds it way round the other leg. I have found numerous 'rings' that have a discontinuous neutral, phase or cpc conductor and it is very frustrating to find as the location of the break can be extremely tedious and time consuming to find and correct. Rings are also very time consuming to test and few are actually fully tested. For example, r1, rn, r2, then cross connecting the conductors at one point and testing across the conductors at EVERY point to prove R1+R2 and R1 + RN. This simply is not done and I would doubt the honesty of anyone who claims that they do, I think I did the full test regime once on my very first ring install and have never done it since.

    So there is a lot to be said for using a radial because they are much easier to install, test and maintain. Any breaks in the conductors will be immediately apparent as the circuit will be dead beyond the break. I accept that cpc is the exception but nonetheless it is still a much easier circuit to use than a ring. As a domestic electrician I prefer to only use one ring in a house, the kitchen, elsewhere I prefer to use 20A radials for the sockets. Remember, lighting circuits are only ever installed as radials in a house anyway. So there are clear advantages of a radial over a ring.
     
    HappyHacker likes this.
  12. unphased

    unphased Screwfix Select

    The diagram shown above is also a misconception of how a ring is installed. A ring is supposed to reasonably distribute the loads around it. That diagram above shows an unevenly loaded ring with all sockets on one half. Another negative point against rings. They are rarely balanced and tend to be just daisy chained sockets with a long wire back to the CU to complete it. You often hear mention of the centre of a ring. It is nearly impossible to identify the true centre if the sockets are all on one side. It won't technically be the middle of the ring, such that both legs are the same length. If the loads are predominantly on one side, the 'middle' will be somewhere amongst the lopsided load, the point where the load is even which might be overloading one leg.
     
  13. ajohn

    ajohn Screwfix Select

    I'm not and electrics man but have been involved in that area at much higher currents and also electronics.

    Rings are superior as they spread loads better than radials. All down to current causing heating and heat causing the resistance of the copper to increase. That means that say one run to the CU is shorter and initially has a lower resistance it will warm up and more current will flow through the longer run. Forget that and the current will share between the 2 circuits anyway. There is also probably more earth cross section area available but personally I don't know what sizes they use for that.

    4mm is the odd one really also 6mm having the same rating as a 2.5mm ring. Heat dissipation may be the reason for that. 4 might be allowed for commercial reasons - already about, pulling a cable through etc.

    I have seen comment that all a kitchen needs is a 2.5mm radial and couple of sockets. Can't say as I would be happy with it.

    John
    -
     
  14. unphased

    unphased Screwfix Select

    As long as the correct sized cable is used for the radial it will be just as effective at coping with its design load. 4mm2 is a lovely cable to install, it is really supple because it has multi-strand conductors. 2.5mm2 and smaller are all single strand conductors making them very 'stiff' in comparison.
     
    Hans_25 likes this.
  15. unphased

    unphased Screwfix Select

    A joint in a cable is always going to be a weak point. So yes you are correct, the more joints the more likelihood of introducing impedance. That is why it is so important to tighten terminals correctly. A loose connection is effectively a high resistance joint and as you know this creates heat, the major cause of fires in electrical installations, loose or badly terminated joints overheating. CU fires are always due to this. Loose tails in the main switch, badly seated mcbs on the busbar, badly tightened terminals on the neutral bar or mcbs, all examples of high resistance joints. A properly designed and installed circuit is never going to overheat.
     
  16. ajohn

    ajohn Screwfix Select

    It's the load into a kitchen that bugs me with 2.5mm radial. Some may even plug a heater in at times. Then kettles, toaster, coffee machine and other bits an pieces.

    I vaguely remember reading somewhere that 4mm had been fine for powering cookers for a very long time without problems. Might be why it's still ok in domestic situations. Some one was arguing , IEEE if I remember correctly that it shouldn't be allowed.

    People might not take the thermal effect I mentioned seriously but current will share according to the resistance that is there no matter how low it is. Watts = I^2 R and watts = heating and as R goes up so does the heating.

    John
    -
     
  17. 2.5 Twin and Earth is readily available as a stranded cable, rather than a solid one,it is a dream to work with although dearer than the solid one.Which is the reason it does not get used as much.
     
    retiredsparks likes this.
  18. Pollowick

    Pollowick Screwfix Select

    What has teh IEEE got to do with domestic UK electrical installlations?
     
  19. HappyHacker

    HappyHacker Active Member

    I generally use 20A radials with 2.5 for power. A kitchen would have more than one power radial. For the reasons mentioned by unphased I much prefer them to rings especially with the low cost of MCBs and RCBOs.

    On the subject of rings many many years ago I was taught to loop the cable into and out of sockets when installing rings so the conductors were never broken, a real PITA to do but removed the risks associated with loose connections, of which over the years I have found many. Usually in a junction box somewhere under the floor which has just been relaid with expensive laminate. Having spent so many hours finding and fixing problems on Ring Final Circuits (RFCs), caused by alterations, age and poor installation, I have come to the conclusion that in domestic premises they should be banned.

    When installed and maintained by competent people ring circuits can be very advantageous especially in the areas of power distribution but no one is going to let an untrained amateur or even an untrained professional loose on designing and installing an 11kV ring circuit.
     
  20. robertpstubbs

    robertpstubbs Screwfix Select

    Is this better? How many connections per socket here?
    RorR3.jpg
     

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