To twist or not to twist?

Discussion in 'Electricians' Talk' started by Factory Cat, Dec 16, 2004.

  1. Factory Cat

    Factory Cat New Member

    Gents
    Just about to start the second fix on my house re-wire (sneaking in before the part P door closes on me) and would like your advice/opinions. When terminating the 2 live, neutrel and earth cores of 2.5mm2 ring main cables into a socket outlet etc,is it advisable to twist the 2 cores together or not?. Checked through the regs book and OSG but cannot find any definate answer.

    Cheers FC
     
  2. dingbat

    dingbat New Member

    Don't twist. And don't leave your tails too short either.
     
  3. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    Do twist. The idea of twisting is that when twisted together and the screwed down, it's almost impossible for one of the wires to slip out. Screw down two single wires and you might not catch them both with the screw.

    Handyandy - really
     
  4. Beanzy

    Beanzy New Member

    Don't twist. If the conductor's two small for the termination then double it back on itself and terminate properly. But remember a socket outlet is designed to take 2x 2.5s.

    Anything else just stresses the conductors.
     
  5. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    Do twist. We're talking two wires here, so if you don't twist, how can you be sure that you have screwed down tight on both wires ? You would have difficulty doubling back both wires and getting them in without making a tight bend and risking snapping off. There always seems to be enough space beside the screw for a single wire to be pushed into when tightening the screw.

    Handyandy - really
     
  6. Beanzy

    Beanzy New Member

    They go in side by side. The big fat screw presses down on them and they get forced together by being compressed into the curve of the termination.

    If the conductors are twisted together then they get stressed when disconnected for testing/fault-finding. The twisting itself may stress the conductors enough to reduce their CSA and leave them more likely to snap once they heat up under load. They may feel fine wen they first go in and are given a tug but with time may deteriorate.

    I've never come across any electrical training craft books that tell you to twist conductors together. I used to do the cpcs as I used to copy one of the old engineers who I trained under. I gave up once the consequences were pointed out to me.
     
  7. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    Sorry to go on about this, but I fail to see how twisting the wires together would put MORE stress on them, than BENDING them over 360degrees. You are advised somewhere that you shouldn't bend the whole cable 90degrees as this is too stressful ?????? And look at the round-ended screw in the round hole pushing one of the single wires to one
    side. You can see it happening as you tighten the screw.
    And now you've dented the single wire you have reduced the strength by half. Take that out once and break it off with your finger, no problem. Eh ???
     
  8. Sam Dingle

    Sam Dingle New Member

    This is a good discussion.
    So far no one has started to hurl abuse and every one is putting forward very valid points!

    My addition would be, how many twists and over what length of strip back!
    I tend to strip back 16mm and depending on how I feel I'll either twist and trim back to 11mm ish
    or
    fold over 180 degrees

    I think if you do twist you should only have 1 full twist.
     
  9. MJA

    MJA Active Member

    I was taught at college that it was bad practice to twist, so don't twist. Also, if your socket outlet has two earth terminals then put 1 in each terminal.
    My on-site experience has shown that in the vast majority of cases where a conductor has broken, they were twisted together!
    Even more annoying is people who twist ring CPC's together in a CU and use 1 piece of sleeving. Bloody nuisance when it comes to testing.
     
  10. part-p.org.uk

    part-p.org.uk New Member

    Well when I started in shipbuiling training we did not twist conductors and always left enough spare in the JB to allow for the connection to be remade. Fussy customers the Navy.
     
  11. l00pd0g

    l00pd0g New Member

    DON'T TWIST

    Andy
     
  12. dingbat

    dingbat New Member

    As a rule of thumb, twisted conductors generally indicates a DIY job (or kitchen fitters, builders, etc). And if a twist has to be undone for, say a change of accessory with terminals in different positions, you end up losing the twisted portion. Do this a couple of times (not unheard of) and you no longer have sufficient conductor to connect.
     
  13. Rabbit Rabbit

    Rabbit Rabbit New Member

    Is twisting something that was done only when stranded conductors were around?

    For my input I dont twist, so NO.

    RR
     
  14. l00pd0g

    l00pd0g New Member

    Some people might say that twisting solid cables will reduce the CSA and therefore the current carrying capacity.

    I wouldn't that twisting stranded pairs would do this. Twising stranded cable may even be a good idea as it ensures that there are no stray strands not getting connected.

    Andy
     
  15. Jonny

    Jonny New Member

    Don't twist. Makes testing a nightmare and introduces a weakness when re-connected. Easy for only one of the two cables to be clamped by the screw in a terminal. Have seen it done many times on older small stranded cables though. I twist larger stranded cables INDIVIDUALLY, so no strands do not get connected, but don't twist the two complete cables together.
     
  16. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    So, there are a lot of you saying "don't twist".
    Some reasons given are that you will lose the twisted portion when removed once - surely you lose the single ends if untwisted as these have been flattened and weakened by the first fit,and should be redone ? And some reactions seem to think that the wires have been twisted to almost breaking point, but only a fool would do this. But a twist just enough to stop the two wires from separating under the screw and will come apart easily when screw is removed.
    This is the way I see it being useful.

    Handyandy - really
     
  17. Addie

    Addie New Member

    Dont twist it is a hellier for testing and fault finding
     
  18. seylectric

    seylectric New Member

    I was taught at college that it was "bad practice" to twist, but nobody knew why!

    If you check your terminations are tight then the "loose wire" problem doesn't arise. I'm not too happy that the latest consumer units only have one screw though, the old "Wylex" units always had two and you never found a loose connection when ripping out the old box to put a new one in. The loose screw problem seems to happen a lot with the latest stuff though.

    Always twist the ends flex though, it does avoid those stray ends, but don't twist two together!
     
  19. BigT727

    BigT727 New Member

    Hiya folks

    Some might know me from the electricians site on MSN nice to see you again fellers. Well Ive been observing your postings and I thought its about time to put my penny worth in, hope I dont offend as this is not my way.

    Right as to the twisting or not, the answer is not. Yes we all have done it and some still do, but if you think about it, when you test its alot easier not to twist. this is when testing to find faults etc you need to disconnect wires, so if they are twisted they may break. This may leave you with a short wire so my advice is dont and I have seen it somewhere where it says its not the right way to do it. Another thing I was always taught to strip twin & earth using a knife, this is a slower method so like everyone I changed to using a pair of side cutters. A mate of mine was at college and was told that stripping cable using side cutters puts stress on the cable, the proper way was with a knife, and that was a question in an exam. Answer me this though, when you have stripped MICC cable ( Piro ) to those who dont know, you pull the core with plyers so whats the bloomin difference, what a load of cods dont you think.

    Also fellers I have seen many postings with regards to the Part P, I think we are all in favour of getting rid of the cowboys and finally electricians getting their worth, but this isnt the way. Part P is only about money, if work isnt done correctly or the installation isnt kept in good working order or tested regularly then the insurers wont pay out, but are they informing Joe public, yes but not quick enough. The other thing is if all has to be certificated then the tax man knows everything we are doing so no chance of cash jobs or discounts. Also if you think about it, why are they allowing some work to be carried out by joe public, the answer is so B&Q, Wicks etc can still sell they wares, or they wouldnt be happy. If we went like the gas we would be the only ones allowed to touch electricity, thats the best way.

    Regards to you all and have a very happy christmas

    to the dam idiot who thought of part P wait till some electrician comes to your house if you have a problem, boy will you be sorry then.
     
  20. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    I see that some are still not reading my posts all the way through, so I say again, NOT to twist them to breaking point, so if anyone says they are liable to break if you twist them, they are still not reading properly. AND you should still have to renew the end if you have removed a singly-wired connection, so if anyone says you will have to renew the end if they were twisted,
    they are still not reading properly.

    Now, I know this below is not definitive law or rules, but
    advise is given thus:

    Step 5: Connect the existing wires to the terminals in the new socket - red to the L-terminal, black to N-terminal and green/yellow to E-terminal. When two or more identical wires are connected to a single terminal, they should be twisted together with pliers to ensure a good connection. Make sure all the wires are held securely and that no bare wire is exposed. At the other end, twist the new wires together with the matching wires from the ring main, and insert them in the terminals of the original socket on the other side of the wall.
    ......B&Q Fitting an extra socket

    Ensuring that the power supply is off, remove the conductors from the last point on the radial circuit. Twist together the conductors from the old cable with the new cable i.e. red to red, black to black and green/yellow to green/yellow, (if the earth wire is bare then it should have a green/yellow sleeve placed over the its bare part). Insert the twisted conductors back in their appropriate screw terminals on the back of the socket i.e. red to Live (L), black to Neutral (N) and green/yellow to Earth (E or ), and replace the socket
    .......Diynot.com Converting a radial circuit to ring circuits

    And surely somewhere you are advised that you should make the best possible connection, and NOT whether it makes it easier to test or not ??????

    Handyandy - really
     

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