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Borrowed neutrals or borrowed lines?

Discussion in 'Electrics UK' started by ericmark, 21 Jan 2020.

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  1. ericmark

    ericmark

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    Just watch John Ward video this is unusual, must be the first one where I don't agree with what he says.
    two-way-real-borrowed-neutral.jpg This is how I would show shared lines, very dangerous as although it will work without having a RCD, the left hand light has two major faults, so shown light is off, switch the left hand switch and all is OK, however if instead right hand switch for left hand light is used then left hand light fed from right hand lamps fuse, and if both switched then lights remain off but the two circuits are connected together.

    If a pair of RCD's are added then clearly it will trip them. I wonder if a video can be re-done? He seems to be using what I call a school boy two way switching, two-way-school-boy.jpg although it will work, it would likely cause interference as it is a large loop, and not easy to in practice wire.
     
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  3. EFLImpudence

    EFLImpudence

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    I can't think why.

    Why? That is not the usual situation.

    Don't wire it like that, then. You have just included an additional fused line for no reason.

    upload_2020-1-21_17-36-28.png

    Are you saying you have made a dangerous circuit just to avoid interference?

    Of course, The circuits will have to be separated if you want two circuits And two RCDs.

    Why?

    It is known as the 'conventional method' for some reason.

    It is the adding of the two-way system which causes the borrowed neutral situation, as JW says.
    Obviously alterations have to be made to bring it up to modern methods - hence the name 'conversion method'.
     
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  4. JohnW2

    JohnW2

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    I thought that the term "conversion method" arose because it provided a fairly easy way of 'converting' one-way twitching to two-way, rather than because it was 'bringing things up to modern methods'?

    I have to say that I only became aware of 'the modern method' relatively late in life, and for decades had been using the old ('conventional') method of 2-way switching, probably as recently as within the last 20 years.

    Kind Regards, John
     
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  5. EFLImpudence

    EFLImpudence

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    As I have always understood it and without searching:

    Two-strapper method is conventional - presumably for the reasons you say, and

    Three-strapper method is conversion - presumably because we convert the conventional.

    It might be one of those things and I have always understood wrongly.
     
  6. JohnW2

    JohnW2

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    It's worth noting that the 'two-strapper method' does not necessarily imply a T+E cable between switches. When I implemented it, I nearly always used 3C+E (carrying N as well as the two strappers), not the least so as to avoid the 'radiation' problems associated with 'unbalanced cables'.
    I have never personally 'converted', and nor have I heard of anyone else 'converting' the 'old' method of two-way switching to the 'modern method'. As I said, my introduction to the 'conversion' method was in relation to 'converting 1-way to 2-way switching.
    ... or me. Who knows?!

    Kind Regards, John
     
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  7. EFLImpudence

    EFLImpudence

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    Ok. Quick look on Flameport's site agrees with you. Couldn't see quickly mention of 'conventional'.

    However, would not curing the borrowed neutral by changing two strappers for three be the same?
    It depends which one one did first, I suppose.
     
  8. JohnW2

    JohnW2

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    I thought it was usually called 'traditional' (which, as I've said, it was for me for much of my life), rather than 'conventional'.
    I'm not totally sure what you're saying - but, yes, if (as was my practice) one runs a neutral conductor as well as the two 'strappers', the the issue of borrowed neutrals should not arise.

    Kind Regards, John
     
  9. EFLImpudence

    EFLImpudence

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    Only if one has neutrals at the switch.
    If not, a lot more work.

    Normally, to get rid of the borrowed neutral on the usual stair circuit, an additional line strapper is required. See 3'40 in the video.
     
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  11. JohnW2

    JohnW2

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    Well, when I (usually) did it (from scratch, not as a 'conversion'), I obviously had a neutral available at the switch, otherwise I wouldn't have been able to rin a neutral in the 3C+E. When one is converting 1-way to 2-way switching there is, indeed, very likely to be an absence of a neutral at the switch.
    Indeed, but I don't think that's usually got much/anything to do with any 'conversion' - the borrowed neutral will usually/often exist because of laziness when installing the wiring in the first place, won't it?

    Kind Regards, John
     
  12. Risteard

    Risteard

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    It is indeed.

    And it's still the most common method in Ireland to this day.
     
  13. JohnW2

    JohnW2

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    ... and probably the only method I've ever used (for new wiring) in England.

    As I've said, I see no problem with the method if it uses 3C+E which carries a neutral as well as the two switch wires ('strappers'), but it's not really nice to have T+E carrying just the two 'strappers' with the neutral path somewhere entirely different (and tempting people to use a 'borrowed neutral!).
     
  14. ericmark

    ericmark

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    May be it is area by area? I was taught from word go to wire two-way-real.jpg as shown here, I used this diagram to make the one showing dangerous method as that is what I have found over the years has been the way the circuits have been split.

    Originally one can often see how the borrowed line would have been OK, however I agree with @JohnW2
    the use of twin and earth clearly has a problem with EMC, but it would have been one circuit for all lights, and the circuit I have shown in first post would be OK if only one fuse feeding both sides.

    It is where at a latter date, some one has decided it would be better if upper and lower floors were split, and often there were two cables in the fuse box, one going up and one for ground floor, so easy job to split and so increase the current that could be used for lights, often found required when down lighters added.

    I found in the early years you would have two reels of cable for lighting, one red and black, and one twin reds, and the boss rarely supplied one with red, yellow and blue so one would need to run two twin reds to do two way switching if you did not borrow a line. I also found twin reds a PITA as one had to work out which was which, far easier with red and black.

    The bringing line into the com was not liked, as it often needed a connector block in the switch. two-way-school-boy-cables.jpg I have put grey circles around each cable, and brown box with yellow centre to show connector block, which was why the other method was used in this area, as did not require those connector blocks.

    I find it interesting that the connector block method was used in other areas of the country, and it does make more sense for John Ward to show that method if that is how it was done down South where he lives.
     
  15. SUNRAY

    SUNRAY

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    I don't think it originates from laziness, in the early days of VIR or cotton/rubber singles in tube it was just done that way. In fact I'll go further and say shared neutrals [so much more descriptive than borrowed IMO] used to be quite a common idea on power circuits too. And 3 phase lighting often uses shared neutrals, certainly used to be if not any more.
     
  16. JohnW2

    JohnW2

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    I suppose it's actually rather moot since, in the days we're talking about, it was probably rare to have more than one lighting circuit in a domestic installation, so the question of borrowed/shared neutrals probably didn't arise, so long as it was a nutral derived from a (the) lighting circuit.

    Kind Regards, John
     
  17. SUNRAY

    SUNRAY

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    The first time I came across the 'conversion method' it was this:
    upload_2020-1-21_22-17-11.png
    with a wire nut behind the switch, it didn't work.

    thinking it was wired wrong I did this:
    upload_2020-1-21_22-18-13.png
    by adding another join it worked OK, no idea why it didn't work initially, but that is how it was left for more than 20 years.
     
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