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Re terminating ancient cables

Martyn
Hi Folks, 


So I may have a job in the offing where I will need to temporally re terminate these 3 cables, the one on the right is only 1m long so I’ll just replace it. 


The other two are rising mains from the 1940’s each feeding 20 flats, I believe them to be armoured PILC’s though happy to be corrected, the lead is being used as the earth. 


Has anyone re terminated similar and are there any pitfalls that may scupper me? 


The re termination will only be temporary whilst the new building network is being installed.89f8b92115c4d5d4e672a2d7771fc855-huge-a8ae4b2d-f17a-4e4e-a594-4469fa0801a0.jpg



Cheers 


Martyn
  • 0
    I would not disturb the old cables in any way, far too much risk of failure.

    Leave the existing cables and the metalwork into which they are connected alone. Use the existing switchfuse, or whatever as a joint box. The existing cable cores are presumably terminated onto some form of terminal in the item illustrated.

    Don't disturb these cable ends or the terminals into which they are connected, but connect new conductors thereto, perhaps by soldering.


    The earth continuity looks a bit dodgy, an upfront time delayed 300ma RCD might be prudent.


    If re terminating the old cables is completely unavoidable, then consider subcontracting this work to the DNO or to whatever subcontractor that the DNO use. They are experienced in this old stuff.
  • 0


    Hi. 


    Cheers for the reply, not sure there will be much option to leave them alone sadly, they are direct on to the Head - which I am hoping the DNO will replace as it and its fuses are physically broken. Looking at Lucy and Ryefield for multi service options at the moment (46 supplies to be re fed)

    1160ed3ca5f3b0e121465eed69b0cf8a-huge-44d147b4-9d80-4c5b-9ea6-5ceccec0eed3.jpg

     

    Cheers


    Martyn

  • 0
    The black box looks in good nick for 1940!  Can you get a pic of what is inside? - The "overbraided" earth suggests to me there maybe  no lead  after all - it may be waxed cotton, or some rubber derivative directly under the strands you can see - which in conjunction with the artful use of builders band, rather look like an addition to provide some  CPC functionality at a later date. Or maybe there is some lead, but what we would now call  Zs was a bit high.


    edit - your second post arrived as I posted this. The bigger photo changes it a little - perhaps the braid was original after all. It will need unpicking with very great care.


    I'd suggest you may want a back up plan for what if - even if it is a roll of swa on "sale or return" that hopefully stays in the van and gets returned, but maybe  gets run out of the landing window and back in again lower down the wall if the worst happens and it all suddenly crumbles before your eyes. (The DNO round here have been known to power a house up temporarily from a neigbouri's cut out using  a roll-end length of ABC across 2 front lawns before coming back for the next couple of days to dig a failed joint out.)

    They also carry tapes, sleeves and rubber 'wizard hats' to form 'site applied insulation' when changing cut outs and so forth. There are certainly techniques worth being ready for


    However, just in case it is not a mistake, for info, the 'how to do' for wavecon and other LV cables too, is illustrated in the UKPN jointer's handbook

    I suggest starting with UKPN jointers manual

     LV Jointing Manual Section 1&2 (big file, lots of pix.)

    LV Jointing Manual Section 3

    for your type of cable and many other situations.
  • 0

    mapj1:

    The black box looks in good nick for 1940!  Can you get a pic of what is inside? - The "overbraided" earth suggests to me there maybe  no lead  after all - it may be waxed cotton, or some rubber derivative directly under the strands you can see - which in conjunction with the artful use of builders band, rather look like an addition to provide some  CPC functionality at a later date. Or maybe there is some lead, but what we would now call  Zs was a bit high.




    The three cables coming out of the box on top of the head are all the same and 2 core they are lugged L1,L2,L3 left to right in to the head, the one on the right looks different but is just missing the steel outer, the phase lugs appear to have had 2 cores in each at some point in the pas as these are about 6" long and are taped up behind that 'make do' bit of trunking lid.


    The Neutrals from each cable are in to a terminal block with its screws missing so all a bit loose.


    The overbraid as you call it is actually very similar to that of the steel on modern swa, although, at no point is there any outer sheathing.


     



    edit - your second post arrived as I posted this. The bigger photo changes it a little - perhaps the braid was original after all. It will need unpicking with very great care.


    I'd suggest you may want a back up plan for what if


    The steal is definetely original, it can be seen throughout.


    I may just opt to run a temporary 2c swa to the ground floor 'Ryefield' style boards, bit of a waste though!

    LV Jointing Manual Section 1&2 (big file, lots of pix.)

    LV Jointing Manual Section 3



    These make for very interesting reading! Thanks.



    Sorry taking a while to reply, This new Forum interface seems pretty lousy at the moment


    Cheers


    Martyn
  • 0
    If they are really lead clad, that is better news.

    Unless it is rubber covered wire clad in lead, which was not really used in that sort of size,  it will be waxed or oiled paper under the lead, which is actually very robust, so long as you do not kink it sharply where the cores come out of the lead sheath, nor wind it up,  or the ends have overheated and lost their 'greaseproofed paper' appearance.

    Section 3.1is the 'how to ' for safely opening up paper insulated lead clad. Note the use of binding with a wire or a hose clip to retain the cable integrity during cutting, and to give a clean end stop to the 'peeling' process.
  • 0
    Cheers Mike, 


    I will have the meter or so spare from the right hand cable to do a bit of a test on and stripping it etc at least that will give an indication as to if I need to be putting some temporary SWA’s in!


    On the waiting game with the DNO at the minute, I am hoping they will terminate their service cable directly in to a new Multi service unit! 


    Thanks


    Martyn
  • 0
    Note the asbestos sticker on the DNO head, they are not going to work on it without throwing a bucket of water over it.


    From experience this will probably mean that a hole is dug outside the building, the supply cable cut and a new PVC cable run in from a joint to a new replacement head. Then a bucket of water can be thrown into the old head prior to it’s removal.


    So nothing is salvageable from outside to building onwards. It seems more sensible to install the new equipment and cables then swap them over in a day.


    I have not done that with more than seven flats and that was a busy day with metering services onsite as well as the DNO and myself, I was there until about half eight in the evening making the final connection as I could not finish until after everyone else had. Then metering services sent a lady the next day to ensure every flat was on the correct meter.


     Andy Betteridge
  • Former Community Member
    0 Former Community Member
    Those cables are almost certainly paper insulated lead covered with steel wire armouring. Originally they would almost certainly had hessian covering with an impregnated denso type paste. They look like they've dried through and lost the covering.


    Difficult to judge but they look as if they are terminated (badly) into an enclosure full of bitumen, or to a dry enclosure and the lead sheath has been formed over what is effectively a conduit coupler to act as a gland, and to allow clamping to the sheath for earthing purposes


    Personally, unless you have good experience jointing and terminating PILC, I would leave them well alone, even on a temporary basis.


    Probably easier to replace with a length of wavecon if acceptable to the DNO as a temporary BNO cable or use a length of SWA




    Regards


    OMS
  • 0
    I can’t remember where the asbestos is in that type of cutout, but it is likely to be in the phase barriers at least. It is conceivable that the DNO will want to cut it out and bag it, without opening it, due to the risk of releasing asbestos fibres in to the atmosphere. The usual method is a “dig and cut” to isolate it outside, then suitable cutters on the cables inside. If it has been obviously interfered with, for example the DNOs seals missing, they may request an asbestos survey of the immediate area first. 


    As OMS has stated, I would have expected the SWA to have an outer hessian wrapping, which may have failed and fallen away due to age, rodent attack, or overheating. If overheating was the cause, the insulating papers may be dry and brittle, the impregnating oil having long since dried. 


    Regards,


    Alan.
  • 0

    Sparkingchip:

    Note the asbestos sticker on the DNO head, they are not going to work on it without throwing a bucket of water over it.


    From experience this will probably mean that a hole is dug outside the building, the supply cable cut and a new PVC cable run in from a joint to a new replacement head. Then a bucket of water can be thrown into the old head prior to it’s removal.


    So nothing is salvageable from outside to building onwards. It seems more sensible to install the new equipment and cables then swap them over in a day.


    I have not done that with more than seven flats and that was a busy day with metering services onsite as well as the DNO and myself, I was there until about half eight in the evening making the final connection as I could not finish until after everyone else had. Then metering services sent a lady the next day to ensure every flat was on the correct meter.


     Andy Betteridge 




    Hi Andy, Cheers for your thoughts, Your correct on the Asbestos, there is a sticker on just about everything there! Most of it is for flash shields etc, they are all over the place. 


    Most of the meters here are in the individual flats which is good I suppose, that said unless there is 15+ on site there is not a hope in hell of doing a 1 day changeover.


    May look at getting a second supply tapped externally and removing the old one at the end... logistical challenges ahead. 



    Thanks


    Martyn

     

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