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Meter Box SWA Meter Tails

  • 29-03-2020 12:34pm
    #1
    Registered Users Posts: 8


    Hi I'm installing 3 x 25 Sq SWA meter tails from meter box to CU (distribution board) for a new build standard 12 kVA domestic supply, larger cable size required due ET101:2008 A2 installation type derating 16 Sq T&E to below 63A. I have a 20M run so will also be fitting a 63A main overcurrent device in meter cabinet. My question is what is the acceptable way of glanding the SWA in the meter cabinet?

    Is the following sufficient:
    Gland SWA into Meter Box by drilling dedicated hole in enclosure. Terminate 2.5 Sq earth cable from gland armour using piranha earth nut with main 25 Sq earth protective conductor in the neutralising link. Since only the phase conductor is permitted in the MOD, glanding the SWA into the MOD enclosure would not be permitted.


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Comments

  • Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    I have a tendency to gland into steel boxes, like 4x4 ones in similar situations, if I was doing this type of job. Inner cable then out through a gland on the other side of the 4x4 box.

    If it was me id prefer to earth the SWA back to the MET in DB.


  • Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,516 Mod ✭✭✭✭2011


    The SWA cable armour only needs to be tied to earth at one end, so as Burthal says this could be dealt with at the distribution board.

    In the meter cabinet you could cut the armour off neatly and then put black heat shrink over it to finish (so as to ensure no sharp ends). You could then use a stuffing gland on the inner insulation of the SWA to gland it to the enclosure for the 63A main overcurrent device in meter cabinet.


  • Registered Users Posts: 193 ✭✭JL spark


    Do you not have to have a suitable gland on each end , I was pulled on this by my inspector


  • Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,516 Mod ✭✭✭✭2011


    JL spark wrote: »
    Do you not have to have a suitable gland on each end , I was pulled on this by my inspector

    In this case I am suggesting an SWA gland on one end ensuring that the armor is connected to earth on the other end there will be a stuffing gland (360 degree connection). As the armor is not the CPC (the is provided by a core within the cable) this is compliant unless there is something in the rules that says different.





    (I can imagine someone desperately checking right now)


  • Registered Users Posts: 8 Pentrep


    Thanks all for quick responses. Would ESB have any issue with metal box inside the meter box considering the meter box has to be made of a non conductive material?


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  • Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,516 Mod ✭✭✭✭2011


    Pentrep wrote: »
    Thanks all for quick responses. Would ESB have any issue with metal box inside the meter box considering the meter box has to be made of a non conductive material?

    I can’t see a problem with that but its up to the ESB.
    You could gland it into a 25 mm conduit box as this cable size takes a 25mm gland:

    https://www.enfieldelectrical.co.uk/pages/swa-cable-gland-chart


  • Registered Users Posts: 8 Pentrep


    2011 wrote: »
    The SWA cable armour only needs to be tied to earth at one end, so as Burthal says this could be dealt with at the distribution board.

    In the meter cabinet you could cut the armour off neatly and then put black heat shrink over it to finish (so as to ensure no sharp ends). You could then use a stuffing gland on the inner insulation of the SWA to gland it to the enclosure for the 63A main overcurrent device in meter cabinet.


    What would prevent the armour from damaging the XLPE insulation of each condutor or the filling material if an SWA gland isn't used. Is the heat shrink placed over the armour?


  • Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Pentrep wrote: »
    What would prevent the armour from damaging the XLPE insulation of each condutor or the filling material if an SWA gland isn't used. Is the heat shrink placed over the armour?

    The armour when cut neatly will not damage the sheath that is over the insulated conductors.


  • Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,516 Mod ✭✭✭✭2011


    Pentrep wrote: »
    What would prevent the armour from damaging the XLPE insulation of each condutor or the filling material if an SWA gland isn't used. Is the heat shrink placed over the armour?

    My suggestion was to strip off the outer PVC and armor at the same point with a hacksaw (as normal). Then place a piece of heat shrink that extends about 40mm either side of where the armor was stripped and shrink it on. That way the full cable goes into the heat shrink and the inner insulation (often grey) containing the 3 insulated cores comes neatly out the other side. The armor won’t damage the insulation. The conductor is protected by 2 layers of insulation.


  • Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    2011 wrote: »
    You could gland it into a 25 mm conduit box as this cable size takes a 25mm gland:

    Yea that can be done with a straight through box.


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  • Closed Accounts Posts: 173 ✭✭Podge201


    I always earth the strands at both ends. Just my preference.


  • Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,516 Mod ✭✭✭✭2011


    Podge201 wrote: »
    I always earth the strands at both ends. Just my preference.

    So would I when practical. I am just trying to offer an alternative.


  • Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,516 Mod ✭✭✭✭2011


    Bruthal wrote: »
    Yea that can be done with a straight through box.

    Yes, that is what I mean. SWA gland one side, bushing the other.


  • Closed Accounts Posts: 173 ✭✭Podge201


    2011 wrote: »
    So would I when practical. I am just trying to offer an alternative.

    I have never had a situation where it was impractical to earth both ends.


  • Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,516 Mod ✭✭✭✭2011


    Podge201 wrote: »
    I have never had a situation where it was impractical to earth both ends.

    Suppose you had an SWA glanding into something plastic ? Yes you could put an SWA gland on it but if you tighten is as much as you should for a proper earth connection with the armor. The risk is you may strip the plastic threads or damage the plastic enclosure. So it defeats the purpose of the gland. Also in many cases the earth tag / banjo will not fit inside the enclosure (such as a commando socket) so it must be external which frequently won’t work.


  • Registered Users Posts: 1,052 ✭✭✭Tuco88


    I agree, You will find alot of stuff in industrial and commercial work is made out of platic or fibreglass. One end of the S.W.A earthed is pretty common and acceptable.

    In some case's you will see an external bango with a fly lead connected to a conduit or exposed conductive part.


  • Closed Accounts Posts: 63 ✭✭Jayzee.


    Prob doesn't matter here but afaik good practice is to gland at the supply side

    I think I'm right in saying you could have problems with disconnection times on final circuits if the swa was glanded only at the far end

    If the swa was then cut accidentally near the supply end


  • Registered Users Posts: 193 ✭✭JL spark


    Pentrep wrote: »
    Thanks all for quick responses. Would ESB have any issue with metal box inside the meter box considering the meter box has to be made of a non conductive material?

    You won’t have room , esb meter ,esb isolater , tails protection and now your steel box 4x4 or 4x6


  • Registered Users Posts: 193 ✭✭JL spark


    Jayzee. wrote: »
    Prob doesn't matter here but afaik good practice is to gland at the supply side

    I think I'm right in saying you could have problems with disconnection times on final circuits if the swa was glanded only at the far end

    If the swa was then cut accidentally near the supply end

    If you only earth the swa at the meter side , don’t forget to run a cpc to earth the amour at the meter box


  • Closed Accounts Posts: 63 ✭✭Jayzee.


    JL spark wrote: »
    If you only earth the swa at the meter side , don’t forget to run a cpc to earth the amour at the meter box

    What other way is there of doing it, obviously you have to connect the swa at one end


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  • Registered Users Posts: 193 ✭✭JL spark


    Jayzee. wrote: »
    What other way is there of doing it, obviously you have to connect the swa at one end

    I’ve seen some earthed from the neutralising link , that was my point , has to be from DB


  • Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,516 Mod ✭✭✭✭2011


    Jayzee. wrote: »
    I think I'm right in saying you could have problems with disconnection times on final circuits if the swa was glanded only at the far end

    As always the disconnection time will be a function of:
    1) The earth fault loop impedance.
    2) The rating and characteristics of the protective device.

    When a disconnection time is calculated for a circuit within a steel conduit the CPC within the conduit used, not the conduit itself.


  • Closed Accounts Posts: 63 ✭✭Jayzee.


    JL spark wrote: »
    I’ve seen some earthed from the neutralising link , that was my point , has to be from DB

    Don't agree with that

    If you have a metallic enclosure at the supply side you would need to earth the swa and enclosure from the supply side imo


  • Registered Users Posts: 193 ✭✭JL spark


    Jayzee. wrote: »
    Don't agree with that

    If you have a metallic enclosure at the supply side you would need to earth the swa and enclosure from the supply side imo

    I’m not saying I’m right or you , this is what safe electric told me ,


  • Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    JL spark wrote: »
    I’m not saying I’m right or you , this is what safe electric told me ,

    They are not infallible. There should only be 1 neutralising conductor, and the swa should not be part of it imo. Anything earthed should be connected to the DB MET.


  • Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    JL spark wrote: »
    If you only earth the swa at the meter side , don’t forget to run a cpc to earth the amour at the meter box
    Jayzee. wrote: »
    What other way is there of doing it, obviously you have to connect the swa at one end

    Well if earthing at one end, running a long earth wire from the DB to the meter end would seem less intuitive than simply earthing the end at the DB.


  • Registered Users Posts: 8 Pentrep


    JL spark wrote: »
    You won’t have room , esb meter ,esb isolater , tails protection and now your steel box 4x4 or 4x6


    Agree the meter box is already fairly conjested.


  • Registered Users Posts: 8 Pentrep


    Bruthal wrote: »
    Well if earthing at one end, running a long earth wire from the DB to the meter end would seem less intuitive than simply earthing the end at the DB.

    Agree would be somewhat impracticle to run an additional earth cable in parallel with the SWA from the meterbox back to the DB MET. I am leaning towards the suggestion of heat shrinking the armour in the meterbox (no metal box due to space restrictions) and just earthing at the DB end. Maybe it could be argued with Safe Electric that it is not reasonably possible to gland both ends. Extract from the Safe Electric December 2018 newsletter below.

    Adequate electrical conductance shall be provided between metal sheaths or armouring of cables and the earthing terminals of equipment. This requires proper design. A proprietary gland is usually required. Please gland both ends of SWA cables (where possible).


  • Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,516 Mod ✭✭✭✭2011


    Pentrep wrote: »
    Maybe it could be argued with Safe Electric that it is not reasonably possible to gland both ends.

    A better argument with Safe Electric is that you are in compliance with the rules. They can not force you to do anything that is not in the rules.
    Adequate electrical conductance shall be provided between metal sheaths or armouring of cables and the earthing terminals of equipment. This requires proper design. A proprietary gland is usually required. Please gland both ends of SWA cables (where possible).

    ......and glanding at the DB end with an SWA gland and earthing the armour there does exactly this.


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  • Closed Accounts Posts: 65 ✭✭Lwaker.


    "Adequate conductance"

    Is that in et101?


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