Using SWA cable

Discussion in 'UK DIY' started by andrewpreece, Dec 17, 2004.

  1. andrewpreece

    andrewpreece Guest

    "jim_in_sussex" <> wrote in message
    news:...
    > Planning to bring my garage supply (which has a workshop section) up
    > to date in Christmas week. (last legal throw before part P)
    >
    > A thread ran a few weeks back on running a supply cable from a house
    > to a (detached) garage & SWA cable was suggested. To take up that
    > suggestion advice is needed as it is a long time since I used SWA
    > cable (& then only once).
    >
    > 1. Rating: It would be buried (as per above thread) about 450mm
    > (18ins) underground (hard drive/path) - about 4m as the crow flies,
    > but 7m-12m after deviations round, up & down. Is it correct to use
    > IEE table 4D1A/ref method 1? (the illustrations for method 1 don't
    > refer specifically to underground use).
    >
    > 2. Ducting: Instead of burying it in bare soil it looks more sensible
    > to run it inside a duct, but attempts to source underground ducting
    > have failed. Does anyone know of a source, or failing that, could
    > semi-flexible 40mm waste pipe be used? If SWA is ducted, how does it
    > affect current rating?
    >
    > 3. Termination: The house end is no problem as that connects into a
    > metal enclosure which I know how to connect, but how do you connect
    > the garage end into a standard plastic consumer unit? Is there a
    > special gland for this? Or do you connect into a service block of
    > some type & then run the last 12 ins or so in tails?


    I bought a metal enclosure box, one with knockout holes in it IIRC, and used
    it as a cable changing box. If you buy the SWA cable glands you will be able
    to bend the steel armouring back over the tapered collet thingy ( need to
    trim it just right though ), and screw the gland together tight, compressing
    the steel armouring and thus getting what I believe to be a very good
    bonding. I think the cable gland kits also come with a terminal washer,
    which I assembled onto the gland as I screwed it into the cable-changing box
    with the nut that is supplied, and soldered a wire onto the terminal washer
    , the other end of the wire going to a stud on the box, sort of belt and
    braces really. I used a metal cable-changing box at both ends actually, as I
    didn't consider the pvc boxes to be strong enough to take the rather stiff
    SWA to, and with metal you get a direct earth bond as well. Use some heavy
    duty terminal block inside the CCB to connect the cables together, at least,
    that's how I did it. You will need a grommet for the PVC cable as it exits
    the ccb.

    Andy.
    >
    > 4. Earthing: I'm not completely happy about relying on a non-copper
    > earth (ie the steel armour). Instead can I use 3 core SWA & use the
    > 3rd core as earth to supplement the armour? Common advice seems to
    > be to avoid using the house earth, but if possible I'd like to avoid
    > the work involved in installing an earth rod. The house supply is
    > 100amp PME/TN-C-S.
    >
    > 5. Cable size: nominally 6mmsq cable is adequate for the garage load
    > (ring + freezer radial + lights), but am wondering about using a
    > larger cable - eg 16mmsq. There'd be 2 benefits - much lower volt
    > drop, plus less light flicker when a machine starts. Relative to the
    > whole project the extra cost is small, but are there any practical
    > snags? Does anyone know the outside diameter of these cables?
    >
    > 6. Finally looking up the ratings for these cables in the IEE regs &
    > comparing with the TLC catalog, why the differences? eg TLC show swa
    > 16mmsq 2 core (6942x) as 91amps, IEE table 4D4A shows 89amps. In fact
    > most cable amp values given by TLC are lower than the IEE tables
    > give.
    >
    > Many thanks for all help offered.
    andrewpreece, Dec 17, 2004
    #1
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  2. Planning to bring my garage supply (which has a workshop section) up
    to date in Christmas week. (last legal throw before part P)

    A thread ran a few weeks back on running a supply cable from a house
    to a (detached) garage & SWA cable was suggested. To take up that
    suggestion advice is needed as it is a long time since I used SWA
    cable (& then only once).

    1. Rating: It would be buried (as per above thread) about 450mm
    (18ins) underground (hard drive/path) - about 4m as the crow flies,
    but 7m-12m after deviations round, up & down. Is it correct to use
    IEE table 4D1A/ref method 1? (the illustrations for method 1 don't
    refer specifically to underground use).

    2. Ducting: Instead of burying it in bare soil it looks more sensible
    to run it inside a duct, but attempts to source underground ducting
    have failed. Does anyone know of a source, or failing that, could
    semi-flexible 40mm waste pipe be used? If SWA is ducted, how does it
    affect current rating?

    3. Termination: The house end is no problem as that connects into a
    metal enclosure which I know how to connect, but how do you connect
    the garage end into a standard plastic consumer unit? Is there a
    special gland for this? Or do you connect into a service block of
    some type & then run the last 12 ins or so in tails?

    4. Earthing: I'm not completely happy about relying on a non-copper
    earth (ie the steel armour). Instead can I use 3 core SWA & use the
    3rd core as earth to supplement the armour? Common advice seems to
    be to avoid using the house earth, but if possible I'd like to avoid
    the work involved in installing an earth rod. The house supply is
    100amp PME/TN-C-S.

    5. Cable size: nominally 6mmsq cable is adequate for the garage load
    (ring + freezer radial + lights), but am wondering about using a
    larger cable - eg 16mmsq. There'd be 2 benefits - much lower volt
    drop, plus less light flicker when a machine starts. Relative to the
    whole project the extra cost is small, but are there any practical
    snags? Does anyone know the outside diameter of these cables?

    6. Finally looking up the ratings for these cables in the IEE regs &
    comparing with the TLC catalog, why the differences? eg TLC show swa
    16mmsq 2 core (6942x) as 91amps, IEE table 4D4A shows 89amps. In fact
    most cable amp values given by TLC are lower than the IEE tables
    give.

    Many thanks for all help offered.
    jim_in_sussex, Dec 17, 2004
    #2
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  3. andrewpreece

    Lurch Guest

    On 17 Dec 2004 14:59:49 -0800,
    (jim_in_sussex) strung together this:

    >1. Is it correct to use
    >IEE table 4D1A/ref method 1? (the illustrations for method 1 don't
    >refer specifically to underground use).
    >

    I don't have any regs to hand, I'm sure someone else will.

    >2. Ducting: Instead of burying it in bare soil it looks more sensible
    >to run it inside a duct,
    >

    Why? Unless you're likely to be pulling it out then bury it direct.
    There's no mechanical advantage to be gained from running SWA in a
    duct.
    The current rating will be the same.

    >3. Termination: how do you connect
    >the garage end into a standard plastic consumer unit?


    Two ways, first is to terminate directly into the PVC enclosure and
    the second is to terminate into an external PVC or metallic enclosure
    then run from this to the CU with T&E or something similar.
    >
    >4. Earthing: I'm not completely happy about relying on a non-copper
    >earth (ie the steel armour).
    >

    I always use 3 core SWA and use the 3rd core as an earth. Common
    practice really.
    Earthing, I'm not going to get into this one.

    >5. Cable size: nominally 6mmsq cable is adequate for the garage load
    >(ring + freezer radial + lights), but am wondering about using a
    >larger cable - eg 16mmsq. There'd be 2 benefits - much lower volt
    >drop, plus less light flicker when a machine starts. Relative to the
    >whole project the extra cost is small, but are there any practical
    >snags? Does anyone know the outside diameter of these cables?
    >

    6mm about 20mm OD, 16mm about 30mm OD. You can use either, I'd go for
    anything from 6mm upwards for a 32A supply over the distance you've
    got.

    >6. Finally looking up the ratings for these cables in the IEE regs &
    >comparing with the TLC catalog, why the differences?
    >

    Email TLC and ask, could be a number of reasons.
    --

    SJW
    Please reply to group or use 'usenet' in email subject
    Lurch, Dec 17, 2004
    #3
  4. andrewpreece

    andrewpreece Guest

    "Lurch" <> wrote in message
    news:...
    > On Fri, 17 Dec 2004 14:46:23 -0000, "andrewpreece"
    > <> strung together this:
    >
    > <snip>
    >
    > Your clocks wrong, thrash your self with 2.5mm T&E now.
    > --

    Only 12 hours out, picky, picky, picky... :0)

    Andy.
    andrewpreece, Dec 18, 2004
    #4
  5. andrewpreece

    John Rumm Guest

    jim_in_sussex wrote:

    > 1. Rating: It would be buried (as per above thread) about 450mm
    > (18ins) underground (hard drive/path) - about 4m as the crow flies,
    > but 7m-12m after deviations round, up & down. Is it correct to use
    > IEE table 4D1A/ref method 1? (the illustrations for method 1 don't
    > refer specifically to underground use).


    I take it you found TLCs voltage drop calculator?

    http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html

    Quite handy for SWA I find.


    --
    Cheers,

    John.

    /=================================================================\
    | Internode Ltd - http://www.internode.co.uk |
    |-----------------------------------------------------------------|
    | John Rumm - john(at)internode(dot)co(dot)uk |
    \=================================================================/
    John Rumm, Dec 18, 2004
    #5
  6. andrewpreece

    Lurch Guest

    On Fri, 17 Dec 2004 14:46:23 -0000, "andrewpreece"
    <> strung together this:

    <snip>

    Your clocks wrong, thrash your self with 2.5mm T&E now.
    --

    SJW
    Please reply to group or use 'usenet' in email subject
    Lurch, Dec 18, 2004
    #6
  7. andrewpreece

    Lurch Guest

    On Sat, 18 Dec 2004 00:34:35 GMT, "Dorothy Bradbury"
    <> strung together this:

    Don't reply to me, I didn't ask the question. Bloody OE users....

    >>>2. Ducting: Instead of burying it in bare soil it looks more sensible
    >>>to run it inside a duct,

    >
    >No need, but do lay a "cable buried below".
    >o Ducting is good at filling with water
    >o Ducting =/= run net/phone cable next to power cable


    No, you use seperate ducts for power and low voltage services.
    --

    SJW
    Please reply to group or use 'usenet' in email subject
    Lurch, Dec 18, 2004
    #7
  8. andrewpreece

    Lurch Guest

    On Sat, 18 Dec 2004 11:03:10 GMT, Mike Harrison <>
    strung together this:

    Sorry Mike but is there any chance you could adjust your line
    length\character width to 70 characters or thereabouts? It makes posts
    rather difficult to read.
    Thankyou.
    --

    SJW
    Please reply to group or use 'usenet' in email subject
    Lurch, Dec 18, 2004
    #8
  9. andrewpreece

    Owain Guest

    "jim_in_sussex" wrote
    | 3. Termination: The house end is no problem as that connects
    | into a metal enclosure which I know how to connect, but how
    | do you connect the garage end into a standard plastic consumer
    | unit? ... Common advice seems to be to avoid using the house
    | earth, but if possible I'd like to avoid the work involved
    | in installing an earth rod. The house supply is 100amp PME/TN-C-S.

    AIUI PME earths should not be exported from the house. It would be normal to
    use 2-core SWA, use an earthing gland at the house end so that the armour is
    earthed, use an insulating gland at the garage end so that the armour is
    insulated. The CU is then earthed to an earth rod (TT) and all circuits
    should be RCD protected. If you use power tools in your workshop you should
    consider discrimination between lighting and power circuits, so that in the
    event of an RCD trip you are not left in the darkness with power tools
    spinning down. An alternative might be a couple of self-contained emergency
    lighting units.

    Owain
    Owain, Dec 18, 2004
    #9
  10. andrewpreece

    Lurch Guest

    On Sat, 18 Dec 2004 17:49:59 GMT, "Dorothy Bradbury"
    <> strung together this:

    >Sorry Lurch.


    Apology accepted! ;-)

    >o Yes I similarly loathe Outlook (in this case)
    >o One reason I'm migrating to Linux - that and multiple O/S fees
    >

    Well done. I started doing that a while ago.

    >Even if the LV is conduited?
    >I guess I'm thinking of the MK etc skirting trunking.
    >That allows LV & Mains in the same trunking due to separated design,
    >ie, it's little more than several trunking c/sections extruded as one piece.
    >

    Theoretically, you're correct, but if there is a duct with an SWA in
    it then it is a mains duct, them's the rules!
    If you were to place a duct within a duct then you could do it but you
    don't need to, you would just bury the SWA direct and use the duct for
    LV.
    --

    SJW
    Please reply to group or use 'usenet' in email subject
    Lurch, Dec 18, 2004
    #10
  11. andrewpreece

    BigWallop Guest

    "andrewpreece" <> wrote in message
    news:41c4e51a@212.67.96.135...
    >
    > "Lurch" <> wrote in message
    > news:...
    > > On Fri, 17 Dec 2004 14:46:23 -0000, "andrewpreece"
    > > <> strung together this:
    > >
    > > <snip>
    > >
    > > Your clocks wrong, thrash your self with 2.5mm T&E now.
    > >

    > Only 12 hours out, picky, picky, picky... :0)
    >
    > Andy.
    >


    But that means the post you sent today didn't arrive until yesterday. So
    you've already missed all the good parts. :)
    BigWallop, Dec 19, 2004
    #11
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