Armoured cable earth

Discussion in 'Electricians' Talk' started by PFI Domestic Services, Oct 22, 2013.

  1. Hi, Replacing PVC 4 mm T+E with armoured cable, 10mm three core from CU in house to garage routing under the lawn. Which end of the armoured sheath should be earthed, viz house or garage, now converted to a workshop. Concerned that both earthed will create a loop that may prove unhelpful! Thanks.
  2. seneca

    seneca Screwfix Select

    Earth either at the supply end or both ends, no problem with earth loops in this application, in fact earthing the armour at both ends will improve your earth loop reading!
    Last edited: Oct 22, 2013
  3. retiredsparks

    retiredsparks Member

    what services are in workshop ?
    What is the supply type in house ?
    How many cores in new cable ?
    RS
  4. seneca

    seneca Screwfix Select

    What difference is all that going to make then RS, he asked a simple question and I gave him the answer, he didn't ask for design instructions did he!
  5. stateit

    stateit Active Member

    'Cos if it's a TN-C-S supply to a remote garage (as opposed to one in the same equipotential zone as the house) then you don't export an earth. So you wouldn't earth both ends.

    In which case you'd earth it at the supply end.
  6. seneca

    seneca Screwfix Select

    Over complicating things there State it! He asked a question and I answered it! Also, if it were TNCS he could still earth the armour at both ends, it's the rest of the installation that wouldn't be connected to that earth if he were going to TT it at the shed but would be earthed to the earth electrode.
    Last edited: Oct 22, 2013
  7. Caddy

    Caddy Active Member

    Oh good lord.. There is no reason you can't "export" the TNCS earth to the garage.. Its irrelevant it's a garage, it could be a single socket on a garden wall a shed or anything else. The only issue arrises if there are Extraneous-conductive-parts that require earthing in the garage, even then there is nothing stopping you using the TNCS earth it just usually more cost effective to convert it to a TT system..
  8. seneca

    seneca Screwfix Select

    The joke is Caddy, no ones even said it's TNCS anyway, that was just Stateit turning a simple question into a complicated one!
  9. Caddy

    Caddy Active Member

    Indeed..
  10. retiredsparks

    retiredsparks Member

    sen
    what earth electrode ?
    you are right he didnt mention what earth system in house... or garage...or how far away ..or what loading in workshop...or protective device ...or rcd protection...or much else.
    So a simple answer to a simple question leaves a lot to be desired, dont you agree ?
    RS
  11. seneca

    seneca Screwfix Select

    I usually just stick to answering the question RS, especially when the op appears to have some knowledge of what he's doing.
  12. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    Yes, but a little knowledge.......

    Mr. HandyAndy - Really
  13. seneca

    seneca Screwfix Select

    That's true Handy but if we stuck to that thought the answer to most of the questions on here would be "get a sparks in"!
  14. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    I know.
  15. retiredsparks

    retiredsparks Member

    Sen
    Know what you are saying.................but as an Engineer I prefer to have as many facts as possible and practicable to form a professional opinion. If the OP knows what he is doing...consult the red book...or give more and pertinent facts to get a more specific answer...;)
    RS
  16. Good evening folks and thank you for the simple answer to my simple question.
    I just wanted to know which end would be best connected. I do have TNCS in the house. I was concerned not to create a TT system in the garage although this would not be a problem given the supply will be RCD protected in the garage. The workshop will have two kilns each of which requires 39Amps so I will wire both to a change over switch. The present cable supply was 2.5 T+E and I have temporarily replaced this with 4mm armoured that was used in the previous garage to power one kiln. The 10mm armoured, the definitive cable is en route. Potters need their goods available at Christmas!!
    The final question was the number of conductors. I went for three so I will have two TNCS earths and will connect at the house supply to the main earth terminal. I appreciate Zs will be affected by connecting both ends but would be concerned that Zs conformed without parallel paths in the first instance. For completeness Ze if fine.
    My thanks for your help and I didn't want to start a ....................debate. Cheers Peter
  17. unphased

    unphased Screwfix Select

    Talk about misunderstanding. No wonder DIYers get in a mess. Why would you be concerned not to create a TT at the garage? As a designer of the circuit you need to decide whether you want a TT or you want a T-N-CS. Its not about "creating" something at the garage. And two T-N-CS earths? Zs will be affected? Without parallel earth paths? Copper conductors? Wires? Tenches? Kilns? Christmas? Potters.....:confused: Stick to pottery. Electricians go to college to understand all this. You're all mixed up. :D

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