!7th Edition Question

Discussion in 'Electricians' Talk' started by Julian1, Apr 29, 2008.

  1. Julian1

    Julian1 New Member

    It seems that with the 17th edition practicaly all circuits need to be RCD protected unless they are buried greater than 50mm or are in earthed steel conduit etc.

    Does anyone know the guidelines in the case of a garage circuit say on a 20A MCB that is non RCD protected in the house consumer unit but has its own CU in the garage with a 30mA RCD protecting the 6A & 16A circuits in the garage if the cable is not buried below 50mm or in steel conduit.

    Does the stretch of cable feeding the CU in the garage have to be RCD too in the house CU. Whats the best way to comply with the 17th.

    Thanks
     
  2. Sam Dingle

    Sam Dingle New Member

    Are both CU's next to each other?
    What is the length of run between the CU's?

    My thought is that the RCD's / RCBO's are there to provide protection when the cable is hidden.

    If the cable is surface in a garage, doesn't it need mechanical protection?
     
  3. Julian1

    Julian1 New Member

    Length of run of the cable from the house CU to the garage CU is about 5 metres, its hidden in the sense that it runs under the floor void but out of reach of someone witha drill/hammer & nails etc.
     
  4. M107

    M107 New Member

    What csa is the cable supplying the garage?
    Is the earthing arrangment TN or TT ?
     
  5. Julian1

    Julian1 New Member

    Cable CSA is 4.00mm & the earthings is T-NS...Thanks
     
  6. splater-and-duck

    splater-and-duck New Member

    I would say that if the cable was fixed in a vulnerable position ie less than 50mm or could get a clout for example then rcd at the front end. I suppose the future design of this type of work will now change since if we do that there’s little point putting a rcd in the garage is there? I guess it another example of how the 17th will change things a little. However from what you say about this job you should be ok as it is. I am assuming its within all other parameters cable size etc.
     
  7. M107

    M107 New Member

    Cable CSA is 4.00mm & the earthings is T-NS...Thanks

    I dont have the 17th regs to hand but (& somebody will confirm or rectify) if possible up the submain ocpd to 32amp then no need for rcd on the submain/distribution circuit.
    As I say no regs to hand at the moment so going from memory.
     
  8. JP.

    JP. Screwfix Select

    There is no requirement to RCD protect a submain..

    However can lumps of T + E feeding a garage and draped over goodness knows what etc be classed as a submain?

    The ''sub'' as portrayed by the OP is surely indicative of RCD/RCBO at DB1 protecting the ''run''..thus RCD in DB2 is purely cosmetic as such unless an S type is fitted in DB1..which surely negates discon times with respect to ''sub'' run.

    Now if the run was in SWA..then hey ho here we go.

    Thankyou.
     
  9. sparkyrj

    sparkyrj New Member

    The requirement for rcd protection is for cables less than 50mm deep in walls not in safe zones , as these are hidden from view from somebody drilling a wall etc, and hitting live cable.surface wiring and underfloor cables are not affected.
     
  10. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    The requirement for rcd protection is for cables less
    than 50mm deep in walls not in safe zones , as these
    are hidden from view from somebody drilling a wall
    etc, and hitting live cable.surface wiring and
    underfloor cables are not affected.



    But the 17th says rcd for all buried cables(except 50mm or conduit) INCLUDING those in safe zones, doesn't it ?


    Which begs a question, does the 17th still have the 'safe zones' described, and if they are safe, why the RCD ?

    RCD on all, means there are NO safe zones.


    Plonkers, the lot of them!


    Mr. Handyandy - really
     
  11. dingbat

    dingbat New Member

    You are correct, HA, in that there are no 'safe' zones...

    ...but then, there never were; that has never been an approved term.

    "Plonkers, the lot of them!"

    Indeed. ;)
     
  12. Mr Sworld

    Mr Sworld New Member

    One interesting point of the new rcd reg is that if it is maintained by a skilled person then you don't need them.

    So, if a sparks wires up his own house, do you need to use rcd's or rcbo's on the circuits?
     
  13. M107

    M107 New Member

    One interesting point of the new rcd reg is that if
    it is maintained by a skilled person then you don't
    need them.

    So, if a sparks wires up his own house, do you need
    to use rcd's or rcbo's on the circuits?


    Yes because you have unskilled persons who use the circuits.
     
  14. Mr Sworld

    Mr Sworld New Member

    One interesting point of the new rcd reg is that
    if
    it is maintained by a skilled person then you
    don't
    need them.

    So, if a sparks wires up his own house, do you
    need
    to use rcd's or rcbo's on the circuits?


    Yes because you have unskilled persons who use the
    circuits.

    The reg is there because unskilled people still bang nails into the wall in 'safe zones', now my GF <u>always</u> gets me to put pictures etc up! :^O
     
  15. sparkyrj

    sparkyrj New Member

    yes your right it does, my mistake.Does capping,steel or plastic count as mechanical protection, thus removing the need for rcd protection on switch drops etc.
     
  16. hores nob

    hores nob New Member

    if any type of capping is used it must be earthed so plastic is out
     
  17. Mr Sworld

    Mr Sworld New Member

    yes your right it does, my mistake.Does capping,steel
    or plastic count as mechanical protection, thus
    removing the need for rcd protection on switch drops
    etc.

    No, capping does not count as mechanical protection for cables I'm afraid.

    Conduit or trunking only in this scenario and it must be earthed.
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice