Routing cable from consumer unit to loft

Discussion in 'Electricians' Talk' started by Acealfa, Apr 7, 2016.

  1. Acealfa

    Acealfa New Member

    Hi all,

    Currently my consumer unit is in a downstairs pantry under the stairs and existing cables are ran in the wall directly upwards into the loft. This means they are in the middle of the wall on the staircase.

    Does the safe zone from consumer unit vertically cover between different floors?

    If not can I use metal sheath protection to provide 'mechanical protection' and meet regs?

    Thanks
     
  2. fire

    fire Well-Known Member

    ??? Do you not have RCD protection?
     
  3. Acealfa

    Acealfa New Member

    Sorry forgot to mention it will be a full rewire. Yes will be rcd protected but I thought this was only acceptable as the only method of protection as long as wiring is within the safe zones. Just trying to clarify If this cable run would be?
     
  4. fire

    fire Well-Known Member

    If all cables running up will be RCD protected then mechanical protection is not needed. If you plan on running a few circuits that will not be RCD protected then you will need mechanical protection yes.

    If you plan on using a fully populated RCBO consumer unit which has no MCB's in it then you are fully RCD protected, if it is a split RCD consumer unit and you want it fully populated so all MCB's are RCD protected then you again you require no mechanical protection.

    If you want to install a circuit on a MCB without RCD while all other circuits are RCD protected then you need provide mechanical protection such as steel conduit for that circuit.

    Simple really, no RCD then cables MUST be mechanically protected. RCD protection and circuits don't need mechanical protection.

    In the wall up to the loft, if fully RCD protected would not require mechanical protection.
     
  5. Acealfa

    Acealfa New Member

    Thanks for the reply, all circuits will be rcd protected.

    So if rcd protection is used there is effectively no regard for safe zones?

    I say this because I've seen conflicting views saying rcd protection on its own isn't sufficient and mechanical protection is needed outside of safe zones.
     
  6. fire

    fire Well-Known Member

    If we are talking about building regulations regarding safe zones, such as around a window, over joists or drilled through joists or even notched in joists or something then things change a bit.

    Cables buried in a wall is one thing, cables run around things that can affect structural stability is building regulation as part p deals with.

    All holes in joists must be 25% smaller than the total hight of the joist and the next hole if any must be 3x away from the edge of the first hole.

    Notched joists which have the cable running across must have some form of mechanical protection due to someone entering the loft space standing on and maybe damaging the cable as they walk on the joists. Common sense really but yes it is in building regulations.

    Safe Zones are generally avoiding the studding in walls, joists, joist supports, wall corners(where metallic corner braces exist) screws fastening a structure like a stairwell(maybe in your case) and so on.

    Hopefully you et the idea of a safe zone but yea mechanical protection is something negated when RCD protection exists.

    Safe zones still exist but regardless of mechanical protection or not you must avoid cabling in that zone full stop.
     
  7. Acealfa

    Acealfa New Member

    Again thanks for the reply. My concern was the cable being more than 150mm from the wall edge and not more than 50mm deep.

    I will be having a good read of part p. Thanks.
     
    fire likes this.
  8. spinlondon

    spinlondon Screwfix Select

    BS7671 requires cables concealed in walls at a depth less than 50mm to be provided with additional protection.
    Earthed metallic sheath,
    Earthed trunking or conduit,
    Be provided with mechanical protection sufficient to prevent penetration by screws or nails.
    Be run in permitted zones and provided with 30mA RCD protection.
    30mA RCD protection for cables concealed in walls outside of permitted zones is not an acceptable method for providing the required additional protection.
     
  9. seneca

    seneca Screwfix Select

    If the cables are running directly up from the c/unit they are effectively whithin a "permitted zone".
     
    madhatter1uk likes this.
  10. Risteard

    Risteard Screwfix Select

    Spinlondon earthed conduit etc. is not additional protection. Additional protection in BS7671 specifically relates to 30mA RCD protection and local supplementary bonding.

    What you are referring to is really enhanced mechanical protection.

    And in answer to the original question safe zones do not extend between floors. And RCD-protected cables without earthed mechanical protection etc. must still be within the prescribed zones (so-called "safe zones").
     
    madhatter1uk likes this.
  11. Sparkielev

    Sparkielev Screwfix Select

    All this info is in osg if you are electrician doing rewire then you will know this
     
  12. Comlec

    Comlec Screwfix Select

    Here is the bit from the regs that may help or possibly confuse

    522.6.202 A cable installed in a wall or partition at a depth of less than 50 mm from a surface of the wall or partition shall:

    (i) be installed in a zone within 150 mm from the top of the wall or partition or within 150 mm of an angle formed by two adjoining walls or partitions. Where the cable is connected to a point, accessory or switchgear on any surface of the wall or partition, the cable may be installed in a zone either horizontally or vertically, to the point, accessory or switchgear. Where the location of the accessory, point or switchgear can be determined from the reverse side, a zone formed on one side of a wall of 100 mm thickness or less or partition of 100 mm thickness or less extends to the reverse side, or

    (ii) comply with Regulation 522.6.204.

    Where indent (i) but not indent (ii) applies, the cable shall be provided with additional protection by means of an RCD having the characteristics specified in Regulation 415.1.1.

    522.6.203 Irrespective of its buried depth,a cable concealed in a wall or partition, the internal construction of which includes metallic parts, other than metallic fixings such as nails, screws and the like, shall:

    (i) be provided with additional protection by means of an RCD having the characteristics specified in Regulation 415.1.1, or

    (ii) comply with Regulation 522.6.204.

    For a cable installed at a depth of less than 50 mm from the surface of a wall or partition the requirements ofRegulation 522.6.202 shall also apply.

    522.6.204 For the purposes of Regulation 522.6.201(ii), Regulation 522.6.202(ii) and Regulation 522.6.203(ii), a cable shall:

    (i) incorporate an earthed metallic covering which complies with the requirements of these Regulations for a protective conductor of the circuit concerned, the cable complying with BS 5467, BS 6724, BS 7846, BS 8436 or BS EN 60702-1, or

    (ii) be installed in earthed conduit complying with BS EN 61386-21 and satisfying the requirements of these Regulations for a protective conductor, or

    (iii) be enclosed in earthed trunking or ducting complying with BS EN 50085-2-1 and satisfying the requirements of these Regulations for a protective conductor, or

    (iv) be provided with mechanical protection against damage sufficient to prevent penetration of the cable by nails, screws and the like, or

    (v) form part of a SELV or PELV circuit meeting the requirements of Regulation 414.4.
     
    madhatter1uk likes this.
  13. madhatter1uk

    madhatter1uk Screwfix Select

    Can you not get them up under the stairs to the landing? The only other thing to do is put a blank plate on the stairs near the ceiling to create a permitted zone.

    What you have to think is, would someone with a basic common sense knowledge of safe zones reasonably expect cables to be there. As an electrician, on a stairs I'd check what's under the stairs.
     
    Deleted member 25896 likes this.
  14. Sparkielev

    Sparkielev Screwfix Select

    If possible when a dB is under a stair I will always try to relocate it when doing a rewire
     
  15. spinlondon

    spinlondon Screwfix Select

    Always used to be called additional protection before tha 17th.
    Not seen anything saying we can't still call it that.
    By the way, a cable with an earthed sheath is not providing mechanical protection.
     
  16. Risteard

    Risteard Screwfix Select

    It is providing mechanical protection but also ADS. It was never called additional protection. Additional protection is what was previously called supplementary protection under the 16th Edition. It is not anything else and is a defined term within BS7671. You can check your copy when you get one.
     
  17. JP.

    JP. Screwfix Select

    Whys that Peter? Myself I always make use of cupboard under stairs unless the space is really small..I've got 2 x db's in mine plus dis amp and wireless etc, however intake is also in there.
     
  18. Acealfa

    Acealfa New Member

    Thanks for the replies. The gas and electric meter is already under in the pantry so couldn't relocate.

    I've had a closer look today and it may be that the existing wires have been ran in the cavity so might be able to pull new wires through.

    My other option would be to go up to the top of the stairs then divert the cables needed for loft elsewhere but with their being an extra step at the top It might cause an issue.

    I'll be using this install as my assessment so want to get it spot on :D
     
  19. Sparkielev

    Sparkielev Screwfix Select

    If cable runs to a under stair cupboard are a nightmare I will relcote dB to more accessible place
     
  20. Well, I'm with MH on this. Irrespective of what the regs may or may not say, if you're doing a complete rewire then I suggest that you run the cables up and under the first floor and then up a stud wall or airing cupboard into the loft and not in the middle of a wall that Joe Average may well hang a picture on. Surely, part of being a professional is anticipating forseeable problems and designing them out?
     
    KIAB likes this.

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