Home  5  Books  5  Magazines  5  News  5  GreenPro  5  HelpDesk  5  Your Cart  5  Register  5  Green Living Forum
Not signed in (Sign In)

Categories

This month's favourite choices




Vanilla 1.0.3 is a product of Lussumo. More Information: Documentation, Community Support.

Welcome to new Forum Visitors
 Join the forum now and benefit from discussions with thousands of other green building fans and discounts on Green Building Press publications: Apply now.




Housing - New Build: How should wiring be fixed in a service void?

Bottom of Page

31 to 60 of 73

  1. <
  2. 1
  3. 2
  4. 3
  5. >
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 26th 2012
     
    Other method is to surface mount the cables, you know where they are then :wink:
  2.  
    Prysmian AFUMEX LSX is a twin & earth cable with a laminated aluminium tape screen in direct contact with an uninsulated earth conductor. If fitted on a circuit with RCD/RCBO protection then it ensures any nail penetrations will causes the breaker to trip.

    David
    •  
      CommentAuthorfostertom
    • CommentTimeSep 26th 2012
     
    Posted By: jamesingram metal conduit of some kind, remember it need to be earthed
    Now there's a thought - what about metal stud partitioning? dryliner's galv angles and flatstraps?
  4.  
    Posted By: fostertomNow there's a thought - what about metal stud partitioning? dryliner's galv angles and flatstraps?
    No, I don't think so - but you need grommets where you pass wires through metal studs.

    I guess one advantage of using metal conduit is reduced EMF emissions - maybe important for such applications as recording studies or for the paranoid delusional types who claim "electrosensitivity" ;)

    Paul in Montreal.
    • CommentAuthorbarney
    • CommentTimeSep 26th 2012
     
    A couple of points:

    BS 7671 (The wiring egs or the UK wiring code) requires cables installed under floor voids or in ceiling voids to be run in such a position that it won't be damaged by contact with the floor or the ceiling or the fixings.

    It could be argued that thebattening suggested by the OP constituts part of the joist so cables installed should be either:

    1 - 50mm away from the ceiling (ie deep enough so normal screws won't contact, or

    2 - Installed in earthed metallic conduit or trunking or incorporate an earthed metallic sheath, or

    3 - Be mechanically protected

    4 - be of safety or protectie extra low voltage.

    In my opinion, options are conduit runs down to the wall junction, a Hi Tuf type cable (earthed metallic sheath) or just batten and then counter batten to create a min 50mm deep service zone and then just clip the cables to the batten edges

    To answer the question about metallic framing systems (in a domestic environment) then you must have a RCD with 30mA tripping characteristics regardless of how the cable is installed or what type it is.

    Your installing electrician should know all this anyway - just talk through the options - you are paying for his skill and knowledge - make use of it

    Regards

    Barney
    • CommentAuthorCerisy
    • CommentTimeSep 26th 2012
     
    All great advice - but how's about taking photos as you go, printing at A4 and putting them into a House folder along with installation / maintenance / etc manuals. Progress photos are great for future memories or sharing, but as installed photos of electrics, plumbing, ducts .... etc could be life saving!
    • CommentAuthorJonti
    • CommentTimeSep 26th 2012
     
    All very good but how do you clip the cables to the batten edges if doing a post build/decorating replacement, upgrade or addition? All electricians I have seen just pull the wire through the void but don't batten meaning it will be close to the plasterboard in many places.

    Jonti
    • CommentAuthorqeipl
    • CommentTimeSep 26th 2012
     
    Pingy,

    Unprotected cable fixed to the sides of the battens? High risk of hitting one with a plasterboard screw. I certainly wouldn't do it.

    If you don't want the hassle and expense of conduit, best keep the cables as far from the battens as possible.

    How about a series of horizontal draw strings that run in notches at the back of the battens?
    Sparky threads the cables between draw strings and membrane, tightens up draw strings and ties them off. Cables are pulled against membrane and can be pushed to towards the centres between the battens.
    Nice and safe from the plasterboard screws and no penetrations through your membrane.
    Granted, the cables won't be 50mm away from the ceiling but that's always been a silly reg. I have plenty of screws and nails on my shelves that are longer than 50mm.

    Malcolm
  9.  
    Posted By: qeiplI have plenty of screws and nails on my shelves that are longer than 50mm.


    Mine too - but I don't use them for screwing drywall to ceilings where I know there are wires that are 50mm away from the front surface!

    Paul in Montreal.
    • CommentAuthorjamesingram
    • CommentTimeSep 26th 2012 edited
     
    Posted By: JontiAll very good but how do you clip the cables to the batten edges if doing a post build/decorating replacement, upgrade or addition? All electricians I have seen just pull the wire through the void but don't batten meaning it will be close to the plasterboard in many places.

    Jonti

    that's true , I believe the regs. makes allowance for 'as far as practicable' when it come to additions and alterations. Once the ceiling is up/floor is down there should be no real reason to screw/nail in the void where the cables run, though where it crosses joists etc. mechanicial protect would be required if <50mm from finish.

    Barney , I think you're right re. floor/ceiling , but I believe the original question was regarding walls , so routing cables in safe zones and rcd protection would be sufficient.
    argh just reread , it's vaulted ceilings/pitched walls , the tricky halfway house
    • CommentAuthorqeipl
    • CommentTimeSep 26th 2012
     
    Posted By: Paul in Montreal
    Posted By: qeiplI have plenty of screws and nails on my shelves that are longer than 50mm.


    Mine too - but I don't use them for screwing drywall to ceilings where I know there are wires that are 50mm away from the front surface!

    Paul in Montreal.


    It's not the drywall screws that are the worry. Pingy's doing the plasterboarding and he knows where the battens and the cables are. It's a new owner 20 years hence, Mr DIY who's using 3" screws randomly to hang the Christmas decorations. He's the one who makes a mockery of the 50mm regulation.
    • CommentAuthordjh
    • CommentTimeSep 26th 2012
     
    Posted By: qeiplIt's a new owner 20 years hence, Mr DIY who's using 3" screws randomly to hang the Christmas decorations. He's the one who makes a mockery of the 50mm regulation.

    Well, just as long as he's not an MP's daughter. But surely everybody is taught at school not to use excessively long screws to mount Christmas (or Diwali etc) decorations? We must be able to expect that people in 20 years will understand the danger. Then again, perhaps we just rely on the RCD.

    I remember when my dad cut through a lighting cable with a pair of scissors. It turned out it was live. There was an almighty bang and a large chunk taken out of the scissors but he was none the worse, although a bit startled.
  13.  
    qeipl , yes that's why they upgraded regs. to 17th edition in the UK giving RCCD protection to all cables unprotected and out of sight.
    • CommentAuthorJonti
    • CommentTimeSep 26th 2012
     
    Posted By: jamesingram
    Posted By: JontiAll very good but how do you clip the cables to the batten edges if doing a post build/decorating replacement, upgrade or addition? All electricians I have seen just pull the wire through the void but don't batten meaning it will be close to the plasterboard in many places.

    Jonti

    that's true , I believe the regs. makes allowance for 'as far as practicable' when it come to additions and alterations. Once the ceiling is up/floor is down there should be no real reason to screw/nail in the void where the cables run, though where it crosses joists etc. mechanicial protect would be required if <50mm from finish.


    'there should be no real reason to screw/nail in the void where cables run' is a bit of a fob off really. What about hanging/attaching one of the many things such as TVs etc. that so many people want to? I agree that with the accepted practice used in the UK it is difficult to do anything else other than what is done now but I would suggest it is the ingrained habits rahter than practical reasons or costs holding good practice back in this area.

    I am not saying it is the answer but having defined conduits makes life a lot easier and safer.

    Jonti
    • CommentAuthorGavin_A
    • CommentTimeSep 26th 2012
     
    not being funny, but you need to discuss this with your spark, and agree it with them in advance of whatever you do here, otherwise you risk having to change it all before your spark will run the cables because you've done it in a non compliant way.

    I'f had experience of this sort of thing, and it's a right pain in the arse -

    'we've got your cable runs all worked out for you, with draw strings in place''

    'oh great, that'll make things simple'

    'Wait, why have you run them outside the safe zones and not used earthed metal capping? I can't use those runs sorry, we'll have to cut the plasterboard away and start from scratch.'

    etc.
    • CommentAuthorGavin_A
    • CommentTimeSep 26th 2012
     
    Posted By: Jonti'there should be no real reason to screw/nail in the void where cables run' is a bit of a fob off really. What about hanging/attaching one of the many things such as TVs etc. that so many people want to? I agree that with the accepted practice used in the UK it is difficult to do anything else other than what is done now but I would suggest it is the ingrained habits rahter than practical reasons or costs holding good practice back in this area.


    If it's in the safe zone around the edge of the wall, or vertically or horizontally in line with a socket / fitting, then nobody has any business banging any nails in there at all - at least not without checking with a wire detector first.

    If you don't know this, then you shouldn't be banging anything in the walls tbh.

    the earth wire, MCB and (probably) RCDs will protect idiot DIYers who don't know the rules, but they'll pay for their ignorance by having to get someone in to replace the cable in the wall.... after which hopefully they'll be a bit more aware of the rules.

    Of course, if someone goes and moves the entire consumer unit after you've used it as a safe zone for your cable, then there can be problems when it comes to the plasterboard guys banging their plasterboard in over 100mm of kingspan, but that's a different story.
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 27th 2012
     
    Posted By: djhWell, just as long as he's not an MP's daughter

    Was a sad case and highlighted bad practice as I am led to believe that Jenny Tongs daughter was not at fault, but the truth gets lost in the mists of time. The fact that we remember it though is a good lesson.
    • CommentAuthorJonti
    • CommentTimeSep 27th 2012
     
    Gavin_A,

    I was just point out that somethings are so vitally important at one stage of the electrical installations life but then totally irrelevant later on when it has become impossible to follow best practice/regs. The reason for this problem is the method of installation but despite there being other ways of installing that would solve this they are ignored or worse still resisted because the attitude is 'this is how we have always done it'.

    As to your comment of ' If you don't know this, then you shouldn't be banging anything in the walls tbh' it is just these sort of people that will be banging nails in there because the don't know any better!

    tbh, I would have thought it a good idea to check for wiring with a detector whether working in a safe zone or not.

    Jonti
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 27th 2012
     
    Posted By: Jontitbh, I would have thought it a good idea to check for wiring with a detector whether working in a safe zone or not.

    I agree, trouble is most people have a hammer and nails kicking about but few would think/know to get a detector.
    Not having had a telly for nearly 20 years (and hated watching GD on the internet because of the adds), do we still have public service adverts like we did in the 70's about a green man showing school kids puppies next to a ice cream van with a nuclear warning siren going off in the background as some drunk drives past?
    Probably not needed as there is an 'app' for it now :wink:
    • CommentAuthorbarney
    • CommentTimeSep 27th 2012
     
    Get a grip chaps - the wiring regs are not there to protect halfwits with DIY tools - you simply cannot protect everyone from every situation.

    That's why the wiring regs (for a domestic installation using typical UK spec Twin and earth cabling), on socket circuits and all circuits to bathrooms, for cables buried less than 50mm deep and for cables inside partitions with metallic componenets) require the use of one (and ideally more than one) RCD of 30mA tripping chatacteristics.

    The RCD is there, (in addition to all the other sensible aspects such as zoning etc) to "provide additional protection in the event of failure of the provision of basic protection and/or the provision for fault protection or carelessness by users.

    ie - it's the backstop position that try to compensate for any and all the permutations you can dream up for 6" nails holding up the tinsel or Mr DIY who thinks he's clever because he bought an SDS drill in Lidl's

    Just be minded that an RCD with only protect about 95% of the population and as it's an electromechanical device that will fail (about 7% of those tested didn't work for a variety of reasons).

    So - test the thing regularly and use a bit of common sense when weilding the hammer or the SDS - don't expect the installing electrician to take on the mantle of protecting everyone from everything possible - it won't happen - there are basic rules, he'll probably follow them - but after that you're on your own

    Regards

    Barney
  21.  
    As it happens I'm just replacing some plasterboard (taking an opportunity to insulate).

    There are some existing cables which I will not be disturbing, that will remain immediately just behind the surface of the plasterboard wall . I would like to put some mechanical protection between plasterboard and cable, to protect the cables from future xmas-decoration installers.

    What protection material do people recommend, that would be strong enough to resist a nail/screw?

    I will not be disconnecting the cables so cannot thread them into a conduit. I'm not changing the CU to add RCBs. I thought about steel cable tray but that has loads of holes big enough to put a screw through. I have some 2mm steel sheet to hand but it was quite expensive and looks like overkill.

    I looked at stuff like http://www.screwfix.com/c/electrical-lighting/steel-channel/cat1660014 but am not sure it really offers much resistance to a drill or not.

    I am a diy-er, I own a cable detector, a hammer and a screwdriver and know how to use them sensibly, I do not own a SDS drill or a copy of the 17th ed...
    • CommentAuthorbarney
    • CommentTimeSep 28th 2012
     
    Well Will, your biggest risk is thermally damaging the cables when you surround them with insulation and they run hot under normal loads. Keeping them in close contact with the plasterboard is the most sensible thing you can do as it acts as a heat sink and also limits the effect of insulation (cos it's only on one side).

    as for protecting against nails or screws - then pick a scenario and then you can find a bit of steel to give you protection - you could use a bit of 12mm plate if you want to stop a 7.62mm round - work back from there depending on how good your gas nail gun, hilti drill, of cordless screwdriver is - and how big a hammer you have.

    It's an exercise in futility - just don't bang nails in the ceiling or drive drywall screws in without knowing where they are going.

    Personally, I would just clip the cables at least 50mm up the side of the joist or truss (you can use offcuts of cable and a couple of plasterboard nails at loops if that's easier) - you'll get much the same heat sink effect I highlighted earlier when you surround the cables with insulation.

    I would encourage you to get a few RCD's fitted - you don't need to swap out the consumer unit - just put the RCD's in a seperate enclosure - you could also just put in a single RCD before the consumer unit - not strictly compliant with the wiring regs in terms of preventing hazards and minimising inconvenience because a single fault kills off the whole house - there are millions who have exactly that scenario though and the overall safety benefit to your potential tinsel hangers is nett positive

    Regards

    Barney
  23.  
    Hehe thanks for that Barney!
    As an aside, in a previous life I have seen said rounds fired through steel plate, but hopefully that wont happen in my back room! I do not currently own a nail gun or a rifle.

    Sorry I should have said, well aware of not insulating cables,
    there are some places where the gap between p/b and projecting bits of external stone wall is only 30mm and there is not room for both cable and insulation at those spots anyway, or to move cable back, so I will miss insulation off there. But while the wall is open I might as well put something hard and heat-conducting over the cable to protect it.

    Do agree about RCDs and that is planned as a future project (but not do-it-myself). Thing is, they protect tinsel hangers from cable, whereas I also want to protect cable from tinsel hangers. (My sons are nearly old enough to take over responsibility for such work)

    Had kind of expected there would be a 'normal' solution that is generally accepted to protect cable for 'normal' indoor situations and available off shelf at builders merchant, doesnt seem so...

    Also got some heating pipes behind there, would like to protect these too.
    • CommentAuthorjamesingram
    • CommentTimeSep 28th 2012 edited
     
    The normal solution is it doesn't need protection in domestic walls if in safe zones and/or protect by RCD.
    If you feel you'd like to do it , just use the 2mm sheet.
    it notes in the onsite guide re. mechanical protection for cable <50mm depth not in earthed steel conduit ,trunking or armoured
    " the requirement to prevent peneration is difficult to meet"

    Barney interesting stats. on RCDs, I was aware they weren't fail safe , but not to what degree, thanks
  25.  
    Will ,
    you can insulate round cable as long as you're aware of the derating factors ,so dont just leave this bit out
    if you dont have to. As you probably know you may get a cold spot there, and get condensation/damp problems as a result .
    easy to work out , play it safe and derate by 50% then check load on circuit , circuit overload protection size (MCB/fuse) etc. Plenty on GBF re. derating for insulation before
    • CommentAuthorEd Davies
    • CommentTimeSep 28th 2012
     
    Posted By: jamesingramBarney interesting stats. on RCDs, I was aware they weren't fail safe...

    Pedantic aside: the expression “fail safe” is not synonymous with “reliable”; instead, it means that when a device fails it fails in a safe condition. The opposite is fail dangerous. An RCD which failed with a mean interval of one week but tripped out as it failed could be considered fail safe but hardly reliable. An RCD which failed with a mean interval of one million years but left the circuit live when it failed would be very reliable but fail dangerous. From what Barney says RCDs are both unreliable and fail dangerous.

    It depends on the circumstances, of course. An RCD in the circuit to a life-support machine would probably be considered fail safe if it failed connected and fail dangerous if it tripped (if you were mad enough to have an RCD in such a circuit - wonder how operating theatres and ICUs are wired).

    Carburettors on cars are sprung so the throttle closes if the throttle cable breaks because it's usually safer for the car to stop than accelerate unexpectedly. They're fail safe. Single engine piston aeroplanes are set up the opposite way - if the cable breaks in flight you want the engine go to full power until you're in gliding range of somewhere nice to land, which is also fail safe for the likely circumstances.

    Slightly less irrelevantly, does foil faced insulation have any effect on the usability of cable or pipe detectors?
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 28th 2012
     
    Then there is 'intrinsicly' safe, which means when the safety device itself fails it does not cause other problems. Very important when dealing with flammable fluids. Met a man that designed a gas sensor and switch that could never cause an explosion as it never drew enough current to heat up, pretty neat idea I thought.
    • CommentAuthorEd Davies
    • CommentTimeSep 28th 2012
     
    Probably more to the point, I imagine it never drew enough current to allow a spark to be drawn when a switch opened, a connector was pulled or a wire was severed.

    http://en.wikipedia.org/wiki/Intrinsic_safety

    Let's not derail this thread from one little aside, though.
    • CommentAuthorbarney
    • CommentTimeSep 29th 2012
     
    It depends on the circumstances, of course. An RCD in the circuit to a life-support machine would probably be considered fail safe if it failed connected and fail dangerous if it tripped (if you were mad enough to have an RCD in such a circuit - wonder how operating theatres and ICUs are wired).

    OP Theatres, ITU, ICU, HDU, SCBU etc etc (ie Group 2 medical locations) are wired using a system of medical isolation transformers (Effectively medical IT systems) - these have no effective connection with earth (although the system is heavily earthed) so the first fault doesn't cause disconnection, just an insulation failure alarm. The second fault would cause a shock - but by then the staff have swapped over to the second independant system at each bedhead, etc. The whole system is usually backed up with UPS and generators.

    Going back to the failure of RCD's try looking for a report by ERA (I think it's published on the ESC site)

    http://www.esc.org.uk/industry/policies-and-research/rcd-research/

    You'll find more information on medical IT systems if you google Bender or Starkstrom

    I do know of at least one domestic property that has a medical IT system installed for all circuits (or several of them in fact) - the owner, however, is just a little strange by any metric - still, he thinks his family is safe from electrical risks so his money, his choice.

    @ WillInAberdeen - I hope those 7.62 rounds were going through something thinner than 12mm - otherwise I'm going to be in serious trouble !!

    I wouldn't leave gaps in the isulation - for most domestic circuits you won't be pulling anything like enough load in normal usage compared to the circuit design, so whilst derating for insulation is something you perhaps want to be aware of, in practice it's never usually a problem due to the ultra conservative cable rating figures used for practical design.

    Have a look for an article called "ESTABLISHING CURRENT RATINGS FOR CABLES IN THERMAL INSULATION" by John Ware, published by IET in thier Wiring Matters magazine - Google should find it


    Regards

    Barney
  30.  
    We will have to use conduit sunk into our internal EPS of our walls to avoid the wiring touching the EPS. Does the fact the conduit is surrounded by insulation mean that the issue of derating should be considered or does that only apply if the wires are directly covered with insulation, does the conduit provide enough air to keep wires cool?

31 to 60 of 73

  1. <
  2. 1
  3. 2
  4. 3
  5. >
   
The Ecobuilding Buzz
Site Map    |   Home    |   View Cart    |   Pressroom   |   Business   |   Links   
Logout    

© Green Building Press