What is "premature" in electricial installations.

Discussion in 'Electricians' Talk' started by MGW, Jan 12, 2018.

  1. MGW

    MGW Active Member

    I would assume long enough for people to evacuate the premises, but I have nearly run out of my Rawlplastic [​IMG]
    and the new plugs will melt, does not matter what you put the cables in, if the screw falls out of the wall, weakest link is screw in wall, so if plastic trunking has clips inside to stop cables dropping the trunking will still drop and so that is not really a help, well likely it will be worse, instead of stepping over burning trunking and cables people will have burning plastic dripped on them.

    I have looked at pictures of fires caused by washing machines, the kitchen was badly damaged, however all the furniture still in place, there was not enough damage for anything to fall off the walls and only plastic melted was on the washing machine, yet people died, it does not take a big fire to kill people and I do not believe in a normal house that cables will fall off the walls due to plastic melting before everyone in the house is dead.

    OK silly sticky back trunking yes, but if screws used to hold it no, the normal size of house will not have a problem, the only people to have a problem is the fire brigade going into the house after the fire would have killed anyone not with breathing gear, so it would need signs outside the house stating the house complied with some level of protection before they can go in. And the Liverpool car park fire highlights the time taken to get to a fire, so unless sprinklers fitted then no real point.

    But the problem is what is "premature collapse" if it holds the cables up long enough for people to escape then that is enough, or is it, and how long to escape, I can get down stairs in minutes when the alarm goes off, even after putting cloths on, my wife takes hours, she it seems has to have a shower first! But this is after the alarm goes off, be it mother falling out of bed, doors opening or smoke alarm until it goes off the fire has chance to get hold before anyone moves.

    So likely the fire will get a hold and will get very hot, when I was on the Falklands we had to get rid of excess Portakabins so they were burnt, it took 3 minutes to reduce on to ashes, by the time the forklift had picked up another cabin and taken it to the fire the one before was ashes. What is the point of tying to keep cables out of the way when the whole unit burns so fast?
  2. Dr Bodgit

    Dr Bodgit Well-Known Member

    I wonder how quickly rawlplugs would melt...on the plus side they're in the wall so well insulated from the heat. On the downside you have a steel screw stuck in them which is a very good conductor of heat. Depends on how deep the rawl plugs go, whether its a vertical wall or horizontal ceiling etc etc.
  3. unphased

    unphased Screwfix Select

    Why have you challenged a perfectly simple concept? Premature collapse is what it means. Collapsing before it can adequately prevent something from happening. If people continually question 'words' and 'meanings' like this , and lets face it, they do, what is the point of having Regulations? People seem to question the intention rather than the result.
  4. Dr Bodgit

    Dr Bodgit Well-Known Member

    I think the point is that regulations stipulate what must be done, but not properly explain what that it is trying to achieve i.e. the objective to be met.

    Its the same in my business (operational risk), we have controls that must be implemented, but they must be tied back to a risk otherwise you have no way of knowing whether the controls are adequate or not.
  5. unphased

    unphased Screwfix Select

    The issue I have, though, with the wording of many of the Regulations, is that they do tend to illicit ambiguity. This is partly due in fact that the Regulations writers are not really good enough at explaining themselves. They try far too hard in every case to convey a message and electricians just love to argue about the true meaning behind a word or a sentence instead of accepting what it is saying. Premature collapse, early failure, unintended failure, collapse before time. How many different weays can you say the same thing before people will accept the meaning? Sorry, MGW, I think your unnecessarily complicating this.
  6. Coloumb

    Coloumb Well-Known Member

    I thought it was to stop cables being laid directly on top of false ceilings so they don't flop down when the ceiling tiles melt or being tied up with placky cable ties. I mean if the cables are properly run in separate metal trays then what's the issue?

    Wasn't this because of that fireman who got trapped in a load of cables that fell out the false ceiling?
  7. unphased

    unphased Screwfix Select

    Yes, Ben, that is the origin of the Regulation being introduced. It is intended to promote thought in to securing wires and cables that cross above a route that people use to get out of a building. Thats all. The death of firefighters trappped by a mess of wires was the reason for introducing it. Knee jerk reaction imho. The Regulation now introduced has , as usual, stretched things too far. Electricians in their infinite wisdom, have tried to think of as many situations as they possibly can that this new Regulation could apply. As I said in my post above, they always read far more in to the actual need instead of just following a basic ask. The ask in this case is to just give some thought in to supporting wires where they cross a route used by people. Simple as.
  8. unphased

    unphased Screwfix Select

    Unfortunately you will get the over zealous electricians who will insist on supporting wires absolutely everywhere and if I am honest you cannot blame them for trying, as the wording of the Regulation does (wrongly) now state "this applies throughout the installation, not just escape routes". How absurd. Its typical do all embrace all madness that allows no thought or common sense. It infuriates me why institutions such as the IET try to be too clever and too all encompassing and get it wrong every time. :mad:
  9. unphased

    unphased Screwfix Select

    In a house rewire, for example, how do you support cables that are dragged through floors and rest on the ceiling without taking the floor board up in their entirety? The ask in the Regulation cannot be physically achieved. You would need to pull a house apart, virtually, to introduce so-called fire proofed supports for all wires. 521.10.202 is more of a thoughtless over reaction than a real thought out requirement. Idiotic and irresponsible use of power.
  10. seneca

    seneca Screwfix Select

    There was a product many years ago, (and i'm talking '70's) called Philplug which you mixed with a little water and poked into the hole and then screwed into that, very good it was too and as it was a sort of asbestos fibre would have been ideal for these fixings. I don't know if it's still available, I doubt it as being asbestos based. H&S view, "oh god, not asbestos, you will die instantly if you get whithin 20 miles of it !! :p
  11. Coloumb

    Coloumb Well-Known Member

    I thought above a plasterboard ceiling was ok?
  12. Coloumb

    Coloumb Well-Known Member

    I would have thought if the raw plugs where melting things would be so hot by that time there would be zero chance of survival in any case, a few wires or no.
    Dr Bodgit likes this.
  13. Dr Bodgit

    Dr Bodgit Well-Known Member

    Good point. Holding up wires by use of plastic cable ties would be more of an issue then, since ties would melt pretty quickly and then you've got wires dangling all over the place.
  14. WillyEckerslike

    WillyEckerslike Well-Known Member

    Sounds like those old bendy metal ties would be ideal in that instance - one end fed through an eye on the other end and bent back on itself to secure it.
    Dr Bodgit likes this.
  15. MGW

    MGW Active Member

    I know in a gas plant we had stainless steel ties every 10 plastic to stop the cables dropping in a fire. However it was a gas plant not a house, and all the tray was metal and all the supports were metal.

    In a car park made of concrete and steel I can see point in having all cables in steel cleats or conduit, but in a house what is the point? I can see how the stick on trunking is a problem where with very little heat the glue goes soft and it falls off, I used caulk after fitting and as the glue went soft so the caulk went hard so it did not fall off again, when I did want to remove it hunks of plaster came with it, so clearly well fastened to wall.

    I have also found the plaster about same thickness to trunking so have in the past removed a line of plaster fitted trunking and then plastered up to and slightly over the trunking simply to make it look better. I would guess if the house did go on fire the cables would remain in the charred remains of the trunking, however I have no way as an electrician to know what will happen in a fire.

    And this to me is a problem, we are being asked to ensure something which is beyond our skill set. If we can go to a whole sale outlet and buy a consumer unit rated as fire resistant that's great, the same goes for trunking, tray, conduit if sold as fire resistant that's OK. Same with down lights again if the instructions say if fitted in a plaster board ceiling with the provided hood, using the recommended fire stop to seal wires in the method shown great. I have fitted bulkhead cable seals and I was trained how to fit them, same with flame proof glands, I went on a course to show me how to fit them, and we were recalled when a problem was found and shown the change in fitting practice.

    So if we get T2 trunking with clips that fit inside and instructions on how the clip should be fitted every meter or 1.5 meters or half a meter after the manufacturer has conducted tests to see how often they are needed, and it tells use to use a set type of fixing, then this is OK. The regulation would simply say in building class x you must use wiring installation type 1x and all we need to do is follow instructions.

    "premature collapse" is meaningless, I have not a clue what is considered as "premature collapse" and today without returning for training I have to ask if I have enough skill to sign as the designer? I can install, I can inspect and test, but even with a degree in electrical or electronic engineering I have to ask the question have I got the skill required to work out how long it would take before the wiring fell, specially after looking at pictures of a Liverpool car park, not even the steel and concrete held the cables from falling.
  16. joinerjohn1

    joinerjohn1 Screwfix Select

    No need to worry lads. I'm sure when you have a customer asking for a CU change, you always tell them the whole house needs re-wiring to bring everything up to date. ( You'll use fibre rawlplugs, and you'll be back in so many years time when the 18th regs come out) :D :D :D :D :D :D :D :D
  17. Mr Rusty

    Mr Rusty Well-Known Member

    If it's any help, we install SELV cable strapped to uPVC (pneumatic) tube around hospitals. Normally cable is strapped using nylon ties, but in exposed areas (where tube/cable is visible) we now use metal ties securing the cable to the metal stud hanger brackets. However, metal ceiling grids are deemed adequate by the main contractors as secondary support to prevent the cables "prematurely" dropping in a fire, so we continue to use nylon ties above ceilings and this gets signed off.
  18. leesparkykent

    leesparkykent Well-Known Member

    Unphased will hate the 18th when it's published as its not just escape routes....it's everywhere.
    Risteard likes this.
  19. leesparkykent

    leesparkykent Well-Known Member

  20. unphased

    unphased Screwfix Select

Share This Page