Suitable CU

Discussion in 'Electricians' Talk' started by snipper1, Jan 28, 2004.

  1. supersparky

    supersparky New Member

    not many children are 6 ft tall, and not many people have wall lights at anything under 5 ft on a wall..

    in my personal view shutters should be fitted on light fittings as a reg on wall lights, because you are normaly 'blind' as to what is above the shade...

    also not many children will get their metal steps out the garage, more likley a wooden table or chair, in which case the voltage ins unlikly to flow across their chest.

    an alternative would be to have a 100mA/30mA split load box, as used in TT instalations, these how ever are pricy, and if i gave most coustemers a choice of one, they wouldent take it, would rather go for the normal split load.

    i do think that we should be combatting the rogues as a priority first, a short while back i came across a volex bored that had been installed next to the original, using 3 of the 5 ways, it was main isolator, supplying sockets that could have been used out side easly, anyways this cu was about 1 foot off the floor and it would have been possible for one of the very young children to directly touch the busbar.

    ss
     
  2. lensman

    lensman New Member

    not many children are 6 ft tall, and not many people
    have wall lights at anything under 5 ft on a wall..

    I've seen a few people (including myself) who have wall-mounted lights by their bed - generally about 4ft off the ground. I don't have any kids, but some of the others do - hadn't occurred to me that it might be dangerous to have them this low, so thanks for the warning.
     
  3. ban-all-sheds

    ban-all-sheds New Member

    But if you unscrew a lightbulb and jam your fingers in there, what are the odds of making contact with live and earth, compared to live and neutral?

    How many light fittings these days have an earth connection anyway?
     
  4. supersparky

    supersparky New Member

    screw connection ones have a neutral surround and the phase is right at the base, you would definatly make a contact with neutral before live, so would have a burnt finger....trust me kids would never do that again!!

    plus like i said, shrouded connections are what i beleve in. without a screwdriver or a bulb its impossible to move the shroud, if you move the shroud with a bulb, you can't put yer finger in aswell!!! if you do so with a screwdriver....you deserve a whack!

    lensman, don't condem just yet, look towards shrouded connections!

    even at 4 ft though, a young child would have to stand on the bed, its unlikly taht this would give a path to earth, and he or she would most likely just get a whack off the mains.

    the problem, like i have said before is that with most high wall lights, you are reaching up 90% of the time, so are blind to where the live parts are, this problem is amplified if the fitting is of the damn plaster type!!

    but, its unlikly to kill, because when reaching up you are unlikly to 'grab' the live if you get a whack, even if you do you will have the full weight of your own body to pull you off.

    but, like always, you will get one person who dosent bother to turn off.

    another point i made was about taht dodgey workmanship on the volex bored, right now, sorting that type of thing where there is not any device that will kill the power. it dosent even bare thinking about what 'could' have happened if one of the kids had touched the bus bar.

    ss
     
  5. snipper1

    snipper1 New Member

    Split load v Non split load CU`s !!!!!!!!!!!!

    Reading these posts have certainly opened my eyes to the many ways in which a house can be designed/wired.

    "Tell me if i`ve misunderstood"

    Split load CU`s are benificial if you want to split-up "say" upstairs from downstairs, normal house/ extentions etc.
    This seem to be a bit over the top considering all i wanted to originally do was to update existing consumer box to bring it up to standard and to pull new cables through to the new build.
    Would`nt a normal CU with suitable rated MCB`s be good enough or is there any reason "which i may of missed" that i need to split the load
     
  6. supersparky

    supersparky New Member

    "Split load CU`s are benificial if you want to split-up "say" upstairs from downstairs, normal house/ extentions etc."
    thats not what is ment by split load
     
  7. jomed

    jomed New Member

    but, its unlikly to kill, because when reaching up you are unlikly to 'grab' the live if you get a whack, even if you do you will have the full weight of your own body to pull you off.>

    Okay in theory, but still a significant risk for children which could be overcome if the lighting circuit is protected by an RCD.
     
  8. supersparky

    supersparky New Member

    the prospect of even 30mA would make me shudder on thinking about a small child coming into contact with it.

    unless you have wall lights at arround 2 ft off the floor, i don't consider them a risk to small children, as to reach higher they would have to stang on something, which is unlikly to bee a good path to earth.
    i can see exactly where you are coming from, and many of my coustemers have a huge, and sometimes go over-bored with plans for saftey, hence they want a long explanation as to why i dont think this, or that or that is a good idea, others, are the same but leave it up to me....and then you get a few that couldent care less either way. its just the way things go

    but in my view, the liklyhood of deth by electrocution off the lighting circuit is almost null

    where as, death by falling down the stairs, on its own poses a bigger risk.

    if i were going to do as you suggest, i would instal emergancy lighting on the stairway.

    i think your going overbored personly, but there is nothing at all wrong with that, as long as you counter the potential dangerous situations that arise from making something 'safer'
    in your case i would have, like i have already suggested, gone for a 100mA/30mA split load CU

    lensman, (i think), was the other person who went well overbored with safty, but did, to his credit counter one of the potential situations that could have arisn from the use of complete rcd protection.

    SS
     
  9. supersparky

    supersparky New Member

    i realy MUST start to read through my posts before hand, some of the typos are terrible 'bee'(be) and 'stang'(stand)

    bare with me....i type faster than i can correct :(

    ss
     
  10. Damocles

    Damocles New Member

    If thats what you understand by split load, then your eyes need opening a bit more. Try looking at some of the old posts and use search to look up interesting words, see what people have said. There was some related recent discussion on different topics, so dont know if you have read them. some of the posts here kind of assume you would have.

    Split load means part of your wiring is protected by a RCD and part is not. Everything is separately protected by mcbs. The advantage is that a RCD detects very small currents escaping to earth and can switch everything off much more quickly. It does not protect against excessively high currents, that is done by the MCBs. The disadvantage of having one RCD covering lots of circuits is that a fault on just one of them switches off the power to all of them. This may be dangerous too, most obviously if you suddenly find yourself in a completely dark house with no electricity.

    Chances are that apart from heating (cooker, water,storage heaters) all the power in your house could be supplied from one 32A circuit. But dont do that. For convenience and other technical reasons it is normal to split up the house into different circuits. SO, socket ring for upstairs, ring for downstairs, ring for kitchen where there may be a lot of power hungry devices. Separate mcb for a shower,for cooker, for anything needing a lot of power. Separate circuits for lights because they require very little power, so it is possible to restrict electrical risk by using 6 or 10A circuits. 6A mcb lighting circuits can be a problem because a bulb which blows can draw enough current to trip off the mcb.
     
  11. snipper1

    snipper1 New Member

    Ok, Personal apologies go out to Supersparky, Damocles and Jomed. !

    Having now read previous posts regarding split-load CU`s BINGO, i think i now understand.

    My scenario-:
    "How does this now sound" ?

    RCD-side.
    Upstairs sockets.
    Downstairs sockets.
    Kitchen sockets.
    Cooker
    Garage consumer unit?

    Non RCD-side
    Upstairs lights.
    Downstairs lights.
    Kitchen lights.
    Kitchen-->FCU-->12v unit lights.
    Kitchen-->FCU-->cooker hood (light/extractor)
    Fire detection.

    X2 questions.

    1. My garage consumer unit supplies a washing machine, tumble dryer and a freezer... would you put it on RCD side or non RCD side "BUT" possible fit a separate RCD in place ?

    2. The bathroom will be fitted with an extractor fan, personally i don't want the fan to come on when the lights on but when either a bath or shower is required! is there an extractor that can be fitted that can be manually activated by a switch.
    ...Having an electric shower anyway is there a way in which you can wire the shower and extractor from the one pull switch.
     
  12. Damocles

    Damocles New Member

    unless you are running separate circuits I would but the FCU's on the RCD protected ring. They are not really mission-critical devices. maybe you need the lights exempted from the RCD if you really need them, but won't you have a standard light on a non rcd circuit?
    freezers are a bit in-between.

    Just don't have two rcds protecting the same circuit.

    I think all the fans can be fitted so they are on a separate switch. not sure what the rules say about this, but I agree with you. I prefer an optional fan. Noisy if you are lying in the bath too.
     
  13. ban-all-sheds

    ban-all-sheds New Member

    unless you are running separate circuits I would but the FCU's on the RCD protected ring. They are not really mission-critical devices. maybe you need the lights exempted from the RCD if you really need them, but won't you have a standard light on a non rcd circuit?
    freezers are a bit in-between.


    Don't agree about the F/F - I would never put them on an RCD. But I agree with the rest - I would approach it from the direction of "protect everything except ones you shouldn't", i.e. lights, F/F, alarms, rather than "only protect the ones you should", e.g. downstairs sockets.

    Just don't have two rcds protecting the same circuit.

    I though this was a fairly common thing to do, with less sensitive and/or time-delayed devices upstream of more sensitive ones, to provide discrimination. Or is that only whith TT?

    I think all the fans can be fitted so they are on a separate switch. not sure what the rules say about this, but I agree with you. I prefer an optional fan. Noisy if you are lying in the bath too.

    I'm wrestling with just this problem now - I want a time-delayed fan controlled by the shower switch, not the lights, so that:

    a) The fan will always come on when the shower is used, no matter whether the light is on or off
    b) The fan won't come on just because the light is on.

    The big problem is that the cable for the fan will be 1 or 1.5mm, and the shower cble is 10mm, and a few problems arise.

    1) You can't get 2 x 10mm into the terminals of the pull switch to get the permanent and switched live

    2) You need to fuse down from 50A to 5A when you go to the thinner cable for the shower, and that means 2 fuses, to fit at the ends of the 10mm. Plan A is to use a couple of unswitched FCUs, Plan B is to use an old rewireable-fuse CU that I have, and saw the busbar in half so that I cna fuse 2 independent circuits.
     
  14. Damocles

    Damocles New Member

    yes, multiple rcds should be lovely with discrimination so they only trip in sequence, but don't think we would get that here. would be a standard one at house cu followed by standard one at garage. not much point in doing that?

    considered having a separate light in the shower connected to the fan, sparate from the main bathroom light? i know, too many switches cluttering up the place.
     
  15. snipper1

    snipper1 New Member

    Sounds a good idea until you think off extraction when running a bath.
    What if you wired a separate shower light to the shower, (off the same pull) and the fan on another separate pull? is this aloud.

    Would it be a better idea to run the garage consumer unit (GCU)on the non-RCD side and place a new GCU with an RCD in situ ....... it appears that my GCU is not covered currently by an RCD (it must be well old)!
     
  16. ban-all-sheds

    ban-all-sheds New Member

    Well - whatever you have that's supplied by the shower switch you still have the fusing problem, and not being able to get 2 x 10mm into the switch terminals. My plan is to use service connection boxes as JBs. They will be accessible (enough), and if they're good enough to connect meter tails carrying 100A they'll be good enough for the shower cable.

    And if I want the fan on when the shower isn't, there's no reason why I shouldn't pull the shower switch cord. At the moment it never gets turned off anyway....
     

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