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Ceiling Flush Light

Discussion in 'Electrics UK' started by Indigogo, 17 May 2021.

  1. Indigogo

    Indigogo

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    Good Evening gents,

    I have a couple of queries about this light fixture. Photos attached.

    The lighting upstairs is on a spur so it's not complicated to wire up. I put a smaller version of this one up in the little room a week ago but this big unit has thrown me a bit. The instructions are crap, it basically says live to live, neutral to neutral, job done.

    The connector block on the smaller one was on the back with space between the ceiling and the backplate, but for some reason this one is inside the light right next to the bulb, although the socket for the bulb seems to be made out of some ceramic material. Does the light look safe?

    Where I want to put this is to replace a crappy old pendant light in the passage but I unscrewed the fixture from the ceiling first to check and there's not enough wire to get around this backplate and through into the light (it's about a foot and a half wide) without moving the flush light off to the side and it will look daft offset that much, so what I intend to do is use a wago junction box and connectors, and put some 1.5mm cable through. However, I don't think I can get the cable through that silly hole with the clear plastic washer you can see, and I'm guessing you're not supposed to. Can I cut the outer sheath of the cable, and just feed the live, neutral and earth through the hole, and cover the earth with sheath, and cover the live and neutral with the white sheathing that these units come with? It's the same stuff that is covering the wires you can see from the block to the lights, both of the fittings I've bought come with it. And is heat an issue? I wasn't sure if heat-resistant flex might be better in this situation.

    Then finally, the current plastic pendant rose is just screwed into the ceiling and it's sitting smack bang between two joists. You screw this thing in on those 4 dimpled holes, and I can't get any of them near the joist without moving the light off centre too much. This light comes with four screws and four cheap grey plastic rawl plugs, I don't really trust them, I only used them on the little room light because there were 3 holes and I could line two of them up with the joist. I can get on top of this easy from the attic so I was considering bolting it to the ceiling with washers but that seemed a bit much, is there a better way? This unit isn't massively heavy but it's probably a good half a kilo or more.
     

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  3. terryplumb

    terryplumb

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    Use heat resistant flex rather than twin and earth cable. 1.5 mm² is way more than what you need to feed that light 0.75mm² is ample. The outer sheath should go into the fitting and the heat resistant sheath( the white stuff) used over the insulated conductors. Screw the fixings into wooden noggins in the loft.
     
    Last edited: 18 May 2021
  4. 333rocky333

    333rocky333

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    You would usually put the connection behind the fitting and run heat resistant flex into the fitting not the single cores,it seems they have tried to make it a DI fitting, personally I would earth it instead.
    Any wires or connections behind need to allow for the heat generated.
     
  5. terryplumb

    terryplumb

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    There is an earth terminal ,outside the connector block ,just aside the lamp holder.
    Poorly designed really.
     
  6. Indigogo

    Indigogo

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    Thanks both of you, very helpful. Hadn't thought of noggins!

    Would you say it's safe? it comes from Marlowe Lighting Company via Wayfair so ... you would hope so. I'm guessing the block has to be somewhere a bit crap because the dome shade is quite low profile, I was considering drilling a hole behind that right bayonet and moving it and trimming the wires but ... on second thoughts.

    In terms of allowing for heat, how would you allow for that? The one I did in the little room was red and black lighting cable with a bare earth wire, I think I might add a wago connector to that and replace with the flex as well... just to be safe. but as I say there was a gap big enough for the connector block on the back and there's hardly any cable behind. On this one, that back plate goes almost to the ceiling surface, with about .. 3-4mm I suppose just enough to sit a cable. What I will do is use the heat-resistant flex and drill a hole through the clear plastic ring when it's on the ceiling, and feed the cable straight through, so the cable is sitting above the plasterboard and there's as little cabling in the fitting as possible. Not much more I can do than that.
     
  7. FrodoOne

    FrodoOne

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    That fitting with heat resistant wiring and porcelain sockets is made to have incandescent lamps installed.

    However, you show a LED, so I presume that you intend to install LEDs.
    While someone in years to come could install incandescent lamps, if you now install LEDs any heat generated (and held without ventilation) is much more likely to shorten the working life of the LEDs than to damage the wiring.

    The LED lamp which you show is of a type which does generate appreciable heat (for a LED) and requires ventilation.
    The fact that about one third of the lamp consists of the "driver" is an indication of this.

    Lamps of the LED filament type have little space occupied by the "driver" (it is all in the base) and generate much less heat than other types.

    https://www.thelightbulb.co.uk/candle-5w-240v-b15-clear-2700k-led-fil-cr-7147-dimmable/

    (Similar lamps with other bases are available.)
     
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  9. JohnW2

    JohnW2

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    There will be variation between designs in how well heat is dissipated/removed but the "amount of heat generated" will, for a given LED 'power' (light output) surely be the same for any lamp whose driver uses the same (electronically) type of driver, regardless of where the driver electronics are located, won't it?

    Kind Regards, John
     
  10. FrodoOne

    FrodoOne

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    One of the main cause of failure in LED lamps is excess heat build-up affecting components in the "drivers" , especially any electrolytic capacitor(s) - by drying them out.

    I suggest that you compare a LED "filament" lamp with the other type of LED (of similar light output (lumens]) and roughly the same nominal wattage.
    I have found that "driver" (in the base) of LED "filament" lamps becomes much less warm than the "driver" of similar rated LEDs of the other types.

    It seems that the LED "filament" lamp does not use the same type of "driver" as the others. As you can see from the examples below, it fits into only the small base !

    See


    In these above examples, the second one contains no electrolytic capacitor.
    While the other does have several small electrolytic capacitors, they are all contained within the base which is away from the heat generated by the LED filaments- and the metal base and socket provide good "Heat Sinking".

    Contrast this with where the electrolytic capacitor (and other components) are in a "chamber" in towards the "base" of the lamp but near a metal heat-sink (heated by the LEDs.)
     
  11. JohnW2

    JohnW2

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    This seems to beg the question as to why, if they can 'get away with' (without flicker) drivers of that design for "filament" LED lamps, why can't they do similarly for all LED lamps? I'm sure that most users (particularly those old enough to have been brought up with incandescents!) would prefer drivers that were fully contained within the base.

    Kind Regards, John
     
  12. FrodoOne

    FrodoOne

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    LED filament lamps are relatively new.
    No doubt manufacturers using "older" technology continue to use the same technology, parts, circuit boards etc. because they they have made the investment in that technology and wish to wring the most out of it that they can.

    While most LED filament lamps are "clear", "frosted/opal" lamps of this type are becoming available https://www.ebay.co.uk/itm/353287080895?hash=item52418d0bbf:g:Sm8AAOSwD9VfuM8w

    A year or so ago, I did find some "Philips" lamps of this type here but those now available seem mostly to be branded "Osram" - or "Sylvania", and it is my understanding that "Sylvania" is now owned by "Osram".
     
  13. JohnW2

    JohnW2

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    That could be at least part of the explanation, although the 'filament' lamps have been around for a fair while, at least here.

    As I implied, I would imagine that many uses would prefer lamps which looked like the old incandescent ones (i.e. with all of the 'driver' in the base), and a good few would probably be prepared to pay a premium for that - so I remain rather surprised that at least some of the manufacturers have not moved in that direction (assuming that there is not some reason why they can't).

    It's not easy to see how any driver could produce anything approaching 'smooth DC' without some significant capacitors involved, so I wonder whether these lamps might somehow be incorporating some 'long'-persistent phosphors or suchlike into the LED elements?

    Kind Regards, John
     
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    DIYnot Local

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