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Wiring multiple LV downlighters

Discussion in 'Electrics UK' started by GeoffM, 16 May 2009.

  1. GeoffM

    GeoffM

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    Ok, I've seen lots of discussion about the cons of downlighters but that's what I'm going with! :LOL:

    What I have now is a standard batten light fitting in the bathroom which I want to replace with 5 downlighters (bathroom zone 1). One would go in the hole of the existing centred fitting with four lights near the corners of the room.

    If I were to do a one-for-one replacement then it's easy, just wire the transformer into the terminals for the existing batten light. But I need five. I bought a transformer which is listed as 20-60W which I *think* means a minimum load of 20W and a maximum of 60W. Using 5x20W bulbs that would be too much for the one transformer. So do I buy a bigger transformer or buy 4 more transformers (one for each light)?

    If I have multiple transformers, how do I wire the mains side of it? Daisy chain the transformers via multiple junction boxes? But wouldn't that create a spur-off-a-spur-off-a-spur-off-a-spur-off-a-ring which is bad?

    Finally (I think!) if I have a transformer supplying more than one bulb, do I need to use heat-resistant wires? The transformer I have is pre-wired with such.

    I'll get a sparky to check the wiring afterwards but want to get it right first. Thanks.
     
  2. Steve

    Steve

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    Then go for mains downlights. No transformers. They are more versatile - you can fit a wider variety of lamps.

    sounds like a good plan

    I'd use that Tx for one light Then buy 4 more Tx's. Buy small electronic ones and fit them just inside the downlight hole (but not OVER the fitting)

    You're not wiring them to a ring main. You can do what you want on a radial circuit.

    I believe fittings dont require heat resistant, their terminations are normally a sufficient distance to not require it. But if you want to go belts and braces, go for it.

    What exactly do you think he's going to do? He wont "sign it off" as his own. This work is notifiable to your local building control dept, who will charge a fee which will cover inspection and testing by one of their sparks.

    This final quote implies a spark wont do it right and you know better?
     
  3. EdwardCurrent

    EdwardCurrent

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    Hello Geoff,
    I would strongly advise against you buying any fittings for your electrician to fit.
    He is taking responsibility of the notification, work, and 'suitable' fittings etc.
    You should talk through the 'suitability' of the fitting first with him and let him do the work required, it is not your problem.


    Ed [/wiki]
     
  4. GeoffM

    GeoffM

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    Oops. Point taken but I've already bought them. I might be able to return though.

    No, far from it. I thought (obviously wrongly) that you can do the wiring yourself but it has to be signed off by a qualified electrician. Just trying to save a little money, that's all! But trying to do it right too.
     
  5. ban-all-sheds

    ban-all-sheds

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    You're going to have some serious hurdles to overcome.

    This is notifiable work, and "signing it off" doesn't work the way you seem to think - see http://www.diynot.com/wiki/electrics:part-p.

    Since it's notifiable, there's no way you're going to be able to get Building Regulations contraventions past the BCO. It isn't just Part P that you have to comply with, it's all of the relevant regulations, and Parts C & L are immediately obvious hurdles.

    If you've got a roof space over the bathroom then you will have to completely seal around the lights as you must prevent warm moist air from entering the unconditioned space because if you don't you'll get condensation up there - a contravention of Part C.

    Part L problems are twofold - if there's insulation in the loft then you cannot remove it, because if you do that will make the degree of insulation worse than it was before, i.e. your degree of compliance with Part L will be less satisfactory than it was before. But you can't leave the insulation in place because the lights will require a clearance all around them to avoid overheating, so you'll need to install some kind of structure around the lights to provide clearance and to allow the insulation to be maintained.

    See these for details of keeping insulation, providing space around the lights and sealing against moisture:

    http://www.nhbc.co.uk/NHBCPublicati...ical/StandardsExtra/filedownload,16553,en.pdf

    Pre-formed cap to seal downlights: http://www.aico.co.uk/firecap_loftcap.htm (It's NOT a firehood....)

    The second Part L issue will be the efficiency of the lights. Whether you use ELV or LV lights they will not be efficient enough - even though the Building Regulations don't actually mandate luminaires which cannot take incandescent lamps that is what Approved Document L says you have to use for a certain percentage of your lights, and rightly or wrongly many councils regard that as mandatory, so you could have a real struggle to get ELV or LV halogens passed.
     
  6. GeoffM

    GeoffM

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    Thanks, BAS. Regarding sealing, these are all zone 1 shower jet proof lights, and have a silicone ring around them which should form the moisture barrier between the fitting and the plasterboard. Only 2 are in zone 1 but there was no price difference - and better to slightly "overengineer"!

    Thanks for the links - I knew I needed an "air box" around the fitting but didn't know what it was called!

    [Edit] - this is replacing a standard incandescent fitting, not a low wattage thingy (other rooms do have those new square sockets, something like 1/3 of the lights in the house are these newer square sockets). I'm not sure where I stand on this issue though...

    So do these satisfy your points or have I missed anything?
     
  7. seasickstevie

    seasickstevie

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    :confused:
    What are these?
     
  8. RF Lighting

    RF Lighting

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  9. GeoffM

    GeoffM

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    Yep, those be them. Very little in the way of lampshades available compared to the older style.
     
  10. ban-all-sheds

    ban-all-sheds

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    Is an IPx5 luminaire completely vapour proof, or just proof against water jets?
     
  11. GeoffM

    GeoffM

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    "IP44.Fitting is protected against solid objects upto 1mm & against water sprayed from all directions (including condensation)"

    I can only go by what it says on the tin![/i]
     
  12. ban-all-sheds

    ban-all-sheds

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    Condensation is not water vapour, water vapour is not condensation.

    Well - it's your roof timbers.
     
  13. GeoffM

    GeoffM

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    True, one gathers, one swirls. But as I said, that's all it states. But one would expect a showerproof zone 1 fitting to be such (well, at least that's what logic says). However, I will be fitting those dome things in the roofspace which IIRC are vapour proof.
     
  14. GeoffM

    GeoffM

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    Just spoke with Swindon Building Control. Although they can inspect the *building* work (re condensation, insulation, structural etc), none are qualified electricians so they have to subcontract to a qualified, competent person with the associated fees being passed on to me! So - as he said as well - I'd be better off just getting that competent person to do it in the first place!
     
  15. ban-all-sheds

    ban-all-sheds

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    They are not allowed to pass the fees on to you - that's what the fee you pay them is for.
     
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