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Light bulbs wattage

Discussion in 'Electrics UK' started by linearamp, 28 Jan 2018.

  1. linearamp

    linearamp

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    Hi
    so i have a light fitting that takes 3 bulbs the sticker on the fitting states 3 x 28w which i understand .
    My question is would it be safe to use 3 x LED 6w equivalent to 40w bulbs ? or am i missing something or just being a bit thick .

    confused.

    Hope someone here can let me know .

    thank you

    Regards
     
  2. Ady J

    Ady J

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    if there's no little transformer in the fitting and it goes straight into the mains, give it a try
     
  3. JohnW2

    JohnW2

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    The "3 x 28W" is really just a maximum, probably arrived at by heat-generation considerations. I assume that you are talking about 'mains voltage' bulbs and LEDs (is that true?), in which case there would be no problem with what you propose.

    Are these lights on a dimmer? If so, you might well find that it's not suitable for dimming (satisfactorily, or at all) LEDs, even if they are 'dimmable' ones.

    Kind Regards, John
     
  4. linearamp

    linearamp

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    Hi John
    sorry i forgot to state that these are mains leds and bulbs.At the moment the light switch is a dimmer ,but quite a old one ,so im thinkng of swapping it for a normal switch or a newer dimmer .
    Just to clarify what was fitted from new are 28w halogen bulbs , the ones i have now info below
    made by a company called LAP

    LED's
    6 kWh/1000h. A+ rated. 25,000 hours average rated life.

    • Warm White
    • Dimmable
    • Wattage: 6W / Equivalent Wattage: 40W
    • Up to 25,000 Hours Life
    • 6kWh/1000h Life
    • Energy Rating: A+
    • 3 Year Manufacturer's Guarantee (T&Cs Apply)
    • Full Instant Light
    • Energy Efficient
    Will these be ok wont cause any fires / overheating or anything dangerous ?

    thanks again

    Martin
     
  5. JohnW2

    JohnW2

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    Normal switch would obviously be no problem. Dimming LEDs can be a bit of a nightmare, and the best bet (and even that not always foolproof) is to get a dimmer designed for the make of LEDs in question.
    They will/would be fine.

    Kind Regards, John
     
  6. ban-all-sheds

    ban-all-sheds

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    As a result of, or because of, what, do you have a light fitting?
     
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  7. James999ft

    James999ft

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    Apologies for hijacking the thread, but I've been curious for a while about maximum power ratings for bulbs and would like to ask others who may understand.

    Say I have a light fitting that says use bulbs with a maximum power of 60w, I have always assumed this is because an old 60w bulb would produce say 50w of heat and only 10w of light - so the light fitting is limited to 60w bulbs as it can only cope with 50w of heat.

    If I now have an energy efficient light bulb that consumes 12w, of which 2w are heat and 10w are light, then this should be as bright as the old 60W bulb but produces only 1/25th of the heat

    Is it right (assuming for a moment I have the relative light/heat efficiencies right) that if a light fitting can be used safely with a 60w traditional bulb then it could also be used safely with a 300w energy efficient bulb - as both would produce 50w of heat? And given how bright a 300w energy efficient bulb would be, even if you could buy such a thing, that there is now almost always no practical limit on the power of energy efficient bulbs that can be fitted to any light fitting?
     
  8. EFLImpudence

    EFLImpudence

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    Yes, you are correct.

    Although I do not know the relative heat values.
     
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  10. JohnW2

    JohnW2

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    You've been given the 'short answer', so now for the 'longer' one .....

    One would expect what you say to be the case, and to a large extent it is, but the situation is, in fact, somewhat more complicated than that.

    You will find fittings which specify 'maximum wattages' specifically for CFLs and/or LEDs which are surprising low in terms of your logic above. One of the reasons is probably the question of where the heat is generated, and where 'it goes'. With traditional incandescent bulbs, the majority of the heat generated is (like the light) radiated into the room - as one can tell by holding one's hand in front of such a bulb.

    With CFLs and LEDs, the actual light producing elements produce little heat. The heat that is produced by such lamps/bulbs is primarily produced by the internal electronics, situated close to the base, and little is radiated directly into the room (again, put your hand in front of one!). Although the amount of heat produced is a lot less than would be the case with an incandescent bulb of similar light output, a lot of what heat is produced is therefore conducted through the base, into the socket and other parts of the fitting. The potential thermal damage to the base/fitting is therefore proportionately greater than one would be the same with an incandescent bulb of the same wattage.

    Light fittings are increasingly coming with 'maximum wattages' stated for particular types of lamps/bulbs, in which case it makes sense to follow the recommendations.

    Kind Regards, John
     
  11. ban-all-sheds

    ban-all-sheds

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    LED elements do produce heat, they are extremely intolerant of it, and to make matters worse they have a NTC, which is why the current through them has to be closely controlled.
     
  12. John D v2.0

    John D v2.0

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    Just to add to the other replies a different perspective.
    The max wattage is there to protect the light fitting. Old school light bulbs aren't really affected by heat so if the fitting can stand 150c then everything is fine.
    Fit an energy saver and get the fitting up to 150c and the fitting will still be fine, but the bulbs delicate electronics will be cooked.
    So in many ways you have to be even more conservative with energy savers in enclosur fittings than normal bulbs. people have issues with fully enclosed outside lights killing retro fitfit ene saving bulbs more quickly. With a standard bulb, the fitting would eventually die through heat damage
     
  13. SUNRAY

    SUNRAY

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    I intended starting a thread about CFL's and heat, then found this one.

    My neighbour has a dawn til dusk bulkhead fitting and used to use a 60w bulb, summer 2016 it blew and got replaced with an 11W CFL, today we changed it for the 3rd or 4th time. So they are lasting 6 or 5 months as opposed to 5 or 6 years or incandescent.

    Are others finding the same issue?
     
  14. ban-all-sheds

    ban-all-sheds

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    No. I have CFLs outside on d-t-d (mine are dusk-to-dawn, as I find that more useful than having them on dawn-to-dusk :ROFLMAO:) and the life seems fine. Never logged it, but it's a hell of a lot more than 5-6 months. And I'd never expect an incandescent to last 5 or 6 years.
     
  15. SUNRAY

    SUNRAY

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    Ah yes but he is using negative light coefficient bulbs:)
    My experience with the early CFL's in domestic situations was quite poor and got to the point where I'd write the date of installation on the base and started taking them back under warranty. Their longevity has of course improved.

    My outside lights are on PIR's and the three fittings along one side of the house I was unable to remove the glass shades to clean them when we moved in in 1994. They were stuck fast and didn't unscrew from the brittle plastic holder so I left them with the intention replacing them soon, or at least when a bulb blew...
     
  16. DIYnot Local

    DIYnot Local

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