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Rewire double T5 luminaire for LEDs?

Discussion in 'Electrics UK' started by Albumen, 5 Aug 2021.

  1. Albumen

    Albumen

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    Both bulbs failed at exactly the same time, and there was a bit of a "pop" sound when they did.

    There's another fitting on the same circuit, on the same switch, which works fine. I've just put a meter across the leads feeding the fitting and got 241 volts. So I'm assuming that the ballast is kaput.

    Replacement ballast seems to be about £35, and is maybe a bit fiddly to replace (are those wires easy to get out and back in?).

    How would I rewire this to take LED T5 replacements?

    It looks to me as thought it's wired so that it will take two types of bulb - either L and N at the same end, or L and N at opposite ends. But I'm just guessing.

    I'm not sure about the colouring of the wires coming OUT of the ballast. Is brown live and white neutral?

    As far as I can tell from search all I have to do (hah!) is join all the lives to the live feed, and all the neutrals to the neutral feed.

    Or of course I could put a new LED fitting in, but it would look a bit cob, as there is another identical fitting in the same room.

    IMG_3315.JPG IMG_3316.JPG IMG_3317.JPG IMG_3318.JPG IMG_3319.JPG

    Any help appreciated.
     
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  3. ericmark

    ericmark

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    The electronic ballast is got rid of, one side only of the LED tube is power in, the other side is a short circuit, so line in to one pin at one end, then a wire from other pin at same end to a fuse which is same shape and connections as a starter, then other side of fuse to pin other end, and remaining pin to neutral so all pins wired in series, that way it does not matter which way the tube is inserted.

    I wired line and neutral to one end only which does work, but if some one replacing tube puts it in wrong way around it is a direct short circuit, so not a good idea.
     
  4. winston1

    winston1

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    Can you get 240v T5 LED replacement tubes?
     
  5. Sureitsoff?

    Sureitsoff?

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    what length of tube was in the fitting
     
  6. chivers67

    chivers67

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    Adding to Eric's comments just label the end up with the Power, when you insert them the Tubes are marked. You don't necessarily have to remove the ballast it just needs by passing.
     
  7. winston1

    winston1

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    It is an electronic ballast. It needs removing. It is also probably faulty as it went pop.
     
  8. chivers67

    chivers67

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    If it's disconnected and by passed it will just sit in the fitting!
     
  9. 333rocky333

    333rocky333

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    28W T5 is roughly 4ft
     
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  11. 333rocky333

    333rocky333

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  12. ericmark

    ericmark

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    There is a debate on fluorescent v LED with tubes, the fluorescent with a HF ballast is around 96 lumen per watt, and the LED around 98 lumen per watt, so very little in it, also the published life of a tube when using a HF ballast is around the same, so power wise around the same, and maintenance time also around the same. But fluorescent gets bad press as they compare the fluorescent using a wire wound ballast to the LED and so not really like for like.

    In real terms fluorescent tubes still cheaper than LED, but often we don't need the lumen output, so we get a corridor lit with fluorescent lamps to get the spread of light, and we could easy have lamps at 2200 lumen instead of 5600 lumen and we can fit a smaller output LED tube, but the florescent is fixed based on length.

    However since a double tube I would assume you need the light, so 28 watt fluorescent tube rated at 2900 lumen with a wire wound ballast, there is around a 10% increase when using an electronic ballast, so 3190 lumen, also a decrease in power when using an electronic ballast, so likely under 28 watt, the 18 watt LED is down to around 1710 lumen so looking at the web sites I found the fluorescent has more lumen per watt, however to get the 6000 lumen of the twin fluorescent you need a 4 lamp fitting, OK 3 lamp would be 5100 lumen so not likely to realise the drop in output, but when moving from tungsten or fluorescent to LED in the main it means more lamps, my single 100 watt tungsten in living room has been replaced with 8 x 6 watt LED.

    So need to consider if you can use LED with the lower lumen output?
     
  13. 333rocky333

    333rocky333

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    As Winston1 said earlier, i do not think you can easily get retrofit T5, let alone 28 Watt, T5 Led lamps in this country.
    T5 tube fittings single or double Afaik, never used Wire wound ballast, always Electronic
     
  14. winston1

    winston1

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    The 4,6,8,13W ones I grew up with certainly did. But these modern longer ones probably not.
     
  15. 333rocky333

    333rocky333

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    Yes I agree, they were the exception and there was no T8 alternative to them. still often found in older emergency fittings
     
  16. aptsys

    aptsys

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    You would probably be better served to replace the fitting with something designed to sink the heat away from the LEDs. Is there a reason to keep the original fitting?
     
  17. Albumen

    Albumen

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    Thanks for all the answers folks. Sorry not to have replied, or acknowledged the answers earlier. For some reason I wasn't getting the notifications.

    In the end, given that a new ballast was going to be £35, or the fact that T5 "shaped" LEDs don't seem to have quite enough output, I just installed a new LED fitting. One of these:

    https://www.bltdirect.com/v-tac-led-batten-50w-daylight-6500k-6000lm-with-samsung-chip?cat=6808

    Also T5 shaped LEDs in old T5 fittings sounds like a bit of a not entirely satisfactory bodge to me.

    This is in my home office/teaching studio. I did the calculations here:

    https://www.bannerengineering.com/za/en/company/expert-insights/lux-lumens-calculator.html

    And figured the 5 ft one gives me 850 lux at desk height. The recommended for "Technical Drawing" is 750 lux. It's not clear, but I think the various recommendations are minima, given that daylight is 10,000 lux!

    https://www.aon2.co.uk/illuminance/

    It's in a room with one of the T5 fittings. The difference is plain to see, and the 6400K colour does feel nice. In fact I'm wondering if I should have gone for the 6ft one now. The fittings are all the same, so I could easily swap a 6 foot one into the same place. Can office lights be too bright? As long as there's not reflective glare and it's well dispersed, presumably not?

    I'm convinced by LEDs. I know when it goes I'll have to replace the whole thing, but the simplicity of fitting, the cheapness, light weight (400g vs 3kg) all appeal.

    One question though - the supply was twin and earth. The fitting only has live and neutral, and it came with a snap-in fitting to join. On the supply I bent the earth back and taped it with electrical tape. Is that OK?
     
    Last edited: 6 Aug 2021
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