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Thread: LED T8 tubes/fixtures

  1. #1
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    Default LED T8 tubes/fixtures

    I picked up a pair of LED T8 4-foot tubes, Honeywell branded, 18W. They advise using only with
    electronic "instant-start" ballast. I got a 2-tube fixture which matches the description.

    First test, one tube lights very dimly, almost looks like leakage current, the other not at all.

    Swapping tubes makes no difference. Both tubes and fixture are new, not suspecting a defect in either, but will
    check (do not use long tubes/fixtures so have no spares around the house).

    I'm suspecting ballast compatibility issue; could someone provide input on this?

    Dave

  2. #2
    *Flashaholic* idleprocess's Avatar
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    Default Re: LED T8 tubes/fixtures

    LED tubes that work with ballasts are a crap shoot - even from name brands like Philips. As I understand it, the purpose of the ballast is to overcome the cold-state physics of the tube with brute force: zapping an arc into existence with multi-kV DC pulse(s) becomes more conductive, transitioning to maintaining the arc with steady AC current as the gas heats up and at something close to mains voltage. LEDs are pretty simple DC devices, so "ballast compatibility" essentially means complexity beyond an AC-DC converter to coax the ballast into immediately supplying hot-state voltage so that it can get down to the business of converting AC to DC for the LEDs.

    I've personally installed hundreds of line voltage operated tubes instead: rewire the "tombstones" to the mains wiring and remove the superfluous ballast altogether. Non-shunted tombstones are pretty cheap online or from local electrical houses as is the ~20 ga wire used to build up new harnesses (unfortunately it's not easy to source such thin wire in solid format from big box home improvement stores).

    I realize that this is not an option with a number of LED tubes, particularly those sold at big box home improvement stores (strangely enough, Philips and other 'name brands' aren't line voltage compatible from what I've seen). But retrofitting the fixture is ultimately a lot simpler than balancing ballast compatibility and removes a superfluous wear item from the system. Buying from specialty suppliers on the 'zon or locally seems to net you a cheaper, more versatile product: in late 2016 I was buying line-voltage / electronic-ballast compatible tubes from a local commercial lighting specialist for >$12 each with a per quad-fixture cost of <$60 total (tubes, tombstones, wiring, wire nuts, DIY labels) ... today the tubes can be had with UL / DLC labels for ~$10 each.
    Last edited by idleprocess; 04-15-2018 at 02:38 PM. Reason: info++
    I apologize that this letter is so long; I did not have time to write a short letter

  3. #3
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    Default Re: LED T8 tubes/fixtures

    Thanks for a helpful response.

    LED tube instructions list a number of compatible ballast vendors/types. Not sure what's inside my fixture, and it would be a hassle to take it apart. Funny that the vendor claims these are Plug'n'Play (right!).

    I took end caps off one tube, notice single wire to one pin on each end. Not sure if the wiring is an issue? I don't want to rewire them.

    I also found that by rotating bulb in socket, at one point there was a brief flash of bright light more indictive of normal brightness.

    In any case I am not out much money. The fixture could be used with regular fluorescents, though hoping to get the LED tubes going. LED output is lower, 1800 lumens v. 2400 for 32W fluorescent, but better efficacy (claimed), 100 l/W versus 75, and 50k hours. Even if the 50k hours turns out to be only half, it would be worthwhile.

    BTW what is risk of damage should a LED tube be used with a magnetic ballast, or just not functioning?
     
    Dave

  4. #4
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    Default Re: LED T8 tubes/fixtures

    I'm reading up on fluorescent lamps, ballasts, wiring, starting etc., unfortunately not yet able to figure out specifics of why this fixture/tube combo is not working.

    I checked wire colours on the fixture sockets:


    BL/BL <--> BL/YL
    RD/RD <--> RD/YL


    This is the closest I can find for 2-lamp ballast:


    http://hmlighting.com/images/products/ballasts/WiringDiagram/2SL15T-WD.jpg



    The sockets are not shunted i.e. no dc continuity between socket pins at each end.


    Wondering if changing the lamp internal connections to one pin at each end cap (but NOT shorting the pins together) might help; but not until I understand a bit better what the ballast connections do (besides the colour code).


    Dave


  5. #5

    Default Re: LED T8 tubes/fixtures

    I'm not an electrician. Perhaps you have a "rapid-start" ballast instead of an "instant-start" ballast. I've seen some with as few as 3 output wires, using shunted tombstones, and maybe that is what your LED T8 tube is expecting.

  6. #6
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    Default Re: LED T8 tubes/fixtures

    The fixture states it is electronic instant-start. Tube instructions specify either instant- or rapid-start but the ballast compatibilty list only gives IS. So unless one is wrong (or both,unlikely) they should work together, but don't.

    Wondering what the function of the connected wires is based on their colour-coding, for example what's the common yellow wire for both tubes.

    Would rather not take the fixture apart as it is a cheaper one using extrusion with end-caps which are press-fit; may try though.

    Dave

  7. #7
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    Scowl Re: LED T8 tubes/fixtures

    I picked up another T8 LED tube (Philips 17W) at HD. This tube also did not light in the fixture. At this point, still suspecting neither the fixture nor tubes are bad, just incompatible.

    Next, picked up a pair of regular T8 32W tubes. First one I tried lit up instantly, instant-start as claimed.

    Additional tubes totalled about $25. No complaint, wanted to do some tests at modest expense. Fixture works fine with fluorescents, and the LED tubes are unlikely defective or damaged. I had hoped to leapfrog into LEDs, not quite so simple.

    So, no question as to hit and miss but I'd like to find the technical reason for this. Meantime have been studying a bit about ballasts, how the electronic ones use resonance to get high starting voltage, etc. Possibly could the ballast initially be seeing the LED load as a fault, prior to "starting", and shut down? Or would it likely be tube internal connections i.e. one pin only per end?
     
    Dave

  8. #8
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    Default Re: LED T8 tubes/fixtures

    Quote Originally Posted by Dave_H View Post
    ... Possibly could the ballast initially be seeing the LED load as a fault, prior to "starting", and shut down?
    Yes - that's my guess. I had a similar problem, and chalked it up to that (with no evidence - just a hunch, though).

    Or would it likely be tube internal connections i.e. one pin only per end?
    I doubt it, but that'd be an easy experiment to run, no?
    Jim

  9. #9
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    Default Re: LED T8 tubes/fixtures

    The Philips tube end-caps are well sealed and unlikely to get them off without damaging the tube. Honeywell tube end-caps come off easily (remove one screw). Most I could do is switch wire from one pin to the other (I would NOT short two pins together)

    Dave

  10. #10
    *Flashaholic* idleprocess's Avatar
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    Default Re: LED T8 tubes/fixtures

    All the tubes I've used that can run from mains power are "single or double ended" meaning that you can apply mains power just at one end or on both ends (just make sure that you're doing so on opposite pins, natch). This ensures maximum compatibility with existing fixtures. My assumption is that they have hot and neutral buses connecting the same pins at both ends.
    I apologize that this letter is so long; I did not have time to write a short letter

  11. #11
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    Default Re: LED T8 tubes/fixtures

    I replaced 76 T8 Fluorescents at my house with with 120VAC input tubes with the non-shunted tombstone swap out. Could not be happier. Kumho Tubes, 5000K, 22 Watt, 2650 Lumens per tube. They don't seem to be making that tube any longer.
    WWII 60" Carbon Arc (Sold), 1.6KW NightSun, 1KW VSS-3A, .8KW TrakkaBeam, 600W M-134 Light, 500W X-500-14s, 500W Starburst, 500W A120b, 450 Watt AEG German Leopard 1 Tank Light, 300W Locators, Megaray, 150W Communicator, Maxabeam Gen3, Syniosbeam by Enderman

  12. #12

    Default Re: LED T8 tubes/fixtures

    I think it could be a ballast issue. Just get an LED ready fixture that is already rewired to work with a direct wire LED tubes. no ballast drama or anything! I saw some shop lights going for around $40 bulbs included on the internet. I always buy these for my clients and been working with a company called Four Bros Lighting recently and they're pretty good.

    Quote Originally Posted by Dave_H View Post
    I picked up a pair of LED T8 4-foot tubes, Honeywell branded, 18W. They advise using only with
    electronic "instant-start" ballast. I got a 2-tube fixture which matches the description.

    First test, one tube lights very dimly, almost looks like leakage current, the other not at all.

    Swapping tubes makes no difference. Both tubes and fixture are new, not suspecting a defect in either, but will
    check (do not use long tubes/fixtures so have no spares around the house).

    I'm suspecting ballast compatibility issue; could someone provide input on this?

    Dave

  13. #13

    Default Re: LED T8 tubes/fixtures

    Quote Originally Posted by idleprocess View Post
    I've personally installed hundreds of line voltage operated tubes instead: rewire the "tombstones" to the mains wiring and remove the superfluous ballast altogether. Non-shunted tombstones are pretty cheap online or from local electrical houses as is the ~20 ga wire used to build up new harnesses (unfortunately it's not easy to source such thin wire in solid format from big box home improvement stores).

    I realize that this is not an option with a number of LED tubes, particularly those sold at big box home improvement stores (strangely enough, Philips and other 'name brands' aren't line voltage compatible from what I've seen). But retrofitting the fixture is ultimately a lot simpler than balancing ballast compatibility and removes a superfluous wear item from the system. Buying from specialty suppliers on the 'zon or locally seems to net you a cheaper, more versatile product: in late 2016 I was buying line-voltage / electronic-ballast compatible tubes from a local commercial lighting specialist for >$12 each with a per quad-fixture cost of <$60 total (tubes, tombstones, wiring, wire nuts, DIY labels) ... today the tubes can be had with UL / DLC labels for ~$10 each.
    Agreed! I do the same for my clients. a little bit harder up front but way better on the long run! I buy my LED tubes for around $6 UL/DLC and sometimes DLC4.0.

  14. #14
    Flashaholic* fivemega's Avatar
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    Default Re: LED T8 tubes/fixtures

    These are not bad for $28 each.
    Sometimes on sale for $20 each at store.

  15. #15
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    Default Re: LED T8 tubes/fixtures

    I recently bought one of the cheapest 4-foot dual T8 ceiling fixtures ($22) and it works with several different LED T8's I have...including Philips and Honeywell. The ballast type is unspecified but obviously electronic by size and weight. Picked up a couple more tubes which had glass shell.One broke, now getting a chance to look inside. Not impressed with construction, LEDs are on a thin flexible strip (which tore on sharp glass edges). No brand mentioned but not a commonly known one. On related subject I found some surplus U-bend 4-foot T8 LED tubes which are direct-connect i.e. self-ballasted, 1800 lumens at 18W, look great... Price appeared to be $10 each but found they were in pairs and the price was down to $5/pair. Dave
    Last edited by Dave_H; 01-02-2020 at 07:24 AM.

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