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Thread: Retrofitting T8 tube fixtures to LED

  1. #11
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    Quote Originally Posted by James L View Post
    I'm curious why all the mention of tombstones being "non shunted" ??
    One of the ballast bypass common methods is to connect a hot and neutral 120 Volt supply to a pair of LED tube pins, but only on one end. If the tombstone slots are shunted together, either internally or externally, when the 120 V supply is turned on, there will be a direct short.

    Quote Originally Posted by James L View Post
    I know the difference, but I'm wondering does that mean everyone is using tubes which are fed from a single end?
    That has been, until quite recently, the UL listed manner to configure a line voltage ballast bypass LED tube. The other end's pair of pins have no electrical purpose, the pins only help mount the tube securely in the fixture.

    Quote Originally Posted by James L View Post
    Also curious if others label their fixtures as having been modified?
    It depends upon the manufacturer's instructions and / or UL listing requirements. If labeling is required to help those who eventually have to replace lamps, this informs them of a bit of what is going on electrically.
    Another Al in Minnesota

  2. #12
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    Kansas Cty, Mo, USA
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    Quote Originally Posted by al hildenbrand View Post
    One of the ballast bypass common methods is to connect a hot and neutral 120 Volt supply to a pair of LED tube pins, but only on one end. If the tombstone slots are shunted together, either internally or externally, when the 120 V supply is turned on, there will be a direct short.


    That has been, until quite recently, the UL listed manner to configure a line voltage ballast bypass LED tube. The other end's pair of pins have no electrical purpose, the pins only help mount the tube securely in the fixture.
    I get the concept. I've installed l.e.d. tubes with both shunted and non-shunted. I was just curious if it's just kind of a running assumption that single-end tubes are used

    It depends upon the manufacturer's instructions and / or UL listing requirements. If labeling is required to help those who eventually have to replace lamps, this informs them of a bit of what is going on electrically.
    I was curious about labeling because I do. That pic I posted is a label I have made, and I stick two on each fixture - whether anyone requires them or not

  3. #13
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    There is a UL type C that is evidently a double end feed 120 V ballast bypass. Phillips is selling them.

    My point is that this LED retrofit market seems to be developing new products and is not settled yet.
    Tapatalk
    Another Al in Minnesota

  4. #14
    Join Date
    Jun 2010
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    1,912
    Quote Originally Posted by al hildenbrand View Post
    There is a UL type C that is evidently a double end feed 120 V ballast bypass. Phillips is selling them.

    My point is that this LED retrofit market seems to be developing new products and is not settled yet.
    Tapatalk
    or do they? I see a link for it but when it says not found when I click on it. The background picture on Canadian Philips shows L and N pins. Interesting. http://www.lighting.philips.ca/produ...hts/instantfit

    ANSI specification defines single capped FL lamp as something like 26W Dulux while normal linear lamps are defined as double capped. There's really no defined standard for feeding direct line to fluorescent lamp sockets. The single end feed is only to make installation faster.

    Some drop-in LED double ended lamps are internally shunted on each end so it can feed from either pin. This type of lamp will cause a short circuit when inserted into a single end direct wire conversion. I have seen generic ballast bypass lamp that is single end fed with line voltage pass through across the length of the lamp to allow another lamp to piggy back off of it to make 8' conversion faster. This type of lamp will cause a short circuit if connected to a "double end fed" direct wire conversion. We know mismatching lamps of all colors end up in the ceiling. It's unrealistic to expect T8 drop-in LED, T8 120v only LED, T8 single end fed LED, T8 double end fed LED to not get mixed up. http://www.birddogdistributing.com/2...st-Bypass.html This suggests possibility of direct 347v exposure from light fixtures.

    Some integral ballast LED lamps are made of glass. As a general expectation, a directly wired 277v and 347v hot is not supposed to be available at fluorescent lamp sockets. You can expect component ruptures or vaporized internal leads with some chance of capacitors or transistors shooting through glass envelope. If the light was switched off first, the breaker will trip upon turning it back on. 3-4 incompatible lamps(as discussed above) already seated to short across the line will probably not clear on their own. Closing a 347v breaker into a short can create a very dangerous situation. Tripping something upstream and causing a significant disruption is expected. Just one of 101 reasons ballast bypass is incredibly stupid.

    Remember. As I said before, a vacuum cleaner cord is a UL listed component. Simply joining it with a UL listed two prong molded female end do not make the whole thing proper. The specifications detailing exact details about the LED lamp and its internal element count on Tamlight advertised as "LED lamp ready" hints that it might have been UL listed as an LED luminaire assembled with off the shelf TLED listed as an appliance component.

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