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I have a single-tube fluorescent light fixture that I would like to convert to LED. However, the wiring is a bit odd.

The left tombstone has two white wires (in one socket) and one blue wire in the other socket. One of the white wires is the white wire to the ballast and the other white wire is connected to the white supply wire. The blue wire is the blue wire to the ballast.

The right tombstone has two red wires (one in each socket) and they lead to the other side of the ballast.

The black supply wire is connected to the black wire to the ballast. The ballast has the black, white and blue wires on one side and the two red wires on the other side.

How do I re-wire to bypass the ballast and convert for a two-sided led tube? Currently, the fluorescent bulb is a single T12?

Any help is appreciated. Thanks.

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  • Can you post photos of the existing wiring please? Commented May 2, 2020 at 0:09

2 Answers 2

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There are loads of questions with answers on this site that address this question and loads of YouTube tutorials on how to do it.

I prefer to remove the ballast, its wiring and the tombstones.

Replace the tombstones with Non-shunted ones and wire directly to one tombstone. Use wire nuts to pigtail 18awg wire to your black and white ( line and neutral ) house wiring and wire them to the two wire inputs on the non shunted tombstone. ( ground to the metal fixtures body. )

Use a direct wire or ballast bypass led tube.

I do not see the point in powering a ballast if it is not needed other than for people who are not comfortable making the electrical changes. ( its a waste of power )

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    No, don't wire 120V to one tombstone. Tombstones are designed only for the voltage differential that preheaters call for. Not raw 120/230V straight up. Single-ended LED tubes are China being cheap; they won't spend the extra penny to run a wire to the other end of the tube. OP wants to use a double-ended LED tube, and really, that's the right call. Commented May 1, 2020 at 18:03
  • @Harper-ReinstateMonica I purchased my LED tubes and tombstones from a local Electrical contractor supply house and this is the way they instructed me to do it. Can you illuminate me as to the difference.
    – Alaska Man
    Commented May 1, 2020 at 18:08
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    In one case, you attach hot & neutral to those tiny tombstone pins less than 1/2" apart that were only ever intended for about 30V. In the other case, you put hot on one tombstone, and neutral on the other tombstone 4 feet away. The LED has to be internally wired to match, of course. If you wire double-ended, and someone puts a real fluorescent tube or a single ended LED into it, nothing bad happens. Commented May 1, 2020 at 18:17
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    Well, non-shunted tombstones were not designed for LEDs, but for fluorescent lights. Real fluorescents have a small filament at each end of the bulb, which is energized with ~20-30V to preheat the tube. This results in a softer start and longer bulb life. That's what the 2 pins are for. Then fluorescents have 100-300V across the two far ends for actual running of the light. It's been that way for 80 years, but very little experience at what happens when you put full-shot mains voltage across the two pins of the same tombstone. I would expect problems. Commented May 1, 2020 at 18:42
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    As for Code, that'll be decided by UL as to whether they will list single-ended LEDs. Can't speak to yours. But since LED "tubes" are not fixtures and not a permanent part of the structure, it is easier for them to sell non-UL-listed tubes. Honestly I haven't looked closely at the issue. I just know those pins are not intended for 120V. Commented May 1, 2020 at 18:45
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OK, see if I have this right, for a single tube fixture with one tombstone ay each end, ignore the wire colors, cut all wire connections to the ballast and cut any wires that might connect the two tombstones together, strip and bundle all the wires going to each tombstone, effectively making them "shunted" if they are not already, connect the bundle from one tombstone to the black (hot) input wire, connect the bundle from the other tombstone to the white (neutral) input wire, AND CONNECT THE GROUND WIRE TO THE FIXTURE ITSELF, mark the fixture so you identify which end is hot and which is neutral, and use double ended bulbs, being sure to orient them properly in the fixture if one end of the bulb is marked for neutral and the other hot.

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