Our condo building switched over to LED tubes years ago from the florescent type and installed a special type of LED tube that bypassed the ballast, so I was told. In other words, it appears that these new LED tubes use 115 volts, and one end is marked "AC end" (not sure what that means). But to my surprise, when I went to change one of the new tubes with an LED tube I had of my own, it didn't work. How many different LED tubes are there on the market, so that I can order the right ones?

  • What else is on the labeling of the tube you're replacing? That's what you're going to need to look for. This really seems like a shopping question (which is off-topic), but without enough detail to tell you what to get (if it were on-topic).
    – FreeMan
    Commented Sep 9, 2021 at 14:54
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    What do you mean by "tube" ? LEDs are very small things placed inside all sorts of shapes. None of them use a ballast. They all require electronics to drop the 120VAC down to a few volts. Commented Sep 9, 2021 at 18:06
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    Please edit your question and title to clarify what it is you're asking. The title question is an off-topic shopping question, but the body seems to indicate you are wanting to know what specific flurescent light bulb/tube you need for a specific fixture... if that's the case, please add information about the fixture, like a photo of the fixture or some specs label on it, and a photo of the light bulb/tube's connector, at least.
    – TylerH
    Commented Sep 10, 2021 at 13:59

2 Answers 2


As you problably know, electricity flows in loops. It needs 2 wires/contacts/etc. to be effective.

You also may know most fluorescent tubes have 2 pins per end, or 4 total. That is more than is needed for LED.

There are 4 kinds:

  • Ballast-Bypass (direct wire), single ended - this is where both of the 120V contacts are on the same end of the tube. These are a fraction of a penny cheaper to manufacture, but have 120V + neutral only 1/2" apart on those little pins. It also necessitates replacement of the lampholders in formerly instant-start fluorescent fixtures.
  • Ballast-Bypass (direct wire), double ended - this is where the 120V contacts are on opposite ends of the tube. These are easy to wire into any fixture, even former instant-start types.
  • Plug-and-Play - this is where the LED is designed to be used with the ballast still installed, and it "emulates" a fluorescent tube as far as the ballast is concerned. Upside: no rewiring, and you can roll back to real fluorescent once the 'charm' of LEDs has worn off. Downside: needs a working ballast.
  • Universal - can do double-duty as both a Plug-and-Play type and a Ballast-Bypass double-ended type. Will work with the power it is provided. Always double-ended because ballasts expect double-ended tubes.

There is no such thing as a universal (single ended) type.

It sounds like your facility was wired with Ballast-Bypass, single-ended. You chose one of the other types of replacement.

You can either re-wire the fixture to use your type of tube, or get the other kind.

Note that if you have plug-n-play LEDs, this will require re-installing a fluorescent ballast. Any instant-start ballast will suffice, avoid rapid-start or programmed-start ballasts as they may require changing lampholders too.

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    Is OP even allowed to be messing around with the condo's wiring ? I'd suspect not.
    – Criggie
    Commented Sep 10, 2021 at 8:06

There are at least 2 types of LED tubes: Those that work with a ballast and those that are direct connected. According to code, the interior of the fixture should have a sticker indicating it was a direct connect, if so. Also, I seriously doubt your LED tubes is using 115 watts...that's a lot for an LED...are you sure you don't mean volts? There's no way a LED tube intended for a ballast will work if it's direct connected (bypassing the ballast).

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    Also the ones that do not use a ballast have to be installed the right way around but physically will fit either way. Hopefully, whoever first did the ballast bypass marked the + and - ends on the fixture.
    – jay613
    Commented Sep 9, 2021 at 14:52
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    You are correct ... volts, not watts. Mistake corrected. Thanks Commented Sep 9, 2021 at 20:59
  • Some LED and fluorescent lights sold in the US will be incorrectly marked with watts in order to indicate the wattage of incandescent bulbs they are equivalent to in terms of brightness. This was done to account for the fact that US consumers have for decades been conditioned to think about lightbulb brightness in terms of wattage rather than lumens (e.g. "This room is too large for a 40w bulb, better use a 60w.") Even though those numbers don't apply to other bulb types. Commented Sep 10, 2021 at 15:18

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