I am looking into converting a T-8 fluorescent tube fixture to a direct-wire LED tube fixture. In addition to removing the actual ballast, I understand that the "tombstone" lamp sockets in an electrical ballast fluorescent fixture are shunted, but for a direct wire LED tube, I should use non-shunted.

Based on the diagram in this vendor article: https://blog.1000bulbs.com/home/shunted-vs-non-shunted-lampholders it seems like it would be pretty easy to convert a shunted socket to a non-shunted socket with some wirecutters. Is this generally unsafe? And/or code-violating?

  • Or you can buy T8 non-shunted replacement sockets and retrofit them to your fixture. Modifying an engineered product (like a light socket) is probably not the best idea. – Chris M. Jun 21 '17 at 21:23
  • Thanks, Chris M. I figured as much. I just didn't want to be the chump that bought new pieces if it was sort of undocumented feature of the sockets that you can just do a one-way conversion. – Justin Jun 21 '17 at 23:16
up vote 2 down vote accepted

You can't hack a shunted lampholder to be a non-shunted unless it's designed to do that. For one thing there is no place to attach the wires. Yes, there are two wire holes, but a non-shunted holder has four.

You have three options:

  • stay with instant-start fluorescent... I am because the CRI is better
  • change lampholders to non-shunted type
  • take care to select LED "tubes" which take power from opposite ends of the tube

You should certainly not be modifying the wiring before you have seen the wiring diagram which comes with your LED tubes. You may find your tubes require a different wiring than what you did.

  • Thanks, Harper. I appreciate the detail. I am surprised by one thing though: I assume CRI = "Color Rendering Index". I have always heard (and personal perception agrees) that fluorescent gives a rather pale and artificial-feeling light. Is that due to a case of "not all fluorescent tubes are the same" and being too cheap with types of tube? – Justin Jun 21 '17 at 23:12
  • @Justin Operative word "always". In recent years fluorescents have gotten spectacularly good. I just relamped our shop, and you can't believe it. I deliberately did not relamp one aisle in a storage area, and it's super obvious, like sodium lamp vs daylight. I paid less than $2/tube for 90CRI at Menards. You can get as high as 98. Try it! – Harper Jun 22 '17 at 3:52
  • @Justin the color temp of the lamp has a lot to do with the "feel" of the lamp, I use 5k and higher as this is closer to natural light, compared to a yellow hue at 3k. – Ed Beal Jun 5 at 6:40

Glad you read our blog. We definitely agree that you should NOT cut into shunted lampholders for the reasons Harper stated above. Chris M. is also right. It's easier to just buy non-shunted lampholders, it will only cost you a few bucks. Since they are direct wire LED tubes, you only need to wire one side of the fixture.

  • Two much like an advertisement, there are led lamps out there that are both ballast compattable or can be wired single ended or double, I just purchased 2 cases of these not long ago. – Ed Beal Jun 5 at 6:49
  • 1
    @EdBeal I think Ashley's response was quite reasonable. Other than the reference to the blog (which the OP linked) it said nothing about the company - i.e., not even "go to our web site to buy them". And the username makes it quite clear that Ashley is not some random DIY (like me). I have bought stuff from 1000bulbs myself and they were a pleasure to deal with, but I have no financial interest in the company. – manassehkatz Jun 5 at 22:44

All of the above answers miss the point. It's perfectly ok to modify shunted tombstones in order to connect double ended LED tubes - cut all wires entering the tombstone then wire them directly to either power or neutral, your choice. Make sure the opposite tombstone is neutral if other positive or the converse.

Make sure you really have a shunted tombstone. You can easily tell what you have with a multi-tester continuity check. Probe left and probe right but only when you have cut the wires away from the ballasts which might feed back to give the impression you are shunted - if it beeps you're shunted creating a problem for single ended tubes. Let me emphasize that I thought I had shunted but I didn't - checked continuity with wires still running to the ballast and it gave me continuity by looping back through the ballast. I actually took one tombstone apart and visually verified there was no bridge even though my meter originally showed continuity.

So now I'm rewiring for single-ended tubes. I will pull four tombstones (four tube fixture) on the side most convenient to incoming power. I have the two pin tombstones that snap in and don't rotate. To be elegant I will withdraw all wires (just twist and pull they'll come right out) then color match four of the same color to the left side of each tombstone (probably red for power) then four white to the right for neutral.

Both ballasts will be removed and all ballast wires cut away. I'll probably shorten or remove the incoming wires to the non-power side just to be tidy. When I'm done I'll have a power supply wire wire-nutted to the four red tombstone wires and the neutral wire wire-nutted to the four white tombstone wires. Your electricity may continue to another fixture so incoming power may be connected to that continuation wire. Some fixtures are grounded so do that just the way it was.

I'll post a picture when I get it done.

You can use shunted or non shunted tombstones but how you wire it will depend on whether the LED bulb is double ended powered or single ended powered.

If you are purchasing double ended powered bulbs you would connect power to one end (using shunted tombstone) and the opposite side (of the fixture) will be to neutral. If you have single ended powered bulbs, you need non shunted tombstones and would put power to one side of the tombstone and neutral on the other side of the same tombstone and only to one side of the fixture.

Connect all powered side wire to the incoming power to the fixture and all neutral wires to the neutral wire coming into the fixture.

For single sided bulbs, make sure you install the correct side of the bulb to the fixture. The bulb should indicate which side you should connect to the wired tombstone.

Most plug and play bulbs (using existing installed ballasts) are double ended powered bulbs. If you are taking out the ballasts and using the shunted tombstones, the wiring will need to be different. Power would go into one side of the tombstone and on the opposite side (of the fixture) would be neutral. Connect all power wire together to the power wire coming into the fixture and all neutral wires to the neutral wire coming into the fixture.

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