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I have an older 4 foot fluorescent fixture (18 years old) in a laundry room that died and I assume it is because the ballast went bad (T8 one inch fluorescent tubes). I was able to locate the exact replacement ballast but the fixture used shunted tombstone sockets which are difficult to find and they are expensive. I am able to get the non-shunted type easily and I wanted to know if it is possible to convert the non-shunted so that it will work with the ballast. There was a posting on this site a few years ago that indicated that you could do that by adding 18g wire between the two sides. I'm not sure what that meant exactly though and if that is the correct way to do it.

My ballast has two wires at one end, which go to each of the two sockets at that end of the fixture. At the other end there is only one wire and the previous installation had a jumper that went from the vacant hole on the socket that was wired to one of the holes in the other socket at that end. I am replacing the sockets because I have been unable to remove the wires that are attached to three of them. The fourth socket is damaged.

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    Why replace an expensive ballast, and still need to change fluorescent tubes once a year or so, when 4 ft LED replacements not using a ballast are readily available, cost less than a ballast, come in different color temperatures, and last longer than fluorescent lamps? Nov 23, 2023 at 4:13
  • The DR is correct, why take the difficult route. LED is the way of now and the future.
    – RMDman
    Nov 23, 2023 at 12:56
  • I agree that LED makes more sense. But decent fluorescent tubes should last a lot longer than a year in typical residential use. A quick search says typical lifetime 7,000 to 15,000 hours. So for a light that is on 24/7, yes that's 1 year-ish. But if it is on a couple of hours a day then it should be many years. As opposed to incandescent where a few hours a day ~ 1 year life. Nov 23, 2023 at 16:03
  • If I were to convert to LED, probably a double ended tube, I would still have to replace the damaged tombstone, while leaving the other shunted tombstones in place. Because I can't find a shunted tombstone I would still have to work with a non-shunted model. So I still have the original question. The non-shunted tombstone has four holes, two on each side. It seems that t he way to wire this tombstone would be to run the hot wire, for instance, to one of the holes on one side and then jump a wire from the hole beside that one to the other side of the tombstone. Is that correct?
    – bj47
    Nov 23, 2023 at 23:42
  • @DrMoishe In my experience real fluorescents outlast cheap LEDs. Target installed a bunch of 6-lamp T8s when they opened around 2014. They all worked and I rarely saw a burnt out one. By 2018 they upgraded to LEDs and by golly, 5% of them were out. And this is Target, who has the purchasing power to get the best the market has to offer. That's been my own experience too, I've installed hundreds of T8s and not had 1 failure, except from a fixture that burned continuously for 5 years. Nov 26, 2023 at 23:23

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The deal with "shunted"

A fluorescent lampholder (tombstone) has 2 pins that talk to the lamp.

A non-shunted lampholder allows you to wire to each one separately. Each side typically has two stab holes - two on the left that go to the left pin, and two on the right that go to the right pin. So four holes total. (this is to allow jumpering onward).

A shunted lampholder internally shorts the two pins together, and you cannot do anything to feed each pin individually. There is no "tab" you could break off to separate the pins. They typically have 2 stab holes total, both connected to the same thing.

Non-shunted lampholders are entirely downward compatible. You can always turn a non-shunted lampholder into a shunted lampholder by making a 2" long jumper of #18 solid wire and jumping the inner two stab holes on a non-shunted. As such, nobody wants shunted lampholders -- except that fixture manufacturers who make 10,000 fixtures a day are able to eliminate a couple of positions on the assembly line by not having to cut, strip and install that jumper. As such, no one sells shunted lampholders, except in million quantity.

Should you mess with your fixture's tombstones?

No, you should not. Novices tend to think lampholders are all interchangeable and there's this one kind that looks like a tombstone. That's nonsense - there are at least 6 different kinds, and while one is more popular, you roll the dice every time you attempt a replacement.

So I recommend you do not mess with them. If you have shunted lampholders (revealed by 1 wire per lampholder), then simply obtain a ballast that matches that. Modern T8 ballasts come in two general formats:

  • Instant-start types use 1 wire per lampholder, and are compatible with shunted tombstones.
  • Rapid-start and programmed-start types use 2 wires per lampholder, and require non-shunted tombstones.

It sounds to me like your "exact replacement ballast" is not an exact replacement at all, but you obtained a rapid/programmed start type when your original was instant-start. My advice is to send it back and get an instant-start ballast (2 blue 1 red wire) which will simply wire up directly and exactly to your old wiring.

Or go LED

The other option, that I ought to mention, is LED replacement "tubes". Most of these involve no ballast at all, and simply connect 120V/277V power wires to the lampholders. (the idea of putting 277V across the 2 pins on a tombstone seems completely insane to me). The gotcha with LEDs is that aside from quality, color temperature (fluorescent is generally 4100k) and CRI (fluorescent is 80-98), you also have to contend with no less than five wiring methods.

  • Universal, works as either of the next two, type A+B
  • Plug-n-play (requires working ballast) - type A
  • Direct-wire, double-ended - Type B
  • Direct-wire, single-ended (bad - do not buy) also Type "B", WTF?
  • Requires External Driver - type C (don't bother with these)

So you can see procurement of these is a bit of a nightmare. But if you choose either Universal or "Direct-wire, Double-ended", then the wiring is extremely simple.

  • Identify one end of the fixture and notice all the wires going to all the tombstones at that end. Gather them ALL and connect them to 120V hot.
  • Identify the other end of the fixture and gather ALL the wires going to tombstones there. Connect them all to neutral.

Ideal In-sure 8-port wire connectors, or Wago 773 8-port wire connectors, can be ideal for this. Do not use no-name Chinese connectors found on eBay/Amazon/Wish/DealExtreme.

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