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Thread: Replacing T12 ballast with T8

  1. #1
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    Replacing T12 ballast with T8

    I added a couple of 48" florescent fixtures in my work area, the newer style using the T8 bulbs and electronic ballasts. Thought I'd also convert some old T12s to T8s to get rid of the buzz and flicker. Replacement ballasts are a lot cheaper than new fixtures so thought that I'd just replace ballasts and get new T8 tubes.

    Did a no-power test fit and the T8 bulbs fit the old T12 sockets - OK so far. I was hoping for an easy remove and replace on the ballast, but when I took a quick peak inside one of the old T12 fixtures, they have twice as many wires running around as the new T8 ballast. The old ballasts connect to both terminals in each socket where the new T8 ballast connects to only one terminal in each.

    I did not take the old T12 down and completely disassemble it to see how the wires are attached to the sockets. Obviously the old wires come out with the old ballast and the new ballast comes with it own leads. If nothing else, one could simply clip old wires and splice the new ones appropriately, terminating the old ones that were not needed.

    Has anyone tried retrofitting T8 ballasts in older fixtures and did it work?

    Thanks,

    Tom

  2. #2
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    HD sells Lithonia T8 4ft lights for around 20.00 a piece. They are hard wired and I've had ten in
    my shop for over 3 years with no issues. It sounds good to swap out the ballests. It in the long run it may be easier
    replace the lights.
    Don

  3. #3
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    I did--it was a pain in the rear. You have to be able to do two things: 1) read and understand the schematic printed on the new, electronic ballast (not difficult); and 2) use a continuity tester to determine how the wires are run to the tombstones (those are what the bulbs plug into) and adapt the wiring to the new ballast. The wires are typically red, yellow and blue, but the colors won't match up from the old to the new.

    The one I re-ballasted was at church, and was a 4-bulb fixture. If you're just re-ballasting a 2-bulb fixture, it will probably be much simpler.
    Jason

    "Don't get stuck on stupid." --Lt. Gen. Russel Honore


  4. #4
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    Northern NJ
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    T8 fixtures use an internally different lamp holder (socket) that has a shunt. You might be able to pick up replacement sockets at a "real" electrical distributor but probably not at HD.

  5. #5
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    I've retroed literally 1000s of old T12 fixtures with T8 ballasts. You do not need to replace the sockets. On T8 ballasts, the pins on each end are common with each other, on T12s they are not. Just splice both wires from each socket together with the ballast wire. In the case of a 2-lamp ballast, one blue wire from the ballast goes to both pins on the end of one tube, the other blue from the ballast goes to both pins of the other tube. At the other end of the fixture, splice the red ballast wire with all 4 socket wires. All thats left is the power wires.

    T8.jpg

  6. #6
    Tom, it depends on the lamp and on the ballast circuit type. Are these 4' or 8' lamps? Look on the new ballast label - does it say "instant start" or "rapid start"? If the lamps are 4' and the ballast is an instant start just connect it the way Matt shows in his diagram. If it's a rapid start ballast it's a different connection so let us know.
    Last edited by Jack Lindsey; 05-22-2012 at 8:37 PM.

  7. #7
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    Piedmont Triad, NC
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    Warehouse-Lighting has the T8 retro-fit kits(ballast, bulb holders & Miro-Reflector cover) for $19.31@(http://tinyurl.com/cgu9o3o). I just purchased two kits to convert 2 lamp 4Ft T12 to 2 lamp 4Ft T5HO Retro-fit. This comes with ballast, bulb holders & Reflector covers for 23.77@ If these works well I have several I'm looking to replace.

    4Ft 2 lamp T8 industrial strip light fixtures are $50.06@
    4Ft 2 lamp T5HO industrial strip light fixtures are $65.71@

    Tony
    Last edited by Tony Joyce; 05-22-2012 at 8:44 PM.
    "Only those who have the patience to do simple things perfectly will acquire the skill to do difficult things easily. Friedrich von Schiller (1759-1805)

    Woodworking since 1972

  8. #8
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    Sort of in order:

    Don: The Lithonia fixtures I would replace have the 12" reflectors, those are $40 at my HD. Ballasts are $14. That's why I wanted to replace ballasts.

    Matt: In that diagram, even though it looks like only one wire to each socket, it is really spliced so there is one lead to both sides of both sockets? Just confirming.

    Jack: These are T12 two lamp, 48" fixtures, two small pins on the tubes. I looked at the replacement ballasts in the store, but did not buy them yet until I worked through the details. The new ones were type REB-2P32-SC but I did not note the manufacturer. The old T12 ballast is an Advance RM-2S35-TP.

    Tom

  9. #9
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    Quote Originally Posted by Tom Blank View Post
    Matt: In that diagram, even though it looks like only one wire to each socket, it is really spliced so there is one lead to both sides of both sockets? Just confirming.

    Tom
    Thats right Tom. A blue ballast wire splices to both wires (pins) at the end of one tube. The other blue ballast wire does the same on the other tube. If you have a single tube fixture, you can use a 2-lamp ballast and cap one blue (albeit at slightly less efficiency than a 1-lamp ballast).

    Here is a diagram that shows the splices.

    T8b.jpg
    Last edited by Matt Marsh; 05-22-2012 at 9:26 PM.

  10. #10
    Tom, that's an Advance instant start ballast. Just follow Matt's instructions.

  11. #11
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    Thank you all for responding and for the education. Not bad getting wiring info on a woodworker forum. 8^)

    Tom

  12. #12
    Join Date
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    Matt is correct, it's very easy to do.

    Take all your sockets out of the fixture.

    On the sockets that aren't connected to other sockets, (the blue wires in Matt's drawing) cut one wire about 2" long. Strip 1/2" of it.

    Remove the other wire from the socket using a straightened paper clip to push into the wire space, that releases the old wire. Bend the short wire over, insert it into the other side of the socket. You have now converted your old t12 socket to a T8 socket with the shorting link.

    On the sockets that have 2 wires between them (the red wire in Matt's drawing) you cut one wire as above at both sockets, leaving the other wire connecting the two sockets together. Perform the shorting trick, you now have two T8 sockets with the jumper between the two sockets.

    From the ballast one blue wire goes to one individual socket, the other blue wire goes to the other individual socket. The red wire goes to the ganged socket.

    That's it, no messy marrettes, a job that's as neat as the original factory wiring.................Rod.

  13. #13
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    Trussville, AL
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    I found a source for new tombstones on E bay. Was way cheaper tyhan buying them locally. i just ripped out all the fixtures guts and used the t8 ballasts with the new tombstones.

  14. #14
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    I swapped a T12 ballast and bulbs for a new T8 ballast and bulbs, put shunts/jumpers on the sockets, hung the fixture back up and have light.

    Acutally I have much more light than before and no smoke escaped from the wires. 8^)

    Thanks to everyone again.

    Tom

  15. #15
    I have a suspended ceiling, grid with troffer 4 bulb lights. Looked at Menards today, they have an ad with troffer lights for 35 $ each, and also sell ballasts, but not sure which one would be the right one, the ends of the T 8 bulbs look the same as the T 12 's, so not sure why you would need new tombstones? How do you determine what ballasts to replace the old ones with? Also a question on insulation over the lights, is it better to cut a hole over the ballast to let the heat get away, or should you insulate right over the ballast and all?

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