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Thread: rewiring old t12 to t8's

  1. #1
    Join Date
    Jul 2009
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    West Tennessee
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    rewiring old t12 to t8's

    I have to replace bout 6 old magnetic t12's ballast in 3 four t12's light bulb fixture. I was just gonna replace them for the electronic t12 ones and put new bulbs. i called my supplier to give the customer an estimate, my supplier told me i'd be better off just getting 3 four light bulbs t8's ballast, and rewire them. It'll save me about $40.00. In the past i,ve always replaced the magnetic t12 ballast with the electronic one, but in this case i think the savings justify the t8 ballast upgrade. i already bid the job, so this will mean more profit as well.

    -Will the t8's light bulbs fit the old t12's sockets?

    - t8's take the power to the socket while t12's take power to ballast

    right? if i remember correctly. . .

    - Which ones you all trust better t8's or t12's?

    The only issue i see here too, is that they have about 4 more fixtures that they work fine and they don't want to upgrade at these moment, so they may confuse when is time to buy bulbs, you know?

    Thanks a lot.

  2. #2
    Join Date
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    Olathe, Kansas 338 mi SE of Wingedhorses
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    Yes the T-8 will fit just fine in the T-12 tombstone.

    The ones that I have upgraded just install the ballast & connect wires color to color

    or whatever scheme works.

    The T-8s are supposed to be more efficient than T-12, T-8s consume less watts

    per lumen than comparable T-12.
    Electricity is Color Blind
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  3. #3
    Join Date
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    T12 will become extinct in the not too far away future. Production of magnetic ballast is supposed to have stopped already. I believe production of many T12 lamps is supposed to end in July 2012.

    Only system I've seen where power is run to socket's is the T12 8 foot 2 lamp instant start.

  4. #4
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    Only system I've seen where power is run to socket's is the T12 8 foot 2 lamp instant start.[/QUOTE]

    Thanks, that's probably what i was thinking about.

  5. #5
    Join Date
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    Portage, Indiana NEC: 2008
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    Quote Originally Posted by Charlie Bob View Post
    Only system I've seen where power is run to socket's is the T12 8 foot 2 lamp instant start.
    Thanks, that's probably what i was thinking about.[/QUOTE]

    Single pin lamps both 8' and 4' have power to the socket so when the lamps are removed it removes the power to the ballast. this lamps are some times called a Slim-Line which I think was a brand name for them, they now have 8' T-8 replacements for them with electronic ballast, that produce almost as much light as an HO lamp.

    As far as replacing T-12 with T-8, I have done many and anytime I have a ballast failure it gets replaced with a T-8 electronic ballast, Motorola/Sylvania make a 3-wire T8 electronic for two lamp fixture, and a 6 wire for a 4 lamp fixture, both will work on any voltage from 120 to 277 and both allow wiring for one less lamp, which covers about every fixture made, good ballast to keep on the truck.

    The ones below are the ones I use and can be found at most big box stores at a decent price, the PDF below also has the wiring diagram, but you must follow the one on the ballast you use, these work in both shunt sockets and regular sockets, by just connecting both wires of each socket together, yellows will each have two lamps on them, and reds will each go to a lamp, very simple.

    http://assets.sylvania.com/assets/do...b52e42e5e9.pdf
    Last edited by hurk27; 04-09-11 at 12:15 AM.
    Wayne A. From: N.W.Indiana
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  6. #6
    Quote Originally Posted by Charlie Bob View Post

    -Will the t8's light bulbs fit the old t12's sockets?
    Yes they do. T8 means 8/8 of an inch, or 1". T12 means 12/8" or 1.5". The lamp is the same length and socket.

    t8's take the power to the socket while t12's take power to ballast
    No, they both require ballast. The ballasts are different specs, which is why you need to replace it.

    Which ones you all trust better t8's or t12's?
    Magnetic ballasts are more resilient, but they cost more in energy. As for lamps, 80+ CRI T8 lamps are $2-3 ea. Equivalent high performance T12s are $7-8 ea. Old cool white 34W T12s are getting outlawed(manufacturing wise) July 2012.

    The only issue i see here too, is that they have about 4 more fixtures that they work fine and they don't want to upgrade at these moment, so they may confuse when is time to buy bulbs, you know?
    That is a REAL problem. It's like putting a sticker on your dash and say "rear right requires a different tire" and expect it to be followed. Put T8s in regular magnetic ballast and it'll freak out, flicker etc. Put T12s in T8 electronic system and they'll just run dim and have short lamp life. Talk to them about energy savings and see if you can convince them to replace all to T8.

    http://www.gelighting.com/na/busines...lasts11x17.pdf

    If they're using 34W cool white 48" T12 lamps with magnetic ballast, you can expect 20% increase in light and 30% reduction in energy. If you fit them with RE835 or 841 lamps (instead of 7xx), they can expect superior color quality. CRI jump from 63 to ~82.

    I'm not sure about other brands/models, but GE UltraMAX ballasts are absolutely silent. You can't hear 'em at all.

    If you install INSTANT START T8, you need to make sure the two pins in each socket are JUMPERED. If you don't, lamps will fail prematurely.

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