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How To Convert T12 to T8 Lighting Ballasts

By Dave Rongey - Summary:

How to Convert a T12 Fluorescent Light Fixture: Wiring a T12 Fluorescent Fixture for a T8 Energy Efficient Ballast, How do I convert T12 light fixtures to T8 electronic ballasts?

Wiring Fluorescent Lighting Fixtures

Electrical Question: How do I convert my T12 light fixtures to the T8 electronic ballasts?

  • I have about 200 2 ballast T12 lights.
  • I want to start changing them over to T8 single ballast.
  • I would like to know how to wire the lights for the single ballast.

This electrical wiring question came from: Jerry, a Property Manager from Carlinville, Illinois.

Dave’s Reply:
Thanks for your electrical wiring question Jerry.

How to Convert a T12 Fluorescent Light Fixture

fluorescent lighting fixtures

Application: Fluorescent Light Fixture Wiring.
Skill Level: Beginner to Intermediate.
Tools Required: Basic Hand Tools and Safe Ladder.
Estimated Time: Depends on personal experience, the light fixture and access to the light fixture.
Precaution: Identify the light fixture circuit, turn it OFF and Tag it with a Note before working with the wiring.
Notice: Replacement parts for the light fixture should be compatible with the type of fluorescent lamps that have been installed.

Wiring a T12 Fluorescent Fixture for a T8 Energy Efficient Ballast

  • Converting a Fixture from a T12 Ballast to a T8 Ballast
    • The following must be identified to select the correct Energy Efficient Electronic T8 Ballast to replace a T12 Magnetic Ballast:
      • The circuit voltage.
      • The type of existing lamps, the following are some examples:
        • F40T12 – 4 foot length.
        • F96T12 – 8 foot length.
        • NOTE: The lamps will be replaced with new T8 lamps as specified on the new T8 Ballast.
      • The number of lamps.
    • Refer to the following example which describes the basic conversion process.

Example of Wiring a T8 Ballast

  • Wiring the Electronic T8 Ballast
    • Each electronic ballast has a complete wiring diagram attached to the ballast which describes the specific wiring configuration from the ballast wire leads to the lamp sockets.
  • Using the Existing Socket Wires
    • You will be able to use the existing socket wires which will connect to the new electronic ballast.
  • The Original Lamp Sockets
    • The lamp sockets will work for both T12 and T8 lamps because the pin configuration is the same.
    • If a socket has signs of wear or if it is cracked or broken then the socket should be replaced.
  • Grounding the Light Fixture
    • Be sure the circuit ground wire is attached to the metal frame of the light fixture.

Check with your local electric utility company who may have an energy efficiency upgrade program that may offer incentives that may apply to your project.

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4 Responses to “How To Convert T12 to T8 Lighting Ballasts”
  1. Johnny Beaver says:

    I have a 2 bulb 4 foot long T12 120volt fluorescent fixture and want to convert it to LED. Do I have to replace the existing sockets or can I just rewire the existing sockets? Is a new ballast required or can the LEDs operate on the 120volt system without a ballast. Does it matter what type LED bulbs I should use?
    Thanks for your help.

    • Dave Rongey says:

      Hi Johnny,
      There are a variety of 4 foot LED lamps available to use for converting a fluorescent light fixture, and new LED products seem to be emerging all the time. Some may require special power supplies while others are now compatible with the existing ballast and sockets where you simply change out the lamps, such as the a new LED T8 lamp that was recently introduced. You may want to visit your local light fixture outlet to see the products and decide which one is right for you and your application.
      I hope this helps,

  2. Bill Zechman says:

    The LED replacement four-foot tube has the familiar bi-pins on each end. Where do I feed the 120 VAC after I eliminate the ballast? Do we apply 120 VAC to each pair of pins on opposite ends? Or do we connect either pin on one end, and either pin on the other end? The LED tube I purchased did not include a wiring diagram, and given the price I paid I don’t want to run the risk of damaging the device.
    Thanks for your help!

    • Dave Rongey says:

      In order to provide accurate information I would need to know more about the exact 4-foot LED lamp that you have purchased, such as the Make and Model Number would be helpful. Many lamps are made to install without and other wiring modifications of the light fixture, but lets make sure we identify which lamp you have first.


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