Introduction: T12 Fluorescent Light Ballast Replacement
Replacing two T12 fluorescent light fixture magnetic ballasts with one t8 electronic ballast.
Step 1: Removing the Old Ballasts From This Fixture
First start by of course turning off the power and disconnecting the black and white wires from your in coming power feed to the old fixture you could reinstall wire nuts on black and white power feed wires as to be able to turn power back on to the rest of the lights on that circuit or leave it off if your the forget full type and might not remember its on when you go to Install the new ballast.
As with all projects, I like to start by snapping a few pictures of how the old fixture was laid out before starting to disassemble. Not real important in this project since we will be rebuilding the fixture.
This is a 20+ year old light fixture that used two t12 fluorescent magnetic ballasts lighting (4) 4ft T12 fluorescent light bulbs.
In this step we will be completely disassembling all of this light fixture down to leaving just the outer shell.
Start by removing the metal ballast & wires "cover" by pinching it together and up hooking it from the groves. Cut out the Red, Blue and yellow wires near each ballast. Than remove the 10mm nuts 1 holding each ballast in place, Note: They will be a bit heavy and if your on a ladder take care to slip off or drop one.
Each side of the fixture has 4 Blub plugs AKA "tombstone connectors" 8 in total. 4 on each side connected to a metal bar that hold them into position. Remove side metal bar by prying the slotted tab holding the bracket in place on both sides. You should see the remainder of the red, blue, yellow and maybe even a black linking wire running in and out of the connectors. this will all be getting removed to the next step.
Step 2: Step 2 Rebuilding Your Tombstones, May They Not Rest in Pieces
Now that you have all the guts removed from the old fixture we can start to work on removing the old wire ends and resetting the old tombstones to be re-used with the new T8 electronic ballast.
I found that two of the old tombstone connectors were cracked so I will show how I replaced them also.
Start here by removing each tombstone from slots on the metal bar. Pay close attention to what groves of the tombstone are in the slots on the bar. Here is where snaping a pic will help reinstall later.
Once removed from the bar, you can pry the staple from the back on the tombstone. I used a small flat head screwdriver, wigle and pryed each corner. Try not to ruin or mangle the staple you will be reusing it. This should free up the carboard backing to be removed and reveal the contact tabs inside.
To remove any old wire ends still in the tombstone simply poke a ale or small phillps screwdriver in next to the wire and the wire should drop out the front. After removing any misc wire be sure to remove each brass contact tab and lightly bend the wire contact tab end up and reinstall them back into the tombstone you will know this is done right when the contact tabs stay in the tombstone on their own and wil not be lose.
Than lay the carboard backing back on the tombstone and reinstall the staple holding it in place. This may require alittle reshaping the staple. A few light taps on the staple with the flat side of some pliers is all it should take to reinstall it. All done with only 7 more to go.
ok, well 5 more in this case. As I had mentioned , I found that two of the original tombstone had cracks in them and some missing pieces. I thought in best to replace them with new ones. You can get them at most home stores in the lighting section.
Please Note: The new tombstones are taller than the old ones I'm replacing so I resolved this by installing them at opposite ends of the same bulb. I know that I could have got mini new replacement tombstones that would not have been so tall however, height clearance was not a problem in this fixture, could be in yours so this is something be aware of. These new connectors also have a little different wire push connection.
Once your done with rebuilding the old tombstones you can reinstall them in the metal holding bar for both sides.
Step 3: Wiring to New T8 Elctronic
Here we will be wiring the new ballast to the old and some new tombstones.
Follow the wiring diagram that came with your new ballast.
My diagram has two red, two blue and two yellow.
Before wiring to the ballast all of the 8 tombstones get a jumper wire to connect one side to the other so you could do that a head of time or as you go.
As you can see in the diagram one of each red wire goes to its own tombstone on one side. Same with each of the blue wires to its own connector. keep in mind to route the wire from under the metal bar. Now on the other side you will wire one of the yellow wires to a tombstone and than run a little wire connecting that tombstone to the next one. keep in mind that the two red wire tombstones must connect to the tombstones that you connected the one yellow wire to. Perform the same procedure for the blue wire tombstones.
You can see what the jumper wires look like along with what my finished rewired ballast looked like.
Step 4: Finshing This Rebuild
Lastly, once you new ballast wired up you can reinstall it into you fixture.
Start by turning the feed power off again.
Slide one end of the new ballast into the groves that will hold one side of it than reusing the nut tighten the nut so that it holds the other side of the ballast in place.
Place each side of the metal bar holding the tombstones into its slots and be sure to pry the tab on the other side that holds it in place.
Once all parts are in you can connected the power feed wires to the new ballast.
Install the ballast cover in the reverse of how you removed it.
Very Important be sure to replace all blubs with new T8 style blubs.
Close it up and your all done!!!
Participated in the
Lamps and Lighting Contest 2016
Question 3 years ago on Introduction
How to wire the T12 ballast to the older 8 ft 2/ single pin bulb fixture