Replacing T12 ballast with T8

[Jack Lindsey]

Jim - no need to change lampholders unless the old ones are loose or broken. The ballast type is dictated by the lamp type. If you are using an F32T8 lamp just look for a ballast rated for that lamp. The info will be on the ballast label and should be on the box. As far as putting insulation over the fixtures, don't. Heat buildup in the fixture will shorten ballast life and may reduce the light output of the lamps.

[Burt Clarke]

I know this is an old post, but it was just what I needed. Bought an old schoolhouse with lots of T12 light fixtures and want to convert to T8's. Thanks for keeping this post on here.

[Rod Sheridan]

Hi Tom, I've done about a thousand of them now.

I pull the ballast and sockets from the fixture.

I cut one wire at each socket about 2" long, strip the end and insert it into the other side of the socket. (Sockets for T8 need both pins shorted together).

One pair of sockets is connected together and only receives one wire from the new ballast. (Check wiring diagram). You'll need to keep one of the existing wires that connects a pair of sockets together.

The other wires in the socket I remove by inserting a straightened paper clip into the hole with the wire, pulling both the clip and wire out simultaneously.

Now you have all the old wires removed except for the one that connects one pair of sockets together, and the sockets shorted.

Now you stick the wires from the new ballast into the sockets as per the wiring diagram on the ballast and put them all back in the fixture.

Simple process and it looks like a factory job without a rats nest of wire nuts.............Regards, Rod.

[Gilbert Vega]

What would be the cost to retro-fit either T12 or T8 to T5HO? Are the kits listed above for more than 1 lamp or several?

[Jim Andrew]

I bought a whole box of ballasts on ebay for much less than the cost at local stores. Bought the bulbs at Menards on a 15% off sale. Buying by the box saved too. I have changed some of the lights, and they work great. Just bought a jar of the small blue wire nuts rather than pulling the wires out of the sockets.

[Tom M King]

Thanks for all the input in this thread guys. You've saved me some time comparing parts, and I'm sure others as well.

[Curt Harms]

What would be the cost to retro-fit either T12 or T8 to T5HO? Are the kits listed above for more than 1 lamp or several?

I haven't done it but did the T12 -> T8 retrofit and briefly researched T5. T12 & T8 use the same tombstone and are the same length so it's pretty straightforward. T5 appears to use a different tombstone and seems to be 45.8" long rather than 48" from a brief search. Another issue for me is that I'd want some sort of diffuser on T5 lamps. I found the T5 lamps I looked at in the borg too bright to look at directly. T8s appear to use about 25%-30% less amps to produce what I perceive to be more light (newer tubes/less dust?). I was happy with my bargain.