[badhaircut]

Hello, can I use a 2 lamp ballast to replace a single lamp type?
I have a small undercabinet light 24"
The old magnetic ballast is dead. I picked up a ballast at a re-store last summer and I was wondering if it would work?
First 3 pics are the old ballast.

 

[badhaircut]

This pic on the new ballast says it can work for a T12 single but I have a T8 bulb. How do I wire it for 1 bulb?

 

[Oso954]

For a 24 inch T8 fixture, you should be using an F17T8 lamp. The ballast should be rated for that lamp.
It appears that neither the new or old ballast is the correct one for that lamp.

 

[user_12345a]

Using the wrong ballast with the wrong lamp could shorten it's life, if it even works.

Use the right ballast.

 

[badhaircut]

This ballast is original to the fixture. I will have to double check the length. It may be 30-36". Its actually at the cottage. Will the new ballast replace the old ballast though?

 

[Oso954]

No.
For best results you should use a ballast rated for the lamp you are using.
The original ballast is related for 36 and 48 inch t12 lamps, plus a couple of t9 circulines. All of those are slow phosphor lamps.

T8 lamps use faster phosphors so the ballasts can run at higher hz. They also are lower wattage than the equivelent length T12. The 36 inch t12 is 30 watts, the t8 is 18 watts.

Using miss-matched lamps and ballasts yield shorter lamp life, or shorter ballast life, or both.

Double check the lamp. If it is a F18T8 (36 in), that's what you want to look for a ballast that has a rating for a single f18t8 use.