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T12 Ballast Replacement

Dwayne wrote: I have a 4 bulb light fixture and uses 2 ballasts and I'm only getting 2 of the bulbs to light what do I need to do?

El101: Looks like you have two 2 lamp series ballasts to light up four lamps. Are they T12 lamps (1.5 inch diameter)?

With series ballasts (rapid start), when one light fails, the other one will not light up. Typically one ballast connects to the two outside lamps, the other ballast connects to the two inside lamps. If the lamps are very dark at the end, they have reached the end of their life cycle. If there is a very dim light coming from the lamps that do not light up, it indicates the ballast is still good and the lamps need to be replaced.

To see if the ballast is good, move the two good lamps to the lampholders of the lamps that do not light up. If the good lamps light up in their new position, the ballast is good. If this is the case, it is best to replace all four lamps.

If the good lamps do not light up in their new position, the ballast will need to be replaced (or get a new fixture). If this is the case, let me know and we will go to the next step.

Dwayne: Yes T12 and I have 2 new Ballast in but I just can't get all 4 lights to come on can you show me which way the wires get connected?

El101: Here is a page the shows how to replace two 2 lamp parallel ballasts with one 4 lamp  series.

Are the new ballasts series or parallel? If they are series, use the diagram at the top of the page.

Replace 4 Lamp Two Series Ballasts with Parallel

Ballast Lamp Compatibility

Robert wrote: Could you please tell me if you think it would be ok to use a F32T12 ballast to operate two 20 watt T12 fluorescent tubes? thank you!

El1011: It’s not a good idea to use a ballast with lamps that are not listed on the ballast. I recommend you convert the fixture to T8 lamps and ballast, convert to LED, or replace the fixture with T8 lamps. Let me know if you want info on any of these options. T12 lamps are very inefficient and for this reason are increasingly hard to find.

Robert: i think the answer i was looking for was mainly about the wattage. As an example a power supply can be rated for more wattage or amperage than the load so i was wondering if it's the same with a ballast, specifically a 32 watt ballast to power a 20 watt fluorescent bulb.  Like a F32T8 ballast for T8 20 watt bulbs, what do you think? thanks again!

El1011: Power supply wattage and ballast wattage are like apples and oranges. What you describe are two totally different situations.

Another Ballast Lamp Compatibility

Chris wrote: I was wondering if it is possible to connect 4x39 watt T5s in a 2x80 watt ballast? Will it work? If i can what is the diagram for that conversion that i should follow?

El101: Lamps and ballasts need to match each other. A 39 watt T5 lamp needs a 39 watt T5 ballast. A 80 watt ballast needs an 80 watt lamp of the same type (T5, T8, T12 etc).

Replace Instant Start (Parallel) Ballast with Rapid Start (Series) Ballast

David wrote: how to replace 2 lamp parallel ballast with 2 lamp series ballast?

El101: If you don't mind me asking, why would you want to do this? Normally a series ballast is replaced with a parallel ballast. Let me know and I will come up with some solutions.

David: This is what I have, an existing fluorescent light with parallel ballast and I have purchase replacement ballast which is series type. Appreciate your comments and assistance.

El101: I highly recommend returning the series ballast and buying a parallel replacement ballast. In order to make the series ballast work, you will need to replace the lampholders (assuming they are shunted) with non-shunted lampholders and completely rewire the fixture. You may have non-shunted lampholders in the fixture, but I doubt it. See the link below. I can show you how to do this, but it may not be worth it.

Fluorescent Lampholder Wiring

Another Replace Instant Start (Parallel) Ballast with Rapid Start (Series) Ballast

Alan Wrote: Can I use a rapid start ballast on a standard (shunted) pin fixture without rewiring fixture?

El101: Why would you want to do this? The answer is no. You would need to replace lampholders with non-shunted. I recommend using an instant start ballast wired in parallel.

Alan: Thanks for the info, someone gave me the ballasts and was wondering if I could use them without rewiring the fixture.

El101: Your welcome. The answer is still no. Other options to consider, install an instant start ballast, buy new fixture, retrofit with LED tubes.