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I want to buy and use some 54W T5 lamps. I have found some ballasts in a nearby shop. I have the following questions:

  1. One of them advises 1x110W T10/T12 or 1X85W T12. Can I use it on two 54W T5 lamps? In general, can we use ballasts for T12 - for example - on T5's - considering the wattage matches?

  2. Some of them are advised for T5/T8 lamps, others are for TL5 lamps. Is there any difference?

  3. Suppose I have a 54W lamp, can I use - for example - two ballasts of 30W and 24W? That is: Can we combine lower wattage ballasts in some way such that it could power a higher wattage lamp?

  4. Some of them are even advised only as 1x54W, without the Tn indicator. Can I use them on T5's?

  5. Can I use ballasts of one manufacturer with lamps from another manufacturer?

  6. There was a very cheap ballast for two 54W T5s and one (more expensive) for just one T5. Is it possible that this single lamp ballast will result in more light output?

If it is helpful, below there is a photo of the ballasts I found more promising for my purpose. Perhaps these questions are extremely common, but the seller didn't look to know about it and when I Googled a bit, there was a lot of doubt.

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    Hello, and welcome to Home Improvement. We really only can answer one question at a time here; please choose one. That said, I'm guessing it's going to be a lot of work/research to properly (and safely) set up so many different circuits. – Daniel Griscom Feb 1 at 11:20
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    I didn't get the impression that the OP was going to install many different circuits, but that he was considering different ballasts for one or two or a few circuits. – Jim Stewart Feb 1 at 14:04
  • Hello Billy. Can you tell us the type of fixture you intend to use with the T5 lamps? – Jerry_Contrary Feb 1 at 15:00
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In lighting, The letter "T" represents the shape of the bulb, which is tubular. The number represents the diameter of the bulb in eighths of an inch. I/E: A T5 is a tubular bulb that is 5/8" diameter. Lengths of these different bulbs (T5, T6, T8, T9, T10, T12) can vary because the wider the bulb, the longer the bulb can be manufactured. There are also some "D" and "U" shaped bulbs. This is why different fixtures require certain bulb types.

Fluorescent tube bulbs have low pressure gas in them (argon) that require ballasts. When power is introduced, the bulb warms up the gas. The ballast then kicks up the voltage in order for the light to start burning brightly. Old fixtures required a ballast and a separate starter to get the bulb brighter, but newer ballasts have the starter built in. Once the bulb is fully lit, the newer ballasts will reduce the line voltage to a normal operating level.

Fluorescent tube fixtures usually require a specific ballast and tube type. Some fixtures can be upgraded to use a different bulb type but the ballast and the sockets would have to be changed. I have mixed different brands of ballasts with different fixture brands. Bulbs can be any brand as long as the voltage and wattage fall within the parameters the fixture calls for. If you want to save energy and modernize your fixture you can eliminate the need for a ballast by switching to LED lights and bypass the ballast.

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If it's not on the label, that ballast doesn't support it!

Your tube is an F54T5/HO. This is one of the most popular types of tube. It means

  • 54 nominal watts
  • T5 tube type (5/8 inch diameter)
  • HO is High Output
  • length is implied, you just have to know it's 1163 mm.

Ballasts support only certain specific tubes, in specific quantities. The popular ones are listed on the label, which will include yours, since your tube is very popular. The ballast's data sheet (hopefully found on the web) will list every tube the ballast can possibly support.

Pay attention to the number of tubes. If it says 2 tubes, it probably won't support 1 tube. Some say "1-2 tubes", those will. Even with popular sizes, sometimes you have to go get the data sheet to see if a 2-tube ballast will support 1 tube. Assume they will not.


  1. Can I use T12 ballasts? Nope!
  2. Can I use T8/TL5 ballasts? Nope!
  3. Can I take two inappropriate ballasts and wack-a-dack them together? One guess
  4. What about ballasts whose label isn't very clear? Maybe, but google the data sheet
  5. Can I use one manufacturer's tube with another's ballast? Yes, no problem
  6. Does price correspond to light output? Nope.

First, at a junk shop, price means absolutely nothing. Every day, the guy wakes up, has breakfast and prices 1000 used items in 100 crafts, none of which he knows well enough to even know what the thing is really. Has no consistency. The same thing will get 3 diffeent prices on 3 different days.

Now, when you are dealing with authorized dealers who have actual price books, the ruling factor on price is competitive/mass production. Oddball size ballasts are higher price because they're oddball, and must split design costs across fewer units sold. Popular ballasts sell plenty, and prices are pushed downward by competition.

Light output is actually decided by a number on the ballast called ballast factor. That will be on the data sheet, and sometimes on the label. Ballast factor is used to make fine tuning in light levels. Say you want to reduce light 20%, and you had 1.05 BF ballasts, youwould change to 0.85 BF ballasts.

Ballast factor is not to be confused with power factor.

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