Replacing a ballast in old aquarium lights

  • #1
Many of us have those old aquarium aquarium lights from the canopy kits. I personally have three of them that are in various stages of disrepair. The best of these merely doesn't have a starter. The worst is completely broken.

So, what do you do with these old things?
You could get rid of them and replace them, but that's kind of wasteful, no?
The other option is to replace the ballast.
You can also replace the ballast to improve efficiency. Not that you're going to save a ton of money or anything, but if you're conscientious about energy use, replacing those old magnetic ballasts with a new electronic one will improve efficiency. Upgrading from T12 to T8 will also improve efficiency.

The first thing you need to do is buy a new ballast.
To do this, you need to do three things:
Figure out what length of tubes the fixture accepts,
Decide if you want to use T12s or T8s (you can throw T5s into the mix, but they need a different type of endcap, so I'm not going to go into them here),
and Take a look at the wattage of the length/type of lights you use.
Ballasts are rated by wattage and bulb width in the following format F##(the "#" is where the wattage number will be)T##(the "# is where the width will be). For example, 24", 17w, T8 bulbs will be listed as "F17T8." I am currently rebuilding a light with this type of bulb, so I went to the ballast section at Menards and looked for a ballast that included "F17T8" on the list of usable bulbs. This list will be written on the ballast itself.

Next, you need to take the fixture apart. Remove the old bulb, and remove the screws from the reflector. This should allow you to remove the reflector and get a look at the light's innards. Remove all of the wires. To get the wires out of the endcaps, get something thin to wedge the clips open (I used a straightened-out paperclip) and pull the old wires out.
You may have to replace the switch, too, as it may be built for a ballast that only has two wires coming from it. There might be a way around this, but I don't know it, and I don't want to risk starting a fire, so I just chipped in the extra dollar or two for a new switch.

My old ballast was attached by little clips that had corroded shut, and I had to break them. Not entirely sure how I'm going to attach the new ballast.

I'll post the next steps once I find my electrical toolbox. I'm kind of stuck until I've got a couple of basic bits.

  • #2
hey great write up. I had a old t12 magnetic ballast with a starter. The thing was going bad, so made a trip to the local store picked up a ballast wired it in, then I drilled through the reflector and installed moonlighting by applying silicone to the bulbs to hold them in place. I put it back together and fired it up, and wow what a change. Just a side note thought most bulbs are still t12, there are t8 availabel just not as wide spread as the t12 bulbs. Mine is a t8 48 inch 32 watt, and I have onlly been able to find a few bulbs. Thanks for the post a lot of fishlorians could save a lot of money by doing the conversion themselves.

  • Thread Starter
  • #3
I can get T8 plant lights for about the same price as T12s at my local hardware store. Their list of ballasts is a little less comprehensive for the T8s, but they had one for a single 24", which is what I needed.
Because the only difference is the ballast, this thread can easily encompass both.
  • #4
One thing to toss into this, depending on where you work and how good your relationship with the properties guys/purchasing people are.

Check into getting the ballast through work.

The ballast I could buy at lowes for like $50 I can get from our building guys for ~$20 since they buy them by the case and them bill them to location by the fractional cost.
  • Thread Starter
  • #5
Okay, to continue:

I've replaced the old power cord with a grounded cord, just for safety's sake.
I don't know that it actually matters, but I'm going with the polarization of the plug. The wider end is the neutral prong, so I followed the cord to the end and attached it to the white (neutral) wire coming off the ballast. The narrower prong is hot, so I attached that to a switch, and then the other end of the switch to the black (hot) wire of the ballast. I'm using a very simple, on/off switch that I got from Menards. The ground prong (the little round one) attaches to the ballast via one of the screws holding it in place.

When connecting wires, I prefer to use the little connector caps, rather than go with the old "twist the wires together and coat with electrical tape." The latter method can end with too many problems, if you aren't careful. The caps are almost foolproof, as long as you get the right size.

At this point, it's probably a good idea to test your light, to make sure it's working. I had what seemed to be an issue (though it turned out to be a bad tube) when doing this. Had I put the whole thing together before testing it, I would have had to disassemble the entire thing again to try to fix it.

After that, attach the ballast to the casing. This will probably require jury-rigging. The ballast I'm using is quite a bit bigger than the old one. It's a really good idea to mount the ballast to a piece of sheet metal to operate as a heat sink.

The switch goes through the hole that the old switch was in. If the old hole is too small, use a drill to open it a bit more. After that, it's easy enough to install.

Then put the entire thing back together.

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