T12 to T8?

[James S]

Hi Folks,

I've got 2 shop lights over my workbench that came with the house and have never put out much light. They are dim and flickery and I suspect that the ballasts in both of them are toast because new bulbs dont fix the problem.

I wanted to get a decent electronic ballast for them, but HD here doesn't carry an electronic ballast for anything but T8 bulbs, and these are the older fixtures for T12 bulbs.

Folks around here love T8 bulbs, more efficient brighter and such. But as I've looked at the specs, it doesn't actually show this. The lumen output on the T8 bulbs is less than the T12 bulbs on the package anyway.

Is this true? If I was going to buy a new ballast, should I get a T8 ballast and put t* bulbs in? or not worry about it.

The other problem I have is the sockets, would a T8 bulb go into a socket for a T12 bulb? just eyeballing it at the hardware store the pins look to be the same separation. They sell separate tube sockets, but they aren't labeled for T8 or T12, just "medium" or something equally as helpful.

I suppose i could just replace the whole fixture if I was going to replace the ballast and the sockets, whats left but some sheet metal But that is more expensive then as I'd want to get really bright 4 tube models or something.

So help me figure out if I can retrofit these for T8 bulbs and if I'd want to anyway?

Thanks!

[jtr1962]

I did almost exactly what you want to do with some old shoplights. The reason I did it instead of buying new shoplights was because they were much sturdier than a lot of the ones you can get today. In my case, I changed the old magnetic T12 ballasts for electronic T12 ballasts. There was nothing wrong with the old ballasts (in fact, I still have them), but they were 20 years old and I wanted to get rid of the annoying flicker. The T12 electronic ballasts also drive T8 tubes, although at a roughly 43 watt level instead of 32 watts.

To answer your questions, yes, the sockets and socket spacing for T8 and T12 tubes are identical, so all you need to do is swap out the ballast. As for whether you would want to or not, that depends how much better your old fixture is than something you can buy (a lot of those old fixtures are very well built), and how much you pay for the new ballast. As a bonus the T8 ballasts still drive T12 tubes, although at a reduced light level.

Regarding lumens, you'll generally get more out of a T8 tube with a given color rendering. My T8 full spectrum tubes give me 2950 lumens with a CRI of 91. The 40 watt T12 chroma 50s I'm using in the retrofitted shoplights only give 2150 lumens with a CRI of 92, and use more power besides. Note that most electronic ballasts have a ballast factor around 0.89, meaning that you'll get 89% of the rated lumens. Here again T8 is better. I've seen T12 magnetic ballasts with very low ballast factors, especially those energy-saving ballasts which only give about 70% of rated lumens. Since T12 cool white is typically something like 2600 lumens (and very poor color rendering) you'll only get about 1800 lumens on a typical energy saving magnetic ballast versus over 2500 lumens for a typical T8 on a standard electronic ballast. You can even buy T8 ballasts with ballast factors of about 1.15 to give you 3200 to 3400 lumens per tube. This is a safe amount of overdrive which doesn't affect the life of the tube. Most T8 tubes are rated at 2750 to 2950 lumens, but I have seen some as high as 3200 lumens. On an overdrive ballast you would get nearly 3700 lumens out of these! Also, T8 tubes dim far less over their lifetime than T12s.

Overall, I'd say make the switch, whether it involves buying a new fixture or replacing the ballast.

[James S]

JTR1968: Thanks! Thats exactly what I wanted to know. So I think I will make the switch to T8 bulbs then since I have to get new ballasts for them anyway. Since they are next to each other and wired from the same feed, perhaps I'll put 1 4 tube ballast instead of 2 2-tube ones

The selection of ballasts at my local stores is pretty limited, LOTS of different old magnetic T12 ballasts and 1 T8 ballast for 3 tubes that they say is "non-residential" and only comes in a 4 pack. Can these be ordered? Or did you find them at a local store? Where did you get your ballasts from?

Thanks again!

[jtr1962]

Originally Posted by James S

Can these be ordered? Or did you find them at a local store? Where did you get your ballasts from?

I bought my ballasts from Home Depot, although they were a bit pricey ($23.77 I think). Ebay seems to be a good source for T8 ballasts of all kinds. In fact, here's one with a ballast factor of 1.15. They also sell the same ballast in quantities of 10 here. These prices are much cheaper than home improvement or lighting stores.

[James S]

Ah, eBay to the rescue once again! I've started buying more and more stuff on eBay lately, but I still dont always think to look there. I ordered some from this fellow and we'll see how it turns out, but it looks good!

Thanks again,