Greg, The T-8 lamps will fit in the t-12 holders, but you have to change the ballast, most of the time. I recently got some ballasts from McMaster-Carr Supply Co. that are rated for either 2 or 4 four foot bulbs and either t-8 or t-12 bulbs. I did not know such an animal existed, but it sure cuts down on required stock, and I always have the right ballast. I quit putting in t-12 bulbs last year if a ballast change is required I always go for the t-8
Life is tough, Life is tougher when you are stupid
This could get interesting when I need lamps for the F96, T-12, HO, for my garage.
T-12, F40s have been gone for a while, replaced by the watt miser 34W. I believe most, if not all of the magnetic, old ballasts are gone; replaced by the nice, lightweight electronic, multi-voltage, ballasts.
I remember my one service truck had a ballast inventory that had to weigh 300 lbs+. And, there was always one that was not in the truck inventory!
A lot of office space has been converting to T-8 for the last few years up here. Same with metal halide/HPS hi-bays, going to T8 or T5 HO with occupancy sensors.
The drop in T-8 into a T-12 from what I remember from the days of tools was a crap shoot. Some lit, some didn't. Life was also questionable.
The T-5s are showing up in the Class AA office tenant fit-ups, as are a influx of LED! Some of the LED luminaires are interesting, albeit on the $$$$ side yet. Comment today from a sparky about the 2x2 lay-in LED fixture being in the $600 range!
I don't think many people actually know this. I know I am going to stock up on bulbs. Lighting is not a big part of my electric bill but I do have a lot of F40s.
My wife's country club is another thing. She doesn't even know how many there are but it is a number. Her electrician is saying that he has a bunch of customers in the same boat and he wonders if the distributors can even source that many ballasts. He is also not sure when he will have time to install them all.
I did see an interesting product (from Leviton I think) at the contractors lunch a while ago. It is a one piece deal that replaces the keystones and ballast in one shot with a T-5. You just keep the can and lens. I bet it is spendy tho. No free samples
It has been many, many Years since I've even held any T-12 size Fluorescent Lamps... along with any Straight Linear Reactor Low Hz Ballast!
For Standard Rapid Start T-12 Lamps - such as the very common F40T12 Medium Bi-Pin 430ma Lamp, or the equally common Energy Saver "34 Watt" 460ma version, the last time I dealt with any of those 1-1/2" Dia. Lamps could not have been any later than March of 1993. Same for the Low Hz Linear Magnetic Reactor Ballasts used to limit the Lamps' Current / Heat the Cathodes during Lamp Start & operation.
For the 800ma "HO" and 1500ma "VHO" T-12 Recessed Bipin Lamps, the last time I dealt with these high output animals was late in 1997. Additionally, this was also the last encounter with hanging those >40 Lb Rapid Start, Multi-Lamp, Linear Magnetic Reactor Ballasts!!!
By the time Y2k Rolled Over, all Ballasts were >20kHz Straight Electronic, or Hybrids (mostly used for Hot Cathode Operations), and Lamps were only 1" dia. (T-8 Medium Bipin). For High Output Lamps, size T-5 has become the Norm...
Scott " 35 " Thompson Just Say NO To Green Eggs And Ham!
Guys, One thing that can come out of a phase-out like this, is better lighting quality with less power usage. Reason I say that, is when I first started my time, the T-12 Halo-phosphor tube was seriously not performing as a lighting source and it was on the way out, here in New Zealand. We had problems with PCB-filled ballasts and over-heating inside poorly designed fittings.
What we installed from there was the T8 single-phosphor tubes, these ran a lot cooler and had significantly greater light output for the supplied watt. However, we were still using fitting lengths of 5 and 6' to achieve the lumens/watt.
When the T8 Tri-Phosphor tubes came out, it was like a revelation, you could now do more with shorter and more compact fittings, because you had less fittings per given lighting level. When Thorn Lighting here bought out the 4 and 5' Slim-Paks, customers were really happy with what we had installed, unlike before.
I have to mention too that up until a few years ago, all of this new stuff used wire-wound ballasts, mainly because most of the electronic ballast gear we had here, just couldn't cut the mustard in terms of reliability, fire safety and RFI problems.
These days though, we are moving more towards the T5 nomenclature and are removing the T8 fittings, these lamps run cooler still, have extremely low levels of mercury and by design are brighter than the T8. Even in so much that T5 is being touted as a REAL alternative to low bay sodium and Metal Halide, and with the reflector design technology that is around these days, I reckon they'll get that.
In 220-240V countries, wire-wound ballasts were used for quite a long time as they're simple chokes that limit the current. The ballasts themselves last forever, usually longer than the entire fixture. In domestic setups, even the tubes can last for a very long time. I still occasionally find T12 tubes in use and they haven't been available at DIY stores for decades.