well hello there! i'm violet, and i work at an amusement park older than any of us. i'm thrilled to have the job i do, and one of the primary responsibilities i have is repairing and restoring the lighting! i just made my account here and i feel i ought to share some of the unique experiences i have in my work! in this post, however, i wish to dig into the entangled mess of fluorescent lamps, and amass what i've learned about how they're designated.

now, there are all sorts of lamps, fixtures, and so on at my work... but this post is about fluorescent lighting, both because that's by far the most prolific lighting technology, and because its bulbs are designated in such a fascinatingly irrational way! after all, one would tend to think that an F96T12 is just that, but what about the /HO version with a shrouded bi-pin base, which operates on the "preheat/rapid-start" principle? it's the same length of tube, and indeed a single-pin 8ft ballast can run such a bulb if the pins are bridged on either end... and yet there are ballasts which operate it at much higher power levels than a single-pin bulb! or how about 2ft F15T8s, coexisting alongside a shorter F15T8 that's the same length as an F15T12? there are many mysteries to fluorescent bulb designations, and i hope to help unravel them here!

to my understanding, there is no functional or electrical difference between normal bi-pin bulbs and shrouded ones, the shrouded ones simply tend to be longer and the purpose of the shrouded connector appears to be to allow for a reasonably easy way to install such a long bulb from one end, in the style of a single-pin bulb. i have to say, it is a huge improvement over trying to twist a bi-pin bulb into most tombstones, yet retains the benefits of preheat/rapid start operation. in my experience thus far, any bi-pin bulb, shrouded or otherwise, can easily be operated on an instant-start ballast, and i've yet to determine the relationship between a lamp's rated current, the current a ballast (especially one not designed for it) will feed, and lamp longevity have. any information on lamp current and operating differences between different ballast designs (8ft single-pin instant start and 2-pin rapid start especially) would be appreciated and you're welcome to email me about it!

now, to the focus of this post: lamp sizes and their nonsensical nature! this is an evolving list, which i intend to update regularly with new info. many of these designations may be specific to a certain period of history, and i am quite interested in dating them. the real question here is whether the order of this list ought to be based on diameter, length, wattage, or some other factor... i shall list lamps in order of length, then wattage. t8 bulbs will be listed after t12 bulbs, although in many cases they were in concurrent use.

- 8ft -
F96T12HO : shrouded bi-pin 8ft bulb. preheat/rapid-start ballast required for full output, will run off single-pin instant-start ballasts at reduced output. ballasts for these are incredibly expensive, sadly.
F96T12 : single-pin 8ft bulb. very common in use with magnetic instant-start ballasts, electronic ballasts are readily available (if overpriced) as of 2021. magnetic ballasts last decades in regular use, these are "the classic" shop lighting.

-f60 through f72 stuff will be here eventually-

- 4ft -
F48T12HO : shrouded bi-pin 4ft bulb. preheat/rapid-start ballast required for full output, will run off single-pin instant start ballasts at reduced output.
F48T12(HO) : single-pin 4ft bulb. instant-start only. works great with electronic instant-start ballasts like the workhorse series.

F40T12 : bi-pin 4ft bulb. probably the most common type in the world. "superceded" by F34T12 but the colour rendition of a cool white F40 bulb is far superior due to a broader phosphor composition and brighter arc. magnetic ballasts for these abound, and many still work great to this day. easily converted to F32T8 for energy savings by swapping out a ballast.
F34T12 : bi-pin 4ft bulb. about all you can get in that length brand new these days. a true trade-off between 6 watts of saved power vs. true colour rendering. great for general illumination when colour rendering doesn't matter, otherwise far inferior to true f40 bulbs.

F32T8 : bi-pin 4ft bulb. the most ubiquitous t8 bulb in existence as of 2021, but a huge number of t12 equivalents are still in service today. colour temperature is usually indicated numerically rather than via the traditional letter-based designations. will start and run off many magnetic F40 ballasts, but with insignificant efficiency gains and reduced lamp life. generally used with electronic instant-start ballasts.

- 3ft -
F30T12 : bi-pin 3ft bulb. relatively common, but not as much so as 2ft and 4ft bulbs. will run fine off magnetic ballasts intended for F40s, as well as electronic ones intended for F32T8s.

F30T8 : bi-pin 3ft bulb. curiously, these are rated at the same 30 watts a t12 bulb of the same length is. i've only encountered them running off switch-start ballast/starter setups but they run fine off instant start electronic ballasts as well.

- 2ft -
F20T12 : bi-pin 2ft bulb. ubiquitous in many applications.

F18T8 : bi-pin 2ft bulb. rated 18W.
F17T8 : bi-pin 2ft bulb. rated 17W.
F15T8 : bi-pin 2ft bulb. rated 15W.

yes, that's right, all 3 of these designations refer to a 2ft t8 fluorescent. i have yet to determine the actual difference between an F18 and an F15 but i assume that 3 watts has to come from somewhere!

- i need to measure these >w< -
F15T12 : bi-pin <length> bulb. rated 15W. relatively common in smaller fixtures. nearly always used with preheat/rapid-start ballasts or switch-start configurations.

F15T8 : bi-pin <length> bulb. rated 15W. similarly common to F15T12, it seems to have been mainly used to give fixtures a slimmer profile, rather than for energy savings. i'm not aware of any t8/t12 ballast differences for these bulbs, and i'd love to know more about them!

F14T12 : bi-pin <slightly shorter than F15> bulb. also very common in small fixtures. similarly, nearly always used with traditional ballasts and switch-start setups.

F14T8 : bi-pin <slightly shorter than F15> bulb. these aren't nearly as common as F15T8s but they do exist. as with F15s, i'm not sure what the electrical differences from the t12 versions are.

all right, that's all for now but i will come back and edit this post in the future. i have plenty more lamp types to add! F24T12, F30"T12, F36T12, F42T12, F60T12, F64T12, F72T12... coming soon!

Hey Violet!


To awsner a few things, those single bi pin non HO lamps are referred to as slimline, and number after f is the lengths of the suckers in inches, not the wattage. So an F84T12 lamps is 7 feet long and an F48T12 lamp is four feet long. Most F15 lamps are 15 inches long, and most F14 lamps are 15 inches long. F18T8 and F17T8 are similar, i have a fixture that does F18T8 lamps with an electronic ballast, you can runF17T8 on that ballast, but not on a magnetic F17 ballast. F18T8 comes in two flavors, 26 and 24 inches long, the 24 being a lot more common. F17T8 is 24 inches long and is a bit easier to find then its F18T8 variant.

Hi Violet, welcome to LG from the frozen North-East of Scotland..! Good to see another female member, there aren't many of us 

As Ria (rommie! ) said, always nice to see some new faces around here! You can set up a member introduction if you want in board for that.

(and keep weary of the slaps! )

thank you both for the warm introduction!

in response to @Bulbman256, i've definitely seen the single-pin lamps coded as "HO" time and time again. hopefully i'll get around to taking some pics and uploading them soon. however the shrouded bi-pin "HO" and "VHO" lamps are a bit more of a mystery to me, they seem to be particularly high-power preheat/rapid-start lamps and the proper ballasts for them are not cheap at all these days! however they seem to start and run off instant-start ballasts ok so i'm curious how long they'll last in such a configuration. i doubt they're producing anywhere near their rated high-current output but i'd hope that means they'll last longer!

as for "F" designations being length in inches vs. rated watts, it seems there's no consistent standard there, and that confused me greatly at first. for example, an F96T12 is indeed an 8ft bulb, generally rated at 60 watts. but an F40T12 is a 4ft bulb, rated at 40 watts! then you have the F48T12, an HO single-pin or shrouded bi-pin 4ft bulb! and of course the t8 equivalent is an F32T8, still 4ft but rated at 32 watts. the convention of using the rated wattage also seems to apply to F30 bulbs, which are 3ft (and interestingly the t12 and t8 versions are both rated at 30 watts!) and F20 bulbs, which are 2ft and rated at 20 watts. when you get to 2ft t8s, that's where all reason completely disappears... F17T8 appears to be the "standard" 2ft t8 designation, but i have F18 and F15 bulbs that are the same exact length as well! i also have numerous F15T8 bulbs that are the same length as an F15T12, and 3 cases of F18T8 bulbs that are the same length as an F30"T12! now, there's a really weird designation.... it says on the box and bulbs, F30"T12, with the " to designate inches! these are obviously 30" long, 6 inches shorter than an F30T12. that's by far the most interesting designation i've come across. when it comes down to it, there seems to be no real rhyme or reason to the "F" designations, and it's important to have the length of the bulb as well as the designation when seeking a replacement. it's really interesting stuff! 

@sox35 indeed, i'm glad i'm in good company! 

@sox35 indeed, i'm glad i'm in good company! 

No problem, glad to have you on board. It always amuses me when you lot from over the pond call fluorescent tubes "bulbs" - they're not very bulbous, are they..?   

Welcome to LG Violet! 

Welcome!

Here are some key differences between HO, VHO, and slimline tubes:

Both HO and VHO tubes use an RDC base while slimline tubes use a single pin base

In addition, each of these 3 tube types runs at vastly different currents and also, shorter tubes have a low arc voltage while longer tubes have a high arc voltage

VHO tubes run at 1.5a, HO tubes run at 0.8a, and slimline tubes run at 0.425a.

Here are some key differences between HO, VHO, and slimline tubes:

Both HO and VHO tubes use an RDC base while slimline tubes use a single pin base

In addition, each of these 3 tube types runs at vastly different currents and also, shorter tubes have a low arc voltage while longer tubes have a high arc voltage

VHO tubes run at 1.5a, HO tubes run at 0.8a, and slimline tubes run at 0.425a.

well, obviously longer tubes have a higher voltage required to strike an arc and i actually have noticed that some ho tubes have "800ma" printed right on them, and there's one bulb with orange(!) end caps that has "1500ma" printed in big proud characters! i really do need to spend some time and get pictures of these, i think some of y'all may be a bit jealous of how many brand new "black-enders" i've got in the bulb supply, which are meant for normal relamp!

here's the thing that really gets me, though. if i connect an ho tube to an instant-start ballast, bridging the pins at each end of course, it appears to start and run just as an equivalent non-ho tube of the same length would. of course, the increased life offered by preheat/rapid start operation is lost, and i'd figure the ballast is still going to be running the tube at that lower current... but i don't see that as a problem, inherently. is there a difference in terms of gas fill/phosphor composition in the ho and vho tubes? if not, what makes them capable of sustaining so much more current? perhaps i should make another topic for this, but is there any reason i shouldn't use f60t12 ho bulbs on magnetic instant start ballasts? this will be a real-world installation, running for several hours on a nightly basis, and i care about getting good longevity out of the bulbs and ballasts. i don't mind lower output than the bulbs would offer on the proper ho ballasts, so long as they run just as "slimline" ones would for a comparable lifespan.

the ballast is still going to be running the tube at that lower current... but i don't see that as a problem, inherently.

Ballasts don't dictate the current demanded by the lamp. They simply limit it to the lamp specifications to prevent destruction due to the negative resistance nature of gaseous lamps.
Without a ballast, a lamp will demand more and more current until it blows. A 800mA lamp on a 400mA ballast will put strain by demanding double than what the ballast is rated for, and you will overheat it.

is there a difference in terms of gas fill/phosphor composition in the ho and vho tubes? if not, what makes them capable of sustaining so much more current?

Yes. Neon gas as a buffer helping warm up in colder temperatures. And larger electrodes in a VHO.

is there any reason i shouldn't use f60t12 ho bulbs on magnetic instant start ballasts?

Yes, see above. Engineered electrical specifications exist for a reason.

this will be a real-world installation, running for several hours on a nightly basis, and i care about getting good longevity out of the bulbs and ballasts.

Yeah, no. Especially if there are people involved.  I've seen some of the worst rigged out crap from the carnival crowd, rides, displays, booths electrical jobs begging to cause trouble.
But hey, if you have a good insurance, knock yourself out 

Without a ballast, a lamp will demand more and more current until it blows. A 800mA lamp on a 400mA ballast will put strain by demanding double than what the ballast is rated for, and you will overheat it.

perhaps there's something i'm missing here, but if all fluorescent lamps demand more and more current as they run, what's so different about an ho bulb that would damage the ballast? i have no doubt a bulb rated at 400mA would rapidly increase to pulling well north of an amp in no time without a ballast, so i'm not sure i follow that line of reasoning. that said, i'm no expert on inductors, so i would love to be pointed in the right direction as to the theory behind your statement. resistance, capacitance, and inductance have quite the "holy trinity" relationship and there's always more to learn about how they interact with voltage and current!

Yes, see above. Engineered electrical specifications exist for a reason.

call me excessively cynical if you will, but that reason, when it comes to fluorescent lighting, often seems to have more to do with regulations and money than it does practical implementation. consider, for example, how many electronic instant-start "t8" ballasts on the market will happily run the corresponding length of t12 tube, despite pointedly not listing them in the compatibility charts. that comes down to regulations that ban ballasts listed as "compatible with t12 bulbs", not any actual technical reason. as an additional example, i offer fulham's, sadly mostly discontinued "workhorse" line of ballasts, which is rated for "any combination" of lamps up to a certain wattage. in my opinion, fulham just has a better marketing department than most of the industry, i doubt there's any special magic in their ballasts that all the "4-foot t8" ones out there lack. it's just a lot easier to get a product to market if you say all it works with is 4-foot t8s.

I've seen some of the worst rigged out crap from the carnival crowd, rides, displays, booths electrical jobs begging to cause trouble.
But hey, if you have a good insurance, knock yourself out 

 

perhaps there's something i'm missing here

Yes.

what's so different about an ho bulb that would damage the ballast?

Gaseous lamps. Makes no difference. Same family.

so i would love to be pointed in the right direction as to the theory behind your statement. resistance, capacitance, and inductance have quite the "holy trinity" relationship and there's always more to learn about how they interact with voltage and current!

Look up those terms above.

how many electronic instant-start "t8" ballasts on the market will happily run the corresponding length of t12 tube, despite pointedly not listing them in the compatibility charts.

Because part of it T12 aren't as efficient as their T8 counterpart, another is those ballasts were designed around the T8 specs first, and so for some manufacturers there is no point in mentioning an obsolete source, if it means the end user isn't getting the most value, light output, energy savings etc of the company's product. That avoids complaints and returns. And another I'll throw in is, most T12 cathodes were initially designed for Rapid Start or Preheat. They will light under an Instant Start set-up, but their life will be shortened.


Hey, I could fill pure ethanol in my car, after all it's a combustible, motor will fire, no different than gasoline, right?
You could, doesn't mean that you should.

it doesn't seem like you really read or considered the points i made in my prior post, but i'll attempt to rephrase them more concisely.

Yes.

to my understanding, the characteristic of negative resistance means that any fluorescent tube will "demand", as you describe it, increasing amounts of current until it fails, unless that current is somehow limited. this means a standard tube, meant to run at 400mA, will "demand" more than 800mA from the ballast, and obviously that characteristic does not cause ballasts to overheat. so again, what is it about an "ho" tube that would cause it to damage a ballast? the ballast doesn't care what's connected to it, it's simply going to limit the current as designed. now, the voltage the output of the ballast settles on to sustain the arc will depend on the length of tube, and indeed connecting excessively long tubes to a ballast meant for shorter ones will cause excess strain on the ballast due to the fact that the tube is drawing more power (voltage x current).

Gaseous lamps. Makes no difference. Same family.

funnily enough, i've spent a fair amount of time reading that article in the past, and nothing in it answers my question. beyond that, your statement that it "makes no difference" is exactly what i understood to be the case, and seems to directly contradict your warnings that running ho tubes off an instant-start slimline ballast will damage the ballast.

Look up those terms above.

having done so once more, all i see is a description of the electrical characteristics of gas discharge lamps in general.

Because part of it T12 aren't as efficient as their T8 counterpart, another is those ballasts were designed around the T8 specs first, and so for some manufacturers there is no point in mentioning an obsolete source, if it means the end user isn't getting the most value, light output, energy savings etc of the company's product. That avoids complaints and returns. And another I'll throw in is, most T12 cathodes were initially designed for Rapid Start or Preheat. They will light under an Instant Start set-up, but their life will be shortened.

as i already said, the primary reason is that department of energy regulations in the us banned the sale of most t12 tubes, as well as ballasts meant to run them. it would seem there are some exceptions, mostly for 4ft and 8ft tubes, but you'll note most "t12" ballasts are now listed as "discontinued" by their manufacturers. this includes some product lines such as fulham's "workhorse" series, as i also already mentioned, which were extremely popular due to their versatility.

as for starting technology, t8 cathodes are also designed for preheat/rapid-start operation. if you look in my gallery, you'll see some photos of F30T8 tubes which run off switch-start (preheat) gear and were never meant for instant-start ballasts. perhaps some modern F32T8 tubes have cathodes meant to stand up to instant-start operation better than some older ones, but when it comes down to it instant-start electronic ballasts abuse all tubes. that characteristic is far from exclusive to t12s, and indeed i've had no issue running F20T12 tubes off "t8" instant-start ballasts with good tube and ballast longevity. the real trick to getting good tube life out of instant-start ballasts is to switch them on and off as infrequently as possible... it's best to turn them on once, then leave them on for as long as needed.

Hey, I could fill pure ethanol in my car, after all it's a combustible, motor will fire, no different than gasoline, right?
You could, doesn't mean that you should.

the lighting equivalent of that would be running a standard 400mA tube on a ballast meant for ho tubes, at 800mA.... not the reverse. sure, putting too much current through a tube will cause excessive stress, just as feeding a gasoline engine fuel with excessive ethanol content will. (at least without an appropriate tune, it is after all quite common to run e85 in turbocharged performance engines)

clearly, i'm just going to have to test the longevity of ho tubes on magnetic instant-start ballasts for myself, as your responses to my question mostly seem to amount to "you can't because you can't, and it's not listed in the spec sheet of the ballast." that's never stopped me before, and as a result i've been able to repair lighting installations it'd otherwise be nearly impossible to find new ballasts for on multiple occasions.

For me, I often get bothered by the philosophy of “you can’t just because you can’t” because it discourages me and other members from doing experiments.