I've looked off-and-on over the past few years for a single electronic
ballast that can run 4 T-12 48" tubes but haven't seen any in the
But they seem to exist for T-8 tubes.
What exactly would happen if T-8 ballast is connected to a bunch of T-12
If you run a t8 bulb on a t12 ballast you will have premature bulb life
as the t12 ballast will over "tax" the bulb. If you run a t8 ballast
running a t12 bulb you will have premature ballast life as the t12 bulb
takes more to run and will over work the ballast.
T12s are becoming obsolete. Buy t8 ballasts and use t8 bulbs. They are
brighter and more efficient.
I'm not sure if I buy your arm-chair or seat-of-the-pants explanation.
Without solid engineering data, I could just as easily suppose that the
extra few watts used by a T12 tube can be easily handled by the
circuitry of a T8 ballast.
I'd have to do more research on this, but I'm guessing that T8 tubes are
NOT more efficient than T12 (in terms of watts per lumen), and that the
only purpose of T8 replacing T12 is part of the energy politics
happening in western countries - other examples of which is subsidized
CFL's and the ban on sale of 100 watt incandescent.
In other words, the "powers that be" have deemed that we don't need 40,
36 or even 34 watt T12 tubes, and that for the good of the planet, our
eyes have become more efficient and 32-watt T8's are now good enough for
Around here, the largest box of T8 I can buy is a 10-pack, and it costs
There are far more boxes of 30-count T12's on the shelves, and they cost
about the same as a 10-pack of T8's.
So tell me again why I should be paying 3X the price for T8, and get 11%
less light in the process?
And I still want to know if they ever made 4-tube electronic ballasts
for T12 tubes.
Given that I can buy a 4-bulb T8 ballast for just about the same price
as a single 2-bulb T12 ballast, it's worth the experiment to run a set
of 4 T-12 tubes off a ballast thats spec'd for T8 tubes.
How about this ballast ?
I doubt you will like the price at around $42.
You can put the bulbs in ballasts not made for them, but speaking as someone
that has replaced thousands of bulbs and hundreds of ballasts, they will not
last long if mismatched.
I would still replace the ballast and go with the t-8 size bulbs.
I've not seen ballasts for 4-T12 lamps. My understanding from my
electrical supplier is that T12 lamps are no longer being made and are
selling whatever is on the shelf.
The "initial lumens" of a comparable T-8 are greater that those of a
T-12, so you do get slightly more light for slightly less wattage, at
least initially. It certainly has been my experience that the T-8 lamps
have a much shorter life, as do the ballasts as compared to the magnetic
ballasts and T-12 lamps.
Given that many fixtures are composed of four 4-ft lamps, why is it we
only see 4-lamp electronic ballasts for T8 and not T12 lamps?
It's ridiculous that I see web-prices for 4-lamp T12 electronic balasts
going for $140 where 2-lamp T12 versions cost $16 and T8 4-lamp ballasts
go for $22 or less.
But why weren't 4-lamp electronic replacement ballasts being made
available for T12 lamps at least several years ago - before this talk of
phasing out T12 lamps?
And that comes with a price - the T8 lamps only achieve slightly better
efficiency when operating at 95f ambient air temperature, whereas T12
reach their peak efficiency at 78f.
The main push behind T8 is to reduce mercury in the lamp. We're being
force-fed a load of horse shit about efficiency - because comparisons
are being made between T8 with electronic ballast vs T12 with magnetic
The lack of 4-lamp T12 electronic ballasts (or lack of a reasonable
priced version) must be a calculated maneouver to limit the cost
effectiveness of converting old magnetic-ballast fixtures over to
electronic when the old ballasts start to leak.
I don't know what the legal situation is in Canada regarding the
legislated ban on manufacture or import of T12's, but you people in the
US have had this ban in place for almost exactly a year now.
So what are you seeing as the price difference between T8 and T12?
In bulk packs (10 or 30 per box) I'm seeing the price of T8 being 3
times the price of T12 here in Canada.
I'd like to see how T8 with electronic ballasts deal with frequent
on/off cycles (typical of a soho or residential situation).
Depends on the ballast. Instant start, rapid start, programmed start?
Programmed start handles continuous on/off issues much easier, but hey,
what do I know, I'm just an arm chair adviser dealing with the lamps and
ballast industry for 11 years.
The above explanation is correct from my experience too. A fluorescent
ballast tries to act like a constant current source and T8 lamps run on a
lower current than T12 lamps. So, if you operate T12 lamps on a T8 ballast,
the lamps will start, but will operate at that lower current. Light output
is reduced and the ballast overheats trying to deliver 40 watts using a
circuit designed to deliver only 32 watts.
Yes, T8 bulbs are more efficient. Check any lamp manufacturers lamp
catalog. The nominal light output of an F40T12 (40 watts) is about
3000-3100 lumens. The nominal light output of an F32T8 (32 watts) is the
same 3000-3100 lumens.
F40T12 lamps are being phased out in favor of T8 lamps and the even more
efficient T5 lamps, but the current high price of T8 lamps is because they
use "rare earth" phosphors. China (the main source of these materials)
restricted the supply a couple of years ago and the result is that the price
of T8 lamps tripled. The F40T12 lamps use a cheaper, less efficient
phosphor which loses its light output faster and so the lamps have not
increased as much in price.
Because your numbers are incomplete and your light output assumption was
wrong. If you're buying light (lumens) over time, the T8 is cheaper. If
all you look at is the price of the bulb, you'll pay less up front with the
F40 and more to the electric utility company over time.
Yes. GE, for one, made electronic ballasts for F40T12 lamps until they
cranked up their T8 lamp production. As I recall, the ballasts were only
sold for a year or so. After that, with T8 lamps and ballasts available,
there was no reason to stay in the business since the T8 system gave the
same amount of light was about 25% more efficient (lumens/watt).
Go ahead. The lamps will be dim and the ballast will be hot; but the system
will work for a while. Don't expect much light if the air temperature is 50
F or less though because the F40 won't be generating enough heat to keep the
mercury inside properly vaporized.
The typical life rating of T8 lamps on standard electronic ballasts is
20,000 hours. The so-called "long life" types are rated for 40,000 hours at
3 hours of operation per start. Starting affects lamp life so frequent
on/off operation is the major reason that fluorescent lamps fail. However,
there are ballasts on the market which "soft start" T8 lamps so
manufacturers will rate some lamp/ballast systems in excess of 40,000 hours
At a higher operating temperature.
And tell me why the exact same process or formulation they're putting
inside T8's can't be done with T12's such that we don't need this
god-damn stupid game of having different ballast requirements.
For one thing, show me where you can even buy 40-watt T12's.
I'll take a 34-watt T12 any day (at $1.25 each) over a 32-watt T-8 (at
$3 each) any day.
Just don't handicap me by making 4-lamp T12 electronic ballasts
artificially scarce and expensive while 2-lamp versions are strangely
Because of mercury. That's the ONLY reason.
And again, the standard T12 lamp has been 34 watts for a long time.
Saving 2 watts (and paying triple for it) doesn't make any sense.
I'm going to stock up and buy a few boxes of 30-count T12 lamps.
Because those will be the real prize to have in the future - not
100-watt incandecent bulbs.
Haven't there been any T12 fixtures sold during the past decade or so
with electronic ballasts?
Even if there hasn't been, there must be many old T12 fixtures
originally with magnetic ballasts that have failed that have been
retrofitted with electronic ballasts.
But no matter, because there are still many 2-lamp T12 electronic
ballasts for sale around here - Lowes, Home Despot, etc.
Home Despot still sells T12 magnetic ballasts - because Canada is not
over-regulated like the US is.
Very few. After T8 lamps arrived from Europe and were redesigned for North
America, they proved themselves more efficient and, until recently, were
less expensive too. So manufacturers moved quickly to promote T8 over T12
systems as more economical. The 4-foot T8 lamp fits into 4-foot T12 sockets
and fixtures, so a ballast change makes it simple to convert. T8 lamps,
until the recent restrictions by China of the rare earth materials used for
T8 phosphors which increased the lamp prices, are smaller, lighter and take
less raw material, packing material and space to ship.
The reason is cost, cost and cost. More costly phosphors have to be used in
T8 lamps because of something called "wall loading" which means the phosphor
particles are exposed to more watts/phosphor area. T8 phosphors can take
that pounding; T12 phosphors cannot and lose light output fast. Good thing
that T8 lamps have less inside glass area than T12s so less phosphor is
4-lamp T12 ballasts are scarce because hardly anyone wants or buys them.
2-lamp fixtures outsell 4-lamp fixtures by a wide margin. Just count the
2-lamp and 4-lamp fixture types that you see walking around any office
building or school. Another consideration is that if one circuit in the
4-lamp ballast fails, the whole ballast has to be replaced. It doesn't make
sense to throw away a 4-lamp ballast which still partially works or try to
add an additional 2-lamp ballast to the fixture to get the lamps on the
failed circuit working.
Not it's not. A T8 lamp/ballast system is 10-15 percent more efficient than
a comparable T12 system, so the phase out is mostly cost driven with some
federal regulations in 2005 and 2007 from the DOE moving it along. The
slightly higher initial cost of a T8 system is usually paid back in 3 years
or less. But, the rising costs of T8 lamps (due to the restriction of
rare-earth phosphors by China) have increased the payback times. U.S. lamp
manufacturers asked for and received a delay in the DOE lamp phase-out
process last year as a result.
I'll still bet on the most efficient system being the cheapest in the long
run because the one cost that's not going to go down is the cost of energy.
Ballast and lamp prices change all the time and that market is very
competitive, but if you end up with a system that uses more energy than
something comparable, you'll end up paying more. With incandescent
lighting, 90% of the cost over the life of the fixture, including
replacement bulbs, is energy. With fluorescent systems, it's a bit less;
but when you buy and install any lighting system, you automatically contract
with the electric utility to power it -- or pay to do it yourself somehow.
In any case, there's an energy cost involved with a big number attached to
it that usually overwhelms the cost of the ballast or tubes. All you have
to do is pay the electric bill and wait.
what I'd like to know is how home guy is going to deal with his
insurance companys refusal to pay on a fire that might be caused by
having an improperly wired light fixture that overheats resulting in a
all theoretical of course
Half of the 3-dozen 4-lamp fixtures I have are mounted to a concrete
ceiling, so you tell me what exactly is the fire threat there.
The other half are mounted _under_ a suspended ceiling.
About 1/4 of all fixtures have had their magnetic ballast replaced with
electronic (so far). All fixtures were originally installed in 1981 or
All lights are turned off when nobody is in the building.
If any lights are on at all, it's between 9-5 on weekdays.
You mean what happens if an electronic ballast gets so hot that
something melts through not only it's own steel casing, but also the
steel shield in the center of the fixture that covers the ballast and
the wires? And then once through the shield, some flaming bits drop
down and melt through the lexan light-diffuser sheet?
What exactly are we talking about here? The acidic blood of the
creature in Alien?
Given that we are talking about electronic ballasts, a single point of
failure (a single electronic part, semiconductor, etc) is likely to fry
itself *if* the use of 34-watt T12 lamps are enough to push it over into
failure vs using 32 watt T8 lamps. I wouldn't expect one or even a
handful of transistors to continue to draw current once they've failed,
resulting in not much more than a puff of smoke to be emitted from the
I'm not aware that explosive materials are used in the construction of
electronic ballasts. Hollywood might beg to differ, but I don't think
that transistors are made from TNT, Semtec or C4.
Now look what you've done - the NSA has just detected this thread...
Uh, no. Ballasts are "black boxes; but that's as dramatic as it gets.
Fluorescent ballasts, both magnetic and electronic, have for years been
equipped with thermal protectors to avoid overheating and fires plus the
smoke, smell and dripping black tar (sometimes laced with PCBs) emitted from
failing ballasts. It's a U.L. requirement called "Class P" protection.
Most Class P ballasts have thermal switches that reset automatically when
the ballast cools off; a few don't so the ballast has to be replaced if it
overheats. A fluorescent lighting fixture which cycles on and off every few
minutes is likely the victim of a failing or overheated ballast -- perhaps
due to the wrong lamp being used.
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