Post by RBMPost by Home GuyWhat exactly would happen if T-8 ballast is connected to a bunch
of T-12 tubes?
If you run a t8 bulb on a t12 ballast
Not interested in that situation.
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.
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.
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.
Post by RBMPost by Home GuyT12s are becoming obsolete. Buy t8 ballasts and use t8 bulbs.
They are brighter and more efficient.
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.
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.
Post by RBMPost by Home GuyIn 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
us.
Around here, the largest box of T8 I can buy is a 10-pack, and it costs
about $34.
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?
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.
Post by RBMPost by Home GuyAnd I still want to know if they ever made 4-tube electronic ballasts
for T12 tubes.
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).
Post by RBMPost by Home GuyGiven 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.
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.
Post by RBMI'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.
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
these days.
Tomsic