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Re: 36 inch lighting

Bob Dixon sez:
> My local Home Depot carries a limited selection of cool whites and 
> plant bulbs in 36", 30 watt.  All of them are T-8.
> Speaking of which, that confuses me.  When folks started talking t-8, the 
> idea was that you could get more light with the same power consumption.  Now 
> that 48" t-8s are everywhere, they are reduced to 32 watts.  They do put out 
> a little more light than a standard T-12, but I have been told I have to 
> re-ballast my fixtures to run them.  What kind of deal is that?

"T-8" is a size designation for the lamps.  It means the lamp is
tubular, and 1 inch in diameter. That's all it means.  The smaller
diameter is inherently more efficient because there is less restrike
in the fixture.  The 48 inch T8 lamps are designed to run at
significantly less current, but higher voltage, than the old F40T12
lamps, so they need a different ballast.  These new F32T8 lamps
produce more light per watt than their F40T12 (now, F34T12)
counterparts, and they are cheaper too!  There is a 36 inch version of
the new technology lamps, F25T8, that will operate on ballasts
designed for F32T8 lamps.  Unfortunately, there are also F30T8 lamps
that are compatible with the old style F30T12 lamps.  The F25T8 and
F30T8 lamps look the same, but they are not compatible.  If you put an
F30T8 lamp on a ballast for F25T8's, it might light but it will be dim
because it is operating on too low current.  If you put an F25T8 lamp
on a F30T8 ballast, the ends will get hot but the lamp will not light
because the voltage is too low.

I reballasted some of my 4' fixtures to convert them to F32T8 lamps
because I was tired of those dim 34W lamps, and real 40W EPACT
compliant lamps were too expensive and hard to find.  I recovered
about half of the cost of the ballasts just on the relamping costs of
the first set of lamps ($3 each, versus about $10).  Then there's the
ongoing energy savings, and recurring savings each time I replace the


"We tend to scoff at the beliefs of the ancients. But
 we can't scoff at them personally, to their faces,
 and this is what annoys me."
--Jack Handey