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Re: [APD] Power Compact Bulb Useful Life: 12 months max -- Unless . ..

My point was a bit different. Even an almost new bulb (a
few months old) will seem dimmer than and brand new bulb. 
The brightness of a brand new fluorescent bulb can give you
a sort of false high -- the brightness is way up there but
won't last long.

Of course how long your bulb lasts and how fast it
deteriorates depends on the ballast and bulb combination.
Overdriven bulbs will tend to decay and burn out more
quickly than others. 

And hotter ambient temps (hot hood) will tend to somewhat
speed things along. (Otoh, cold hoods tend to be dimmer)

And diff brands of bulbs -- well, some are better than
others. Even if two "brands" of bulbs are made in the same
factory, they aren't necessarily made to the same specs and

That's one of the reasons I like to get my stuff from AHS.
They pick very good bulbs and match them up well to the

Like all things plant related, you have to judge mostly by
your plants and how they are performing. If they used to
get enough light but aren't now, by all means change the
bulbs. If you have to do this way too often, consider
getting more bulbs over the tank and using them longer. But
I wouldn't take it as a rule of thumb that PCs are only
good for about a year, there are too many exceptions. A
better rule of thumb might be 1-2 years or 1-3 years.

If one wanted maximum brightness, one could change the
bulbs every 300-400 hours, before that initial, say, 10%
decay in brightness occurs fully. I can think of some
gardeners that might consider that -- but they are very
well healed ones ;-) .

Btw, a 50% drop in a PC's output in one year sounds like an
overdriven bulb to me. If your bulbs are rated for the
ballast you're using, you might consider trying another
brand of bulbs.

Scott H.
--- Dave Millman <dave at tactics_com> wrote:
> At 12:04 PM 11/12/2003 -0500, Scott Heiber wrote:
> >The first few hundred hours can give a roughly 10% drop,
> and the next 10% 
> >takes a year or two.
> Scott,
> I only have my four data points, but I measured between 1
> and 1.5 f-stops 
> drop in output on my four bulbs. That's more like 50+%
> than 20%, again 
> recognizing that the light meter may not have been
> measuring spectrum 
> usable to the plants.
> But you're right, you don't notice it until you plug new
> ones in!

S. Hieber

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