[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: CF bulb life -- or Compact notes onthe power of PCS

Chad Sutton asked:

> Are compact florescent bulbs good for the entire time
> they provide visible 
> light or do they become ineffective over time? 

This is a good question and you're bound to get different
answers from different folks.  But fluorescent bulb
engineers will tell you that a Power Compact, like the
55watts and 96watts keep more than 80% of their brightness
just about until flame-out, that is, until one of the
filaments/electrodes becomes incapable of working.

Bulbs have the highest loss in brightness during the first
1,000 hours and most of that within the first few hundred. 
The more they are used the slower the rate of decrease in
light output.  Many bulb manufacturers rate their bulbs'
output after that initial "burn-in."  But a brand new bulb
will almost always seems much brighter than an older bulb
for this reason.  Some of the mercury in the bulb gets
stuck in the glass tube, some of the phosphors degre, and
the filaments evaporate over time and slowly coat the
inside of the glass tube.  Overdriving a PC will, of
course, speed up these processes.  Running a PC (or any
fluorescent bulb) hotter will also speed up these
processes.  You don't have to overdrive a fluorescent to
run it hotter, it's a matter also of ambient temps and

Depending on your setup, turbidity, kinds of plants, your
tank might be more or less sensitive to the slow loss of
light output over time.  For example, if you have driftwood
leaching tanins and darkening your water, that can have
significant effect on how much light reaches your plants --
probalby more than the age of a PC over it lifetime.  And
the color temp of your bulb will make a visual difference: 
the hotter rated PCs (the bluer ones higher than 5000 K)
tend to appear brighter to humans, other things being

You shouldn't be able to measure a significant shift is
spectral output over the life of the bulb -- anyway,
nothing near as much as you find with MHs.  You can have
very successful planted aquaria using PCs for several years
-- especially if you have multiple bulbs and rotate them --
don't change them all at the same time.  Maximum effect can
be achieved by changing bulbs every few months but that is
unnecessarily expensive, and imo wasteful.  A much smaller
difference can be acheived by changing out your bulbs every
year or so.  Plan your light setup for longer use.  If you
have a blackwater tank, plan on needing 20-50% more light,
depending on dark the water is, than you would with clear
water, other things being equal.

But don't get fooled by the new bulb syndrome ("I just put
in a new bulb and it showed my older bulb was really dim")
or the color temp syndrome ("The newer bulb has remained
much brighter than the older bulbs, which happened to be
warmer color temps bulbs).

CF bulbs, those twisted tubes with convetional bases that
fit in incadescent lamp sockets are often made more cheaply
than PCS, and may degrade much more quickly than PCs.

Hope that's some help,
Scott H.

Do you Yahoo!?
SBC Yahoo! DSL - Now only $29.95 per month!