[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: replacing CF bulbs
> There is no way to predict when an inividual lamp will have to be
True, but the quality of the name brands is quite high and most bulbs
will reach the rated life span if used on cycles of no less than 3
hours. They will last (keep burning) longer if the cycles are
typically longer,m say 10-12 hours "on."
There is a wide variation in lamps even form the same manufacturer.
Manufacturers will tell you the expected life span or lumen maintainance
of a lamp but they will not specify it. A suprisingly large percentage
of lamps fail altogether within a few hundred hours and a suprisingly
large percentage far exceed their rated life. The only way to be sure of
replacing lamps in a timely manner is to get a Lux meter.
Mostly the rated life of a lamp is not all that important. It is the
lumen maintenance that is of most concern. Nobody cares if a lamp lasts
for 40,000 hours if it only produces half it's initial output at that
time. I would tend to not want to use a lamp if I could not find out it
what the expected lumen maintainance would be. Major manufacturers
typically provide this info with every lamp and believe me it makes a
difference in the frequency of lamp changes and the cost of operating a
system. PCs are not cheap and knowing the expected lumen depreciation
before you buy should be something of great interest. Lumen maintenance
is a critical piece of info in sizing a lighting system and determining
the freqency of lamp changes.
Now that I think about it, I think I would size a light system based on
the lumen output at 40% of rated life as that is a piece of data that is
often provided by lamp manufacturers. So, a 55 watt PC gets changed
after 5200 hours and a 30,000 hour T8 gets changed after 12,000 hours.
Since the PC loses more light than the T8 it should start off with a
somewhat higher initial output that the T8.
All flouresecents lose about 10-20% of their acdtual lumen output after
their intitial burn-in period of several hundred to about a 1,000
This is too sweeping a statement. Some do some don't.
> This is not a consideration with most T8 lamps they
> can go until near failure but it is somewhat true with PCs and with
Some PC makers would say that this is not true.
Well I got my information for Phillips and Sylvania websites. I figure
if you start off with 20% more light than you need then you can run most
PCs close to failure otherwise you have to replace early.
All flouresents are brighter for the first few hundred to 1,000 hours
-- after this steep drop-off in brightness, the drop-off is much
slower, but steady and persistent until the bulb fails. Most makers
rate the lumens for the output *after* the initial burn in. Some even
rate it lower than that and then tell you the bulb keeps 90% (or
whatever high percentage) of its output all the way until failure.
The lumen rate of lumen drop off lessens with age. The first 100 hours
is the worst. Lumen depreciation is much less significant in the last
half of a lamps life. All lumen maintainance curves I have seen look
If you buy from trustworthy and knowsledgeable vendors that come highly
recommended by a wide variety of experts, you can follow their advice
and forget about all these details.
I have never seen so many people scammed as in the the aquarium retail
business over "special" lamps. It is better to figure these things out
for oneself and then seek out venders who don't lie.