Article on Fluorescent Lamps and Ballasts
To: Aquatic-Plants at actwin_com
Subject: Article on Fluorescent Lamps and Ballasts
From: "ian (i.b.) philips" <ianphil at bnr_ca>
Date: Wed, 6 Dec 1995 11:54:00 -0500
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I am a member of the Ottawa Valley Aquarium Society (OVAS). It is a very
modest little society. We also have a newsletter we try to put out on
an irregular basis. I decided to put together an article for the news-
letter based on information gleaned from the Aquatic Plants digest.
I am submitting it for your approval and to get feedback.
I have taken a lot of people's postings, condensed them and tried to
put them together into a unified article. I have also tried to attribute
quotes where possible. I hope no one is offended by me doing this.
My whole purpose is to share the information I have access to via the
Aquatic Plants digest with my society members.
Unfortunately the article is still too long and will have to be cut
further. In the meantime, the editor had a question: "Why are T8
lamps brighter than equivalent T12s?". This assumes that one already
accepts that they are (is this generally accepted?). Can anyone help
Fluorescent Lamps and Ballasts
by Ian Philips
There has recently been a lot of discussion on the "Aquatic Plants Digest"
about fluorescent lighting and T8 vs. T12 bulbs. I thought that a summary
of the discussion would be of value to our aquarium society members. I have
distilled many postings down to a unified article. The bottom line was that
T8 bulbs in combination with an
Electronic rapid start ballast.
The benefits being:
More light for the same number of bulbs.
Longer bulb life with lower lumens drop off.
Significant power ($) savings.
Most of the people quoted are well known in the *.aquaria newsgroups. In
fact George Booth has published articles in the Aquarium Fish Magazine, and
Neil Frank has published in The Aquatic Gardeners Association, so I value
the "net wisdom" more than any information taken from a manufacturer's sales
pamphlet. I suppose a disclaimer is also in order. All of what follows are
different people's opinions condensed by me. I may have altered the
information in doing so. My advance apologies if something incorrect
What's the difference between T8 and T12 lamps?
T8's are 1" in diameter, T12's are 1 1/2". T8's run on an electronic ballast,
and will not run (efficiently) in a fixture with a regular ballast. The same
length of lamp also runs on less electricity, a four foot T8 is 32W, while
the four foot T12 is 40W.
It seems that the commercial lighting industry is rapidly shifting towards
the more energy efficient T8 bulbs. The driving force in the US are the new
US Federal Minimum Energy Standards for fluorescent lights. The old F40T12CW
cool whites may be a thing of the past.
Relative amount of light
T8 bulbs are brighter than comparable T12 bulbs. Paul Krombholz found that
measured with a light meter, four T-8 bulbs put out about twice as much light
as three T-12 bulbs.
All fluorescent bulbs dim as they get older. The rated lumen depreciation
of T12 fluorescents is about 10 percent after 3,000-4,000 hours of operation
and 20 percent after 7,000 hours, while for T8 lamps, running off electronic
ballasts, the loss is even slower--10% total after about 7,000 hours of use.
That's a two-year period if the lights are on 10 hours a day. However several
people on the net have measured higher lumen drop-offs after much shorter
The following was measured by George Booth:
Bulb New 1800 hours change
--------- ------- ---------- ---------
TriLux (T8) 7800 7100 - 8.97%
TriLux (T8) 7600 6800 -10.53%
Triton (T12) 6100 5400 -11.48%
Triton (T12) 5700 5000 -12.28%
Douglas Bardell reported that on 26 May 1995 he installed 4 x 40 watt
fluorescent tubes over his aquarium. His hour meter read 1786 and according
to his Sekonic Lux meter the light measured 2200 lux. The next time he
checked, the hour meter was 3879 (about 168 days, a little less than 12
hours per day) and the lux meter read 1700. A loss of nearly 25%.
Karen Randall reported a conversation with a lighting specialist who said
that the kind of lumen drop-off George Booth observed on the Tritons and
Triluxes is to be expected if the bulbs are used without an electronic
ballast. (ed note: from all that I have read from George, I'd be surprised
if George didn't use electronic ballasts).
Some people are suspicious of the lumen depreciation because they don't see
commercial places replacing their banks of lights every six to twelve months.
The reply to this was that the human eye is a very poor judge of brightness.
As long as the ambient light level is adequate for whatever activity is
taking place, the lighting is "fine". Most homes or offices don't replace
bulbs until they burn out or start to flicker.
Types of ballasts
The Time-Life book "How Things Work in Your Home (and What to Do When They
Don't)", contains one of the better descriptions of fluorescent lights. It
explains that there are three types of starting technology. (1) Preheat
where an auxiliary starter is used to heat the tube ends and strike an arc
across the tube. (2) Rapid start where a special ballast applies a relatively
low voltage directly to special, quick-heating cathodes (tube ends).
(3) Instant start where the ballast supplies a voltage spike of a magnitude
up to 4 times the normal operating voltage of the bulb.
Another factor affecting lumens and power consumption is the "ballast factor".
"The ability of a ballast to cause a lamp to produce a percentage of its
initial rated lumens is called its ballast factor." Magnetic ballasts have a
bf less than 100 percent while electronic ballasts can have a bf of more than
100 percent. This is probably one of the reasons T8 / electronic ballast
combinations give more light for less power.
Most aquarium hoods are of the preheat type. Shop lights and most 40W systems
are of the rapid start type, which Time-Life says requires special cathodes
in the bulbs. One person felt after reading this that although a rapid-start
ballast may light a preheat bulb, excessive wear will be caused at the
cathodes, reducing the lamps brightness and useful life. Since old bulbs are
usually indicated by dark spots at the bulb ends corresponding to deterioration
of the cathodes, he felt that this explanation seemed plausible. He also
questioned whether there really is any difference in bulbs designed for
preheat and rapid start systems. However, since many of the fixtures say
"Rapid start bulbs only," he assumes that there is, at least theoretically,
a difference. Does anyone in the Ottawa society know if there is a difference?
According to the Valmont Ballast technical guide, short lamp life (which may
be different than reduced lumens) is attributed to:
1. Improper voltage
2. Improper wiring
3. Poor lamp to lamp holder contact
4. Extremely short duration cycles (many lamp starts per day)
5. Defective starters (applies only to preheat)
6. Defective lamps
7. Improper ballast application
8. Defective ballast
Neil Frank believes that numbers 6 and 7 seem like possible candidates. He
doubts that specialty aquarium bulbs or ballasts made for aquarium application
are produced with the same quality control as other commercial lighting.
Improper matching of bulbs and ballasts may also be a contributing factor.
He suspects that most people randomly combine a ballast with a lamp. There
are electronic, conventional magnetic and hybrid ballasts. There are T12
and T8 bulbs; instant start, rapid start and pre-heat. Which combination
do you use? He doesn't know himself what he uses.
Karen Randell believes number 4 can be a big factor. In the "Philips Lighting,
Guide to Fluorescent Lamps" she reports that there is a graph that shows
average life for a variety of different fluorescents based on burn hours
per start. Double the bulb life expectancy (in thousands of hours) is
possible with a 12 hour burn cycle as with a 4 hour burn cycle. (This
would argue against the practice of an afternoon "rest" period in terms
of lighting cost!)
The following is a quote from the same text: "Longest lamp life and best
*lumen maintenance* (emphasis Karen's) will be obtained with 1) good voltage,
2) proper auxiliaries, and favorable operating conditions such as are
ordinarily encountered in a well-designed lighting system. If in any
installation the number of lamp failures exceeds the theoretical number
which should fail according to the formula:
Number of (Hours burned/year) (# of lamps)
failures = ----------------------------------
per year (rated lamp life in hours)
and this excess persists for an appreciable length of time, it would be well
to look for some unfavorable condition in the installation or the method of
operation which is adversely affecting lamp life." Does anyone have an
opinion on whether we operate our lights under "adverse conditions"?
Greg Tong did some research of his own. His data comes from "The Lighting
Management Handbook" by Craig DiLouie. He concludes:
Choose "rapid start electronic ballasts."
Keep temperatures around lamps near 77F.
Greg Tong elaborates:
1. Temperature. Heat may be the main reason our lamps don't last as long. The
light output of fluorescents peaks at 77F. Higher temps greatly reduce lumen
output and lamp life, with a 10 percent loss from peak at 100F. The lesson
here seems to be to try to keep our lamps as close to 77F as possible.
High-output lamps seem more sensitive to higher temperatures as their light
output peaks at 60F. At 100F, their light output is down almost 20 percent
2. On-off periods. Fluorescents are usually rated on a cycle of 3 hours on
and 20 minutes off. They should last longer as the on period gets longer.
In fact, leaving some lamps on continuously can double their rated life!
3. Lamp/ballast combination. For best lumen output and lamp life, the lamp
needs to be matched to its ballast. Ballast factor is one thing to consider
but there are others, including the quality of current the ballast generates.
Greg recommends "rapid start electronic" ballasts. Rapid start refers to
the type of circuitry in the ballast. Pre-heat circuitry, which requires
a starter, represents obsolete technology. Instant start circuitry lights
lamps with a burst of voltage and the jolt takes its toll. Rapid start
circuitry keeps the cathode in the lamp warm all the time so it can start
the lamp quickly and more smoothly. Note that there are instant start and
rapid start circuits for both electronic and magnetic ballasts. An instant
start on an electronic ballast can cut lamp life in half.
4. The lamp itself. Different lamps of course are designed differently. It
would be interesting to get information about the rated life and lumen
depreciation under standard testing conditions of the aquatic plant lamps
The experience on the net with the inexpensive shop lights has not been
good. The fixtures are not especially long lived, and even worse, they
appear to burn out bulbs faster than normal. This was reported by two
people who had shop lights burn out tritons and vitalites in less than
one year. It has also been reported that bulbs in shop lights do not
produce as much light as they normally should.
Sources in Ottawa
There are a number of specialty lighting stores in Ottawa that sell
ballasts and lamps. If you phone around you will find that you can find
T8 rapid start electronic ballasts by Advance (Philips) for 2-tubes for
about $30 and for 4-tubes for about $40. Places selling these include
Buchanan, Marchand, and Litemor.
Hopefully this provides a starting place on deciding what lighting system
you should use over your tank. If anyone has better information on anything
discussed here, please submit it to the editor so that all members can
benefit from it.
I myself am in the process of building a hood for my 48 gallon tank
(13 x 48 inches), thus the reason for my interest in the subject of lighting.
The hood is finished, it just needs the electronics and reflectors. I plan
on putting in four T8s powered by a single remotely located electronic
ballast. Perhaps this hood might be the subject of a future article.
The references used by the people on the net include "The Lighting Management
Handbook" by Craig DiLouie, a technical guide to retrofitting lights to save
energy, the Time-Life book "How Things Work in Your Home (and What to Do
When They Don't)", the "Valmont Ballast Technical Guide", and the "Philips
Lighting Guide to Fluorescent Lamps". You can find other similar references
in your public library.