Article on Fluorescent Lamps and Ballasts

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
out here?

Thank you 
Ian Philips


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 
people prefer:
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.

Lumens Maintenance
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:
                            Measured lux
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?

Bulb life
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 
from peak.

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 
we use.

Shop lights
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.