I have kind of made a study of CFL's but it seems more and more members are having success in both veg and flower with high output fluorescent tubes (HO)

In trying to learn more about their efficiency and luminosity I came across this interesting article on an architectural web site....it shows some of the difficulty in understanding and believing the specifications of different bulbs types

T5: Is There Truth in Advertising?

With high lumen values and high efficiencies, the claims of the T5 lamp seem too good to be true. And, like many advertisements, sometimes they are.



Source: ARCHITECTURAL LIGHTING Magazine
Publication date: November 15, 2001

By Peter Franck, PE, LC
With high lumen values and high efficiencies, the claims of the T5 lamp seem too good to be true. And, like many advertisements, sometimes they are. In fact, there is often a discrepancy between the efficiency values and the rated lamp lumens that adds to the confusion. The problem can be stated quite simply: 1) Lamp manufacturers, wanting to publish the most impressive lamp lumens, published the (higher) output at 35°C (5000 lumens for the 4-ft. T5/HO lamp); 2) Luminaire manufacturers, eager to publish the most impressive efficiency values, published the (higher) efficiencies at 25°C; and 3) Thus, by incorporating the increase in both the efficiency and the lamp lumens, many projects are being designed with the assumption that there will be 8-percent more light than is actually there. Eight percent is a lot!

Not that the lamp manufacturers have made a mistake in making a lamp that has peak light output at 35°C. A compact lamp invites a compact fixture and architects appreciate slimmer luminaires. Tighter spaces usually mean heat buildup, so it's good that the lamp actually gives more light output in such locations. But the question comes up whether this increase in light output should be reflected as a higher efficiency or a higher rated lamp lumens. The immediate danger is that many people are reflecting the change in both!

Some argue the improvement in light output due to the lamp heating up in the fixture shouldn't be reflected as increased efficiency. They imply that end users can't understand that luminaire efficiency is a combination of optical efficiency and thermal effects. But this has been the understanding ever since relative photometry was standardized-if heat buildup in the luminaire reduces light output, this is reflected in a reduced efficiency, not by a change in the rated lamp lumens. Or, too much ventilation in some fixtures could make the lamp run cooler than its optimum operating temperature, also resulting in a loss of efficiency. The change is reflected in the efficiency, not in a change to rated lamp lumens.

Rating the T5/HO lamp lumens at something other than 25°C goes against the established industry standard. This is certainly true of fluorescent lamps. Some have said that this is a unique case because it is designed to give maximum light output at 35°C, rather than 25°C. But this is not the first time a lamp has been designed to perform better at a higher light output. Just look at the amalgam compact fluorescent lamp. It is usually designed to operate at a higher light output, around 35°C. If a luminaire is designed with the proper amount of heat buildup, the efficiency will go up. With too much ventilation, the efficiency will go down. Are these rated lumens published at 35°C? No, they're published at the long-established industry standard of 25°C.

Sound familiar? The T5 lamp is also designed to operate at 35°C and increases in output in a luminaire without too much ventilation. Yet, unlike any other fluorescent lamp in North America, the rated lamp lumens are being published as 5000 lumens (at 35°C, the small print confesses), not as 4650 lumens (at 25°C).

An expressed concern is that with such high-efficiency luminaires and the temperature effect in the value of luminaire efficiency, it is potentially possible to achieve a luminaire efficiency of more than 100 percent. People would look at this and assume it was incorrect because it's impossible to get efficiencies greater than 100 percent, right? This is only true if it is optical efficiency that is reported. But it is difficult-if not impossible-to measure only the optical efficiency, so it was standardized earlier in the 20th century to measure what is called 'luminaire efficiency.' This combination of optical efficiency and thermal effects can be measured accurately and consistently. These thermal effects can either reduce or increase the efficiency-even above the 100-percent mark.

It shouldn't be difficult for the lighting industry to understand this. After all, we're accustomed to percentages greater than 100 percent. A company's sales can increase by 147 percent. A ballast can run a lamp at 114 percent of the output from the reference ballast. So is it such a stretch to accept that luminaire efficiencies, properly understood, could exceed the 100-percent mark? It has already been empirically proven in independent labs with concept luminaires using special high-reflectance materials.

So why is this issue so important? Because while the higher rated lumens have been accepted by many, a lot of luminaire manufacturers and testing labs are still testing luminaires according to the IES guidelines (which is what they're supposed to do). The IES says that a fluorescent luminaire shall be measured at 25°C, the bare lamps at 25°C and the ratio between the two is the efficiency. This efficiency is only accurate if the rated lumens are also at 25°C. If you use a luminaire tested and reported exactly according to IES procedures and then use the lumen value of 5000, your calculations will predict 8-percent more light than you will ever get from your installation So there is this dichotomy between the way many lamp manufacturers are reporting rated lamp lumens for T5 lamps and the way many luminaire manufacturers are reporting luminaire efficiency for T5 luminaires. And the two methods are incompatible.

What is the solution? The most appropriate and consistent thing to do is to report the rated lamp lumens at 25°C (4650 lumens for the 4-ft. nominal T5/HO), as is indeed the standard for every other fluorescent lamp, and continue to do photometric reports according to the current IES standard (at 25°C). Yet I'm aware of only a few manufacturers, lamp or luminaire, that have heeded these suggestions.

It is important to report the performance of T5 lamps honestly and accurately so as to compare it fairly to other options, such as improved T8 lamps or high-wattage twin-tube lamps. If you are doing calculations with luminaires that seem to have very high efficiencies and are also using the rated lumens that were measured at 35°C, beware of your results. If you think these light levels seem too good to be true, you just might be right.


Peter Franck, PE, LC is a research engineer at Lightolier.


Editor's note: Have something on your mind? Please send your ideas for 'Endpoint' to ctrauthwein@vnubuspubs.com or aliao@vnubuspubs.com


October/November 2001 Architectural Lighting Magazine

you can see the charts more clearly at the website

http://ecmweb.com/ops/electric_fluorescent_lamp_coming/

T5 Fluorescent Lamp: Coming on Strong

Sep 1, 2003 12:00 PM, By Joe Knisley, Senior Editorial Consultant
Technological advances in high-performance lighting increase lighting efficiency and provide designers with several new lighting options
“Efficiency” continues to be the buzzword in the lighting industry, and as its use continues to grow, the lamps used to meet its demands continue to get smaller. The smaller-is-better trend has been particularly evident in the fluorescent lamp market as manufacturers have consistently decreased sizes since the days of the standard T12 lamp.
The newest family of linear fluorescent lamps is the T5 line of lamps, which consists of standard and high-output (HO) T5 lamps. The standard T5 lamp was developed in Europe several years ago, and then introduced to the North American market in 1996. While some lighting designers began specifying the T5 luminaires immediately, market penetration wasn't great; one reason being that both the lamp and ballast were, and still are, more expensive than T8 systems. Then in 1998, the T5 HO lamp was introduced to the North American market, offering about twice the lumen output in the same length.



Like T8 lamps, straight-tube T5 lamps are available in nominal 2-, 3-, 4-, and 5-ft lengths. The 4-ft T5 lamp is actually 45.8 in. long from pin end to pin end. Generally, the standard T5 lamp and electronic ballast system has light output and efficacy comparable to a T8 lamp/electronic ballast system (Table).
Similar to T8 lamps, the T5 is available in correlated color temperatures of 3,000°K, 3,500°K, and 4,100°K. While T8 lamps are available with a color-rendering index (CRI) of 75 or 85, all T5 lamps have a CRI of 85 or 82, depending on the manufacturer.
While the standard T5 and T5 HO are the same diameter and length, the 4-ft T5 is rated at 2,900 lumens, similar to the lumen per watt output of a T8 lamp. On the other hand, the 4-ft T5 HO lamp is rated as high as 5,000 lumens, offering twice the maintained light output of a T8 lamp. This means that on some projects a designer can use fewer fluorescent fixtures or lamps, thus providing certain savings on installation and long-term maintenance.
With a mini bi-pin base and a .625-in. bulb diameter, the T5 lamp lends itself to low-profile fixtures, such as those used for cove lighting and display cases. The thinness and high lumen output of the lamps also allow for sleeker indirect and direct/indirect pendants and shallower profile recessed troffer-type luminaires.
A variety of new fixture designs take advantage of the T5 lamp's dimensions and other characteristics; thus, these fixtures distribute the lumen output uniformly and achieve a good brightness ratio across the ceiling. With conventional T8 or T12 indirect fixtures, good uniformity can only be achieved by suspending luminaires 24 in. or more from the ceiling (Photo on page 30). In a typical office with a low ceiling, the bottoms of the fixture would hang below 7 ft, which isn't allowed by building codes. But the T5 lamp allows the fixture to be smaller, the optics of the reflector to be more precise, and the suspension to be as little as 15 in.
Because the T5 lamp is only available in metric dimensions, and since it can't be easily retrofitted into existing T8 or T12 fixtures, the T5 lamp family is generally not misapplied.
Lamp and ballast characteristics

The ballasts for the entire T5 family are unique for a number of reasons. This is the first linear lamp type to be served only by electronic ballasts. Within the standard T5 line, a single ballast model can power either one or two standard T5 lamps of any wattage (14W, 21W, 28W, or 35W), since all lamps in the T5 line operate at the same current (170 mA). Additionally, all of the lamp wattages have the same surface brightness, so regardless of the length of the lamp in a cove application, the perceived brightness is uniform.
As mentioned above, with power ratings of 24, 39, 54, and 80, the T5 HO lamp produces as much as twice the lumen output of the standard T5 lamp, and nearly twice the light output of a T8 or T12 system. Each HO lamp requires its own dedicated ballast model. Providing from 83 to 94 lumens per watt, the T5 HO lamps are about 10% to 15% less efficacious than standard T5 lamps and as much as 8% less efficacious than a T8 system. A number of T5 HO ballasts have features, in addition to a dimming function. For example, one model can operate one, two, three, or four F54 lamps, while allowing remote mounting and a high-low switching option.
Temperature is a consideration

One result of enclosing a smaller lamp with a relatively high output in a smaller fixture is heat — and lots of it. For that reason, the T5 lamp provides peak light output at 35°C (95°F) air temperature, whereas the T8 and the T12 lamp provide peak light output at a 25°C (77°F) ambient air temperature. Thus, in an indirect luminaire, where there is little or no air circulation, the T5 lamp can have a higher lumens-per-Watt efficacy than a T8 lamp of about the same wattage because of this thermal characteristic.
Temperature can also come into play as a lamp ages. Because of the lamp's small diameter and high-frequency operation, temperatures can rise at the lamp base ends as the lamp nears end of life because cathode emission material is depleted. This can cause a rise in voltage and result in cracking in the bulb wall. For this reason, all T5 ballasts have what is called “end-of-life circuitry.” This feature shuts off power to the lamp when the ballast senses a rise in voltage across the lamp.
Another important advantage of the T5 lamp is its low mercury content. The lamp has a coating on the inside of the glass wall that stops the glass and phosphors from absorbing mercury. This barrier coating drastically reduces the amount of mercury needed from approximately 15 mg to 3 mg per lamp. Minimizing the amount of mercury also brings another very important advantage: since mercury absorption causes the lamp's light output to depreciate over its life, the coating helps to keep light levels much closer to initial output. The T5 lamp has only 5% depreciation in the first 40% of life (Figure on page 32).

It's easy to see that both the T5 and T5 HO lamps have increasing uses in both office and industrial applications. Now readily available, the T5 HO systems are a viable option for virtually any application with ceiling heights higher than 15 ft, including warehouses, industrial buildings, and gymnasiums. Compared to a conventional 400W metal halide system, T5s offer energy savings of nearly 53%, assuming equal hours of operation. Additional savings are possible where occupancy-based switching is used.

Thank you, very interesting and helpful

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Great post, Scott!

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"They've outlawed the number one vegetable on the planet."

Timothy Leary

2001 was a long time ago. I know from my indoor grow the T5 did an exceptional job. At the time I didn't realize how exceptional until I did an outdoor grow with tons more plants and have no even (so far) come close to the yield I got indoors.