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post #1 of (permalink) Old 09-19-2005, 08:41 PM Thread Starter
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ODNO measurements: power consumption vs light output(LONG)

I started doing ODNO about early last year after reading this great thread:

My first setup was a single 40W T12 bulb over a 55 gallon, using Advance REL-4P32-SC ballast. I was able to grow many low/medium light plants, including crypts, hygrophilas, pearl grass. I always wondered exactly how much light I was really getting(some self doubt, did I really wire this correctly?), although it does look brighter than normal 40w bulb. Being in california where juice is expensive, I also wonder how much power I am "wasting" because I read that 4x OD only give you 2x light, so I am throwing away that additional 2x power, right? Then post #233 from "ksand" in the above thread caught my eye: roughly only 2x power is used when OD 4x! That means, no electricity is wasted doing ODNO!

Being a geek that I am, I still want to find that out myself. Here are the tools of the trade I bought:

A KILL-A-WATT to measure power consumption:

I found that typically, when you first turn on the lights, the power reading goes from low and build up. It usually overshoots by a few watts and then stablizes after 5-10 minutes when the bulb fully warms up. But if you turn off and then turn on the light while the bulb is hot, you get the final wattage almost immediately.

I realized that I already have a cheap light meter that I bought for orchids couple of years ago:

I gave it some thought on how I want to measure the light. Obviously it is impossible to stick the light senser into the tank, it is not water proof. Since what I am most interested in is to find out the light output changes from the SAME bulb with ODNO, I decided to stick the light sensor directly against the bulb to eliminate the environmental variables(ambient light, restrike, variations in distances/angle from the bulb, reflector factor, etc). I would rock the sensor around a little to find the maximum reading because the bulb has curvature, and use that as "my final answer" I found that the readings from that method is EXACTLY repeatable every time.

NOTE: you can NOT compare readings from bulbs of different sizes directly with this method, because larger bulbs has less surface intensity but compensate with larger area. Mathematically, I can integrate the intensity over the entire bulb surface(a simple cylinder in this case) to get the lumens output. I found that the Lumen numbers are in the same ball park of manufactor's published numbers, but always LOWER, by more than 50% in some cases. This is understandable: the light sensor is NOT infinitesimal and the bulb has curvature. The measurements favor the larger/flatter bulbs(T12), penalize the smaller bulbs(T6/T5). So again, don't try to compare the raw light readings between different bulb sizes in my results that will follow!

Speaking of bulbs of differrent sizes, you know the T numbers represent the diameter of the bulb: Tx bulb has a diameter of x/8 inches, where x can be 12, 8, 6, 5, .... In general, the smaller the tube size, the more efficient they are. They produce the same amount of light with less watts. In terms of 48" bulbs, these NO bulbs produce roughly the same amount of light: 40W T12, 32W T8, 28W T5. Because the smaller tubes have less restrike and can better use the reflectors, they produce more usable light in the tank with good reflectors even when total light output is equal. T5s are great, but they are not compatible with existing T8/T12 light fixture, because their length and pins are a bit different. There are these new T6 bulbs on the market now, which are fully compatible with existing T8/T12 fixtures. All the ones that I have seen are HO T6 bulbs. With a NO T6 48" bulb, you expect to see something like 29W-30W bulbs, but the bulbs I have seen are 40w or 55w, so they are "factory" overdriven to a degree.

You would think that all T6 bulbs would have exactly the same size 6/8 inch diameter because that is a standard, right? You would be wrong.
I bought this 48" 40w Quantum LightningRod 7K dayligiht bulb:

And this 55w 5500K T6(no name brand):

And look at them side by side:

The top one is 55w and one below 40W. The 40W looks right at 6/8 inches, while the 55w looks a lot like T5! I think the manufacturer of the 55w bulb cheated: they used the same thing as a HO 54w T5 bulb but adjusted slightly for length and pins!

Getting these delicate bulbs undamaged is a real challenge! It took BigAls three tries to get a good one to me, and out of the two from NaturalLighting, one has a hairline crack across the entire length, but the bulb works fine.

Now onto the "meat" of this thread, the hard data.

48" bulb results
Ballast: Advance REL-4P32-SC (4xF32T8)
Bulbs tested: 40W T6 and 55W "T6". plus two Philips 40W T12 softwhite 3000K bulbs, one was never used, one was used for 18 months ODNO4x!
Phillips 6500k Daylight Deluxe T8: I bought it just to do this test, what a geek I am!

First the results from spreadsheet, followed by explanations.

Let me explain what those columns mean. The second column numbers 1x - 4x means how many leads were used from the ballast. Remember each lead is supposed to drive a single 32W T8 bulb normally.

The next column is the raw readings from the light meter(10X, foodcandles). For example, 300 means 3000 footcandles.

The next column is the watt consumption measured by KILL-A-WATT. This is the total watts including ballast heat, not just used by the bulb.

The next column is the ratio of previous two column.

The last column is from dividing the previous column by the 1x number of the SAME bulb also in previous column. It measure how the efficiency changes with different OD for the SAME bulb. Greater than 1 means it becomes more efficient being OD, less than 1 means less efficient than using 1 power lead.

Comments and Observations
a. The most we can coax the ballast to give out is about 70 watts. We just can't seem to fool it into pumping out the max 128 watt juice with just one bulb. I wonder if it eventually will give out 128watt if I stick a 128watt bulb and wire it 4x(edit: correction. max power is 112watts at 0.88 ballast factor)

b. Let's look at those T12 numbers. Are you surprised? I sure was.
1. the old bulb draws slightly less watts than the new bulb, but outputs the exact same light as new bulb(except a bit less at 4x)! Now folks, it seems them Phillips guys know how to make long lasting NO bulbs! For those who throw away bulb after 6-12 months, they need to re-examine their practice. At least with Phillips bulbs. The old T12 has been used ODNO4x for 18 months, and absolutely no decrease in light output except a bit blackening at the ends. And it looks just as bright visually as well.
2. when these 40W bulbs are underdriven at 1x (still more than 32watts nominal from ballast), the efficiency really suffers. Note that the nomimal "40W" will fall between 1x and 2x here.
3. Light/watt number increases all the way to 4x(levels out for old bulb). It confirms that we are not wasting any electricity doing ODNO 4x!

c. The fake 55w T6 has the peak light/watt efficiency right at its nominal wattage at 2x(54w). Underdriving and overdriving beyond 2x results in slightly less efficiency. I am going out on a limb here, but this implies one thing: overdriving the HO T5 bulbs will also have decreasing efficiency, for example, those 54w 48" T5 bulbs, because they are factory OD to the max efficiency already. Probably because they get really hot. I read some reef folks suggest that extra cooling gets you more light from hot bulbs in general.

d. The efficiency of 40W T6 increases all the way to 4x. Interestingly, the ballast will not give out more than 60 watts. Based on the 55w numbers above, I suspect the peak efficiency for the 48" T6 bulb is right around 60w. Smart ballast, yeah right, hehehe.

e. so 40W T6 peaks at 60W, 55w "T6" peaks at 70w with Advance ballast, which is brighter at those wattages? Logically the 55w should be brighter, because it uses more watts and the tube is smaller, both favors the 55w. However, the light measurement does not directly support that. One could argue that because the 55w has smaller tube/higher curvature, it skewed the measurement lower. So I resorted to my digital camera, took pictures at exact same exposure. I can't tell any difference at all. My verdict: the no name brand 55w bulb is not a good example of how this bulb should be made. I will stck with the 40W T6.

f. How do the T6 bulbs compare with T12? I can't really anwser that without a more elaborate setup to measure the output in the aquarium directly, because that is the only relevant comparison. Visually I can say that the T6s are a lot brighter on my tank, partially because they are close to white daylight while the T12 used is "warm white", very yellow. My AHSupply reflectors have to work better with smaller tubes. After all, mathematically, a parabola reflects light best when the light source is a point at its focus. The smaller the tube is, the closer it is to a point source(cross section). I will just go with conventional wisdom here that smaller tubes are always more efficient, when manufactured similarly otherwise.

g. the gaping hole right now is the 32w T8 bulb measurements. I have a good guess of what they should be based on T12 and T6 numbers: you will get best efficiency at 4x OD. But I think I will spend a few dollars at Home Depot and get couple of bulbs.
.....ok, I bought some 18" and 48" T8 bulbs today from Home Depot just to do this test. I have updated the spreadsheet above with 48" T8 resuts. Take a look. My observations with T8:
1. I noticed, that just like with other bulbs, a single T8 was drawing more power than nominal 32w, actually it was drawing 40W. Then I realized in my testing, only one out of four wires is connected. In a 4xT8 bulbs setup,
you connect each red/blue lead to a bulb. So the ballast is pumping more than 32w at 1x in my setup.
2. the most power output is only 69 watts at 4x, similar to other tests.
3. from the first observation, the natural question to ask is, how does OD compare to 4 bulbs non-OD setup? In that case, you expect about 28 watts from each bulb because ballast factor of this particular model is 0.88.
Well, I did a rough estimate by extrapolating the power to 28 watts, the light intensity is around 84, translate to 3.0 (light/watt). Just like with T12, overdriving 48" T8 can achieve higher efficiency, light/watt. Over 50% free light(efficiency ratio is more than 1.5) in this case, compared to NO at 28W, when OD 3x or 4x! The total light output is an astonishing 3.8x at 4x OD, while power consumption is less than 2.5x! Again, I don't have the 4 bulb setup, so this is pure mathematical extrapolation, but I believe it is really close to actual numbers.

In short, there is no reason not to overdrive those 48" T8 and T12, if you want more light cheap. There is a lot of free light to be had due to higher efficiency, CONTRARY to conventional belief that OD wastes electricity.

18" bulb results
Ballast: Advance REL-4P32-SC (4xF32T8) for OD measurements. Fulham Pony(for single bulb) for 1x and 1x in Series measurement. The reason the second ballast was used: it is next to impossible to pull the wires out of some endcaps without destroying it! Any reason to combine all wires going to the same end and use a single extra wire to connect to endcap. That way, you can easily reconfigure ODNO.

Bulbs tested: 15W Quantum LightningRod 7000k daylight T6 and 15W Philips NaturalSunshine 5000k T8.

First the results from spreadsheet, followed by explanations.

When T6+T8(only bought one T8 for this experiment) was done in series, the total power consumption was devided by 2 and applied to each one in the results table. This might be slightly off, but should be minor.

Comments and Observations
a. Notice that when connecting two bulbs in series, it results in UNDER-driving(< 15w) at 1x(from single bulb ballast). Not sure if using the 4x ballast would result in same.
b. Look at T8 results. With increasing power consumption, efficiency becomes higher, but only slightly. Compare this to 48" T8, where efficiency increases a lot more when OD.
c. the T6 results are a little muddled by the two cases when T8 was connected in series. Nevertheless, you can see that efficiency actually drops a bit when OD.

Finally, another reminder once again, do not compare the Light and Efficiency numbers between bulbs of different sizes directly.

General conclusions
a. In all cases tested, T8 and T12 bulbs always have higher efficiency when overdriven. Surprisingly (contrary to previous ODNO threads), the LONGER bulbs gain more efficiency with OD than the shorter bulbs.
b. The new T6 bulbs are already OD to some degree at nominal wattage by design. The gain of efficiency is less than T8/T12 at 48", and the efficiency actually decreases slightly at 18" when OverDriven.
c. Based on results of the "fake T6"(T5), it is logical to conclude that HO T5 and PC bulbs will have much less gains when OD further, compared to normal output bulbs. Excessive heat is another concern because they are already quite hot to begin with.

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Flourite, wet/dry, AHSupply 302w PC, PinPoint controller

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15w T6+15w T8

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40w T6 ODNO4x, no CO2. Discus grow out.
10gallon Tonina tank, 2x15w T6 ODNO 4x
I will do aquascapes after I collect all the plant species and grow them to perfection.

Last edited by shalu; 10-07-2005 at 12:47 AM.
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