Lighting FAQ

[Simian]

Ok boys n Girls, here's a simple guide to Fluorescent fittings and tubes, it crops up all the time so please sticky this.

Before all the myths come in and pollute this thread, unless you have verified proof please do not make statements that will confuse people pose it as a question and I will fact check it.

Please feel free to ask questions and request clarification.

I in no way advocate DIY electrical work and any information given is in the context of education only.

I am an Electrical Engineer & Registered Electrician and will not post a statement here without the proper proof to back it up.

Glossary

Lumen Output or Luminous Flux. Unit Lumen

Luminous efficacy Luminous Output per Watt of power consumed. Unit lm/W

Colour Rendering, scale from 0-100. Unit Ra

Colour Temperature, Colour appearance. Unit Kelvin (K)

[Simian]

What do the colour numbers on my fluro tube mean?

When people refer to a colour tube as eg colour 840 it is a basic code which covers two main things.

The first part of this number is colour rendering (Ra) the Ra scale is from 0 (monochromatic) to 100 (OMG! Thats soooooo pretty).

In the case of the 840 tube the 8xx denotes a colour rendering of 80 (pretty good)

Important Note a higher colour rendering will result in lower light intensity

FYI : a standard incandescent or halogen lamp has an Ra of 100

The best colour rendering tube commonly available from electrical suppliers is Colour 940 or the "butchers tube". Ra=93

I will cover the second part of the numbers in another post.

 

 

[Simian]

Ok got that so what do the other #'s mean?

The second part of the number indicates the colour temperature in expressed in Kelvin or K.

2700K is a warm yellow light

3500K is a neutral white

6500K is getting quite cold and harsh (often called a daylight tube)

The higher the number the whiter the light i.e. the light shifts into the blue end of the spectrum.

Back to our standard reference tube colour 840

the x40 indicates a colour temperature of 4000K

Likewise a colour 865 (Daylight) Tube has a colour temperature of 6500K

 

 

 

 

 

 

 

 

 

 

[whetu]

Good idea for a thread, Simian. As you said the same questions come up over and over again so it will be nice to have a standard guide we can point people to.

I have a question: You have explained what the colour numbers on the tubes mean in a technical sense, but what do they mean in a practical sense? For example if I want to grow plants, or show off my fish to their best advantage, how do these numbers apply?

[supasi]

Great idea Simian

(that man deserves a DB,lol)

[Simian]

I have a question: You have explained what the colour numbers on the tubes mean in a technical sense, but what do they mean in a practical sense? For example if I want to grow plants, or show off my fish to their best advantage, how do these numbers apply?

Good Question Whetu, and quite a contentious one amongst some people here, I will answer the showing off the fish question now and get back to you on the plant growing one.

To show off your freshwater fish ie Africans to the best effect use a mixture of High colour rendering (Ra) tubes colour 940 and a high output or Efficacy (Lumens per watt lm/W) tube colour 840 (will make the tank appear warm and inviting) or colour 865 (will bring out the whites on the fish and give a sharp contrast some people find this light quite harsh tho).

Because Ra and Efficacy tend to be mutually exclusive you will need different tubes for each effect.

Bear in mind I am not talking about specialist aquarium tubes here, there are a myriad of different special tubes for various applications if you have a massive budget use those ones.

Salt water tanks tend to have very high colour temperature (sometimes 20,000+) as this tends to correspond with an increase in UV light which corals require to grow (metal Halides are good for this but I am sticking to fluros at this point)

[richms]

Ok, 3 questions.

Is there any limit to the number of tubes I can run in series off a single ballast - a pair of 2 foots is common off a 36 watt magnetic ballast, with their own starter on each, is there a reason I cant have 4 off an 80 watt one?

Secondly, When wiring an electronic ballast to endcaps, and one end of the pair of tubes is in series, is there any benefit in making the connection close to the tubes vs separate cables back to the box I have put the ballast in. (meaning no need to cut the cables shorter and join in the hood)

Thirdly, do you know a source of replacement ends for thorn fittings, I had something fall on my pile of ones I bought a few years back off trademe and smash the plastic at one end, lamp specs dont want to know about it.

[suphew]

Maybe you could explain the difference between T5, T8, T12, in terms of size, output, and effiency. Also (I think for T5 only) there are high output and very high output tubes???

Also electronic and magnetic ballasts

People might be interested in power compacts and CFL's as well??

Think you might have started yourself a monster here, good luck!

[Ant N]

Well Done, Simian. Thanks. A moment spent talking to a wise man is worth a month's study of books!

[Simian]

Looks like I have started something here, you guys will have to be patient, I only have limited time and am a slow typer Also I want to cover the basics first before I get into the really deep stuff (it will give me a chance to dig out my old text books)

Lets start with busting a few myths re T8's & T5's etc. :bounce:

[Simian]

Maybe you could explain the difference between T5, T8, T12, in terms of size, output, and effiency. Also (I think for T5 only) there are high output and very high output tubes???

The number after the T relates to 8ths of an inch so T8 is approx 1" in diameter T5 is 5/8 of an inch. Forget T12's they are old cr*p.

Myth 1 T5's are more efficient than T8's

This is not necessarily the case a T8 on electronic gear is very similar to a T5 fitting. And in the case of high output T5's (yes only in T5's) they are less efficient than a T8.

Why is this? Most of the gains to be made are due to the start gear or the ballasts.

T5 technology will outstrip T8's from about the current generation onwards this is due to the amount of R&D budget spent on the technology.

T8's will slowly disappear from the market over the next 8-12 years.

 

[Simian]

Whats the difference in the ballasts?

The old style ballasts are wire wound coils (yes they work more or less like a coil in a car)

They need a starter (the little cylinder with the 2 little prongs on it) to give the tube its kick start. These guys give the traditional flicker flicker flicker start

These are the least efficient with up to 17% (I need to check this figure tomorrow) of power lost as heat in the ballast.

The next type are the first generation of "electronic" ballast which effectively just got rid of the starter, they are marginally more efficient and don't flicker on start up. (BTW this extends lamp life)

And finally we have fully electronic or high frequency start gear,as used in all T5 fittings (this is why they are considered more efficient) and the new generation of T8 fittings that are coming into the country at the moment. These guys are very efficient and give a nice smooth pulse to ignite the tube this greatly extends the life of a tube.

 

[Simian]

Are there any other advantages to T5?

The smaller diameter means you can pack more tubes into a smaller area. The reflectors on T5 light fittings tend to be better developed to give more precise optical control and focus.

[Simian]

Why do the ends of my fluro tubes turn black?

Inside the end of the Fluro fitting is a part called the electrode or emitter. this has a small amount of mercury on it. Basically every time a lamp starts a small amount of this mercury spatters off the electrode and onto the phosphor coating of the lamp, once that mercury is gone from the electrode the tube wont work anymore.

Electronic starters cause less mercury spatter and hence the tubes last longer.

The more you switch a Fluorescent the shorter the life span of the tube.

Be aware that Fluro tubes should be disposed of properly, the mercury will leech into the groundwater at landfills and that is not good.

Return your old tubes to an electrical wholesaler or a reputable sparky, they will dispose of them for $1 each.

Philips fluro tubes (the ones with green end caps)have the lowest mercury content on the market, if you are feeling particularly eco friendly

 

[HaNs]

 

http://www.lightenergysource.com/images/LES - Kelvin Scale.jpg

[SpidersWeb]

Are there any other advantages to T5?

The smaller diameter means you can pack more tubes into a smaller area. The reflectors on T5 light fittings tend to be better developed to give more precise optical control and focus.

T5 and T5HO fittings have a higher watt per inch ratio as well. More power, brighter light.

Another thing that is more of a 'plant' topic than lighting, is most aquarium plants (green ones) need red and blue light. This is why we often recommend daylight 6500 kelvin or thereabouts, because it produces fair amounts of both red and blue. Warm white (2900 kelvins approximately) doesn't provide enough of the blue. I could give specific wavelengths for the various types of chlorophyll but that's beyond the scope of this topic.

 

[Simian]

Thankyou for the pretty picture Hans, its an accurate portrayal of colour temperature. (the numbers down the side are in Kelvin K)

Thankyou for the info on plant colour spiders web, I know very little in regards to the spectrum's of light required for photosynthesis and am happy to defer to you on that subject.

I will stick to the engineering information.

I would like to point out that "Watts per inch" is a pretty meaningless unit, if the luminous efficacy is poor on a tube then the lumen output can be very low regardless of how much power you pack into it, or how long the tube is.

To Clarify what Spiders web was saying, a T5HO (T5 High Output Tube) does tend to have a much higher Lumen Output when compared to T8 or T5 tubes of the same length. Bear in mind that this comes at a cost in regards to Efficiency (equivalent efficacy to a T8 with an old electromagnetic ballast)

I'm not trying to shoot you down, I just want to keep the terms clearly defined that people do not get confused by too many units and terms.

[Simian]

A quick Glossary added in my first post.

[Caper]

Oh so sorry, but I just don't understand alot of what was posted. I know how to turn on a light and change a light bulb but that's about it. But I will read again to try and make some sense, looks like you've done an excellent job Simian

Anyway, since this was about lights I thought I'd post this here. I was reading in "fish" book last night and it recommends that lights should be changed every 6 months to a year max. Now I don't have nay fancy fluorescent lighting but does this sound right???

Caper

[Ira]

Only matters if you're trying to grow plants. The light intensity drops off and the color spectrum changes a bit when the tubes get old. If you only have fish in your tank then it doesn't matter, fish don't particularly care if their light is a bit dim and not ideal for photosynthesis. So you might as well leave the tubes in until they won't start, imo.

[Simian]

Ok as far as relamping your fittings.

each type of lamp (Fluorescent or Metal Halide) has a number of rated hours till failure. i.e. how long a tube will last before it dies completely (this is an average some may last forever before the stop working).

In the case of a standard T8 18watt fluorescent tube (I dont have data sheets for some of the specialty tubes) this is approximately 13000 hours.

But what will happen is you will slowly lose light output over the life of the tube. at 13000 hours you will only have approximately 40% of the original light output.

At approximately 8-10000 hours you will down to about 80% of your original output, this is when I would recommend you relamp when you are lighting your average tank.

This rated life will change depending on some other factors which I wont get into.

You can also also expect to see some colour shift in the lamp output (see ra or colour rendering) as the lamp ages.

So for specialist applications ie planted or high colour rendering situations you may need to relamp a little earlier.

IMO 6 months seems a bit excessive that would only be about 2000 hours. for a planted tank I'd probably go with 5-6000 hrs. or 12-18 month cycle.

[alanmin4304]

I have been advised that electronic flouro lamps do not like water and should not be used over an open tank, is this so?

[Ira]

What part of it? And how much humidity would they get? The tubes themselves don't really care. Maybe if they're closed in with no airflow so they get really hot and then get a large splash on them they might break, but otherwise glass does not care about its proximity to water.

[alanmin4304]

I was advised not to use an electronic light fitting near water by someone in a specialist lighting shop who I would respect the opinion of. I assume it is the electronic ballist and that it would be OK if wired remotely and kept away from water.

[Caper]

Thanks Ira and Simian

No real plants so my lights are ok then.

Caper