Rewiring_Tips Kitchen worktop lighting twice!!!!

[George (dicegeorge)]

worktop lighting twice...

and what does the K stand for in Fluorescent tube types

3500K cant mean 3500 KW can it, as in a 100watt bulb...

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "George \(dicegeorge\)" saying something like:

Colour temperature.

[John Rumm]

So it does... different words the second time as well ;-)

Kelvin.

No its a way of describing colour temperature based on the frequency of radiation you would get from a perfect black body radiator. (same concept as "red hot, white hot" etc)

[NOSPAMnet]

K stands for Kelvin as in Lord Kelvin and relates to Colour Temperature .

[Dave Plowman (News)]

K stands for Kelvin - the unit of colour temperature. Which in practice means the colour of the light. Lower numbers tend to the red end of the spectrum, higher, the blue.

Approx 6500K is daylight - 3500K is warm white.

[Andrew Gabriel]

2700K is warm white (colour of a filament lamp). 3500K is white (used on offices, and suitable for home use in areas of high lighting levels). Above 3500K and below 5000K is cool white. 5400K-6500K is daylight. (Real daylight is much more complex, but midday sun with no cloud is 5400K at lattitude of Washington DC.)

The only one which is really standardised is warm white, and that's fixed as it has to match tungsten filament lamps so it can be mixed with them without any mismatch.

[Dave Plowman (News)]

Ah - should have checked first.

Which of course it rarely does.

[meow2222]

I thought warm white fl tubes were generally 3000K, and known for poor CRI.

NT

[meow2222]

Thanks, will address those when I get a tuit.

NT

[Andrew Gabriel]

CRI and colour temperature are not related. All the well known/respected makes of CFL default to 2700K quite accurately. Where I see deviations are cheap unheard of makes (and including IKEA's). Strangely, the original GE Genura warm white was 3000K, but GE had to change it to

2700K after too many complaints from lighting engineers who noticed the mismatch. (There always was a separate White one available at 3500K anyway for office lighting.)

All the well known/respected makes of CFL are CRI between

80% and 89% (a 2700K phosphor in this range has a colour designation of 827 - first digit is CRI / 10, and second two digits are colour temperature / 100). Again, I would not be surprised if the cheap unheard of makes are below 80% CRI. CFL's can be made with a CRI of 90-93% (designation 927, 935, 940, etc), but I only see these available in the types with external ballasts, and not in the CFL retrofit products. Fluorescents can go higher than 93%, but that requires halophosphate or other specialised phosphate tubes; it can't be done with tri-phosphor used in compact fluorescents.

[meow2222]

I was talking about linear FLs, where the tubes marked warm white have long been halophosphate 3000k, and invariably low CRI due to the limitations of halophosphate technology. It is because of the poor CRI that 3000k tubes havent been widely recommended.

CFLs are a different animal, being almost all triphosphor.

NT