LED under-cabinet lighting

My old fluorescent under-kitchen-cabinet tubes are failing at an ever faster rate, so I'm thinking of replacing with LEDs, particularly flexible LED tapes.
A few things I'm not sure about...
The light output is quoted in lumens per metre, but how many do I need? I've seen outputs from 290 to 780 lm/m for 12V systems and up to 1200 lm/m for 24V. The tapes will be 45cm above a dark textured work surface. I suppose you can put 2 tapes side-by-side for a higher output.
The kitchen layout is U-shaped with the sink in front of a window with cabinet runs either side. At each side of the sink the runs are finished off with a little angled/corner shelf unit at right angles to the main run. I'd like to run the last bit of tape around this corner if possible. Is it possible to twist it through 45 degrees or will a I have to cut it and use a wired connector?
Can I just stick the bare tape to the underside of the cabinets or does it need to be mounted into a holder such as RS Stock No. 797-2432, a horrendously expensive product!
Then there's colour temperature. My fluorescents are 2700K but a lot of the white LEDs seem to be 3000+. I don't suppose that's a big deal in this application.
What about drivers. I assume I'll just need a couple of basic 12V drivers, one each side of the sink - though the hob interrupts the run on the right, so I'll either have to route some cable round that of use a 3rd driver for the last cabinet which will only has a 55cm LED run. I have easy access to the 240VAC that's feeding the 6 existing tubes. Something like a couple of RS number 773-6949 drivers giving 1 amp each?
Any advice much appreciated, and any recommended suppliers/brands.
Phil
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On 17/12/2017 22:38, Phil Addison wrote:

We tried with just one tape, and the light is very meagre compared to a fluorescent. You'd need several, not just one or two.
A fluorescent tube is about 3000 - 4000 lumens per meter. So, you can work out exactly how many tapes you need for equivalent light output.

It doesn't bend that way. There are 90 degree connectors, but I haven't seen 45 degree ones.

It can just be stuck on. It doesn't get hot. However, the strip may get dirty, particularly in a kitchen, and it would be virtually impossible to clean. Those housings can just be wiped with a soapy cloth.

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On 17/12/17 23:06, GB wrote:

These are upto around 1300 lm/m:
https://www.led-lighthouse.co.uk/led-strip-lights/white-led-strip-lights/24v-white-led-strip-lights/nano-tech-flexible-led-strip-2835-60led-m-waterproof-24v
But bear in mind all of that is going down, rather than up, backwards and forwards.
I have some (in a different application) and they are *bright*. Blindingly so if you look at them directly without a diffuser.
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On Monday, 18 December 2017 09:20:14 UTC, Tim Watts wrote:

Thanks for the links Tim. I think I'll be getting a short piece of middle of the range lm/m to experiment with!
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On 17/12/2017 23:06, GB wrote:

For under cabinet lights pointing downward to a work surface do you actually need 3000 lumens per meter?
I doubt that most shorter tubes fitted in under cabinet lights are a higher wattage item giving that much light.
Lower wattage tubes may be comparable with the figures for LEDs
Typical figures https://www.tlc-direct.co.uk/Technical/Lighting/L1_Regs/Lumen_Complies.htm
Unlike a fluorescent tube LED is a directional light source and all the light will be directed towards the work surface.
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On Monday, 18 December 2017 10:53:32 UTC, alan_m wrote:

m
Brilliant. That's the data I've been wanting.

I haven't checked them all but the first few are 120 degree beams so around 23% will hit the wall behind the worktop, and another 25% will head toward the floor missing the worktop altogether. But I don't know if the spread i s uniform across the 120 deg. Probably not.
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On 17/12/2017 23:06, GB wrote:

The typical under cupboard T5 tubes are significantly less than that. more like 1500 lumen/m tops.
The tapes are often 1000 lumen/m - however you can have a continuous run without needing to stop for the ends of the tubes / fittings.

If you get the waterproof version, its dipped in a clear silicone jacket that is smooth and can be wiped down.
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On Sunday, 17 December 2017 23:06:21 UTC, GB wrote:

Doesn't that depend on the size of the tube?? Mine are T4 (1/2" dia) 16W 2700K 455mm long ROBUS. And Robus is a make I'll avoid as these are failing in less that 1 year. I have tried to find out their claimed output with no success.

As I suspected. It will be the wired solderless types then.

Good point, thanks.
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On 18/12/2017 21:07, .phil_a wrote:

https://www.tlc-direct.co.uk/Technical/Lighting/L1_Regs/Lumen_Complies.htm
suggests around 60 lumens/watt and a 450mm 15w = 900 lumens when new and perhaps 40% lower at end of useful life.
The same table indicates around 60 to 80 lumens per watt with the higher figures for the higher wattage longer tubes so 2000l/m may require a 30W tube and 3000l/m a 38W tube.
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On 18/12/2017 21:07, .phil_a wrote:

I have found most of the slim under cabinet fl tube lamps to be fairly poor in life expectancy - either the tube of the fitting failing within a couple of years.
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On 18/12/2017 21:38, John Rumm wrote:

A random search of 4 brands all give an average life of 5000 hours at which point the light output could be <600 lumens for a 450mm tube.
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On 18/12/17 21:38, John Rumm wrote:

I'll be interested to see how mine fare. Having looked, it's basically a 24V LED tape inside as far as I can see - so in theory, would be repairable, if it comes apart!
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On 19/12/2017 13:53, Tim Watts wrote:

The LED ones are IME significantly better - much lower premature failure rate.
My former neighbours had both over and under cabinet lighting in their kitchen. With the slim conventional tube fittings (of which they probably had a ten), after a couple of years they were getting a failure every couple of months. I swapped em all out for new fittings with LEDs a couple of years ago, and no failures since.
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I have standard size florries here as under cabinet lighting. Tubes seem to last forever. Most plinths seem to be big enough to hide my size of tube, so no real reason to use smaller? Except that so many of those plug together under cabinet fittings seem to use T4 tubes. A good reason to make up your own.
Although I've got a couple of short T4s as panel lamps elsewhere. They seem to have a pretty decent life too - far better than the tungsten they replaced. But will probably change to LED there if and when they fail.
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On 17/12/2017 22:38, Phil Addison wrote:

See https://www.tlc-direct.co.uk/Main_Index/Lighting_Menu_Index/LED_Undercupboard_Fittings/index.html
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On Sunday, 17 December 2017 23:51:35 UTC, alan_m wrote:

Yes, I saw those, but then found bare tapes and wondered why buy a fitting if you cab just stick the bare tapes on. I have my answer now, thanks.
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On Sunday, 17 December 2017 22:38:05 UTC, Phil Addison wrote:

How long is a piece of string. What do your current lights put out, estimate from there.

of course

if out of sight you can twist it on the corner. If visible that wouldn't look good.

yes. If out of sight you could cover it over with velcroed clear plastic bottle strips to keep them clean.

there's never any reason to buy anything from RS.

3000K is not as yellowy tinged as 2700K. I'd avoid higher CCTs unless you know you want them.

12v 1A is 12watts.

I'd give them at least one dimmed setting. For relaxed use it looks better and extends LED life hugely. A series cap on the mains feed can do that, as long as the PSUs don't misbehave.
NT
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On Monday, 18 December 2017 03:57:01 UTC, snipped-for-privacy@gmail.com wrote:

See previous reply

I certainly wasn't suggesting I'd buy them from RS, just pointing out an example.

ok

No shit Sherlock

Its only under cabinet lighting. There is an on-off wall-switch for when they are not wanted.
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On Monday, 18 December 2017 21:26:16 UTC, .phil_a wrote:

there wasn't any lumen info in it. Look up typical lumens/watt and work it out.

:) you were asking a very basic question
NT
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On 17/12/17 22:38, Phil Addison wrote:

You can get ali channel with clip on diffusers for this purpose - these have screw on clips.
But for ease, I used:
https://www.tlc-direct.co.uk/Main_Index/Lighting_Menu_Index/LED_Undercupboard_Fittings/index.html
24V - I got a *decent* 24V SELV PSU from RS (over heat, over current protection).
If you want to go with tapes, you can get self adhesive LED tape that is waterproof (it's coated with a film):
https://www.led-lighthouse.co.uk/led-strip-lights/white-led-strip-lights
I see they have a new LED in those - the brightest of the tapes a few months ago was absolutely mental.
I would go with 24V - then you don't worry about volt drop problems over distance. All quite safe (with a quality SELV PSU) too.
Those guys also sell the ali channel I mentioned.
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