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Topic Title: LEDs
Topic Summary: 3W (lots) or 7W (few)
Created On: 01 November 2013 09:35 PM
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 01 November 2013 09:35 PM
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bakey

Posts: 8
Joined: 25 November 2010

I am about to prepare a design/ quotation for kitchen lighting using JCC Fireguard LED non-dimmable Cool White downlights.

My question is: from a point of view of eveness of light spread, would it not be better to use more of the 3W fittings than fewer of the 7W fittings.

E.g. In a kitchen whose dimensions are: 3.6m x 2.9m:

Option 1: 9 x JC94175 @ 450 lumens = 4050 lumens total, (on a 3/ 3/ 3 matrix).

Option 2: 14 x JC94199 @ 300 lumens = 4200 lumens total, (on a 4/ 3/ 4/ 3 matrix ).

I accept that with Option 2 there is a gain of 150 lumens (if my data is correct), but it is the even spread of available light to reduce dark spots that I am considering.

Is it this simple, or are there other issues that I need to consider as I have not yet used the 3W Fireguard downlights.
 01 November 2013 09:50 PM
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antric2

Posts: 1034
Joined: 20 October 2006

Hiya Bakey,
There are alsorts of calcs you can do and it can be hit and miss.
Emitted lumens are not the same as delivered lumens.
The delivered light from the LED is determined by height of ceiling,angle of LED lense colour of light warm or white.
Based on a 3mtre high ceiling I tend to space the my fittings at about linear 900mm centres as a minimum, based on leds I use which I try not to go below 400lumens. with a spread of < than about 55 degrees.

Best thing to do is have a sample kept on your van of 2 Leds in their fittings with a long lead on and a 3A fused plug.You can then get an idea of what spacing is needed by using your 'demo kit to hold from the ceiling and will be able to gauge better what you want for the particular room they are intended.
Sorry if this might not be much of a help but there is no sure fired calc to determine how many.....but I am open to be proven wrong
Regards
Antric
 01 November 2013 09:58 PM
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bakey

Posts: 8
Joined: 25 November 2010

Thanks Antric.

Yes, the idea of a couple of fittings on alength of cable is a good start, particularly to demo light spread and lamp colour. I will give that a go.

It wasn't so much getting the amount of lamps/ lumens/ lux right (albeit an important issue), but the different effect obtained by using fewer higher output lamps (7W) against more lower output lamps (3W).
 01 November 2013 10:08 PM
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antric2

Posts: 1034
Joined: 20 October 2006

We have been there and done that and alsorts and we are still learning because just as we feel we have cracked it we then find other products are out.....its a mine field.But the sample lighting assembly we use has been our best indicator but on a slightly differing note just have a read of my post in the OP about Dimming Led Lighting
Antric
 01 November 2013 11:00 PM
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HarryJMacdonald

Posts: 254
Joined: 15 May 2002

I've had a look at these lamps and I can't see which lamp they use. The spec says "integral" which might mean it is hard to get spares.

My experience with the GU10 types is that many don't last nearly as long as they claim. I've had one batch of 72 lamps nearly all fail within 2 years (i.e. 8000 hours not the 50,000 claimed).

The advert also says guaranteed for 120 months but it might be quite a hassle to claim on this guarantee which is unlikely to include fitting anyway. I've had much better success with the SMD types, several little square chips that are yellow when turned off. These seem to run cooler so probably last longer for that reason.

As regards the number needed, I have a flat with 8 x 50W downlighters in a small kitchen. The last time I went round only one was working and the tenant said he liked it like that, 8 was far too bright.
 01 November 2013 11:17 PM
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westfield6

Posts: 100
Joined: 12 October 2007

Originally posted by: HarryJMacdonald


As regards the number needed, I have a flat with 8 x 50W downlighters in a small kitchen. The last time I went round only one was working and the tenant said he liked it like that, 8 was far too bright.


****ing hell. 400 watts to light a small kitchen. No wonder he said one was OK. Must have seen his leccy bill. What is wrong with a 4 ft fluorescent?
 02 November 2013 08:20 AM
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dickllewellyn

Posts: 1131
Joined: 19 March 2010

I find, particularly in domestic, much better effects can be achieved by lighting what needs to be lit rather than making a nice grid of lights on the ceiling. You need client cooperation, but with a bit of creative thinking and using downlights washing down walls, on edges of windows, spaced over work tops, all generally about 300mm from the wall you can get some really nice homely effects. Particularly in older buildings if you can try and find features to light or light around then you can really turn an ordinary room into a picture of homely comfort.

As for fittings, I'm not a huge fan of the JCC offering. The terminals are a faff, and the warranty registration procedure is difficult. We tend to use the 6.5w megaman lamps in cheapie fittings or in the aurora ones where the lamp is recessed and there is a black anti glare baffle which suits the clients used to having John Cullen lights in their lives! They are awful to dim though, much better to have multiple switching options. We have dimmed them successfully, but only really in banks of 3 or 4. If dimmable is a requirement I tend to drift toward halers fittings.

One thing to remember with retrofit led lamps is that they need cooling to keep the life. Fitting in a fire rated can isn't a good idea.

-------------------------
Regards
Richard (Dick)

"Insert words of wisdom and/or witty pun here"
 02 November 2013 11:48 AM
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HarryJMacdonald

Posts: 254
Joined: 15 May 2002

Going back to the original question, lots or few, the trouble with kitchen lighting is that you are usually casting a shadow over the place you are working, especially if the lights are ceiling mounted.. The more lights the less this happens.
 02 November 2013 10:20 PM
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sparkiemike

Posts: 1513
Joined: 24 January 2008

If you have shadows the lights are In the wrong place. IMO the lights needs to be 600mm from the wall where there are work tops so that you get light on your work area. I tend to user halers, they now have fitting with 60deg spread. I would also be looking at 1000mm to 15000mm spacing depending on budget and joist layout using 8W fittings, I would not even consider 3W fittings.

As Richard says put them where you need them
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