recessed lighting questions (having read previous posts)

[meow2222]

correct.

mean bulb life yes, quality no, unless theyre so bad they fail prematurely in significant numbers, as halogens do.

not really

Oh lord. If you want to make comparisons and look at the interactions with heating, see how much heating halogens offset and what the costs are, you need to work out the numbers, otherwise you simply dont know. Take a sample case and work it out.

Andy I dont think youve thought this through at all. It is easy enough to calculate how halogen lighting interacts with heating and what the extra end costs are.

?

I get the feeling you did, since the figure you give isnt even close.

not at all

dont forget they last 5 to 10x longer, so imagine them having 5-10x the shelf space and you'll get a better picture.

Time for some science.

The prime factor is competition. People typically consider point of sale cost and not run cost, and that price is always higher for fl lights. A small BC holder is cheaper than 2 holders, ballast and starter.

Anyway, if you want to know the cost of halogens you need to work out the numbers.

NT

[meow2222]

Thanks for the info there. Re deterioration, its light quality that drops as well as output.

NT

[Brian Sharrock]

> Puts a nice even light just where you want it. snip

Whereabouts, in relationship to the worktops, have you positioned these five foot monsters? Are there any cupboards above the worktops?

[Tony Bryer]

More or less over the front edges of the worktop. There are wall cupboards but not up to the ceiling height (ceiling is 2.5m).

With experience, the four foot ones would have been fine - the reflectors in these fittings push virtually all the light downward, unlike the normal batten fluorescents I had before.

[meow2222]

Whereabouts, in relationship to the worktops, have you positioned these five

I suspect next to the sunglasses.

NT

[Ian Stirling]

As I understand it that also depends on the LED, and more specifically the phosphor mix. If it changes colour, or stars changing emitted colour, then the colour of the light can change. If it just dims... (the system I proposed also runs the LEDs substantially under their sticker power, for efficiency. If the power was ramped up over time (very slowly - 30% at 6 years runtime) then it wouldn't actually dim. I'll look for info on colour changes.

[Andy Hall]

Except that they don't. Out of a couple of dozen, I doubt if I change more than one a month so it is not a big deal at all.

Well, yes it is, longer lifetime means lower rate of change.

I did. From an order of magnitude comparison, it's a non-issue.

Actually I have.

I did a calculation based on a month by month reckoning of outside temperature and hence heating requirement coupled with average lighting use in that month.

Taken over a 12 month period, the cost difference is second order at best. Given that situation, I am not going to worry about whether I can make a 2 or even 5% difference to overall energy cost when the light quality is so appalling (to my taste) from fluorescent lights in a domestic setting. When it comes to the workshop, different issue. That's an "industrial" environment and I use a large amount of fluoresecent light for it..

One can pick a number or a range.

Do you have another range in mind?

I don't buy that argument.

Do people buy based on science? generally I factor that in, however, the human senses can't be precisely defined scientifically - there are too many factors and variations from person to person.

In that sense you are right. People do buy on point of sale and not lifetime cost. Given that situation, it does rather explain the reason for the low retail space given.

[Brian Sharrock]

I have wall mounted cupboards which are surmounted by 'built-up' closures to the 8'6" ceilings - I hate space above cupboards - things get shoved there, forgotten and end up covered in 'goo'.{ When the house was built they used English measurements}. I wasn't too sure whether you'd positioned the luminaires below the cupboards.

[meow2222]

seems you've thought of everything. The only remaining issue would be the light quality and the increase in colour temp over time due to phosphor degradation - which as you say will do better under reduced power.

NT

[Ian Stirling]

I don't know the mechanism - if it goes opaque to blue, the colour temp could even decrease. I can't find any mention of colour shifts in the literature, I've mailed them.

[meow2222]

Well I could be wrong on this, but ISTR it being discussed on sci.engr.lighting.

NT

[Ian Stirling]

True, but it's not completely possible to generalise across all LED types, it's going to depend on why it's changing in colour, or dimming. Is it the matrix that the phosphor is in yellowing due to the heat/irradiation/age, or is one of the phospors aging or changing.

[noos999]

Thanks to all for the useful advice/discussion. I've ordered some conventional and some low energy R80 and GU10 lamps so I can compare them. I see that Megaman now have dimmable (in steps rather than continuously variable) low energy GU10 lamps..

Julian

Chris J Dix>