James (Oz variety)

I'll copy this to my friend Ken who is intimately involved in finding a
good answer to thse question for a whole house - and is too discerning for
his own good and dislikes almost all locally available solutions.

This is [EE] I wot. Even if you do not build the LEDs with your own hands
(nor mine, smelt & purify the Copper, nor ...) :-).

Lumens are lumens by definition - they include eye response as part of the
spec.

CT change is easy. If people are discerning about colour rendition you'll
want to look at high CRI and full spectrum LED lamps.
CRI properly relates to colour rendition in yukky orange incandescent light
so this needs to be understood in any CRI musings.

Rule of thumb is 5:1 power reduction BUT this very very very much deep-ends
on the manufacturer both of the LEDs and the overall lamps.
The very best LED lamps probably run at a 10:1 gain over incandescents  but
the makers (eg Cree) seem utterly uninterested in getting them into these
markets.


           Russell





On 24 January 2015 at 19:37, James Cameron <quozl@laptop.org> wrote:

> G'day,
>
> This is not my field of expertise, but I know enough to know I'm
> ignorant, and lighting experts are rather thin on the ground.
>
> I've been asked to help replace and augment a set of PAR38 150W ES
> 240V incandescent lamps in a meeting place, mounted on wooden beams
> about 5.5m off floor, lighting a floor area of 7.29m by 9.9m.
>
> Design goals are:
>
> - same or greater illumination,
>
> - change colour temperature to match the fluorescent lamps elsewhere
>   in the building, probably 4000-5000k,
>
> - reduce future maintenance (ladder climbing),
>
>
> Is it reasonable to assume that the existing PAR38 lamps are 2400
> lumens?  (Wikipedia suggests incandescent is 16 lumens per watt).
>
> How many lumens at 4000-5000k are the equivalent of 2400 lumens at
> 2700k?  Is it a direct translation?
>
> Are there any interesting products available out there?  Even better
> if available in Australia.
>
> A high CRI would be nice too.  ;-)
>
> (Is this EE or TECH?)
>
> --
> James Cameron
> http://quozl.linux.org.au/
>
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