"Andrew Gabriel" wrote in message
...
In article ,
"Nick" writes:
The open areas of our works are floodlit. Originally incandescent, then
tungsten and now metal halide.
We use 150w, 250w & 400w mh lamps. All on 9m stands and operated by
dusk/dawn sensors. Some of these lamps are now again degraded.
I am thinking that these metal halides would 'roughly' equate to 500, 750
and 1000w tungsten lamps.

That's probably not far off (although when you get to 1000W mains
filament lamps, they are significantly more efficient than 100W
and lower lamps).

Thinking of converting to led. Not for greenery but for (1) reduced
running
cost and (2) ease of replacement as I'm the one one that maintains them.
Never have had much fondness of heights.
I haven't a clue as to what size led replacements I might be looking for
and
would appreciate help on this.

To a first approximation, look at the lumen output figures for the
different lamps.

One important thing this doesn't take into account are the losses
in the luminare. Yours probably have reflectors to redirect most
of the light out of the front, but these are never 100% efficient
(or anywhere close). This is where LEDs have an advantage as they
are implicitly directional (to varying degrees), so don't tend to
lose as much light inside the luminare.

Another important area is what proportion of the light is directed
where you need it, and how much is lost in spillage over areas you
don't need (or want) to light up. Again, because of the much smaller
light source in LEDs, it's possible to focus the beam much more
accurately so more of the light is directed where it's needed and
less wasted.

LED streetlighting downsides - they currently seem to be significantly
less reliable than they should be.

What a surprise.

And only 10 years ago CFLs for household lighting was going to save the
world:-)

This may be because many companies
have entered this area with little experience in producing electronics
for outdoor street furniture. I've seen a number of local authorities
install and then give up on LED streetlighting, when they turn out not to
live up to their longevity claims. Some of the manufacturers have
responded
to this by guaranteeing to replace their products (including doing the
on-site installation) if they fail, although that's not practical in all
cases (e.g. a motorway where planning and night time lane closures need
to be put in place, at vastly more cost than the luminare replacement
itself).

Care to name and shame? At least the LED lights I fitted at Collingham train
station car park can be lowered to allow the LED head to be changed if it
fails.

--
Adam