Regular 500W uplighters are around 9000lumens, 18Lumens/Watt. You can get subtly better ("C" rated rather than "D") 400W tungsten with allegedly the same o/p lumens, ie 22.5Lumens/Watt.

Cheapie mains powered off-the shelf led bulbs are around 50Lumens/Watt, so you'd still need 200W of power to get the equivalent brightness - ie 20 off 10W £10 GU10 lamps. And you couldn't put them close together, or they would overheat, fade, and fail. You could pay more or DIY it and get 100Lumens/Watt, but still tricky to keep it cool in such a small footprint without a fan! So I think LED's are out for such high power uplighters.

HID might be good, I have no experience of them.
How about big CFL's ? I found a 125Watt one, giving 44Lumens/Watt ie. 5500Lumens I think here:
http://www.amazon.co.uk/Energy-saving-daylight-light-Bayonet/dp/B007T6GS4A/ref=sr_1_58?s=lighting&ie=UTF8&qid=1350298829&sr=1-58

Thanks for the comments so far - especially on the lumen output.

To explain the situation further, the current lamps are hidden from below by a 'spun reflector' - essentially a metal dish (400mm diameter) which we would be keen to reuse if possible since these dishes and the rod system that supports them (and distributes the power cabling) were made bespoke. Each dish sits about 500mm below a square board painted white which diffuses the light.

Since the fittings are circular we wouldn't be able to go down a linear T5 route and are essentially stuck with single point source lamps. As before though, if there is no 'circular' solution then we may have to bin (recycle) the lot and pursue an alternative setup.

I've noticed some 60w circular T5's on some websites - is it feasible to sit these concentrically if we could get different diameter lamps or is that asking for trouble?

Posted By: atomicbisf

quote

Posted By: Doubting_ThomasI've noticed some 60w circular T5's on some websites - is it feasible to sit these concentrically if we could get different diameter lamps or is that asking for trouble?

A lamp fitting with two concentric circular fluorescent tubes seems to be the commonest domestic light fitting in Japan so I think it's feasible, if the diameter is not too much.

I'm using T5 triphosphor straight tubes to wash a ceiling and it works really well. Are the uplighters the main/only source of working light or primarily to show off the pretty ceiling? If the latter you may be able to get away with less light output.


These T9 circulars pack up to 60w into a 225mm diameter not sure how close that is to 500w halogen.

http://www.lampspecs.co.uk/Light-Bulbs-Tubes/T9-9-8-Inch-Diameter-Circular (random pick)

RobinB

I guess the problem is going to be the home for the control gear - there isn't any on 500W Tungsten halogen

If you go for HID (High Intensity Discharge) by means of CDM (Ceramic Mercury Halide) you need igniters and ballasts - if you go for concentric rings of fluorescents (say 60W @ 380mm, 55W @ 300mm and 22W @ 225mm) you'll also have to house the ballasts for those (they may just fit in th einner circle of the 22W)

The alternative is to have the control gear at the ceeiling level (sort of an extended terminal box).

Unless everyone is particularly fond of the system or it has some architectural merit, personally I'd bin it and start again with a more sensible lighting design solution. It could still have uplighting for accent, but a bit more downlighting wouldn't go amiss in there I suspect

Regards

Barney

One battle at a time tony, I'll get to the draughtproofing once we've stopped illuminating half of North London..!

Seriously though, it's an office building and the uplighters are only in the meeting rooms where there's intermittent occupancy and more than enough warm bodies and hot air being generated to keep the place toasty when in use. (Plus if it does start to get colder, that makes a great argument for improving the airtightness next.) I don't want to go near the high grade v. low grade energy argument but I'm pretty sure we can light and heat the space more efficiently than we do currently.

Barney, thanks for the clarification on HID, CDM and all the other lingo. I don't think they'll go for the 'extended terminal box' approach as there isn't much room up there but the nested ring ballasts might just work. As for architectural merit, I'm hoping we can find a more elegant solution which also uses less energy. It's just a lot of existing kit (with all the inherent embodied energy) to get rid of.

RobinB - the lights are mainly for 'accent' but they tend to get switched on in the winter time when the directional spots don't provide enough 'working light'. I'm hoping we can reduce the lumens slightly without anyone really noticing but if it is a marked difference then the whole thing may seem like a poor substitute...

Google found one LED uplighter that claim to be brighter than a 300W Halogen..

http://www.accoladeplc.com/browse/lighting/47745/47746/product-289039

Edit: Oops I take that back. Says LED in the title but its not.

Does this 5.5kW of lighting do anything more than 'look nice'?

If not why not just get rid of them completely and put in some light that actually lights the room where people need to see? Accent lighting effects round the arches can be done with a few watts of LEDs in various ways.

HIDs are about 60lm/W (at least in the bike light/car headlight sizes I am familiar with). So about the same as average LEDs, and as you've discovered the ballasts are expensive. You can get pretty manly LED lights now, e.g High Bay lights, and 30W panel lights. Do I understand that these lights are sat in a dish somewhere near the top of the arch, which has the white board in it that reflects much of the light, presumably leaving a dark circle below where light is blocked by the dish? Why not replace the reflective board with an LED panel light?

Something like this: http://www.pcbuyit.co.uk/carbon8-ceiling-panel-light-4500k-colour-p-1625.html (there are lots of these around) 600x600mm. That one puts out 2400lm (actually measured, outside fitting!) How big is the existing board? Ah it's currently curved. Plenty of flexible panels on alibaba - probably something suitable could be found.

Here's a low-bay light which is 60W, 5300lm. 435x435 possibly too big to be direct replacement inside the dish?
http://www.gemmalighting.com/products/ledinternallighting/sovereign48/index.html

Any of that help?

Yes, hooray for pictures - that's very little like what I had imagined :-)

Get rid of the dish'n'struts and put an LED panel where the white square is looks like a good plan to me. If you want to keep the curve you might have to look around a bit or DIY something with a thin acrylic sheet

Photo helps a lot.
Looking at the setup, it's crying out for the CDM HID you mentioned. Not much else gets close to that for efficiency and light quality. Still, for similar light output you would still need 100+ W at each location. Common CDM ratings are 70W or 150W I think. So it's still quite a lot of total power.

Those Class-D lamps are being phased out soon - closest replacement will be the only slightly more efficient Class C halogens like RobL mentioned. Things like this:-
http://www.tlc-direct.co.uk/Products/LXTHE230.html

What you really want I suppose is something like this (see datasheet, minus the fitting, but stilll to look tidy somehow)
http://www.tlc-direct.co.uk/Technical/DataSheets/Elite/ASD_SFL.pdf

I also was initially thinking that LEDs would be ruled out by the high light/power levels however on thinking some more i wonder about some of the LED lamps/fittings being used for streetlights. The PDF refd above says 300W Halogens put out around 4000 lumens. I think LEDs are avilable in 50+W that might come close enough to be useable. I don't have a specific example though.