Fluorescent lamps

[Tim Watts]

Hi,

My daughter's bedroom is north facing, so as part of the design I'm thinking of providing a powerful fluorescent ceiling wash light with one of two long tubes mounted on a white shelf about 4-5" deep and 3" down from the ceiling (ie you don't see the tubes in normal use but access is easy for changing). This will all be painted with ceiling emulsion which should make it disappear to some extent.

I'd like to choose particular control gear (good HF stuff) and particular tubes (nice daylight with a good spectrum) rather than use a stock fitting.

Option 1: Tubeless fittings with electronic HF gear - can't seem to find any, anyone have any ideas?

Option 2: DIY. Found the connector caps, and could mount the tube on terry clips. Regarding the control gear, I'd need to enclose that (or at least the terminals at both ends). This could be mounted above the ceiling.

How hot do the electronic ones get? Would they object to being mounted in a plastic box - would it need air vents?

TIA

Cheers

Tim

[NT]

Shelf or trough lighting is a good plan generally. But 3" from the ceiling? It wont look good. You'll get very bad light distribution, and the low light angle means the flaws of the plastering will be writ large across the ceiling.

I presume you can mount it lower, but if for some reason you really can't, eg a 6' high ceiling, then to make 3" down work you'd want to put the lights all round the room perimeter and run them at low power on dimmable ballasts.

Daylight is one of the worst tube choices available, and will look truly grim in the evening. 3500K is much better for home lighting. For good quality light pick a high CRI tube, preferably triphosphor.

For ballasts any electronic ballast will do the job. You might or might not want to pay extra for dimming, it saves operating energy in a bedroom as well as looking much better.

Ballasts: sounds like you need a gear tray, which has everything on it. These are common in commercial use. HPF or LPF doesnt really matter if youre using an electronic ballast, LPF is cheaper. If you wanted to use an uninsulated ballast you can enlose it using EML if you fix it properly, then no ventilation problems.

NT

[Tim Watts]

NT wibbled on Friday 09 July 2010 11:35

3" was a starting point - but I take your point. The ceiling has been replastered so it's on the "winning" side

Because the room is L shaped (well, sort of) I was thinking anyway to light the two long sides, which will soften the funny wall opposite.

OK - I hadn't fully specified the tubes yet (partly which I want to divorce the tubs from the fittings). What I wanted was good honest bright light with a good spectral spread and no flickering so it's a bit more like a well lit south facing room (on demand).

Dimming is an option. There's already a GU10 multispot going in the middle of the room for "bedroom lighting". The tubes were an afterthought to add background lighting when I realised that even in summer the internal lighting from the large window is dreadful. So for normal "bedtime", she'd probably have the tubes off and use the GU10. The tubes are there for daytime use to liven up the room, which is why I initially though of using daylight.

Cost of running is not an issue for me for 100W +/- of tubes.

I thought about gear tray - seemed to suddenly get more expensive (being industrial)...

Cheers

Tim

[Andrew Gabriel]

You almost certainly don't want daylight - it will look pale blue and your daughter will look very ill ;-) Depending on the lighting level you are going for, you'll want somewhere between 2700K and

4000K. I mentioned the Kruithof curve recently in another article, but if you look at and assume you aren't going to get above 400 lux, you want a max of about 3500K.

Most tubes in this country are tri-phosphor (i.e. red, green, and blue phosphors mixed, to give the desired white), and I wouldn't bother considering anything else unless you have tried this and find there's a problem.

I have been using the newer T5 tubes in this application. The smaller tube size means they're easier to hide on top of cupboards (or shelves). You also have a choice of two different power rating per tube length (three in one case), depending on your lighting requirements. You can find these in the range 3000K - 4000K. I wrote a wikipedia section on them some time back (although someone else recently moved it into a different wikipedia article for no good reason, but that's wikipedia for you!)...

Option 1: Tubeless fittings with electronic HF gear - can't seem to find

eBay is the best source of HF control gear IME, although you sometimes have to wait until someone is selling exactly what you're after.

Modern ones don't get very hot, but they must still be allowed to cool, either by ventilation or by conduction to a metal case. One solution I have used is a small plastic project box, cut in half, and each half fitted over just the ends and connections of the control gear, with the body exposed for cooling. Note that the T5 tubes do get hot, the HO ones particularly so.

[NT]

If you hold a bulb 3" from the ceiling with all other lighting off you'll soon see what I mean.

Electronic ballast gets you no flicker. Good spectral spread is hard to come by in fluorescent lighting, but a triphosphor tube of 82 CRI satisfies almost everyone. If you've got oil paintings on the wall and demand precise colours, you can get CRI 90+ tubes.

In that case I'd go dimmable. It'll pay back all its cost and give much more pleasant and flexible lighting.

NT

[Graham Jones]

Hello,

I would think very hard about use fluorescent lighting, personally I find it very unpleasant, it has a very poor quality of light. Instead I would recommend you fit halogen lighting, this produces by far the best quality of light.

You don't have to use the small recessed bulbs, there are GLS sized halogen energy savers available (saving 30% to 50% of an ordinary bulb)

Depending on the size of the room you could get away with just one ordinary sized bulb. In my office I have just one ordinary light fitting which contains a 105W halogen energy saver giving an equivalent of 150W of light output. e.g.

madness of this bulb is that because it is an energy saver it is not restricted to the 100W bulb ban, so you could directly replace all your

100W bulbs in the house with these and actually use more energy!

My local Homebase had these on offer a couple of months back at about £1.30, I stocked up!

Another alternative are LED bulbs, there are now LEDs available that can replace an existing GLS bulb and give a quite good level of light. e.g.

7W gives an equivalent of 40W and has a life of 45000 hours. The downside is obviously the price. Also what about installing some GU10 down-lighters and using:

could use 4 GU10s in the room each with one of the above bulbs and only use 28W of energy, giving an equivalent of 200W and lasting 45000 hours.

LEDs are just going to get better and better and should be the only realistic choice in a few years.

Anyway just my thoughts,

Graham

[Tim Watts]

Andrew Gabriel wibbled on Friday 09 July 2010 12:35

Thanks Andres. Having read the Wiki, that makes sense.

I "understand" CRI now. I suspect tri-phosphor will be fine.

I think for this application, T8 would be fine, but I'm looking at your suggestion too.

OK - need to search harder - there wasn't much with my terms.

looks just the ticket for an un-enclosed device. 2 5' tubes off one box. Very cost effective.

In fact I could probably get 2 el-cheapo 5 foot fittings from somewhere local, throw the ballast and tube away, shove the above into one fitting and crimp some T+E along to the other fitting (they will be adjacent). Possibly cheaper and easier than buying the caps, terry clips and random plastic box... (Allowing for P&P on the above!)

That sounds like a plan if I can't house the gear into a fitting.

Cheers

Tim

[Tim Watts]

Graham Jones wibbled on Friday 09 July 2010 13:12

This will be in addition to a 5-way GU10 halogen fitting. The tubes are to bring up the general illuminance of the room when required, but the regular light will be the incandescent.

Yes - I've used similar before - most impressive.

That's my long term plan with the GU10 fittings - sensible lamp format lends itself to LEDs. There seem to be some headway already, so I'm confident that in a few years when I'm fed up with replacing blown GU10s, that LEDs will have "arrived".

Cheers

Tim

[Tim Watts]

Tim Watts wibbled on Friday 09 July 2010 10:16

On a related note, for anyone interested, I just noticed my favourite CFL supplier has a bunch of bits I've never noticed before:

are some really decent looking T8 end caps there so I will dispense with the fitting and roll my own so to speak. T5 too.

Now all I need is a design for the lighting trough.

Off to google now, but I'm looking for a bit of MDF with a curved end-on profile available in long lengths. I don't have coving in that room (yet) so if I can get something pretty that I can hide tubes in, I could run it all the way around to make it look "designed" rather than ad-hoc. Paint it all white and start the wall colour just below.