Confused about lightbulbs

[Harry Bloomfield]

No, they simply become much less efficent at turning moving electrons into light. Less power is consumed, but very much less light is produced. Something like 50% power = 10% light out.

[Jim S]

I'm sure you're right, but the web has not been my first stop for light bulbs (so far) :-?

[Dave Plowman (News)]

I'd assume if you dim a lamp you are no longer interested in its maximum output or efficiency. Think everyone knows the actual efficiency drops when a filament lamp is dimmed - but then so does the current consumption.

[Dave Plowman (News)]

If all that matters is the cost of lighting, surely a fluorescent tube is the answer?

However, in the home, it usually does rather more than just provide a means of avoiding tripping over the cat...

[Vir Campestris]

I think everyone _here_ knows the efficiency drops... that's not necessarily true of the general population.

Andy

[Dave Plowman (News)]

It's fairly academic anyway. If you dim lights you're not really interested in their performance. And that will save some electricity over them being full on.

[Terry Fields]

I replaced every possible tungsten lamp[1] in the house with LED, nearly a year ago. I can't recall the exact figures, but something like 1kW of lighting was reduced to less than 100W. Specifically, in the kitchen/utility room 430W of halogens was replaced by 36W of LED, and it's a brighter room than before.

The claimed life of the LEDs lies between 15000 and 30000 hours. Over that period alone replacement tungstens will cost about the same as the LED they replace, leaving massive gains on electricity consumption. I estimate I'll save about £1000 over the life of the LEDs. Buying cheap filament lamps that have a high power consumption is a no-no. Do the capital investment and reap the financial benefits.

Come the power cuts of 2015, a 900W inverter generator will run the lights, TV, fridge-freezer, and central heating...while my neighbours shiver in the dark.

[1] There are two fittings flush to the ceiling that take a G9 lamp; I can't yet find an LED replacement for these that has the 800-lumen output of the 43W Xenon tungsten currently fitted, so for the time being these will stay.

[Martin Brown]

There are now a fair number of 40W and 60W equivalent LED bulbs that are as bright or brighter than the nominal tungsten filament lamp they are supposed to replace. You also have to choose a colour temperature and hope that your preferred bulb stays around long enough.

My solution is gradual replacement as the old bulbs fail.

One catch with halogen lamps is they also emit a lot more IR as well which can make them a bit of a fire hazard in some fittings.

The corresponding numbers for LED would be lower at 7W and 10W respectively but the initial capital cost would be higher.

Not any more it doesn't. The only catch is that most of the light goes into the forward half of the room leaving a darker ceiling.

NB this one is a daylight white not warm incandescent white. Best incandescent fakes I have seen are Philips spots (again well made)

If anything slightly too compact a beam at 25 degrees (there is a 45 degree one but I've never seen it offered at an acceptable price). This one can be mixed with incandescent spots and most people don't even notice that some are LED and some are not. You can feel the warmth from IR output of the incandsecents though when in the beam.

Also look for ones with decent heat sinking on them. LEDs are efficient but what waste heat they do produce mostly ends up as hot air.

Also worth noting that some dimmers have a minimum working load that they will tolerate so that if you switched to all LEDs your 380W would come down to 5 x 7W + 3 x 10W = 85W (>40W so probably OK).

Some of them will go crazy if the total load is under ~30W and not all of them that do carry a health warning to that effect. Older ones tend not to have considered the possibility of future high efficiency lamps.

You basically have to compute ROI over three years to get an idea if it is worth doing or not. And pray that the claimed MTBFs are realistic!!!

Too early for me to comment on the latter. I have had some past disappointments with CFLs cooking their electronics.

[Martin Brown]

The cheapest replacement option would be tight spiral CFLs 5W or 7W according to taste. I have been using them for about 5 years and bought enough to do a chandelier at a time. It looks silly with mixed bulbs in!

I can't point to the one I used which was elegant in that the control electronics is the same diameter as the candle it stands on and the open spiral fluoro tube stays inside the same overall cylinder.

It was a bit like this one would be if the control electronics were slimmed down. I had to buy a box full to get them. Never seen them offered for sale in any retail channel in the UK.

It isn't flame shaped but it does the job in a hypermodern sort of way.

You can get flame shaped LED devices but I have no experience of them.

I still have half a box of CFL candle bulbs to go...

The decrease in annual electricity bills is noticeable!

[Dave Liquorice]

If people still are on tungsten then it probably is worth changing to CFL/LED, due to the large drop in consumption, particulary for areas that are lit for long periods. The understairs cupboard entered/lit for 5 mins once a fortnight isn't worth worrying about.

"claimed" the jury is still out on the real world life of LED.

Have you tested that the fridge/freezer kicking in with everything else on (and pulling full power) doesn't trip the overload protection?

And for the lighting I assume you'll have to connect the genset into the house wiring. That opens up several cans of worms, from not "accidentally" back feeding the grid, to someone forgetting that you are on generator and putting the kettle on, via what to do about earthing.

We have 2kVA diesel genset after looking at the worms and thinking about it we run extension cables to stuff that needs to be maintained during power cuts and use gas lanterns for light. This means that the "L" and "N" are floating with respect to earth as niether phase from the alternator is bonded to the generator chassis or connected to an earth spike. One day I might swap the double module isolator switch on the generator for double module, double pole, 10 or 16 A RCBO, if they are avaialble that small.

[Dave Liquorice]

In GLS style with decent light distribution? Please show me.

There are a few "corn cob" ones about but with only 300 to 400 lm output compared to 600+ of a 60 W GLS. I spoted a Philps one the other day, with a central frosted pillar but that was Not any more it doesn't. The only catch is that most of the light goes

A "diffuse spot light" in my book. Not acceptable. B-)

[Martin Brown]

Brightest I have found yet is 1080Lm and 200+ degree beam. Anything at

840Lm and above will do for a 60W bulb. Getting a colour temperature you can live with and no unwanted whines or hums is the main thing.

It isn't truly warm white though and it does hum audibly at about 500Hz. (it is faint enough that most people can ignore it)

Light output varies roughly as A(1 + cos(theta)) where theta is measured from the axis of the bulb pointing away from the socket. This can be advantageous when one is over a table since less light is wasted on the walls and more falls on the eating area.

The main difference is that there is a dark ring on ceiling centred on the ceiling rose. This might offend some sensitive souls....

[Dave Plowman (News)]

The problem comes when the LEDs *don't* have anywhere near the claimed life, given the very high costs.

And my - albeit limited - experience of LEDs used as replacements for tungsten say they don't. Perhaps if used with fitting designed for them they may have.

[Dave Plowman (News)]

Rather the same as with car bulbs. Lots of these 'corn cob' types around said to replace an ordinary 21 watt stop lamp etc bulb. And they simply don't - to the point of being dangerous.

[Mark]

+1.