Light bulbs

[D4N1EL]

Hi, I've bought a new light fitting for my daughters bed room, there is a sticker on it saying 40w max, I'm guessing it's to do with the heat given off? Anyway I've bought an energy saving light bulb rated at 20w, it says in brackets trad 85w. I'm assuming it gives off the same light as a 85w bulb (1150 lumens) but will it give off the same heat an melt the bulb holder?

Thanks

 

[PrenticeBoyofDerry]

It will give off the heat associated with a 20W lamp, as that is what it is.

 

[D4N1EL]

Thanks

 

[ban-all-sheds]

I'm assuming it gives off the same light as a 85w bulb (1150 lumens)

Chances are that it won't, or if it does it won't do for long.

But it will give off considerably more light than a 40W incandescent.

 

[D4N1EL]

Why do they compare them to 85w bulbs then? When they don't use 85w and don't give off as much light?

Thanks

 

[D4N1EL]

Why do they compare them to 85w bulbs then? When they don't use 85w and don't give off as much light?

Thanks

 

[ban-all-sheds]

They don't use 85W because they don't use 85W. They produce far more lumens/w than incandescent lamps. An 85W fluorescent lamp would be pretty bright - think how much light comes out of a 6' tube, and imagine that concentrated into a bulb you could get into your light.

The people who sell them and say that they are equivalent to an 85W incandescent light are either extreme optimists or cynical charlatans who want to mislead you in order to take your money. You choose which interpretation you prefer.

That said, I'm sure that a 20W CFL will be fine for a bedroom. But in any event, you have it. Stick it in and see if it does what your daughter wants. If not, buy a brighter (or dimmer) one. Unless you have a bare pendant dangling down you will not be able to buy a CFL which is so powerful that it puts out as much heat as a 40W incandescent - it just wouldn't fit.

 

[ban-all-sheds]

It will give off the heat associated with a 20W lamp, as that is what it is.

Actually no - it will be more efficient, therefore it will give off less heat than a 20W incandescent.

 

[JohnW2]

The people who sell them and say that they are equivalent to an 85W incandescent light are either extreme optimists or cynical charlatans who want to mislead you in order to take your money. You choose which interpretation you prefer.

That may be true, but it seems that most manufacturers of 20W CFLs claim that they are equivalent to at least 85W incandescent (some say 100W) - and I think it is probably true to say that 20W CFLs are widely used as replacements for the once-ubiquitous 100W incandescents.

Kind Regards, John

 

[JohnD]

the lumens should be on the packaging of the CFL.

When Energy Saving lamps first came out, they were oversold, claiming that an 18W CFL was equivalent in light output to a 100W incandescent, so there are still old people who claim that energy saving lamps are dim. Additionally, modern lamps have better light output and shorter start-up time than the old ones of 20 years ago.

In fact, a 24W CFL is about equivalent to a 100W incandescent, and will not disappoint on light output. A 8W to 12W CFL is enough for a bedside light but not enough for a living room, unless you have several table lamps.

Browsing the "Which" tests, I see that the GE 23W T2 Spiral from Wilkinsons gives 1590 lumen, which they say is equivalent to a 100W incandescent. I can't find a table of incandescent outputs.

Spiral and stick CFLs are somewhat unsightly. In an open shade I like the Globe lamps from Philips and GE which have a 6" opal globe which is fairly free from glare, gives softer shadows, and to my eye looks quite attractive. I usually get 24W.

LEDs are getting very good now, but they are still more expensive than CFLs. I am sure they will come down in price long before the end of life of any lamp you buy today.

 

[ban-all-sheds]

I like the GE Extra Mini Biax - quick to get to full brightness, and physically small, so you can often get a brighter lamp in than when you use a more typically sized one.

 

[JohnW2]

the lumens should be on the packaging of the CFL.

Indeed - although lumens are obviously only part of the story when comparing the perceived 'brightness' of lamps of different types.

Kind Regards, John

 

[Astra99]

The problem here is simple. Terminology. Historically we have referred to the light output of a lamp by the power it consumes, that is, its wattage. When all lamps were incandescent, (whether tungsten in vacuuo or tungsten-halogen) and florescent lamps were long tubes all was well. (I am excluding Na/Hg discharge from this discussion).

Now we have different lamp technologies coming along, all with different power to light output ratios. To approximate back to the "well known" incandescent lamp was the best option for many, but it does have its shortcomings, as perceived light output is subjective.

Thus the Lumen has now become the de facto standard for measuring light output. Once we get used to it, we will all wonder what we got in such a tangle about.

It's a bit like (for those who remember it) the change to decimal currency in 1971.

 

[JohnW2]

Now we have different lamp technologies coming along, all with different power to light output ratios. To approximate back to the "well known" incandescent lamp was the best option for many, but it does have its shortcomings, as perceived light output is subjective. ... Thus the Lumen has now become the de facto standard for measuring light output. Once we get used to it, we will all wonder what we got in such a tangle about.

I'm sure that a lot of what you say is true - but as I said, lumens are never going to be all of the story in terms of perceived 'brightness', any more than 'incandescent watts' were. There is, for example, always going to be the issue of the extent and pattern of distribution of light (I doubt that any lamp is ever going to precisely uniformly illuminate the entirety of a sphere surrounding it).

Kind Regards, John

 

[JohnD]

do you know anything better?