Max power - light bulb

[User]

 

[albion]

Start up power needed for CFL ?

 

[twentysix by twentyfive]

Not sure why the difference but I always took the power to be the electrical input power. CFT's need less power so..............

Perhaps it's just that a 60W GLS gives the same light out as a 23W CFT. In which case it's to do with the heat created in the fitting when light is absorbed.

 

[Andy_R]

'tis to do with heat. A 23W cft will put out almost twice as much light as a 60W incandescent bulb but emits a similar amount of heat (slightly less but not by much)

 

[albion]

I'd possibly go with that. Start up surge would not have time to generate that much heat.

But yet I would have thought that 60W would be nearish 60 watts of heat and the 23 watt would be nearish 23 watts of heat.
So maybe the air heat dissipation is better with incandescent ?

 

[TheDoctor]

No...a 60W incandescent puts out about 55W of heat, a 23W CFL puts out about 5W of heat.
The luminous efficacy of a typical incandescent bulb is 16 lumens per watt, compared to the 60 lm/W of a compact fluorescent bulb.

 

[albion]

hmmm
From the Wiki
"CFL lamps have lighting efficiency ranges of 7–10%,[27] versus 1.5–2.5%[28] for incandescents.[29]"

At the maximum efficiency of 10% that likely leaves 20.7 watts of heat for a 23W CFL.
Of course 23W will be very close to only 7% efficiency.

 

[classic33]

And over the estimated lifetime of both types of bulbs.

The light given out will also harden the plastic itself.

 

[Yellow Fang]

I would have thought a 23W CFL bulb would put out much more light than a 60W GLS bulb (those are the old incandescent light bulbs, right?). The heat from a 60W GLS bulb would be nearly 60W. The heat from a 23W CFL bulb would be about 20W. It can't be the heat melting the fittings. Perhaps it is due to the initial power load on switching on.

 

[Profpointy]

It does rather sound like tosh to me - unless someone genuinely in-the-know can convince me otherwise.
I do have a science background, so view based on less heat is bound to be less of a problem, but no specific electrical regs knowledge.

i really don't believe the "starting current" notion as it would be for such a short time,

 

[Profpointy]

'tis to do with heat. A 23W cft will put out almost twice as much light as a 60W incandescent bulb but emits a similar amount of heat (slightly less but not by much)

Well that can't possibly be right. total watts of heat + total watts of light = power of bulb - there ain't anything else. So if the lower power bulb is emmitting twice as many watts of light, it must be emmitting a good deal less heat.

(By "heat" I mean localised heating, rather than "radiated" heat - which counts as light in this context if that makes any sense)

 

[slowmotion]

A 60 watt bulb consumes 60 watts. A 23 watt bulb consumes 23 watts. Give or take a few percent. The light output varies depending on the type of bulb but the rated power of the bulb all comes out as heat. The fitting manufacturers don't want you to put an incandescent bulb in their fitting if it is usually used with a CF bulb that gives the same light output at a third of the power. The fitting isn't designed to take the extra heat.

Edit: I suspect that the fitting manufacturers are also being careful about their liability. They don't want somebody to assume that a fitting rated for the heat output of a 23 watt CF will take a 100 watt incandescent because they chuck out roughly the same amount of light.

 

[Andy_R]

Well that can't possibly be right. total watts of heat + total watts of light = power of bulb - there ain't anything else. So if the lower power bulb is emmitting twice as many watts of light, it must be emmitting a good deal less heat.

(By "heat" I mean localised heating, rather than "radiated" heat - which counts as light in this context if that makes any sense)

a 60W bulb is rated as such because it CONSUMES 60W of power per hour. It doesn't emit 60W of power.

 

[Tim Hall]

a 60W bulb is rated as such because it CONSUMES 60W of power per hour. It doesn't emit 60W of power.

No it dosn't. Not watts per hour. Watts.

 

[Profpointy]

a 60W bulb is rated as such because it CONSUMES 60W of power per hour. It doesn't emit 60W of power.

assuming you're not just teasing us - where do you think the rest of the wattage goes? Does it simply accumulate in the bulb ? Is that why bulbs fail when they are full of joules...

Piss taking aside - here's the school.physics lesson : the unit of energy is a Joule and a watt is a joule each second (power). Energy is a "conserved" quantity - can't be created or destroyed - so energy in = energy out. Losses (heat in this case) is still energy.

A motor is similar 100W in = 100W out - only some as useful work - rest as heat & noise - but total is still 100W