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questionboy
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On Light bulb appliances there is often a 60w limit. I would guess that a halogen bulb of 70w would produce less heat so should be fine to put in similar fittings.
questionboy said:On Light bulb appliances there is often a 60w limit. I would guess that a halogen bulb of 70w would produce less heat so should be fine to put in similar fittings.
256bits said:You should access and read the following two sites, both of which are informative about light sources:
http://en.wikipedia.org/wiki/Incandescent_light_bulb
http://en.wikipedia.org/wiki/Luminous_efficacy#Overall_luminous_efficacy
There you will find out that for a thermal radiator such as the incadescent bulb the theoretical luminous [efficacy] is 95 lumens per watt, or about 14%, but this is at a temperature of 6300 C. For a typical tunsten bulb, where the filament remains solid, (below 3683 kelvins), most of its emission is in the infrared and the overall luminous efficiency is about 2%.
I believe the OP's question is whether a 70 W halogen bulb can be put in a 60 W appliance fitting.
As yet there is no answer.
However, from the posts I've seen here, I would tentatively conclude that one shouldn't.
questionboy said:On Light bulb appliances there is often a 60w limit. I would guess that a halogen bulb of 70w would produce less heat so should be fine to put in similar fittings.
Bear in mind also that such power ratings are unlikely to produce an outright 'hazard', simply that higher powers result in higher surface temperatures, and at some point someone has made a judgement call as to how hot they are permitting surfaces to get before it raises a 'burn-injury' risk. One might expect some margin has been built into that decision.
Studiot said:You should not (in general) use a 25 watt halogen lamp in a fitting designed for a standard 60 watt lamp.
Studiot said:Try reading the information supplied in this thread again and see if you still feel this way.cmb said:Bear in mind also that such power ratings are unlikely to produce an outright 'hazard', simply that higher powers result in higher surface temperatures, and at some point someone has made a judgement call as to how hot they are permitting surfaces to get before it raises a 'burn-injury' risk.
Right, but there is an equivalently 'less of' a halogen bulb. Newton's rate of cooling doesn't describe that you'd have twice the heat flow for twice as much stuff.Studiot said:cmb, you seem to focus on heat input alone.
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3) Newton's law of cooling tells us that the higher temperature promotes more rapid heat transfer.
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Why does a thermal flux of 1 W/cm^2 from one bulb differ to 1 W/cm^2 from another?
Studiot said:Yes the heat passes through the holder and onto the general surroundings, but what damage does it do on the way?
Studiot said:You should not (in general) use a 25 watt halogen lamp in a fitting designed for a standard 60 watt lamp.
Most of the confusion here seems to stem from Studiot's assumption that the halogen will be physically smaller than the standard, which is not necessarily true.
So, if you're saying that you need to run a 25W halogen in place of a 60W incandescent
and that it is because of heat conduction up the bulb stalk, then how much power are you saying is going up the stalk in each case?
Really? So are you instead saying that two bulbs of identical dimensions and heat outputs can have different temperatures?Studiot said:Where did I say that?
If I did I am sorry because I agree it is not true.
However your other line of reasoning needs revising since there are other factors, besides heat flow determining the element temperature.
So you're saying that two bulbs of identical dimensions and heat outputs can have different temperatures?
That is not true. First, some have a lamp-in-a-lamp design, but second, a higher bulb temp means more heat transfer and more wattage. You can't have a higher temp for the same size bulb and the same wattage. As a result, a higher filament temp for the same wattage must mean a physically smaller filament and therefore the same gas and envelope temp.Studiot said:2) Filaments in halogen lamps run at considerably higher temperatures than standard. Actual figures are already given here by others. Since the filament is hotter the surrounding lamp internal atmosphere will be at a higher temperature, as will its envelope material.
Rate of heat transfer is a function of temperature. You can't separate them like that.4) Regardless of the rate of heat transfer contact with a body above its softening or melting temperature...
Studiot said:How do you think the filament in a halogen source achieves its different colour temperature, if it is at the same temperature as the one in a standard bulb?
Really?Vanadium 50 said:CMB, this is much simpler than you are trying to make it, partly because many of your "facts" are not.
Halogens and ordinary incandescents operate at the same filament temperatures, around 3300K.
I did not make that association '..because..'. That is falsely attributing something to me that I did not say. I made it clear that a '60W' rating is making it clear that a '100W' bulb is unsuitable, that being the next power rating up, and that the consumer should be cautious over using 'similar' ratings in the new technology but that it is unlikely to make much difference.Your suggestion that it is safe to exceed the posted limit because surely someone somewhere put in a safety margin is irresponsible and dangerous.
AlephZero said:Most of #13 - #31 seems to be a (fairly hypothetical) discussion of the normal operation of the lamps.