[clickclickboom]

I use 220v lightbulbs in some of my fixtures. Running 220v bulbs at 110v gives the filament a brown antique glow. My question is if the bulb is 25w @ 220v does it still consume 25w @ 110v? The bulbs also last a long time I have some that have been running 12hrs/day for 11years.

[yakev724]

The bulb most likely uses less than 25W, but no way to tell how much exactly.

At low temperatures, the tungsten filament inside still has little resistance, so even if light output is low (as it would be if you're driving a 220v bulb with 110v), doesn't necessarily mean it's consuming the same proportion of electricity. The efficiency of a low-temp burning filament plummets, and nearly all energy is being converted to heat.

You're better off buying the CFLs that use ~20W and give you tons of light. CFLs typically have about a 10fold greater efficiency than standard halogen bulbs, and with your setup, probably closer to 100x. You can always buy a dimmer to reduce the output and electricity used.

[clickclickboom]

I use these bulbs for aesthetics to get the look of antique Edison bulb. Efficiency is not a great concern. I was just curious as to what happened to the wattage. I joke with friends that my house(inside and out) has 1400w worth of light bulbs running when I'm asleep.

[yakev724]

I like the look as well (in certain rooms), but unfortunately don't have the luxury. My desk lamp has a beanie stretched over the light surface end because the CFL bulb is too bright lol

..and the bulbs in my kitchen interfere with the TV remote, so when they're on and warmed up, the remote doesn't work. At all.

[Maestro]

okay, simple Electrical 101 lesson

V=I*R = 220V
W=V*I = 25W = 220*I therefor I = 25/220 or .114amps

given the above R = V/I = 220/.114 = 1936 Ohms

For 110V inputs the following is true

I = 110/1936 = 0.0568 amps
W = 110*0.0568 = 6.25 watts

It is putting out a lots less wattage, but as it was pointed out the resistance of the filament is dependent on how hot it gets and that is a function of input voltage so the resistance I calculated assume it is operating at the max temp. At lower voltage the resistance could be higher or lower, I do not remember which way it goes.

[jpsum]

Just put an amp meter on the damn thing already!

[jpsum]

Originally Posted by Maestro

okay, simple Electrical 101 lesson

V=I*R = 220V
W=V*I = 25W = 220*I therefor I = 25/220 or .114amps

given the above R = V/I = 220/.114 = 1936 Ohms

For 110V inputs the following is true

I = 110/1936 = 0.0568 amps
W = 110*0.0568 = 6.25 watts

It is putting out a lots less wattage, but as it was pointed out the resistance of the filament is dependent on how hot it gets and that is a function of input voltage so the resistance I calculated assume it is operating at the max temp. At at lower voltage the resistance could be higher or lower, I do not remember which way it goes.

Lower the voltage, higher the amp. Stun guns have super high voltage, but very little amp.

My guess with the 220v bulb is that he is probably using the same amount of ampage, if not more. The bulb does last longer at the expense of a dimmer bulb.

[yakev724]

Originally Posted by Maestro

okay, simple Electrical 101 lesson

V=I*R = 220V
W=V*I = 25W = 220*I therefor I = 25/220 or .114amps

given the above R = V/I = 220/.114 = 1936 Ohms

For 110V inputs the following is true

I = 110/1936 = 0.0568 amps
W = 110*0.0568 = 6.25 watts

It is putting out a lots less wattage, but as it was pointed out the resistance of the filament is dependent on how hot it gets and that is a function of input voltage so the resistance I calculated assume it is operating at the max temp. At at lower voltage the resistance could be higher or lower, I do not remember which way it goes.

Resistance of a cold filament would be significantly less, so it'll be eating more electricity, probably closer to 25W than to 6, but I can't back this up with anything more than an educated guess.

What's significant is that at that temp, the bulb is extremely inefficient, since output is exponentially proportional to temp.

[Maestro]

Let me put this way, I am en Electrical Engineer by education and by profession for a number of years so I am more right than wrong. In most applications the V and R in the equations is mostly constant it does not change for the most part. I know the filament R changes a bit as it heat up but not drastically, and with a light the Watt rating is based on when it equalizes, yes a bulb pulls more current when you first turns it one but quickly goes to it constant state.

So it pretty safe to assume in this case the R does not change whether you put 220V or 110V across it so the only thing changing is I (current). So I would say it drawing closer to 6W at 110 than it is 25W.

Also, keep in mind watt rating on the light is power is consumes are the rated input power, it has no real baring on how much light it outputs that is Lux rating which most people have no clue about. So my statement about putting out wattage was wrong but everyone says it this ways.

http://en.wikipedia.org/wiki/Lux

[Maestro]

ops double posting...

[yakev724]

Originally Posted by Maestro

I know the filament R changes a bit as it heat up but not drastically, and with a light the Watt rating is based on when it equalizes, yes a bulb pulls more current when you first turns it one but quickly goes to it constant state.

Noted, but don't you think it's possible that since he's never turning it on at it's rated voltage, it's possible that the resistance doesn't really stabilize (even after a long time) and nearly all the power is being converted to heat (more so than during proper operation)? Would be interesting to see the filament properties of reduced voltage, but regardless of the result, I think it's safe to say that CFLs are advantageous in nearly all situations

[jpsum]

again, OP needs to put an amp meter on the light and see.

[Maestro]

Originally Posted by yakev724

Noted, but don't you think it's possible that since he's never turning it on at it's rated voltage, it's possible that the resistance doesn't really stabilize (even after a long time) and nearly all the power is being converted to heat (more so than during proper operation)? Would be interesting to see the filament properties of reduced voltage, but regardless of the result, I think it's safe to say that CFLs are advantageous in nearly all situations

Yeah if the op was looking for efficiency, you are correct a CFL put out more LUX of light per consumed power, But as he said that is not what he is doing, it sounds like he is looking for the color yellow glow of the light than the hotter white blue glow you would get at the higher voltage.

Also, no mater the voltage you apply to the incandescent light over 90% of the power consumer is converted to heat. A CLF is about 4x as effecient so about 50% to 60% comes off as heat.

A little side affect I have notice at my house converting a number of light in the house to CFL or LED, my winter heating bill has increased. I notice it most in my home office, in the winter time I could sit in there all day without the heat coming on when I had incandescent lights, now the office never heats up, I have to run the furnace.

This is one of the things I do not think they factor in when they say yopu will save money. Yeah you save money because the lights use less power but at same time they also put out less heat so in cold weather you have to have the heat on as well as lights.

[yakev724]

Originally Posted by Maestro

Yeah if the op was looking for efficiency, you are correct a CFL put out more LUX of light per consumed power, But as he said that is not what he is doing, it sounds like he is looking for the color yellow glow of the light than the hotter white blue glow you would get at the higher voltage.

Also, no mater the voltage you apply to the incandescent light over 90% of the power consumer is converted to heat. A CLF is about 4x as effecient so about 50% to 60% comes off as heat.

A little side affect I have notice at my house covering a number of light in the house to CFL or LED, my winter heating bill has increased. I notice it most in my home office, in the winter time I could sit in there all day without the heat coming one when I had incandescent lights, now the office never heats up, I have to run the furnish.

This is one of the things I do not think they factor in when they say will save money. Yeah you save money because the lights use less power but at same time they also put out less heat so in cold weather you have to have the heat on as well as lights.

Interesting, something to consider. I think the heat would dissipate much better from bulbs scattered around than from traditional heaters. I stay warm with a wall-mounted plasma (which does use a good amount of power)

[clickclickboom]

Thanks for the education. I figured someone on here knew the answer.