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# Heater efficiency

ocalhoun
My landlord says that his 220 volt electric heater is 'more efficient' than my 110 volt electric heater.

--Not more efficient at moving heat around the room or anything; the two are basically identical except for the input voltage... they even have similar wattage. They are both oil-filled radiator designs.

Now, this offends my ideas about how thermodynamics works.
Sure, no machine can be 100% efficient... but I'm thinking that heaters are actually the exception to this rule.
Waste energy is given off as heat (or will eventually be converted to heat) -- for any other machine, this is indeed waste... but for a heater, that's the goal in the first place.

So, my questions are:
A) Is my landlord indeed ignorant to say that one electric heater is more efficient than another at producing heat?
B) Am I correct in saying that pretty much any electric heater is 100% efficient?
110 or 220 volts - Calculate watts generated: http://www.csgnetwork.com/ohmslaw2.html
100 percent efficient? As long as no fans or pump are involved. http://toad.net/~jsmeenen/electric.html
zaxacongrejo
Nothing in what concerns to energies as 100% efficiency
About the subject here my opinion you are both speaking of the same probably the 220v can get hot faster but I’m not sure.
Try to do this volts x amps 220v x amps will tell you the watts
johans
based on my knowledge 110 or 220 volts is totally different because 220 volts gives more faster and higher voltage and can define literally by its value while 110 volts are smaller.

in heater case the higher the voltage the more efficient volts. Well, if it comes to output measure it is just the same either 110 or 220 volts. lets say output Ampere in 110 is 5 ampere and in 220 volts is 5 ampere then it is the same out.

if the ampere changes of course the higher the ampere the effective it is either from 110 volts or 220 volts.

I hope that helps.
ocalhoun
 standready wrote: 110 or 220 volts - Calculate watts generated: http://www.csgnetwork.com/ohmslaw2.html

I've got an associate's in electronics... I think I can calculate wattage.
 Quote: 100 percent efficient? As long as no fans or pump are involved. http://toad.net/~jsmeenen/electric.html

Well, that's the closest thing here to an intelligent reply. The link you provided there actually has just what I was looking for.
(And confirms my suspicion that even fans or pumps don't decrease the heater's efficiency, because all that movement will be stopped by friction... turning into heat.)
Dennise
 Quote: So, my questions are: A) Is my landlord indeed ignorant to say that one electric heater is more efficient than another at producing heat? B) Am I correct in saying that pretty much any electric heater is 100% efficient?

A. Well yes - ideally - if you confine either heater to a small restricted space and measure the heat output in that space. But NO if you look at the big picture in a real world. Then, the 220V heater is (just slightly) more efficient. Here's why.

The 110v heater will of course draw more current (2X for the same wattage) than the 220V heater. But assuming the house feed wiring is one size for both heaters, then there will be more heat produced (i.e. lost) for the 110V heater in the feed wiring because of the greater 110V heater current flowing in the non-zero feed wiring resistance. It all depends on what you include in the calculation. If the 220V wiring is smaller than the 110V wiring, the overall efficiency calculation comparisons get more complex. Have you ever felt the supply cord connecting a heater to a wall outlet. Ofter these get quite warm, especially on cheaper heater units. Does this heat loss get included in the calculations?

B. Yes if you only include the space immediately surrounding the heaters and ignore heat losses in the feed wiring.
jajarvin
 Dennis wrote: The 110v heater will of course draw more current (2X for the same wattage) than the 220V heater.

The case is the opposite.

If the resistance of a heater is R then it takes from voltage 110V the following current I1:

I1 = 110V / R where as the same heater takes fom voltage 220V a greater current (2x) I2:

I2 = 220V / R
Dennise
Jajarvin, you have assumed the resistance in both heaters is the same .... R. This is not correct if both 110v and 220v heaters output the same heat.

For a 1,000W 110v heater. the resistance would be 12.1 ohms and the current = 9.09 amperes.

For a 1,000W 220v heater, the resistance would be 48.4 ohms and the current = 4.55 amperes.

The lower 220v heater current draw (4.55A vs. 9.09A) results in less electricity lost in the supply (house) wiring which makes the 220v heater slightly more efficient. This assumes the same supply wire size for both 110v and 220v heaters.
ocalhoun
 Dennise wrote: The 110v heater will of course draw more current (2X for the same wattage) than the 220V heater. But assuming the house feed wiring is one size for both heaters, then there will be more heat produced (i.e. lost) for the 110V heater in the feed wiring because of the greater 110V heater current flowing in the non-zero feed wiring resistance

Ah, good point there. (Though I'd only count wiring outside the house as actual loss, since heat generated inside the house still accomplishes the purpose.)

So, the loss from doubling the current passed through the feed wiring from the power meter to the house it is.
While that would be a very small difference, I'm afraid it does make my landlord technically correct.
Dennise
Correct .... ya got it!