High efficiency electrical heater claims

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  #1  
Old 09-19-11, 08:35 AM
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High efficiency electrical heater claims

I had a discussion with a friend yesterday about advertisements for various infrared quartz and other type heaters that imo are making outlandish claims of efficiency. It seems that at this time of year these advertisements pop up, many of them making claims of Ďrevolutionaryí discoveries in heating, capable of heating rooms/houses at a fraction of the cost of traditional heat sources.

Not withstanding the benefits of infrared to heat near-by objects, my argument as to why these heaters donít live up to their claim is the btu to wattage calculations. Specifically if an electrical device produces around 5000 btu then itís power requirement is around 1500 watts. Therefore my argument is that any device that consumes 1500 watts will produce approximately 5000 btuís and is no more efficient than a traditional baseboard heater of 5k watts. Adding a small fan to disperse the heat more evenly throughout a room would help, but that doesnít make the device any more efficient.

Am I right or wrong?
 
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Old 09-19-11, 10:42 AM
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You are correct. By definition one kilowatt equals 3,412 BTUs.
 
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Old 09-19-11, 10:45 AM
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You are correct. The manufacturer's claims of space heater efficiency are based on their assumption that you can turn down your central heating system and use the space heater to only heat the room you are sitting in, therefore saving energy overall compared to running the central heating system higher. To me it sounds like 100% BS.
 
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Old 09-19-11, 11:31 AM
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Originally Posted by ednu99 View Post
I had a discussion with a friend yesterday about advertisements for various infrared quartz and other type heaters that imo are making outlandish claims of efficiency. ...

Not withstanding the benefits of infrared to heat near-by objects, my argument as to why these heaters donít live up to their claim is the btu to wattage calculations. Specifically if an electrical device produces around 5000 btu then itís power requirement is around 1500 watts. Therefore my argument is that any device that consumes 1500 watts will produce approximately 5000 btuís and is no more efficient than a traditional baseboard heater of 5k watts. Adding a small fan to disperse the heat more evenly throughout a room would help, but that doesnít make the device any more efficient.

Am I right or wrong?
IR radiation does a spectacular job of NOT heating the air. It must first warm a solid body object that can then transfer the heat energy through conduction into the air. As a result, the air in the room(s) remains cold unless you really heat up your furniture which is a thoroughly inefficient way of heating your home. The wattage calculations are almost irrelevant when discussing IR heating units because of variations in the environments for what is being heated and the related (lack of) efficiencies to conduct that heat energy back into the air.

Think about standing in the sun on a cold day. You're warm until you walk into the shade. Same thing here. Once you move away from in front of the unit, you're gonna be cold.
 
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Old 09-19-11, 01:20 PM
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The shame is, IR heaters have their applications and which can result in lower heating costs. Why they have to make such exaggerated claims, I don't understand.

We have older homes in my area that cannot be fully heated in the winter. Even keeping the heat at a point that the pipes will not freeze is outrageously expensive, think $1,000 a week during a cold spell and that's with the stat set to 45į. Yet we need to keep those home owners, often the elderly, from freezing to death. Add a safe electric heater directly in front of them, or an electric blanket, and they will survive. In less desperate situations, the same principle applies, heat just the small space needed when you are there, otherwise keep the entire home as cool as possible.

I just don't know what is wrong with the truth.

Bud
 
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Old 09-19-11, 03:54 PM
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The truth won't sell as many heaters to the uneducated.

Electric heaters are 100% efficient. That means 100% of the electricity put into them is turned into heat. A fossil fuel heating appliance is less than 100%. That makes the electric heater sound cheap to operate, but it isn't because electricity is more expensive to start with.
 
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Old 09-19-11, 05:50 PM
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Electric heaters are 100% efficient. That means 100% of the electricity put into them is turned into heat. A fossil fuel heating appliance is less than 100%. That makes the electric heater sound cheap to operate, but it isn't because electricity is more expensive to start with.
The problem with electric is its generation isn't 100% efficient. Alot of energy is wasted in the form of heat and steam which is just blown into the air.

I'm going too off topic arent I?
 
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Old 09-19-11, 06:21 PM
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It's something like 40% efficient. There is a lot of loss through long distance transmission.
 
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Old 09-19-11, 07:23 PM
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There is a lot of loss through long distance transmission.
Not as much as you may think.

Transmission and distribution losses in the USA were estimated at 6.6% in 1997[10] and 6.5% in 2007.[10] In general, losses are estimated from the discrepancy between energy produced (as reported by power plants) and energy sold to end customers; the difference between what is produced and what is consumed constitute transmission and distribution losses.
Electric power transmission - Wikipedia, the free encyclopedia
 
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Old 09-19-11, 08:13 PM
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That's still a significant number, but not what I did think it was. I'm sure there is some theft of power in there as well.
 
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Old 09-20-11, 06:33 AM
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Originally Posted by Furd View Post
You are correct. By definition one kilowatt equals 3,412 BTUs.
kilowatt-hour, actually. KW is power, BTU is energy.
 
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Old 09-20-11, 08:49 AM
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Originally Posted by tldoug View Post
Think about standing in the sun on a cold day. You're warm until you walk into the shade. Same thing here. Once you move away from in front of the unit, you're gonna be cold.
Very good point. I've been in buildings where they located IR panels in drop ceilings. The panels would turn on when you turned on the lights. So, in the bathroom, if they put the panel over the toilet, you're warm while you're there. If they put it over the sink, you're warm there. But that's it. Move a foot away and you're cold.

The solution is to mount your IR panel on a robotic tracking system that follows you around all day. I suspect robots start at about $25,000.
 
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Old 09-20-11, 11:23 AM
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Not quite, Telecom guy. One kilowatt HOUR is equal to 3,412 BTUs PER HOUR. One kilowatt is equal to 3,412 BTUs. The time frame must match in both units.
 
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Old 09-20-11, 11:30 AM
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Drooplug and Casual Joe, the losses from long-distance transmission are quite low, probably less than 5%. The major cause of the difference between power generated and power sold is the power that is used internally by the utility and sometimes given away at no charge. Internal usage can be a significant amount, probably equal to the transmission losses.

The 40% figure is the overall thermal efficiency of a steam-electric generating facility. It is measuring the ultimate energy of the fuel (never achieved) compared to the energy of the electricity leaving the plant. There are LOTS of individual losses that contribute to this figure.
 
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Old 09-20-11, 12:59 PM
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It's also ignoring the fact that many steam plants do have productive uses for the still-pretty-hot steam after it's run through the turbine such as piping it to nearby industries or heating buildings in winter. So 60% of the energy isn't completely wasted, but it does not go into producing electricity.
 
  #16  
Old 09-20-11, 03:26 PM
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The usage of the term "BTU" can be confusing and is often misused. BTU, is the energy needed to raise a pound of water a degree F. Air conditioner people use the term incorrectly to indicate heating or cooling power, and when they do that they drop (incorrectly) the time units, typically, hours. ie; a 12,000 "BTU" air conditioner is actually 12,000 BTU/hour. see this: British thermal unit - Wikipedia, the free encyclopedia
 
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