240 volt versus 110 volt?

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  #1  
Old 01-26-05, 09:00 AM
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240 volt versus 110 volt?

I have 2 space heaters, one that plugs into a standard 110 volt outlet and draws 1500 watts. Then I just installed another one that runs on a 240 volt, 30 amp line that puts out 5600 watts. My question is, the guy in home depot was telling me something about how when you use 110 volt lines you are only really using half of the available power and throwing away the rest? He said that by using a 240volt line you are using the full power scale and getting the most bang for your buck?

so he was explaining to me that running the 240 volt heater won't actually cost that much more than running the 110 volt heater... is this true?

I am new to household electric..
 
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Old 01-26-05, 09:12 AM
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Where do these guys come up with this stuff?!?! This story goes around from time to time, but there is absolutely no truth to it. You get what you pay for. The power company and its meter are not that stupid.
 
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Old 01-26-05, 10:20 AM
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Please don't talk to the guys at Home Depot other than to ask questions about inventory.

Using a 240 volt heater won't actually cost ANY more than using a 110 volt heater. It takes the same amount of heat to maintain a temperature no matter how much voltage you apply to make it! Think of a wire like you would a water pipe. A 220 volt connection gives 2 pipes instead of one and makes it possible to get twice as much water in a given amount of time, but you still only pay for the total amount of water that's used.

Hope that helps.

Doug M.
 
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Old 01-26-05, 10:29 AM
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Saying that a 240-volt appliance is cheaper to run than a 120-volt appliance is like saying that it's cheaper to water your lawn with a 3/4" hose than it is with a 3/8" hose. The water costs the same per gallon no matter which hose you use.
 
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Old 01-26-05, 10:38 AM
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I might get this wrong, but the guy was telling me about how the AC sign wave goes... like if you look at an AC current it goes up and down in waves. He was saying that in 110volt, it's only using one side of the wave (lets for this example say the bottom of the wave), so in theory he was saying, you are wasting the top half of the wave so it's like for the same amount of electricity being pushed you are only taking advantage of half of it in 110volt.

so if you compare to 240volt, you are using both sides of the wave thus you are using the FULL energy being pushed down the line...

like I said, I don't know if he is right, he seemed like he knew a lot about electric but who knows..
 
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Old 01-26-05, 10:38 AM
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But John, I pay the gardner by the hour...

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Old 01-26-05, 10:45 AM
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This HD guy is really starting to scare me... Sign wave huh... Does he, by chance, have a bad case of acne? I know where he's getting this thought, but he doesn't know what he's talking about.

Doug M.
 
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Old 01-26-05, 10:45 AM
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The guy has a partial understanding and is using pseudo-science to come up with a completely bogus conclusion. He's convinced himself, and thus sounds convincing.

I don't know if he is right
Yes you do.

If you were to connect an oscilloscope up to either a 120-volt outlet or a 240-volt outlet, you would see a perfect sine wave in both cases. This "using one side of the wave" stuff is pure garbage.
 
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Old 01-26-05, 10:48 AM
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okay lets make this easy and ask this...

if using a 1500 watt (110 volt) heater on high and using a 5600 watt (240 volt) heater on high, which is more bang for your energy paying dollar?

do you get more heat output per dollar with the 5600 watt heater or not?
 
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Old 01-26-05, 10:48 AM
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John and Doug, those are great analogies. I work with some pretty bright non-electrical engineers, and it wasn't until I started comparing electricity to water delivery that I could get these guys to understand me. The only difference, I tell them, is that their "product" can be seen and mine cannot - unless there's a leak!

Squale - the utility company charges you for watts consumed in an hour. The wattage of heat required for the cubic feet of air in your room is just as Doug explained. If you ran that 1500 watt heater, at 110 volts, for one hour, the utility company will charge you 1.5 kilowatt hours. If you run that 5600 watt heater for 1 hour, the utility will charge you for 5.6 kilowatt hours. If the 1500 watt unit can't maintain the comfort level you want it's worth the extra money in your utility bill to use the 5600 watt unit. Also, the smaller unit may run continuously while the more powerful unit will likely cycle on and off and not be constantly spinning your meter. If the smaller one can maintain 72 degrees but must run continuously, and the 5600 watt unit cycles on and off to keep it at 72 degrees while cycling on and off, you will use the same amount of energy and which one you use doesn't matter. Your utility bill to heat that area to a constant 72 degrees will be the same in the end. But I would not expect that the 1500 watt unit can maintain 72 degrees in a 12 x 16 foot room with 8 foot ceilings.

Juice
 
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Old 01-26-05, 10:58 AM
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Originally Posted by John Nelson
This "using one side of the wave" stuff is pure garbage.
No it is not, it is known as a very cheap half wave rectifier with a bad cap.

Using half a sine wave is one way to get DC out of AC.

And to get technical, it actually saves you some small amount of pennies to run an appliance on 240 as opposed to 120. You all are correct that the load power is the same with either, but you forget that you also pay for the power that is lost in the wiring of your house. This power is equal to the current squared times the resistance of the wire. So if the current is half at 240, the power lost in the wire is one fourth of that at 120. Because (hopefully), the resistance is very small, this is a relatively small amount of power, but if you want to be technical, 240V does save money over 120.
 
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Old 01-26-05, 11:02 AM
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Heat per dollar is exactly the same with either heater. You should choose the heater that is most effective in providing the amount heat you need, distributes the heat well, and has the safety features you need. Operating cost is not a factor. Based on these other factors, but not on operating cost, most people choose 240-volt heaters for anything except localized heat for small areas for a limited amount of time and where constantly attended.
 
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Old 01-26-05, 11:06 AM
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Blizzard, I didn't say there was no such thing as half a sine wave. I only meant it had nothing at all to do with what we are discussing here. And the <0.1% extra efficiency of the 240-volt heater due to less voltage drop in the wiring is of course correct, but not generally worth mentioning.
 
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Old 01-26-05, 01:10 PM
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Originally Posted by John Nelson
Blizzard, I didn't say there was no such thing as half a sine wave.
Sorry, that is just my sad sense of humor.
 
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Old 01-26-05, 02:05 PM
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Actually, if most of the wiring is within the heated space of your house you don't lose the power dissipated in the wire due to voltage drop, it just heats up (very, very slightly) the rest of the house....
 
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Old 01-26-05, 02:08 PM
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well so we all know what I am talking about, this is the heater I have hooked up in my 2 car garage that is 24' wide x 20' long with I believe 8 or 9 foot ceilings..

http://www.grainger.com/Grainger/pro...541217&ccitem=

now if you look at the specs on this heater it says that while running at 240 volts it puts out 5600 watts and 19,110 BTU per hour using 23.3 amps

now here is a couple things I am trying to figure out..

1.) Since this heater is using 5.6 Kilo Watts per hour to run it, let's say I run it for 1 hour straight.... my electric company charges I believe .10 cents per kilo watt hour, so this heater would cost me $0.56 cents per hour to run (.10 x 5.6) .... is this correct? because to me, this sounds very cheap for a heater this big running on electric. I was comparing it to putting a propane wall heater in my garage and I would be paying like $2.50 a gallon of propane and I would think that it would burn at least 1 gallon an hour? so really I don't know which one is cheaper now...

2.) If you look further into the specs on this heater you will see that it is either a 240 volt or 208 volt heater depending on what you have in your local area. Now my house is only 2 years old but I am in a neighborhood that has been there much longer than the house. So how do I know if I have 240volts or actually 208 volts? Beause I really don't know if my heater is putting out the full 5600 watts (19,110 BTU) of if I am only getting 4200 watts (14,335 BTU)

3.) Does this heater sound to be the right size for my garage for temporay heating when I am working in there? I live in Northern New Jersey and this time of the year it is on average about 10 degrees outside and ranges anywheres from -10 thru 20 degrees outside all winter long. My garage being unheated and not the best insulated usually stays about 10 degrees warmer than the outside temperature... so I was wondering if I got enough heat...
haven't had time to really try it out for a while yet. I wonder how long it will take to bring my garage from like 20 degrees up to about 60 degrees..?
 
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Old 01-26-05, 02:42 PM
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John, this doesn't just go around, some people outright believe this. My old boss was one of them, he replaced everything he could with 220 equipment to 'save money because it was more effificent'. Our break room had a 5000btu 110 air conditioner, when it died we had to pull new wires and put a 220 12000btu unit in. I can get the room down to under 55degrees on high in the name of saving money. He did the same thing to our main office. Some people hear something like this and think its the next best thing since sliced bread. Listening to anything at a box store is just silly, its like asking a proctologist about your sore throat.
 
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Old 01-26-05, 03:16 PM
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1) The only valid comparison is how much heat you get for a buck. Comparing how much it costs per hour to operate is meaningless.

2) If you live in a house in the U.S., there's a 99.999% chance that you have 240, not 208. If you want to check, call your power company or use a voltmeter.

3) How much heat you need is a very complicated calculation, only properly done by an HVAC guy. It's especially complicated in a uninsulated or poorly insulated drafty garage with high ceilings. It also depends on how toasty you expect it to get. Do you work in the garage barefoot in your pajamas? Probably not. It also depends on whether you work primarily in one spot or move around a lot. If you work in one spot, you might get more benefit from those radiant heaters rather than one that heats up all the air in the whole garage. Try asking this question over in the heating forum. When all is said and done, some experimentation is probably necessary.
 
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Old 01-26-05, 04:15 PM
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its like asking a proctologist about your sore throat.
Run if you see him put on a glove!

Darn, John beat me to the reply button again. Let me add this

1) Your calculation for cost of electricity is correct, but your calculation for propane usage is not. A gallon of propane yields about 91,600 BTUs. A kilowatt of electricity yields about 3400 BTUs. So at the costs you gave Electricity is about $.000029 per BTU and propane about $.000027 per BTU. Close, but electricity is easier to get and safer to use.

3) There are many factors that have to be taken into consideration, including R-value of insulation, number of windows and outside wall exposure. You could post over on the heating and cooling forum, as John suggested, where some of the HVAC experts might be able to point you to a web site that allows you to plug in numbers and makes the calculations for you. My gut feel is that you're way under what you really need to keep the space at 60 in -20 weather, but you may have enough heat to keep your hands from going numb while changing your brake pads. If you used the 110 volt heater, you now have almost twice as much heat, almost twice as much comfort and almost twice as much cost so you can gauge your expectations accordingly.

Doug M.
 
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Old 01-26-05, 05:05 PM
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This one made me laugh.
 
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Old 01-26-05, 05:55 PM
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Look at it this way.

Your room is a 5 gallon bucket. You have 2 ways to fill it.
1/2" pipe with 15psi.
1" pipe with 30psi.
It will fill faster using the bigger pipe. But in the end you still spent the same using either pipe. You just filled the bucket faster using the 1" pipe.
 
  #22  
Old 01-27-05, 08:47 AM
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how do you figure? If you used the 110 volt heater, you now have almost twice as much heat, almost twice as much comfort and almost twice as much cost so you can gauge your expectations accordingly

I don't see how a 1500 watt 110 volt heater would give me twice the heat I am already getting from a 5600 watt 240volt heater?

Originally Posted by dougm
Run if you see him put on a glove!

Darn, John beat me to the reply button again. Let me add this

1) Your calculation for cost of electricity is correct, but your calculation for propane usage is not. A gallon of propane yields about 91,600 BTUs. A kilowatt of electricity yields about 3400 BTUs. So at the costs you gave Electricity is about $.000029 per BTU and propane about $.000027 per BTU. Close, but electricity is easier to get and safer to use.

3) There are many factors that have to be taken into consideration, including R-value of insulation, number of windows and outside wall exposure. You could post over on the heating and cooling forum, as John suggested, where some of the HVAC experts might be able to point you to a web site that allows you to plug in numbers and makes the calculations for you. My gut feel is that you're way under what you really need to keep the space at 60 in -20 weather, but you may have enough heat to keep your hands from going numb while changing your brake pads. If you used the 110 volt heater, you now have almost twice as much heat, almost twice as much comfort and almost twice as much cost so you can gauge your expectations accordingly.

Doug M.
 
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Old 01-27-05, 09:01 AM
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doug,
if electric and propane are that close in price to heat with, then why is it cheaper to heat my whole house with propane than it is to heat the whole house with electric?

where did you get these btu numbers from?
and how does this compare to natural gas and oil?


Originally Posted by dougm
Run if you see him put on a glove!

Darn, John beat me to the reply button again. Let me add this

1) Your calculation for cost of electricity is correct, but your calculation for propane usage is not. A gallon of propane yields about 91,600 BTUs. A kilowatt of electricity yields about 3400 BTUs. So at the costs you gave Electricity is about $.000029 per BTU and propane about $.000027 per BTU. Close, but electricity is easier to get and safer to use.

3) There are many factors that have to be taken into consideration, including R-value of insulation, number of windows and outside wall exposure. You could post over on the heating and cooling forum, as John suggested, where some of the HVAC experts might be able to point you to a web site that allows you to plug in numbers and makes the calculations for you. My gut feel is that you're way under what you really need to keep the space at 60 in -20 weather, but you may have enough heat to keep your hands from going numb while changing your brake pads. If you used the 110 volt heater, you now have almost twice as much heat, almost twice as much comfort and almost twice as much cost so you can gauge your expectations accordingly.

Doug M.
 
  #24  
Old 01-27-05, 09:59 AM
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Electrical energy may be converted to heat energy with nearly 100% efficiency by resistance heating.

1 kWh of energy is equal to 3412 BTU of energy.

1 gallon of propane will burn to produce approximately 91000 BTU of heat energy.

So for raw heat production, propane at $2.50 per gallon is approximately equal to electricity at 9 cents per kWh.

Electricity is 'higher grade' energy than thermal energy from burning fuel, and using a pure resistance heater is a pretty poor use of electricity. If you install a heat pump, then 1 kWh of electricity may be able to pump 7000 to 10000 BTU of heat into your heated space, cutting your electricity consumption to produce heat by 50-70%.

It is usually much cheaper to heat with fuel because resistance heating is such a poor use of resources, and fuel is usually much cheaper. Kerosene is about 135000 BTU per gallon, and costs less than $2 per gallon. But with fuel prices going up, heat pumps are looking more and more attractive.

-Jon
 
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Old 01-27-05, 10:10 AM
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so a heat pump is electric? I don't get what a heat pump actually does?
 
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Old 01-27-05, 10:14 AM
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why is using a pure resistance heater is a pretty poor use of electricity when above you say that Electrical energy may be converted to heat energy with nearly 100% efficiency by resistance heating? it sounds almost like first you say electrical energy is the most efficient and then you say it's very poor for heating.. so I am confused..?

is the Dayton heater that I have a pure resistance heater? I thought it just heated up the coil and then a fan blew the air over the coils to produce heat.. where does the resistance come in?

sorry for all the newbie questions.. lol
 
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Old 01-27-05, 10:25 AM
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Originally Posted by squale
so a heat pump is electric? I don't get what a heat pump actually does?
To make it simple, a heat pump is essentially an air conditioner running in reverse. Instead of removing heat from your house and putting it outdoors, it takes heat from the outdoor air and puts it in your house. Even though it may not feel like it to us, there is still latent heat available in cold winter air that the heat pump can use to create heat for your house.

The colder it gets the less efficiency it has until eventually it has to use electric heat strips to supply the heat. A lot of people hate heat pumps because the air they supply to the house just feels warm (or cold to some people) where as air from you furnace feels hot.
 
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Old 01-27-05, 10:46 AM
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Electric resistance heating is only 100% efficient--it only puts as much energy into your garage as it uses.

A heat pump is more than 100% efficient--it puts more energy into your garage than it uses because it is stealing energy from outside.

P.S. For you, this is just a theoretical question. A heat pump won't work for you because your winters are too cold.
 
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Old 01-27-05, 11:47 AM
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I guess that's why when I was looking at a bunch of houses to buy, I never saw one with a heat pump here in northern nj... everybody either as forced hot air via propane, oil or natural gas, baseboard hot water (like me) or electric heat. and those unfortunate to have none of the above usually use wood stoves or pellet stoves... I used to have a pellet stove and wow did that thing throw off some nice heat, but you do get some dust in the air and my wife has bad allergies so it doesn't help her much. She is doing much better now with the baseboard hot water fired off of propane in the new house..

I also have central air ducts in the ceiling and the central air unit is in the attic and the condenser is obviously outside, so I think I have a pretty good setup.. only thing better would be if I had natural gas available in my area but I don't.. so it was either dirty smelly oil or propane, I went with propane..
 
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Old 01-27-05, 12:03 PM
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I didn't phrase that correctly. Let me try again... If you are used to using the 110v heater (wasn't sure if you ever actually used a 110v heater or just looked at it at the store...), you now have, with the 220v heater, almost twice as much heat, almost twice as much comfort and almost twice as much cost.

Sorry about the confusion.

Doug M.
 
  #31  
Old 01-27-05, 12:18 PM
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actually I have almost 4x the heat with my 240v heater... it puts out 5600 watts (19,110 BTUs per hour), and the 110volt heaters only put out 1500 watts (about 5,000 BTUs per hour)
plus the 240volt heater has a much more powerful fan to more the hot air around better...

is there a direct translation between watts and BTUs per hour?

are BTU's always measured per hour? meaning if the heater is a 19,110 btu heater that means that if you run it straight for 1 full hour it will put out a total of 19,110 BTUs?

is this the same for all heat measurements? meaning any heating appliance is measured in the number of BTUs it puts out in 1 hour?

I think my propane boiler for my house is like 115,000 btus per hour or something..
 
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Old 01-27-05, 12:22 PM
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