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Cost to run central A/C
I'm trying to figure the cost of running the central AC in my house.
Inside was fairly easy, a 1/2hp fan motor. Outside the numbers on the plate from the factory are long gone. I found on the fan motor that it is 1/8hp. Now the compressor.... On it is listed the voltage but not the amps or watts but it does list the LRA (locked rotor amps) of 105.0 It is a Copeland CR38K6-PFV-370. I found this site but even this isn't very useful to me only giving me the RLA of 19. I read the RLA is "rated load amps" and does not mean "Running Load Amps". RLA being the most current it should draw under the harshest conditions. http://www.nordyne.com/literature/8569%20Compr.pdf |
Cost to run central A/C
Tony wrote: I'm trying to figure the cost of running the central AC in my house. Inside was fairly easy, a 1/2hp fan motor. Outside the numbers on the plate from the factory are long gone. I found on the fan motor that it is 1/8hp. Now the compressor.... On it is listed the voltage but not the amps or watts but it does list the LRA (locked rotor amps) of 105.0 It is a Copeland CR38K6-PFV-370. I found this site but even this isn't very useful to me only giving me the RLA of 19. I read the RLA is "rated load amps" and does not mean "Running Load Amps". RLA being the most current it should draw under the harshest conditions. http://www.nordyne.com/literature/8569%20Compr.pdf None of those numbers are of much use in calculating operating costs since none of those items runs 24x7. All those numbers will tell you is how big a circuit the items require. |
Cost to run central A/C
Pete C. wrote:
Tony wrote: I'm trying to figure the cost of running the central AC in my house. Inside was fairly easy, a 1/2hp fan motor. Outside the numbers on the plate from the factory are long gone. I found on the fan motor that it is 1/8hp. Now the compressor.... On it is listed the voltage but not the amps or watts but it does list the LRA (locked rotor amps) of 105.0 It is a Copeland CR38K6-PFV-370. I found this site but even this isn't very useful to me only giving me the RLA of 19. I read the RLA is "rated load amps" and does not mean "Running Load Amps". RLA being the most current it should draw under the harshest conditions. http://www.nordyne.com/literature/8569%20Compr.pdf None of those numbers are of much use in calculating operating costs since none of those items runs 24x7. All those numbers will tell you is how big a circuit the items require. I've kept track a few times and during a hot 90F days with lows of 70F it runs between 8 to 10 hours/day. That may be a low estimate, I'm going to put a time meter on it for a much more accurate figure. |
Cost to run central A/C
On Jun 26, 12:31*pm, Tony wrote:
I'm trying to figure the cost of running the central AC in my house. Inside was fairly easy, a 1/2hp fan motor. *Outside the numbers on the plate from the factory are long gone. *I found on the fan motor that it is 1/8hp. *Now the compressor.... *On it is listed the voltage but not the amps or watts but it does list the LRA (locked rotor amps) of 105.0 * It is a Copeland CR38K6-PFV-370. I found this site but even this isn't very useful to me only giving me the RLA of 19. *I read the RLA is "rated load amps" and does not mean "Running Load Amps". *RLA being the most current it should draw under the harshest conditions. http://www.nordyne.com/literature/8569%20Compr.pdf Time wont do it nor will ratings on the fan or compressor take into account the controll board, other components in the condensor and how age and condition of unit play a big part in total useage. Use a clamp on amp meter at the circuit panel, an old fan or compressor near failure can use alot more power, air restrictions you are unaware of will also affect everything. |
Cost to run central A/C
Tony wrote: Pete C. wrote: Tony wrote: I'm trying to figure the cost of running the central AC in my house. Inside was fairly easy, a 1/2hp fan motor. Outside the numbers on the plate from the factory are long gone. I found on the fan motor that it is 1/8hp. Now the compressor.... On it is listed the voltage but not the amps or watts but it does list the LRA (locked rotor amps) of 105.0 It is a Copeland CR38K6-PFV-370. I found this site but even this isn't very useful to me only giving me the RLA of 19. I read the RLA is "rated load amps" and does not mean "Running Load Amps". RLA being the most current it should draw under the harshest conditions. http://www.nordyne.com/literature/8569%20Compr.pdf None of those numbers are of much use in calculating operating costs since none of those items runs 24x7. All those numbers will tell you is how big a circuit the items require. I've kept track a few times and during a hot 90F days with lows of 70F it runs between 8 to 10 hours/day. That may be a low estimate, I'm going to put a time meter on it for a much more accurate figure. Depending on the system, even a run timer may not quite get you accurate numbers. On my HVAC the air handler has a 90 second post run after the compressor turns off in order to increase efficiency. |
Cost to run central A/C
In article ,
Tony wrote: I'm trying to figure the cost of running the central AC in my house. Inside was fairly easy, a 1/2hp fan motor. Outside the numbers on the plate from the factory are long gone. I found on the fan motor that it is 1/8hp. Now the compressor.... On it is listed the voltage but not the amps or watts but it does list the LRA (locked rotor amps) of 105.0 It is a Copeland CR38K6-PFV-370. I found this site but even this isn't very useful to me only giving me the RLA of 19. I read the RLA is "rated load amps" and does not mean "Running Load Amps". RLA being the most current it should draw under the harshest conditions. http://www.nordyne.com/literature/8569%20Compr.pdf Now that my g.f. has a smart meter, she can go online with her iphone and see a little graph that shows her electricity usage doubling during my visits. But you could do that yourself with any meter. Just run the A/C normally one week, and not at all the next. Compare results and you've got your answer. |
Cost to run central A/C
In article
, Smitty Two wrote: Now that my g.f. has a smart meter, she can go online with her iphone and see a little graph that shows her electricity usage doubling during my visits. But you could do that yourself with any meter. Just run the A/C normally one week, and not at all the next. Compare results and you've got your answer. Depends on the weeks. This week, we had most days high 80s to mid-90s. Next week the forecast is calling for at least 3 days with highs in the mid 70s to low 80s. So just turning or now tells you next nothing by itself. -- I want to find a voracious, small-minded predator and name it after the IRS. Robert Bakker, paleontologist |
Cost to run central A/C
On 6/26/2010 1:31 PM, Tony wrote:
I'm trying to figure the cost of running the central AC in my house. Inside was fairly easy, a 1/2hp fan motor. Outside the numbers on the plate from the factory are long gone. I found on the fan motor that it is 1/8hp. Now the compressor.... On it is listed the voltage but not the amps or watts but it does list the LRA (locked rotor amps) of 105.0 It is a Copeland CR38K6-PFV-370. I found this site but even this isn't very useful to me only giving me the RLA of 19. I read the RLA is "rated load amps" and does not mean "Running Load Amps". RLA being the most current it should draw under the harshest conditions. http://www.nordyne.com/literature/8569%20Compr.pdf The best would be to compare the electric meter with the unit running and not running. This way you will have actual watt-hours and you don't have to think of things like power factor, etc. But, it will change depending on temperature. And the run time will vary when the temperatures are cooler than when it is just plain hot outside. |
Cost to run central A/C
ultimately is the comfort you gain worth the larger electric bill?
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Cost to run central A/C
"Art Todesco" wrote http://www.nordyne.com/literature/8569%20Compr.pdf The best would be to compare the electric meter with the unit running and not running. This way you will have actual watt-hours and you don't have to think of things like power factor, etc. But, it will change depending on temperature. And the run time will vary when the temperatures are cooler than when it is just plain hot outside. Many electric bills give a 13 month use history. Mine even gives the average temperature for the month. Look at months like April and October when neither heat or AC is used much and compare to July and August and you get a pretty good idea. Aside from that, the only accurate method is a recording ammeter over time. |
Cost to run central A/C
Ed Pawlowski wrote:
"Art Todesco" wrote http://www.nordyne.com/literature/8569%20Compr.pdf The best would be to compare the electric meter with the unit running and not running. This way you will have actual watt-hours and you don't have to think of things like power factor, etc. But, it will change depending on temperature. And the run time will vary when the temperatures are cooler than when it is just plain hot outside. Many electric bills give a 13 month use history. Mine even gives the average temperature for the month. Look at months like April and October when neither heat or AC is used much and compare to July and August and you get a pretty good idea. Aside from that, the only accurate method is a recording ammeter over time. I think you mean a recording watt-meter. Amps don't account for power factor. |
Cost to run central A/C
"Tony" wrote in message
I'm trying to figure the cost of running the central AC in my house. If your heating is other than electric, then the cost is the difference in your electric bill from the winter to the summer. Or if there is a month in the spring when you don't use heating or A/C, then the difference in the electric bill from that month and a summer month. Hint: If you get a couple of window air conditioners and just cool the room(s) you are using, the cost will be lower. So just cool the living room during the day and just cool the bedroom at night. If you have 6 kids and 7 bedrooms, then not much savings of course! |
Cost to run central A/C
"cjt" wrote I think you mean a recording watt-meter. Amps don't account for power factor. Correct. I was first thinking Amprobe and doing the math yourself but that does not take time run into consideration. |
Cost to run central A/C
A couple of years ago, I hooked up an amprobe to my 3 ton carrier unit
outside and it read 16 amps (220V). My inside fan blower I think used 5 amps (120V). So that's about 4,120 watts total full load. Keep in mind I usually keep my inside fan on continuosly, and my outside unit cycles on and off throughout the day. |
Cost to run central A/C
On Jun 26, 11:29*pm, Mikepier wrote:
A couple of years ago, I hooked up an amprobe to my 3 ton carrier unit outside and it read 16 amps (220V). My inside fan blower I think used 5 amps (120V). So that's about 4,120 watts total full load. *Keep in mind I usually keep my *inside fan on continuosly, and my outside unit cycles on and off throughout the day. Find an old mechnical clock that has time and date. Those ones with the litte flip numbers work well. Set it to 1/1/2000 midnight and hook it into the blower circuit. At the end of a month you'll have the number of days and hours the unit ran. You could also buy an old meter and run a circuit through it. You'll need a subpanel though. |
Cost to run central A/C
Pete C. wrote:
Tony wrote: Pete C. wrote: Tony wrote: I'm trying to figure the cost of running the central AC in my house. Inside was fairly easy, a 1/2hp fan motor. Outside the numbers on the plate from the factory are long gone. I found on the fan motor that it is 1/8hp. Now the compressor.... On it is listed the voltage but not the amps or watts but it does list the LRA (locked rotor amps) of 105.0 It is a Copeland CR38K6-PFV-370. I found this site but even this isn't very useful to me only giving me the RLA of 19. I read the RLA is "rated load amps" and does not mean "Running Load Amps". RLA being the most current it should draw under the harshest conditions. http://www.nordyne.com/literature/8569%20Compr.pdf None of those numbers are of much use in calculating operating costs since none of those items runs 24x7. All those numbers will tell you is how big a circuit the items require. I've kept track a few times and during a hot 90F days with lows of 70F it runs between 8 to 10 hours/day. That may be a low estimate, I'm going to put a time meter on it for a much more accurate figure. Depending on the system, even a run timer may not quite get you accurate numbers. On my HVAC the air handler has a 90 second post run after the compressor turns off in order to increase efficiency. No delays here. Anyway that doesn't sound like it would increase efficiency much, if any. I wouldn't like it blowing all that moisture from the evaporator back into the house again as it warms up. If it's cold when it turns off as it warms up it is still taking heat away from what ever is around it. And if it doesn't cool off much in between cycles, then it blows cooler air faster when it kicks on again. |
Cost to run central A/C
Art Todesco wrote:
On 6/26/2010 1:31 PM, Tony wrote: I'm trying to figure the cost of running the central AC in my house. Inside was fairly easy, a 1/2hp fan motor. Outside the numbers on the plate from the factory are long gone. I found on the fan motor that it is 1/8hp. Now the compressor.... On it is listed the voltage but not the amps or watts but it does list the LRA (locked rotor amps) of 105.0 It is a Copeland CR38K6-PFV-370. I found this site but even this isn't very useful to me only giving me the RLA of 19. I read the RLA is "rated load amps" and does not mean "Running Load Amps". RLA being the most current it should draw under the harshest conditions. http://www.nordyne.com/literature/8569%20Compr.pdf The best would be to compare the electric meter with the unit running and not running. This way you will have actual watt-hours and you don't have to think of things like power factor, etc. But, it will change depending on temperature. And the run time will vary when the temperatures are cooler than when it is just plain hot outside. That is very difficult with the newer digital electronic meter I have and the way it's set up. With it on a current transformer the meter hardly moves at all. The readings have to be multiplied by 20 for the actual usage. |
Cost to run central A/C
On Jun 27, 10:21*am, Chief Two Eagles wrote:
On Sat, 26 Jun 2010 13:31:37 -0400, Tony wrote: I'm trying to figure the cost of running the central AC in my house. Run it one month and then look at your electric bill. I see two approaches. For the macro view, as per the above, just comparing electric bills for summer with months in Spring or Fall with no AC or electric heat use would give a decent approximation. My utility bills show usage by month over the last year. I can easily see the effects of running the AC. Of course, if you had some other seasonal load, like pool pumps, etc, that could complicate things. For the micro view, as someone else suggested, record the electric meter for a time period on a day with no usage and then do the same with the AC on. |
Cost to run central A/C
Van Chocstraw wrote:
On Sat, 26 Jun 2010 13:31:37 -0400, Tony wrote: I'm trying to figure the cost of running the central AC in my house. Inside was fairly easy, a 1/2hp fan motor. Outside the numbers on the plate from the factory are long gone. I found on the fan motor that it is 1/8hp. Now the compressor.... On it is listed the voltage but not the amps or watts but it does list the LRA (locked rotor amps) of 105.0 It is a Copeland CR38K6-PFV-370. I found this site but even this isn't very useful to me only giving me the RLA of 19. I read the RLA is "rated load amps" and does not mean "Running Load Amps". RLA being the most current it should draw under the harshest conditions. http://www.nordyne.com/literature/8569%20Compr.pdf Best method. After they read the meter start using it for a month. Next time they read the meter, stop using it for a month until the next reading. They usually read it the same day of the month. Take it your self to make sure they are not estimating your bill and the reading is actual. You could also take your own reading daily and run it one day and not the next to get an idea of daily usage. Using stamped values and ideal math is not accurate and won't count load, wear, age and your comfortable temperature setting. You can also get an amp clamp and check one leg of the supply power from the box which will vary when the fan/ compressor cycle on/off. (Is the inside fan on the same circuit?) I can guess the date they read the meter give or take a day or two. They read it from their office, no more meter man. Besides, I think I'd die without AC for a day. Also, with my meter I could be off almost 20 kwh's a day without knowing it. My meter reading must be multiplied by 20 for actual kwh's. |
Cost to run central A/C
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Cost to run central A/C
Bill wrote:
"Tony" wrote in message I'm trying to figure the cost of running the central AC in my house. If your heating is other than electric, then the cost is the difference in your electric bill from the winter to the summer. Or if there is a month in the spring when you don't use heating or A/C, then the difference in the electric bill from that month and a summer month. Hint: If you get a couple of window air conditioners and just cool the room(s) you are using, the cost will be lower. So just cool the living room during the day and just cool the bedroom at night. If you have 6 kids and 7 bedrooms, then not much savings of course! That's exactly what I getting at. I'm almost positive it costs less to run 1 or 2 8,000 BTu window units than the central ac, even if I close off the rooms not being used. I suppose if I compared oranges to oranges and converted both central and window rattler to a basic BTU's/watt that would be very helpful, but I still need the specs on my compressor. |
Cost to run central A/C
Tony wrote:
Bill wrote: "Tony" wrote in message I'm trying to figure the cost of running the central AC in my house. If your heating is other than electric, then the cost is the difference in your electric bill from the winter to the summer. Or if there is a month in the spring when you don't use heating or A/C, then the difference in the electric bill from that month and a summer month. Hint: If you get a couple of window air conditioners and just cool the room(s) you are using, the cost will be lower. So just cool the living room during the day and just cool the bedroom at night. If you have 6 kids and 7 bedrooms, then not much savings of course! That's exactly what I getting at. I'm almost positive it costs less to run 1 or 2 8,000 BTu window units than the central ac, even if I close off the rooms not being used. I suppose if I compared oranges to oranges and converted both central and window rattler to a basic BTU's/watt that would be very helpful, but I still need the specs on my compressor. Have you sought help from your electric company? |
Cost to run central A/C
"LouB" wrote in message ... Tony wrote: Bill wrote: "Tony" wrote in message I'm trying to figure the cost of running the central AC in my house. If your heating is other than electric, then the cost is the difference in your electric bill from the winter to the summer. Or if there is a month in the spring when you don't use heating or A/C, then the difference in the electric bill from that month and a summer month. Hint: If you get a couple of window air conditioners and just cool the room(s) you are using, the cost will be lower. So just cool the living room during the day and just cool the bedroom at night. If you have 6 kids and 7 bedrooms, then not much savings of course! That's exactly what I getting at. I'm almost positive it costs less to run 1 or 2 8,000 BTu window units than the central ac, even if I close off the rooms not being used. I suppose if I compared oranges to oranges and converted both central and window rattler to a basic BTU's/watt that would be very helpful, but I still need the specs on my compressor. Have you sought help from your electric company? Have you looked on your bill and read the $/kwh? Compared the chart for month to month, and this year vs. last year comparisons? AC, in my estimation, has to do with keeping things cool. Once a room is cool, it takes less power to keep it cool than to cool it down from warm. With central units, they will do this better than room units that have to cool a warm room. Up. Down. Up. Down. But, then, the only way you find out is to install central, and do a post mortem analysis. Sometimes a large central AC won't have to work as hard as several smaller ones. But then, there's the thing of cooling unused space ......... It's hard to say. Steve visit my blog at http://cabgbypasssurgery.com watch for the book A fool shows his annoyance at once, but a prudent man overlooks an insult. |
Cost to run central A/C
LouB wrote:
Tony wrote: Bill wrote: "Tony" wrote in message I'm trying to figure the cost of running the central AC in my house. If your heating is other than electric, then the cost is the difference in your electric bill from the winter to the summer. Or if there is a month in the spring when you don't use heating or A/C, then the difference in the electric bill from that month and a summer month. Hint: If you get a couple of window air conditioners and just cool the room(s) you are using, the cost will be lower. So just cool the living room during the day and just cool the bedroom at night. If you have 6 kids and 7 bedrooms, then not much savings of course! That's exactly what I getting at. I'm almost positive it costs less to run 1 or 2 8,000 BTu window units than the central ac, even if I close off the rooms not being used. I suppose if I compared oranges to oranges and converted both central and window rattler to a basic BTU's/watt that would be very helpful, but I still need the specs on my compressor. Have you sought help from your electric company? I don't see how they can help, what kind of help would I be seeking? |
Cost to run central A/C
Tony wrote:
LouB wrote: Tony wrote: Bill wrote: "Tony" wrote in message I'm trying to figure the cost of running the central AC in my house. If your heating is other than electric, then the cost is the difference in your electric bill from the winter to the summer. Or if there is a month in the spring when you don't use heating or A/C, then the difference in the electric bill from that month and a summer month. Hint: If you get a couple of window air conditioners and just cool the room(s) you are using, the cost will be lower. So just cool the living room during the day and just cool the bedroom at night. If you have 6 kids and 7 bedrooms, then not much savings of course! That's exactly what I getting at. I'm almost positive it costs less to run 1 or 2 8,000 BTu window units than the central ac, even if I close off the rooms not being used. I suppose if I compared oranges to oranges and converted both central and window rattler to a basic BTU's/watt that would be very helpful, but I still need the specs on my compressor. Have you sought help from your electric company? I don't see how they can help, what kind of help would I be seeking? Part of their biz need is estimating electric usage. Its not going to cost anything to ask so why not? Also, tried google? Here is a start: http://www.google.com/search?sourcei...s+window+units which got About 396,000 results (0.35 seconds) |
Cost to run central A/C
Steve B wrote:
"LouB" wrote in message ... Tony wrote: Bill wrote: "Tony" wrote in message I'm trying to figure the cost of running the central AC in my house. If your heating is other than electric, then the cost is the difference in your electric bill from the winter to the summer. Or if there is a month in the spring when you don't use heating or A/C, then the difference in the electric bill from that month and a summer month. Hint: If you get a couple of window air conditioners and just cool the room(s) you are using, the cost will be lower. So just cool the living room during the day and just cool the bedroom at night. If you have 6 kids and 7 bedrooms, then not much savings of course! That's exactly what I getting at. I'm almost positive it costs less to run 1 or 2 8,000 BTu window units than the central ac, even if I close off the rooms not being used. I suppose if I compared oranges to oranges and converted both central and window rattler to a basic BTU's/watt that would be very helpful, but I still need the specs on my compressor. Have you sought help from your electric company? Have you looked on your bill and read the $/kwh? Compared the chart for month to month, and this year vs. last year comparisons? Yes. But comparing last years to this years has too many variables. AC, in my estimation, has to do with keeping things cool. Once a room is cool, it takes less power to keep it cool than to cool it down from warm. I'm with you there. With central units, they will do this better than room units that have to cool a warm room. Up. Down. Up. Down. No up down up down here. In this 93F weather the little 8000 BTU unit runs on high 24/7 unless it gets too cool, then I turn it down. Cycling it makes it less efficient. But, then, the only way you find out is to install central, and do a post mortem analysis. I have central. I believe it costs much more to operate than a window unit or two, but it's hard to say without the right numbers. Right now I have one 8000 BTU unit and one fan to circulate the air. Running it 24/7 30 days would cost me less than $60. It never runs all night so it's maybe $45-$50 a month to cool 960 sq ft. Forgot the fan to circulate the air, add about $4. per month. Sometimes a large central AC won't have to work as hard as several smaller ones. But then, there's the thing of cooling unused space ......... It's hard to say. I always considered "work as hard" an odd expression in this context. I had a Fedders, maybe 7000 btu run pracically 24/7 each summer for 15 years and it never stopped working. I left it at my old house because it wasn't nearly as efficient as the newer ones. |
Cost to run central A/C
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Cost to run central A/C
"Tony" wrote in message ... Steve B wrote: "LouB" wrote in message ... Tony wrote: Bill wrote: "Tony" wrote in message I'm trying to figure the cost of running the central AC in my house. If your heating is other than electric, then the cost is the difference in your electric bill from the winter to the summer. Or if there is a month in the spring when you don't use heating or A/C, then the difference in the electric bill from that month and a summer month. Hint: If you get a couple of window air conditioners and just cool the room(s) you are using, the cost will be lower. So just cool the living room during the day and just cool the bedroom at night. If you have 6 kids and 7 bedrooms, then not much savings of course! That's exactly what I getting at. I'm almost positive it costs less to run 1 or 2 8,000 BTu window units than the central ac, even if I close off the rooms not being used. I suppose if I compared oranges to oranges and converted both central and window rattler to a basic BTU's/watt that would be very helpful, but I still need the specs on my compressor. Have you sought help from your electric company? Have you looked on your bill and read the $/kwh? Compared the chart for month to month, and this year vs. last year comparisons? Yes. But comparing last years to this years has too many variables. AC, in my estimation, has to do with keeping things cool. Once a room is cool, it takes less power to keep it cool than to cool it down from warm. I'm with you there. With central units, they will do this better than room units that have to cool a warm room. Up. Down. Up. Down. No up down up down here. In this 93F weather the little 8000 BTU unit runs on high 24/7 unless it gets too cool, then I turn it down. Cycling it makes it less efficient. But, then, the only way you find out is to install central, and do a post mortem analysis. I have central. I believe it costs much more to operate than a window unit or two, but it's hard to say without the right numbers. Right now I have one 8000 BTU unit and one fan to circulate the air. Running it 24/7 30 days would cost me less than $60. It never runs all night so it's maybe $45-$50 a month to cool 960 sq ft. Forgot the fan to circulate the air, add about $4. per month. Sometimes a large central AC won't have to work as hard as several smaller ones. But then, there's the thing of cooling unused space ......... It's hard to say. I always considered "work as hard" an odd expression in this context. I had a Fedders, maybe 7000 btu run pracically 24/7 each summer for 15 years and it never stopped working. I left it at my old house because it wasn't nearly as efficient as the newer ones. But as you say, there are so many variables ...... insulation, reflectivity of roof, roof venting, single or dual pane windows, airtightness of the structure, even natural shade tree placement. You have asked a complicated question with no answers, and are shooting down people who are answering you. If you know all these things, just go ahead and do whatever it is you were going to do from the get go. Unless it is new construction where you can control the variables, you're pretty much stuck with a WYSIWYG situation. Steve visit my blog at http://cabgbypasssurgery.com watch for the book A fool shows his annoyance at once, but a prudent man overlooks an insult. |
Cost to run central A/C
The real factors are how clean the units are, and what type of
compressor. Rotary scroll is far more efficient than an old piston compressor. I've seen outdoor AC unit drawing about 4.5 amps at 220 volt. (2 or 2.5 ton, can't remember). Rotary scroll compressor. Dirty units draw a lot more power. -- Christopher A. Young Learn more about Jesus www.lds.org .. "Tony" wrote in message ... I want to compare what 1 or 2 8,000 BTU window units use compared to the central AC. I'm almost positive the window units are much more energy efficient than the central air. |
Cost to run central A/C
Steve B wrote:
"Tony" wrote in message ... Steve B wrote: "LouB" wrote in message ... Tony wrote: Bill wrote: "Tony" wrote in message I'm trying to figure the cost of running the central AC in my house. If your heating is other than electric, then the cost is the difference in your electric bill from the winter to the summer. Or if there is a month in the spring when you don't use heating or A/C, then the difference in the electric bill from that month and a summer month. Hint: If you get a couple of window air conditioners and just cool the room(s) you are using, the cost will be lower. So just cool the living room during the day and just cool the bedroom at night. If you have 6 kids and 7 bedrooms, then not much savings of course! That's exactly what I getting at. I'm almost positive it costs less to run 1 or 2 8,000 BTu window units than the central ac, even if I close off the rooms not being used. I suppose if I compared oranges to oranges and converted both central and window rattler to a basic BTU's/watt that would be very helpful, but I still need the specs on my compressor. Have you sought help from your electric company? Have you looked on your bill and read the $/kwh? Compared the chart for month to month, and this year vs. last year comparisons? Yes. But comparing last years to this years has too many variables. AC, in my estimation, has to do with keeping things cool. Once a room is cool, it takes less power to keep it cool than to cool it down from warm. I'm with you there. With central units, they will do this better than room units that have to cool a warm room. Up. Down. Up. Down. No up down up down here. In this 93F weather the little 8000 BTU unit runs on high 24/7 unless it gets too cool, then I turn it down. Cycling it makes it less efficient. But, then, the only way you find out is to install central, and do a post mortem analysis. I have central. I believe it costs much more to operate than a window unit or two, but it's hard to say without the right numbers. Right now I have one 8000 BTU unit and one fan to circulate the air. Running it 24/7 30 days would cost me less than $60. It never runs all night so it's maybe $45-$50 a month to cool 960 sq ft. Forgot the fan to circulate the air, add about $4. per month. Sometimes a large central AC won't have to work as hard as several smaller ones. But then, there's the thing of cooling unused space ......... It's hard to say. I always considered "work as hard" an odd expression in this context. I had a Fedders, maybe 7000 btu run pracically 24/7 each summer for 15 years and it never stopped working. I left it at my old house because it wasn't nearly as efficient as the newer ones. But as you say, there are so many variables ...... insulation, reflectivity of roof, roof venting, single or dual pane windows, airtightness of the structure, even natural shade tree placement. No wonder you say it's complicated! I'm talking about using the same house for both *tests*, factoring in the weathers "cooling degree days". You have asked a complicated question with no answers, I didn't think my question was so complicated. What is the rated current draw on the compressor I listed? That's all. It seemed like somewhere there would be an easy answer, another web page maybe? I guess not. and are shooting down people who are answering you. If you know all these things, just go ahead and do whatever it is you were going to do from the get go. I'm trying to use the abilities I have to do a simple comparison. Using my electric companies meter isn't very accurate as I explained. It's presision is +/- 19Kwh. |
Cost to run central A/C
On Jun 28, 12:39*pm, Tony wrote:
Steve B wrote: "Tony" wrote in message ... Steve B wrote: "LouB" wrote in message ... Tony wrote: Bill wrote: "Tony" *wrote in message I'm trying to figure the cost of running the central AC in my house. If your heating is other than electric, then the cost is the difference in your electric bill from the winter to the summer. Or if there is a month in the spring when you don't use heating or A/C, then the difference in the electric bill from that month and a summer month. Hint: If you get a couple of window air conditioners and just cool the room(s) you are using, the cost will be lower. So just cool the living room during the day and just cool the bedroom at night. If you have 6 kids and 7 bedrooms, then not much savings of course! That's exactly what I getting at. *I'm almost positive it costs less to run 1 or 2 8,000 BTu window units than the central ac, even if I close off the rooms not being used. I suppose if I compared oranges to oranges and converted both central and window rattler to a basic BTU's/watt that would be very helpful, but I still need the specs on my compressor. Have you sought help from your electric company? Have you looked on your bill and read the $/kwh? *Compared the chart for month to month, and this year vs. last year comparisons? Yes. *But comparing last years to this years has too many variables. AC, in my estimation, has to do with keeping things cool. *Once a room is cool, it takes less power to keep it cool than to cool it down from warm. I'm with you there. With central units, they will do this better than room units that have to cool a warm room. *Up. *Down. *Up. *Down. No up down up down here. *In this 93F weather the little 8000 BTU unit runs on high 24/7 unless it gets too cool, then I turn it down. *Cycling it makes it less efficient. But, then, the only way you find out is to install central, and do a post mortem analysis. I have central. *I believe it costs much more to operate than a window unit or two, but it's hard to say without the right numbers. Right now I have one 8000 BTU unit and one fan to circulate the air. Running it 24/7 30 days would cost me less than $60. *It never runs all night so it's maybe $45-$50 a month to cool 960 sq ft. *Forgot the fan to circulate the air, add about $4. per month. Sometimes a large central AC won't have to work as hard as several smaller ones. *But then, there's the thing of cooling unused space ......... *It's hard to say. I always considered "work as hard" an odd expression in this context. *I had a Fedders, maybe 7000 btu run pracically 24/7 each summer for 15 years and it never stopped working. *I left it at my old house because it wasn't nearly as efficient as the newer ones. But as you say, there are so many variables ...... insulation, reflectivity of roof, roof venting, single or dual pane windows, airtightness of the structure, even natural shade tree placement. No wonder you say it's complicated! *I'm talking about using the same house for both *tests*, factoring in the weathers "cooling degree days". *You have asked a complicated question with no answers, I didn't think my question was so complicated. What is the rated current draw on the compressor I listed? *That's all. It seemed like somewhere there would be an easy answer, another web page maybe? *I guess not. The answer as to how many amps the compressor is rated out may not be complicated, but it also doesn't answer the question you are seeking, which is how much it cost to run your AC. If you want to know how many amps the compressor is actually drawing, just buy a cheap clamp-on amp meter from HarborFreight or similar. They have them for around $12. But that leaves out power factor and how much the rest of the system, eg blower is using. As I and others suggested, why can't you turn off any loads that might come on, eg electric water heater, attic fan. refrigerator, etc, then run the house for a couple hours of continuos AC and a couple hours without AC and record the electric meter readings. That will give you how many Kwh it takes to run and you'll be way ahead of where you would be with the amp rating of the compressor. * and are shooting down people who are answering you. *If you know all these things, just go ahead and do whatever it is you were going to do from the get go. I'm trying to use the abilities I have to do a simple comparison. *Using my electric companies meter isn't very accurate as I explained. *It's presision is +/- 19Kwh.- Hide quoted text - - Show quoted text - |
Cost to run central A/C
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Cost to run central A/C
On Jun 28, 5:42*pm, Tony wrote:
wrote: On Jun 28, 12:39 pm, Tony wrote: Steve B wrote: "Tony" wrote in message ... Steve B wrote: "LouB" wrote in message ... Tony wrote: Bill wrote: "Tony" *wrote in message I'm trying to figure the cost of running the central AC in my house. If your heating is other than electric, then the cost is the difference in your electric bill from the winter to the summer. Or if there is a month in the spring when you don't use heating or A/C, then the difference in the electric bill from that month and a summer month. Hint: If you get a couple of window air conditioners and just cool the room(s) you are using, the cost will be lower. So just cool the living room during the day and just cool the bedroom at night. If you have 6 kids and 7 bedrooms, then not much savings of course! That's exactly what I getting at. *I'm almost positive it costs less to run 1 or 2 8,000 BTu window units than the central ac, even if I close off the rooms not being used. I suppose if I compared oranges to oranges and converted both central and window rattler to a basic BTU's/watt that would be very helpful, but I still need the specs on my compressor. Have you sought help from your electric company? Have you looked on your bill and read the $/kwh? *Compared the chart for month to month, and this year vs. last year comparisons? Yes. *But comparing last years to this years has too many variables. AC, in my estimation, has to do with keeping things cool. *Once a room is cool, it takes less power to keep it cool than to cool it down from warm. I'm with you there. With central units, they will do this better than room units that have to cool a warm room. *Up. *Down. *Up. *Down. No up down up down here. *In this 93F weather the little 8000 BTU unit runs on high 24/7 unless it gets too cool, then I turn it down. *Cycling it makes it less efficient. But, then, the only way you find out is to install central, and do a post mortem analysis. I have central. *I believe it costs much more to operate than a window unit or two, but it's hard to say without the right numbers. Right now I have one 8000 BTU unit and one fan to circulate the air. Running it 24/7 30 days would cost me less than $60. *It never runs all night so it's maybe $45-$50 a month to cool 960 sq ft. *Forgot the fan to circulate the air, add about $4. per month. Sometimes a large central AC won't have to work as hard as several smaller ones. *But then, there's the thing of cooling unused space ......... *It's hard to say. I always considered "work as hard" an odd expression in this context.. *I had a Fedders, maybe 7000 btu run pracically 24/7 each summer for 15 years and it never stopped working. *I left it at my old house because it wasn't nearly as efficient as the newer ones. But as you say, there are so many variables ...... insulation, reflectivity of roof, roof venting, single or dual pane windows, airtightness of the structure, even natural shade tree placement. No wonder you say it's complicated! *I'm talking about using the same house for both *tests*, factoring in the weathers "cooling degree days". *You have asked a complicated question with no answers, I didn't think my question was so complicated. What is the rated current draw on the compressor I listed? *That's all. It seemed like somewhere there would be an easy answer, another web page maybe? *I guess not. The answer as to how many amps the compressor is rated out may not be complicated, but it also doesn't answer the question you are seeking, which is how much it cost to run your AC. If you want to know how many amps the compressor is actually drawing, just buy a cheap clamp-on amp meter from HarborFreight or similar. They have them for around $12. *But that leaves out power factor and how much the rest of the system, eg blower is using. As I and others suggested, why can't you turn off any loads that might come on, eg electric water heater, attic fan. refrigerator, etc, then run the house for a couple hours of continuos AC and a couple hours without AC and record the electric meter readings. * That will give you how many Kwh it takes to run and you'll be way ahead of where you would be with the amp rating of the compressor. Like I said before... A couple hours run time using a kwh meter with an accuracy of +/- 19Kwh??? *That may show my AC runs for free.- Hide quoted text - - Show quoted text - Have you even taken a look at your electric meter? When that AC is running, the meter is going to be flying and in a couple of hours you will indeed have enough usage to increase the least significant digit or two digits, substantially. Certainly enough to get a good enough reading to determine the approx cost of running the AC continuosly for those two hours. There is no way you could falsely conclude that it's "running for free." Assuming you did what I suggested, which is to turn off any other large loads that might come on, ie electric water heater, pool pumps, etc. just taking the entire usage during that test period and counting it as AC usage isn't going to be too far off. Think about how big your ENTIRE bill is during months with no large loads, ie no heating, no AC. Divide that down to 2 hours, and it isn't much compared to what the AC will use. If you want to get a better read on the low usage from the rest of the house when the AC isn't running, measure it for 8 hours, or whatever it takes to move the meter enough to get a good reading. Or better yet, just open all the other freaking breakers so there is no other load other than the AC for two hours. This ain't rocket science. |
Cost to run central A/C
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Cost to run central A/C
cjt wrote:
Ed Pawlowski wrote: "Art Todesco" wrote http://www.nordyne.com/literature/8569%20Compr.pdf The best would be to compare the electric meter with the unit running and not running. This way you will have actual watt-hours and you don't have to think of things like power factor, etc. But, it will change depending on temperature. And the run time will vary when the temperatures are cooler than when it is just plain hot outside. Many electric bills give a 13 month use history. Mine even gives the average temperature for the month. Look at months like April and October when neither heat or AC is used much and compare to July and August and you get a pretty good idea. Aside from that, the only accurate method is a recording ammeter over time. I think you mean a recording watt-meter. Amps don't account for power factor. Another question maybe you can help? If I buy a clamp on type ammeter that plugs into my DMM to display the current... if my DMM measures AC with true RMS, will that fix the problem of the power factor? |
Cost to run central A/C
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Cost to run central A/C
Tony wrote:
cjt wrote: Ed Pawlowski wrote: "Art Todesco" wrote http://www.nordyne.com/literature/8569%20Compr.pdf The best would be to compare the electric meter with the unit running and not running. This way you will have actual watt-hours and you don't have to think of things like power factor, etc. But, it will change depending on temperature. And the run time will vary when the temperatures are cooler than when it is just plain hot outside. Many electric bills give a 13 month use history. Mine even gives the average temperature for the month. Look at months like April and October when neither heat or AC is used much and compare to July and August and you get a pretty good idea. Aside from that, the only accurate method is a recording ammeter over time. I think you mean a recording watt-meter. Amps don't account for power factor. Another question maybe you can help? If I buy a clamp on type ammeter that plugs into my DMM to display the current... if my DMM measures AC with true RMS, will that fix the problem of the power factor? No. Power factor arises from the phase relationship between the voltage and current. For purely resistive loads, they are in phase and the power factor is one. For reactive loads, they are not in phase. It's not a question of RMS vs something else. BTW, if you're willing to try something a bit more interesting, you can measure total daily power use and minutes your A/C is on each day over a period of time. Plot the two against each other and fit a line to the data using a least-squares fit. Done correctly (including scaling minutes to hours, making the correct choice of axes, etc.), the slope will be A/C watts and the intercept will be your background use (i.e. the average energy consumed by the rest of your appliances) within a margin of error that you might even be able to quantify statistically (although if your background use varies too dramatically or is correlated to A/C use, the analysis might fall apart or at least become difficult). The longer the time period you incorporate in your analysis (within reason -- you don't want seasonal changes in efficiency, etc. to get involved), the more accurate you can be. :-) |
Cost to run central A/C
cjt wrote:
Tony wrote: cjt wrote: Ed Pawlowski wrote: "Art Todesco" wrote http://www.nordyne.com/literature/8569%20Compr.pdf The best would be to compare the electric meter with the unit running and not running. This way you will have actual watt-hours and you don't have to think of things like power factor, etc. But, it will change depending on temperature. And the run time will vary when the temperatures are cooler than when it is just plain hot outside. Many electric bills give a 13 month use history. Mine even gives the average temperature for the month. Look at months like April and October when neither heat or AC is used much and compare to July and August and you get a pretty good idea. Aside from that, the only accurate method is a recording ammeter over time. I think you mean a recording watt-meter. Amps don't account for power factor. Another question maybe you can help? If I buy a clamp on type ammeter that plugs into my DMM to display the current... if my DMM measures AC with true RMS, will that fix the problem of the power factor? No. Power factor arises from the phase relationship between the voltage and current. For purely resistive loads, they are in phase and the power factor is one. For reactive loads, they are not in phase. It's not a question of RMS vs something else. BTW, if you're willing to try something a bit more interesting, you can measure total daily power use and minutes your A/C is on each day over a ^^^^^ make that energy ;-) period of time. Plot the two against each other and fit a line to the data using a least-squares fit. Done correctly (including scaling minutes to hours, making the correct choice of axes, etc.), the slope will be A/C watts and the intercept will be your background use (i.e. the average energy consumed by the rest of your appliances) within a margin of error that you might even be able to quantify statistically (although if your background use varies too dramatically or is correlated to A/C use, or if the background use is too large relative to the A/C use the analysis might fall apart or at least become difficult). The longer the time period you incorporate in your analysis (within reason -- you don't want seasonal changes in efficiency, etc. to get involved), the more accurate you can be. :-) |
Cost to run central A/C
cjt wrote:
Tony wrote: cjt wrote: Ed Pawlowski wrote: "Art Todesco" wrote http://www.nordyne.com/literature/8569%20Compr.pdf The best would be to compare the electric meter with the unit running and not running. This way you will have actual watt-hours and you don't have to think of things like power factor, etc. But, it will change depending on temperature. And the run time will vary when the temperatures are cooler than when it is just plain hot outside. Many electric bills give a 13 month use history. Mine even gives the average temperature for the month. Look at months like April and October when neither heat or AC is used much and compare to July and August and you get a pretty good idea. Aside from that, the only accurate method is a recording ammeter over time. I think you mean a recording watt-meter. Amps don't account for power factor. Another question maybe you can help? If I buy a clamp on type ammeter that plugs into my DMM to display the current... if my DMM measures AC with true RMS, will that fix the problem of the power factor? No. Power factor arises from the phase relationship between the voltage and current. For purely resistive loads, they are in phase and the power factor is one. For reactive loads, they are not in phase. It's not a question of RMS vs something else. BTW, if you're willing to try something a bit more interesting, you can measure total daily power use and minutes your A/C is on each day over a period of time. Plot the two against each other and fit a line to the data using a least-squares fit. Done correctly (including scaling minutes to hours, making the correct choice of axes, etc.), the slope will be A/C watts and the intercept will be your background use (i.e. the average energy consumed by the rest of your appliances) within a margin of error that you might even be able to quantify statistically (although if your background use varies too dramatically or is correlated to A/C use, the analysis might fall apart or at least become difficult). The longer the time period you incorporate in your analysis (within reason -- you don't want seasonal changes in efficiency, etc. to get involved), the more accurate you can be. :-) Not sure I understand all that. But if you mean to use the power companies kwh meter, keep in mind that it only changes one kilowatt hour for each 20 KWh used. This makes it difficult to estimate usage since it can display the same number for hours even if I am using electric. It wont add 1 kwh at a time, only 20 kwh at a time. |
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