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  • Freezer Wattage

    Question for y'all: I recently bought the following monitor:

    http://www.amazon.com/gp/product/B00...ls_o00_s00_i00

    to measure the wattage of multiple appliances / devices in my house so I could figure out what my future solar panel system would cover. I had always used tables like these as a rough approximation: http://www.i4at.org/surv/wattage.htm and figured I would not have a big enough system for things like AC or fridge/freezers. My system was emergency power only (e.g., lights, fans, etc).

    The monitor seemed pretty accurate as I tried it on numerous items in my house like lamps, TVs, laptops, water heaters, electric fans, etc. But when I plugged it into my upright freezer (Frigidaire, forget the size in cubic feet, but it stands about 5 feet high) it shows only between 120-125 watts. I've had it plugged in for several hours now and it still says that.

    Is this true? If I google "freezer" and "wattage" I get anywhere from 500-800 watts on average, yet my fridge is showing only 121 watts and it's sitting in my garage and it's 100 degrees outside in Dallas. I thought maybe the meter was reading incorrectly but (1) it's read all my other appliances pretty much what i expected and (2) this guy on youtube seems to have a similar reading: http://www.youtube.com/watch?v=vEQsjPhZ80c

    Am I missing something? Thanks in advance for any help.

  • #2
    Originally posted by Living Tribunal View Post
    Question for y'all: I recently bought the following monitor:

    http://www.amazon.com/gp/product/B00...ls_o00_s00_i00

    to measure the wattage of multiple appliances / devices in my house so I could figure out what my future solar panel system would cover. I had always used tables like these as a rough approximation: http://www.i4at.org/surv/wattage.htm and figured I would not have a big enough system for things like AC or fridge/freezers. My system was emergency power only (e.g., lights, fans, etc).

    The monitor seemed pretty accurate as I tried it on numerous items in my house like lamps, TVs, laptops, water heaters, electric fans, etc. But when I plugged it into my upright freezer (Frigidaire, forget the size in cubic feet, but it stands about 5 feet high) it shows only between 120-125 watts. I've had it plugged in for several hours now and it still says that.

    Is this true? If I google "freezer" and "wattage" I get anywhere from 500-800 watts on average, yet my fridge is showing only 121 watts and it's sitting in my garage and it's 100 degrees outside in Dallas. I thought maybe the meter was reading incorrectly but (1) it's read all my other appliances pretty much what i expected and (2) this guy on youtube seems to have a similar reading: http://www.youtube.com/watch?v=vEQsjPhZ80c

    Am I missing something? Thanks in advance for any help.
    First question: Do you hear the compressor of the freezer running at all during that several hour period? If you have a frost-free modle it is possible that you have hit the time interval, typically once or twice per 24 hours, during which the freezer is defrosting the cooling coils. Also some units have an optional heated gasket feature to reduce accumulation of moisture around the door seal. If your freezer allows you to turn this off, try that and see what happens. This would be a constant power consumption when the compressor is not running.
    SunnyBoy 3000 US, 18 BP Solar 175B panels.

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    • #3
      LT - Does the little meter you linked to show WattHours or just current Watt draw?

      This one http://www.amazon.com/P3-Internation.../ref=pd_cp_e_0 will allow you to better calculate for a variable load (like a freezer) as it will show total watthours used if left plugged in for a period of time and also keep the highest wattage used.

      WWW

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      • #4
        Originally posted by inetdog View Post
        First question: Do you hear the compressor of the freezer running at all during that several hour period? If you have a frost-free modle it is possible that you have hit the time interval, typically once or twice per 24 hours, during which the freezer is defrosting the cooling coils. Also some units have an optional heated gasket feature to reduce accumulation of moisture around the door seal. If your freezer allows you to turn this off, try that and see what happens. This would be a constant power consumption when the compressor is not running.
        I did hear the compressor running (at least I thought I did). I checked it multiple times over a 4-5hr time span, including once after my wife loaded a bunch more groceries into the freezer (so I was pretty sure the compressor kicked on after that). The reading never went above 125. I don't believe I have that heated gasket feature you mention. I'm at work right now but I'll check when I get home.

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        • #5
          Originally posted by Wy_White_Wolf View Post
          LT - Does the little meter you linked to show WattHours or just current Watt draw?

          This one http://www.amazon.com/P3-Internation.../ref=pd_cp_e_0 will allow you to better calculate for a variable load (like a freezer) as it will show total watthours used if left plugged in for a period of time and also keep the highest wattage used.

          WWW
          I believe that it was showing watthours, but I may be wrong. Here are other measurements I took of other devices, if it helps:

          Small Lamp w/ CFL bulb: 11.8
          Mini Fridge (3 cubic feet, I think): 81
          Vornado Fan: 40.2
          Small $25 fan from Walmart: 33.4
          My Ansmann battery charger (charging 2 AAs): ~5
          My Dell Inspiron Laptop (1520, I think): ~38

          The manual (located here http://g-ecx.images-amazon.com/image...rveInsight.pdf) just says watt usage. I may go ahead and get that monitor you referred to. Always good to have a 2nd opinion.

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          • #6
            Originally posted by Living Tribunal View Post
            I did hear the compressor running (at least I thought I did). I checked it multiple times over a 4-5hr time span, including once after my wife loaded a bunch more groceries into the freezer (so I was pretty sure the compressor kicked on after that). The reading never went above 125. I don't believe I have that heated gasket feature you mention. I'm at work right now but I'll check when I get home.
            If I read the instructions correctly once it is plugged in more than 45 minutes it goes into averaging mode It will average the watts used over the time it was plugged in for.
            NABCEP certified Technical Sales Professional

            [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

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            • #7
              Originally posted by Naptown View Post
              If I read the instructions correctly once it is plugged in more than 45 minutes it goes into averaging mode It will average the watts used over the time it was plugged in for.
              That's what I read as well, which is why I let it sit for several hours. So that means I average 125 watts / hr using the freezer? I told my wife about my building a solar battery backup system, and she said she'd mostly be interested in something that kept the freezer running. I had assumed that if I started off w/ a single 100ah 12v battery that'd give me roughly 1200 watts, which in theory would mean I could keep it running 9hrs? I know that it's not a good idea to discharge a battery that deeply (and I wouldn't want to) but I was just wondering in an emergency how long, w/ a single 12v 100ah battery I could keep that fridge going. If it does average 125 watts per hour it seems like even just discharging 50% I could run it for at least 4 hrs, whereas before I read freezers use 500-800 watts. Do you still think my monitor is off or are my numbers correct?

              I also know that a regular gas-powered generator is best for stuff like this, but I really like solar power despite the fact that for stuff like this it's not as cost effective vs a gas generator.

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              • #8
                Originally posted by Living Tribunal View Post
                That's what I read as well, which is why I let it sit for several hours. So that means I average 125 watts / hr using the freezer?
                To keep the terminology standard, you are averaging 125 watt-hours per hour. 125 wh/h = 125w.

                So the meaningful number is that you would use 3000 wh each day, or 3Kwh/day. To give you one day's worth of freezer operation, allowing for 3 days without good sun and a 50% maximum worst-case drawdown on your batteries, you will need 18Kwh worth of batteries, which at 12 volts would be about 1500 Amp-hours of battery. Not an encouraging number, especially since I have not adjusted for any inefficiency in the system. (The preferred real world solution would actually be a 48-volt battery string, using 375 AH batteries. But the total mass of battery would be the same, just arranged differently.)

                Since you said the number never went over 125, you should let it run at least 24 hours to allow for lower cooling requirements at night and see if that can knock your requirements down a factor of 2 or so.
                SunnyBoy 3000 US, 18 BP Solar 175B panels.

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                • #9
                  Originally posted by inetdog View Post
                  which at 12 volts would be about 1500 Amp-hours of battery. Not an encouraging number, .
                  Put it in terms they can clearly understand.. A 1200 pound battery that cost $2700 needing replaced every 5 years or less.

                  People can understand those numbers clearly.
                  MSEE, PE

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                  • #10
                    Originally posted by Living Tribunal View Post
                    If it does average 125 watts per hour it seems like even just discharging 50% I could run it for at least 4 hrs, whereas before I read freezers use 500-800 watts. Do you still think my monitor is off or are my numbers correct?
                    There is nothing wrong with your monitor. Freezers work only fraction of time on nominal wattage. If your 500W freezer works 2.5 hours out of 10 hours, and idling the rest of time, average wattage is 125W.

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                    • #11
                      Originally posted by Shmel View Post
                      There is nothing wrong with your monitor. Freezers work only fraction of time on nominal wattage. f your 500W freezer works 2.5 hours out of 10 hours, and idling the rest of time, average wattage is 125W.
                      Completely meaningless information. If your freezer uses 500 watts, it uses 500 watts period. If it uses 500 watts for 2.5 hours it consumed 1250 watt hours.
                      MSEE, PE

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                      • #12
                        Originally posted by Sunking View Post
                        Completely meaningless information. If your freezer uses 500 watts, it uses 500 watts period. If it uses 500 watts for 2.5 hours it consumed 1250 watt hours.
                        But if the "watt meter" used to monitor the freezer is one which, instead of displaying the total power consumption from start time to end time, displays the "average" wattage (summing KwH and dividing by hours) then it is relevant to the meter reading the OP is seeing.

                        If the compressor is on 2.5 hours out of ten, then the 1250 watt hours total would lead to a meter display of 125 watts.
                        SunnyBoy 3000 US, 18 BP Solar 175B panels.

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                        • #13
                          Originally posted by Sunking View Post
                          Completely meaningless information. If your freezer uses 500 watts, it uses 500 watts period. If it uses 500 watts for 2.5 hours it consumed 1250 watt hours.
                          If I understand OP correctly, his monitor averages out power consumption over time. I.e. it is plugged in for 10 hours. During this time his fridge is running at 500W for 2.5 hours and idles for 7.5 hours. 1250 watt hours of energy are consumed during 10 hours, not 2.5, giving 125W of average power consumption. This number is displayed by the monitor.

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                          • #14
                            Originally posted by Shmel View Post
                            If I understand OP correctly, his monitor averages out power consumption over time. I.e. it is plugged in for 10 hours. During this time his fridge is running at 500W for 2.5 hours and idles for 7.5 hours. 1250 watt hours of energy are consumed during 10 hours, not 2.5, giving 125W of average power consumption. This number is displayed by the monitor.
                            Average is meaningless, it what it consumes. With your information one could make a huge mistake and think all they need is a 250 watt inverter to run it. It would not work. You need the power it uses, and the energy it consumers over a period of time. Average power is worthless information that cannot be applied in any meaningful calculation.
                            MSEE, PE

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                            • #15
                              Originally posted by Sunking View Post
                              Average is meaningless, it what it consumes. With your information one could make a huge mistake and think all they need is a 250 watt inverter to run it. It would not work. You need the power it uses, and the energy it consumers over a period of time. Average power is worthless information that cannot be applied in any meaningful calculation.
                              This makes sense to me and I'M a solar 1st grader. Thanks for explaining it in simpler language. To be more specific, would you say a battery back up system for the OP is not worth the investment?

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