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superinsulated refrigerator freezer.
I want to know, using my smart meter data, if the refrigerator's standby energy use is any different (hopefully less) with the "blanket" of insulation I added to the freezer compartment. My previous test was inconclusive because the ambient temperature was different from the one measurement I made before I added the blanket. I wish now I had taken more measurements.
The standby electrical usage of a thermal box type applicance, like a refrigerator, a freezer or even a hot water heater varies mainly with the temperature of the air around it (the ambient temperature) and the insulation.
In order for me to make a meaningful comparison, all things (controllable variables) should be kept the same. The ambient temperature is not really a controllable variable but it is from an experimental point of view.
So I am taking snapshots of my smart meter data and reading each manually. I see a graph of my usage at any time and I can pick out the appliance. I can measure it very accurately. But with the software I have now, I cannot tabulate or totalize usage by appliance over say a month or a year. So I am estimating to get an idea for ranking, highest to lowest. I am also learning a lot about how my appliances behave as electrical loads and explaining as I go (the INDEX). I can "see" my electricity use with my smart meter data, but just how useful is it?
The nights here are still pretty warm. About the same as for the previous test 20C so this will qualify as a repeat for comparison. And to shake down the method. There were a few mistakes this time also.
Not as careful as I should have been, I see this morning that I left the Exterior Moisture Control ON last night. This switch activates a heater in the door gasket. I want that OFF! I had thought I left it OFF. I am going to put a piece of tape over the switch so that it stays OFF.
One thing I notice about the chart is that the fridge seems to be coming ON for shorter periods each time across the chart. I remember that my bedtime snack was a small dish of ice cream, so I had opened the freezer door about an hour before the chart. Its possible that the fridge was still recovering. I should make sure next time that the fridge has not been opened for at least several hours before the measurement.
The chart covers from about 22:30 to 01:30. The width of the peaks are 0.92cm, 0.80, 0.76 then 0.72. I am using cm as an analog for time. Time on the chart I measure to be 1.92cm = 1 hour.
The peaks also seem to drop down slightly, the first two are higher than the last two. I see that the base load drops about 25 watts at about midnight. I am not sure what turned OFF in the house. I was asleep. This is my whole house electrical usage so the fridge is riding on top of the base load.
Let's do some calculations anyway.
For the first two peaks, the fridge is using (275-125=) 150 watts and for the last two (250-100= 150 watts so the instantaneous power is the same as the last tests.
For the first peak, run time is 0.92 and cycle time is 1.84 so the duty cycle is (0.92/1.84=) 0.5. The second is (0.80/1.69=) 0.47. The third (0.76/1.65=) 0.46. I cannot calculate the fourth since I don't see the complete cycle. Doing the same calculation as before (power x time x duty cycle) I calculate for the three peaks 1.8, 1.69 and 1.66 kWh per day or 1088, 617 and 604 kWh per year. Quite a wide spread and more usage than before.
I know the insulation does not make the refrigerator use MORE power. Something about my measurement or the method is not right. And there was that dish of ice cream.
There must be an easier way to do this. I should let a computer monitor my energy use!
I am not discouraged.
Thanks for your interest
Lion's Head, Ontario, Canada
Update - The metal frame of the fridge where it touches the door gaskets is now covered with dew (condensation) so I see that the switch for Exterior Moisture Control really is activating heaters in the door frame. The dew isn't usually there. I wonder how much energy that takes and when the heaters come on? I think I remember reading that the heaters are activated by a time delay relay in the fridge that starts when the door is opened using the same switch that turns on the fridge light.
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