Post by papaof2 on Jul 16, 2023 8:05:44 GMT -6
Testing freezer power usage
You're probably aware that I'm test-equipment-impoverished because I think there's a need to be able to test just about everything that you must replace, whether car batteries (a 100 amp tester of ancient design with scales for 6 and 12 volt batteries) or those convenient pocket-sized power banks that can charge a phone once or twice. If you look at my collection of power banks, you'll find things like "1.618AH @ 1 amp" or "2.42AH @ 1 amp" because the small power banks are mostly useful for small jobs - not to fully recharge my phone every time but to keep it going for the two or three hours I'll be away from the house.
Is it more energy efficient to run the freezer on the backup power system all the time or is it better to turn it off for a few hours and then let it run an hour or two to cool it back down? Think on that while I go through the testing I've done the last few days. Note that I only needed to be on my feet long enough to unplug the freezer or plug it back in and then be up once an hour or so the check the progress of the testing.
Because the backup power system didn't last as long as the spreadsheet said it should have, I've been investigating how much power the freezer and fridge use and how long the freezer can safely be without power - no matter what the owner's manual or the CDC might say about 24 hours being OK. Over several days of testing, I've determined how long it takes for the internal temperature of the freezer to rise 20 degrees F (from -10 to +10) and how long it takes for the freezer to cool down 10 degrees F (from 0 to -10). No, those aren't the same timeframes, but both can be converted into hours or minutes for a one degree change to occur - which is useful in determining when the freezer should be put on backup power. The freezer has been recovering from the most recent testing: 8 hours, 46 minutes to warm up 20.3 degrees F and then 5 hours, 51 minutes to cool down 10.3 degrees F.
Did you notice that warming 20 degrees took 526 minutes but that cooling 10 degrees took 351 minutes? Cooling 10 degrees took 2/3 the time of warming 20 degrees. In simple arithmetic, that means cooling 20 degrees will likely take more than double the time that it took to cool 10 degrees or at least 11 hours and 42 minutes. How do I know? A Kill-A-Watt has been monitoring the freezer since it was stopped and then re-powered after the time for cooling 10 degrees. The freezer has been running 8 hours, 38 minutes since then and I can still hear it running. The Kill-A-Watt shows the freezer has consumed 900 watt hours in that time which works out to 104.24 watt hours per hour - and historically the freezer draws around 104 watts when it's cooling. I think we're at the point of replacing the freezer - but it's only 16 years old ;-)
At the moment there are two 13.8 / 13.9 cubic foot freezers in the running.
1. Home Depot has a Danby garage model that can be either a freezer or a refrigerator. It's the lowest energy usage (kWH/year) of all the freezers in that size I looked at and the warranty is 5 years. That's $799.99 (plus tax) delivered. Danby has been making off-grid (LP, 12 volt) fridges and freezers for years so they have a good reputation.
2. Amazon has a Whynter garage model with similar specs but it's only available in stainless and is $699.99 plus tax delivered inside the door. This model is not a problem to move once it's inside because it has a roller under each corner. Whynter is probably better known for their 12 volt and 24 volt fridges and freezers in vehicle sizes (powered coolers). All the laundry appliances are white but I'd take purple or green polka dots for $100 off because the freezer is in the laundry room and you usually won't see that unless you're family ;-)
Because these are garage-rated freezers, I could put it in the garage if wee needed more space in the laundry room for pantry expansion or a folding clothes drying rack or whatever (the freezer would have a power usage penalty in the summer but would have reduced power usage in winter - that might be an interesting difference to test).
Both of these freezers have lower yearly power usage than the current freezer (less than 2/3 as much for one of them and I'd have to dig out my notes about the other one). That also means they need less power when they are on backup power which increases the effective capacity of the battery bank without touching the batteries ;-)
The freezer stopped while I was writing that, and the Kill-A-Watt says it used 930kWH getting back to "normal" which would be 930 / 104.24 = 8.92 hours, or 8:55 to cool those other 10 degrees. That adds up to 14 hours, 46 minutes which is more than double the time for the first 10 degrees of cooling (5:51). For this freezer, the concept of "Let it warm for an hour or two and then just run it an hour to catch up" absolutely does not work. It uses less power to let the freezer run normally than it does if you turn it off for a few hours and then let it run until it gets back to "normal" temperature. Which way would you have answered that question?
They do NOT offer pictures of the back of the freezers but I would prefer a freezer with an exposed condenser coil or with a fan-cooled condenser coil in the usual cubby hole under the freezer - those can have extra insulation added to the outside of the freezer (more of my "Don't care how it looks") and make them even more efficient as my frugal gene comes into play. If power has been off for several days, having a purple freezer with sheets of Styrofoam on it but that freezer's still at -10F would be absolutely beautiful in its frugal usage of power ;-)
You're probably aware that I'm test-equipment-impoverished because I think there's a need to be able to test just about everything that you must replace, whether car batteries (a 100 amp tester of ancient design with scales for 6 and 12 volt batteries) or those convenient pocket-sized power banks that can charge a phone once or twice. If you look at my collection of power banks, you'll find things like "1.618AH @ 1 amp" or "2.42AH @ 1 amp" because the small power banks are mostly useful for small jobs - not to fully recharge my phone every time but to keep it going for the two or three hours I'll be away from the house.
Is it more energy efficient to run the freezer on the backup power system all the time or is it better to turn it off for a few hours and then let it run an hour or two to cool it back down? Think on that while I go through the testing I've done the last few days. Note that I only needed to be on my feet long enough to unplug the freezer or plug it back in and then be up once an hour or so the check the progress of the testing.
Because the backup power system didn't last as long as the spreadsheet said it should have, I've been investigating how much power the freezer and fridge use and how long the freezer can safely be without power - no matter what the owner's manual or the CDC might say about 24 hours being OK. Over several days of testing, I've determined how long it takes for the internal temperature of the freezer to rise 20 degrees F (from -10 to +10) and how long it takes for the freezer to cool down 10 degrees F (from 0 to -10). No, those aren't the same timeframes, but both can be converted into hours or minutes for a one degree change to occur - which is useful in determining when the freezer should be put on backup power. The freezer has been recovering from the most recent testing: 8 hours, 46 minutes to warm up 20.3 degrees F and then 5 hours, 51 minutes to cool down 10.3 degrees F.
Did you notice that warming 20 degrees took 526 minutes but that cooling 10 degrees took 351 minutes? Cooling 10 degrees took 2/3 the time of warming 20 degrees. In simple arithmetic, that means cooling 20 degrees will likely take more than double the time that it took to cool 10 degrees or at least 11 hours and 42 minutes. How do I know? A Kill-A-Watt has been monitoring the freezer since it was stopped and then re-powered after the time for cooling 10 degrees. The freezer has been running 8 hours, 38 minutes since then and I can still hear it running. The Kill-A-Watt shows the freezer has consumed 900 watt hours in that time which works out to 104.24 watt hours per hour - and historically the freezer draws around 104 watts when it's cooling. I think we're at the point of replacing the freezer - but it's only 16 years old ;-)
At the moment there are two 13.8 / 13.9 cubic foot freezers in the running.
1. Home Depot has a Danby garage model that can be either a freezer or a refrigerator. It's the lowest energy usage (kWH/year) of all the freezers in that size I looked at and the warranty is 5 years. That's $799.99 (plus tax) delivered. Danby has been making off-grid (LP, 12 volt) fridges and freezers for years so they have a good reputation.
2. Amazon has a Whynter garage model with similar specs but it's only available in stainless and is $699.99 plus tax delivered inside the door. This model is not a problem to move once it's inside because it has a roller under each corner. Whynter is probably better known for their 12 volt and 24 volt fridges and freezers in vehicle sizes (powered coolers). All the laundry appliances are white but I'd take purple or green polka dots for $100 off because the freezer is in the laundry room and you usually won't see that unless you're family ;-)
Because these are garage-rated freezers, I could put it in the garage if wee needed more space in the laundry room for pantry expansion or a folding clothes drying rack or whatever (the freezer would have a power usage penalty in the summer but would have reduced power usage in winter - that might be an interesting difference to test).
Both of these freezers have lower yearly power usage than the current freezer (less than 2/3 as much for one of them and I'd have to dig out my notes about the other one). That also means they need less power when they are on backup power which increases the effective capacity of the battery bank without touching the batteries ;-)
The freezer stopped while I was writing that, and the Kill-A-Watt says it used 930kWH getting back to "normal" which would be 930 / 104.24 = 8.92 hours, or 8:55 to cool those other 10 degrees. That adds up to 14 hours, 46 minutes which is more than double the time for the first 10 degrees of cooling (5:51). For this freezer, the concept of "Let it warm for an hour or two and then just run it an hour to catch up" absolutely does not work. It uses less power to let the freezer run normally than it does if you turn it off for a few hours and then let it run until it gets back to "normal" temperature. Which way would you have answered that question?
They do NOT offer pictures of the back of the freezers but I would prefer a freezer with an exposed condenser coil or with a fan-cooled condenser coil in the usual cubby hole under the freezer - those can have extra insulation added to the outside of the freezer (more of my "Don't care how it looks") and make them even more efficient as my frugal gene comes into play. If power has been off for several days, having a purple freezer with sheets of Styrofoam on it but that freezer's still at -10F would be absolutely beautiful in its frugal usage of power ;-)
