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Old 03-29-2023, 11:51 AM   #1
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Residential Refrigerator Power Consumption

Looking for comparable situations to determine if something amiss in my motorhome. Class a diesel pusher 40 foot with a full size residential side x side Frigidaire refrigerator. The plate inside the fridge says 8.5 amps at 115 volts. My situation is (not on shore power) turn on inverter, looking at magnum inverter remote inside coach shows volts at 12.8 and amps at 0. Turn on refrigerator as it has an on off button remote shows 12.7 volts and amps at 20. Within a few minutes amps drop to 16 and then to 13 after it seems to settle down after a bit. If I watch the remote then I can see it flashing periodically between 0 amps and 13 amps. Anyway my question being, it seems to be drawing a lot more amps than stated in the refrigerator and wondering if others have seen such?
Thank you for your consideration
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Old 03-29-2023, 01:05 PM   #2
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Originally Posted by Webmorris View Post
Looking for comparable situations to determine if something amiss in my motorhome. Class a diesel pusher 40 foot with a full size residential side x side Frigidaire refrigerator. The plate inside the fridge says 8.5 amps at 115 volts. My situation is (not on shore power) turn on inverter, looking at magnum inverter remote inside coach shows volts at 12.8 and amps at 0. Turn on refrigerator as it has an on off button remote shows 12.7 volts and amps at 20. Within a few minutes amps drop to 16 and then to 13 after it seems to settle down after a bit. If I watch the remote then I can see it flashing periodically between 0 amps and 13 amps. Anyway my question being, it seems to be drawing a lot more amps than stated in the refrigerator and wondering if others have seen such?
Thank you for your consideration
115 volts @ 8.5 amps = 977.5 watts max
12.8 volts @ X amps = 977.5 watts max (x=76.37 amps)

Sounds like it's behaving well within its parameters. Amps vary with different source voltages.
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Old 03-29-2023, 01:09 PM   #3
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And just an FYI, it is the defrost cycle that pulls all the juice in your fridge. What you have observed so far is the cooling side of it.
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Old 03-29-2023, 01:43 PM   #4
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20 amps at 12 volts is 2 amps at 120 volts.
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Old 03-29-2023, 02:26 PM   #5
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Average of 9 amps or so DC over a 24 hour period. Always draws something...
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Old 03-31-2023, 10:40 AM   #6
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Average consumption

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Average of 9 amps or so DC over a 24 hour period. Always draws something...
Thanks to all the replies. Can i assume then Sbrownstein you have a battery monitor kit installed in your coach and that is what you have witnessed yourself for your refrigerator?
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Old 03-31-2023, 11:10 AM   #7
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Can i assume then Sbrownstein you have a battery monitor kit installed in your coach and that is what you have witnessed yourself for your refrigerator?
Yes. Ran some extended tests when the coach was new with a Trimetric battery monitor connected to a remote data acquisition system.

Using the most pessimistic integration it uses 113 AH in a 13.5 hour test, or an average of 8.37 amps.

Results are attached.
Attached Files
File Type: pdf Long Reefer Power Consumption Test Annotated.pdf (412.8 KB, 4 views)
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Old 03-31-2023, 03:06 PM   #8
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When turning your fridge on the compressor uses a lot of power until it reaches the desired temp. Once at temp then itís usually just a fan running with the compressor kicking on as needed.

We have a residential fridge in our trailer. How much power it uses depends on the time of year. During the winter it uses 1 kWh per day, during the summer itís 2.5 kWh per day.
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Old 03-31-2023, 04:44 PM   #9
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The type of fridge matters. I got a 18CU fridge only fancy one Frigidaire FPRU19F8WF and it doesn't use over 130 watts ever. I have a cerboGX and smart shunt to monitor. Very low power consumption
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Old 03-31-2023, 06:01 PM   #10
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It all depends on the unit itself. Modern Energy Star reefers use variable speed compressors and run virtually 24/7. Nameplate load is usually the defrost heaters, which are often 700 watts or more. Specification wattage for the last 1/3 of the cycle for my 22 cu/ft unit is listed as 30 to 50 watts at 60 degrees ambient and 50 to 70 watts at 90 degrees ambient. Pretty much what I measured.
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Old 03-31-2023, 08:18 PM   #11
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Yes, understood that first startup until desired temp met will draw the most power other than defrost. Let me then ask another question. How accurate might one think the readout at a Magnum ME-RC remote be as far as volts and amps shown? I understand that it being instantaneous and not reflecting over time as a battery monitor kit would show.
Thanks again...
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Old 03-31-2023, 08:23 PM   #12
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Yes, understood that first startup until desired temp met will draw the most power other than defrost. Let me then ask another question. How accurate might one think the readout at a Magnum ME-RC remote be as far as volts and amps shown? I understand that it being instantaneous and not reflecting over time as a battery monitor kit would show.
Thanks again...
You're correct if you want to know the consumption get a killawatt meter and it'll show you.
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Old 03-31-2023, 10:47 PM   #13
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Apparently not that accurate! "This meter converts AC amps to display DC amps, so the accuracy below one
amp AC (~10 amps DC @ 12 VDC) is not detected. When the current in or
out of the batteries is greater than one amp AC, the accuracy of this meter
is Ī20%."


Wouldn't use it to monitor power usage from your reefer. There is a networked ME-BMK that will show you SOC of your battery bank.
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