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Old 01-06-11, 06:18 PM   #1
RobertSmalls
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Default Lower ambient temperature = huge fridge power savings

I mentioned in a different thread that I heat my house to 50F at night and 40F while I'm at work. The lower average ambient temperature means my fridge has to work much less hard.

In the summer, I reported that my fridge uses 1kWh/day. Well, it's now at 0.53kWh/day, as an average of the past five days.

Btw, if you press the kWh button on the KaW twice, it displays a clock. Letting it run for at least 72 hours is probably the right way to measure a fridge, as mine seems to vary quite a bit from day to day.

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Old 01-06-11, 09:48 PM   #2
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I've also noticed quite a bit of variation in fridge power consumption over time.

BTW, I've read that you shouldn't operate a fridge/freezer out in a garage or other real cold places. Does anyone know why that is?
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Old 01-07-11, 12:01 AM   #3
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something to do with the refrigerant would be my guess. Having said that I had a chest freezer on the back porch where I'd regularly have to shovel the snow off to get stuff out, it's still working fine now that I've moved and have space in my basement for it.
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Old 01-07-11, 01:18 AM   #4
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The reason fridges don't like being to cold is that the freon never changes from a liquid to a gas.
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Old 01-07-11, 01:48 AM   #5
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Quote:
Originally Posted by Ryland View Post
The reason fridges don't like being to cold is that the freon never changes from a liquid to a gas.
Wonder if this is harmful to the equipment?
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Old 01-07-11, 09:20 PM   #6
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Originally Posted by kbhale View Post
Wonder if this is harmful to the equipment?
Other then the grease in the motor turning to a solid and not acting as a proper lube, I don't think the compressor will care, it will just be pumping a liquid around instead of a liquid that then turns in to a gas and back in to a liquid.
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Old 01-08-11, 07:53 AM   #7
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Does anyone here know the actual temperature below which this becomes a concern for R-134a? I have "steam tables" for R-134a, but I don't know what pressure fridges operate at.

Based on Strider's chest freezer, it's below the point at which my kitchen pipes would freeze.
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Old 01-08-11, 12:02 PM   #8
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Remember I had a freezer keeping things frozen sitting outside where it was below freezing. There is no guarantee the freezer even turned on out there in those conditions. I just know that it didn't end up seriously damaged from the experience.
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Old 01-12-11, 09:33 PM   #9
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Using figures from an example fridge in Thermodynamics (Cengel and Boles), the R134a is compressed from 140KPa to 800KPa in the compressor. This particular fridge would have liquid in the evaporator at -19C, so I figure any ambient temperature lower than that could potentially cause problems. However, -17C is the typical set point for a freezer, so I'm going to say the freezer would never turn on under such conditions, and this is a non-issue, at least for this particular example fridge.

Btw, the fridge in this example has a CoP of 3.9, excluding heat transfer from the refrigerant lines, any auxiliary energy usage such as an air circulating fan, and losses in converting electricity to torque. Which is to say, I have no idea what the typical CoP of a fridge is.
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Old 03-25-11, 07:30 AM   #10
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It wasn't a blip. My usage for the past 32 days has averaged 0.59kWh/day.

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