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Running a Refrigerator Efficiently


Shel_B
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I recall someone telling me that a refrigerator will run most efficiently when filled with food, leaving as little "free space" on the shelves and in the bins as possible.  Is this correct?

 

If so, since I don't like to keep lots of food around (I sometimes forget or lose what's in there and end up wasting food) I was thinking that I can fill some empty milk cartons with water and stick them in the back to fill the shelves and maybe something similar for the bins.  Does that make sense?

 

Thanks!

 ... Shel


 

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Freezers run best when chock-a-block. Refrigerators require air circulation, otherwise you get unfortunate warm and cold spots.

 

Thermal mass might be useful if you have young 'uns deliberating over their snacks for extended periods with the door open, but I don't know how you'd do that effectively. In an ideal situation, your most perishable items would be surrounded by the milk cartons (or whatever receptacles you ultimately use to hold the water).

“Who loves a garden, loves a greenhouse too.” - William Cowper, The Task, Book Three

 

"Not knowing the scope of your own ignorance is part of the human condition...The first rule of the Dunning-Kruger club is you don’t know you’re a member of the Dunning-Kruger club.” - psychologist David Dunning

 

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Replacing the lightbulb with an LED version will save energy and help the unit function as the LEDs do not give off large amounts of heat the way conventional bulbs do. Most stores do not carry the sizes used in fridges, but, most online LED bulb retailers do have them.

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1 hour ago, Shel_B said:

I recall someone telling me that a refrigerator will run most efficiently when filled with food, leaving as little "free space" on the shelves and in the bins as possible.  Is this correct?

 

 

I don't see how it could run more  efficiently. The more mass the more the refrigerator has to work to keep it cold.

 

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I don't know if it would be more efficient as you have to cool the large mass initially, but I imagine it would keep the compressor from cycling on and off as often, as the large mass would keep the interior temps from fluctuating as much as it would if it were empty.

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Air loss, air gain, more food, less food, are not significant factors relative to operation efficiency of a refrigerator. The thermal mass of air per cubic foot is extremely small.

Actually more food can be a negative. The more food in the box, the more moisture the compressor has to extract which takes a lot of energy to freeze and defrost.

 

There are two main factors which are very critical for refrigerator efficiency;

 

1. Insulation - It is all about insulation. If you want to save power, go to HD and buy some insulation board to surround the sides. You will have noticeable savings.

 

2. Good ventilation of the condensing coil in the back, and the bottom. Clean the coils, please.

 

dcarch

 

 

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1 hour ago, dcarch said:

2. Good ventilation of the condensing coil in the back, and the bottom. Clean the coils, please.

 

Ugh, yes. We cleaned the floor-level coils of the fridge in our rental a month or so ago, and they were packed tightly with the felt-like corpses of ancestral dust bunnies. We had to empty the vacuum three times (!!) before it was cleaned out.

 

We plan to do this every 3 to 6 weeks...or at least, will do so once the vacuum is replaced. I don't *think* cleaning the coils was what made it crap out after just a few weeks, but wouldn't care to hazard a firm opinion on the subject. 

“Who loves a garden, loves a greenhouse too.” - William Cowper, The Task, Book Three

 

"Not knowing the scope of your own ignorance is part of the human condition...The first rule of the Dunning-Kruger club is you don’t know you’re a member of the Dunning-Kruger club.” - psychologist David Dunning

 

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if you have pets...pet hair will get in there and clog up the works even worse. We used to pull dust kitties out of ours.

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"Only dull people are brilliant at breakfast" - Oscar Wilde

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23 hours ago, Shel_B said:

I recall someone telling me that a refrigerator will run most efficiently when filled with food, leaving as little "free space" on the shelves and in the bins as possible.  Is this correct?

 

If so, since I don't like to keep lots of food around (I sometimes forget or lose what's in there and end up wasting food) I was thinking that I can fill some empty milk cartons with water and stick them in the back to fill the shelves and maybe something similar for the bins.  Does that make sense?

 

Thanks!

 

I have an even better idea to save energy big time.

 

If you have that much empty space, get a smaller refrigerator.

 

dcarch

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21 minutes ago, dcarch said:

 

I have an even better idea to save energy big time.

 

If you have that much empty space, get a smaller refrigerator.

 

dcarch

 

That doesn't make sense for me.  While I usually don't keep a lot of food in the fridge, there are times when the space is needed, such as when I may be having dinner with friends and have more and different food than usual on hand.  The refrigerator is already not very large.

 ... Shel


 

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21 hours ago, dcarch said:

2. Good ventilation of the condensing coil in the back, and the bottom. Clean the coils, please.

 

dcarch

 

 

 

The fridge is moved and cleaned every three months or so.  The last time I pulled it for cleaning it showed no obvious dust or dirt.

 ... Shel


 

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21 hours ago, KennethT said:

I don't know if it would be more efficient as you have to cool the large mass initially, but I imagine it would keep the compressor from cycling on and off as often, as the large mass would keep the interior temps from fluctuating as much as it would if it were empty.

 

That's what my thought has been.  So, does the large mass really keep interior temps from fluctuating, or is that a myth?  Many people talk about it but, as yet, I've not come across anything definitive, such as a test done by a reputable organization or individual.  Personally, I believe it to be true, but have yet to see something that proves it.

 ... Shel


 

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22 hours ago, Lisa Shock said:

Replacing the lightbulb with an LED version will save energy and help the unit function as the LEDs do not give off large amounts of heat the way conventional bulbs do. Most stores do not carry the sizes used in fridges, but, most online LED bulb retailers do have them.

 

Isn't the light off when the refrigerator door is closed?

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 ... Shel


 

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The light should be off when the door is closed! haha...

 

Yes, the inside temp is definitely more stable with more mass inside.  So the thermostat in most refrigerators is a "bang-bang" type where the compressor is on or off, set with some hysteresis to keep it from cycling all the time.  So, just as an example, the compressor may turn on when the thermostat hits 36degF and then turn off when the temp reaches 33degF.  So the interior temp cycles back and forth between them.  The more thermal mass you have, the longer it will take for the interior to heat up once the compressor turns off - but it will also take longer for the compressor to cool it back down once it turns on.  So, while it may not be more energy efficient, it will keep your compressor from cycling as often, which is better for it.

 

On the other hand, some newer style and expensive refrigerators use a different style compressor that doesn't just turn on and off, but will speed up and slow down according to thermal demand.  This refrigerator is much more energy efficient since it is very inefficient for the compressor to turn on from dead still, and is less dependent on the mass stored inside at the moment.  Whether this difference in efficiency will ever make up the cost difference in the prices of the refrigerators is another question....

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1 hour ago, Shel_B said:

 

That's what my thought has been.  So, does the large mass really keep interior temps from fluctuating, or is that a myth?  Many people talk about it but, as yet, I've not come across anything definitive, such as a test done by a reputable organization or individual.  Personally, I believe it to be true, but have yet to see something that proves it.

 

The cumulative refrigerator on/off time, it makes not much difference by the quantity of food inside the refrigerator.

The heat gain/loss is only determined by the R factor  of insulation, which cannot be changed by food inside.

 

dcarch

 

Edited by dcarch (log)
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1 hour ago, Shel_B said:

 

Isn't the light off when the refrigerator door is closed?

 

Yes, but people have been known to open the door on occasion. It takes about 3-4 years to start saving money on an LED fridge bulb. An average household LED bulb (you can get them for about $2 each at Costco) takes about 6 months to start giving back a return on the investment.

 

There are several types of refrigerator bulbs. My current unit came with a relatively large Reveal bulb that was hot to the touch within 20 seconds of lighting.

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On ‎4‎/‎6‎/‎2017 at 10:55 AM, Lisa Shock said:

 

Yes, but people have been known to open the door on occasion. It takes about 3-4 years to start saving money on an LED fridge bulb. An average household LED bulb (you can get them for about $2 each at Costco) takes about 6 months to start giving back a return on the investment.

 

There are several types of refrigerator bulbs. My current unit came with a relatively large Reveal bulb that was hot to the touch within 20 seconds of lighting.

 

I understand your point, and it's something to consider, certainly for some situations.  Some years ago I had a housemate who was very thrifty (as a student he was on a limited budget, and so he watched expenses carefully) and he impressed upon me the value of not leaving the refrigerator or freezer door open longer than absolutely necessary.  I suppose that approach would have an effect similar to using an LED bulb, which I may consider at some point.  Just about every other bulb in my apartment is an LED, so why not the reefer bulb?

 

In the FWIW and Who Cares, Dept, the bulb in my fridge is pretty small and doesn't seen to put out any noticeable heat during the short time the door is open.  One of the sites I checked to get tips for running a refrigerator efficiently suggests that "when opening the doors to your refrigerator and freezer, make sure you've already got a pretty good idea what you're looking for. Keeping the door open while you  'take inventory' is a bad habit that you should try to break."  Knowing what's in your refrigerator, and where it's located is a good idea.

 ... Shel


 

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I think the only benefit is that a smaller amount of warm air is allowed to enter the unit if it is kept full, applies to upright models obviously.    As cold air drops out the bottom warm air is drawn in, and has to be cooled down once the door is closed.   If you have an EnergyStar Rated appliance I really wouldn't  worry about the minimal savings you would get unless you are opening and closing your fridge excessively . 

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16 hours ago, Ashen said:

I think the only benefit is that a smaller amount of warm air is allowed to enter the unit if it is kept full, applies to upright models obviously.    As cold air drops out the bottom warm air is drawn in, and has to be cooled down once the door is closed.   If you have an EnergyStar Rated appliance I really wouldn't  worry about the minimal savings you would get unless you are opening and closing your fridge excessively . 

 

That's the folk wisdom, but it doesn't turn out to be a big deal. The amount of thermal mass of the air in the fridge is minute ... it takes very little energy to chill a few cubic feet of air from room temperature to 30-something. 

If you calculate the thermal mass, of say, 20 cubic feet of air, and look at the amount of energy it takes to raise it from 4°C to 22°C, it's equal  to 0.0004 kilowatt hours. If you assume a refrigerator isn't that efficient, and takes twice as much energy to cool that air back the other way, you've got .0008 kwh. At our current price of 19.2 cents per kwh in NYC, this is 0.015¢ to open the door and let out every molecule of cold air.

 

So it should go without saying that it makes no difference if you open the door for 5 seconds or half a minute. You use more energy putting in a jug of room temperature water and letting the fridge cool it.

Edited by paulraphael (log)

Notes from the underbelly

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On 4/5/2017 at 11:38 AM, Shel_B said:

... a refrigerator will run most efficiently when filled with food ...

 

This seems similar to an idea I had when working at a job two hours away.  I had a big heavy air compressor in the back of my SUV and it occurred to me I should take it out to improve mileage.  But, I reasoned, once it was up to speed on the highway, the added inertia was actually helping to keep the car at speed on the highway.

 

I knew that couldn't be right, but it seemed so plausible....

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1 hour ago, IndyRob said:

----- But, I reasoned, once it was up to speed on the highway, the added inertia was actually helping to keep the car at speed on the highway.

 

I knew that couldn't be right, but it seemed so plausible....

 

Every time you accelerate, you pay a price in time. The car is slowed down by the extra weight. and you pay a price in extra gasoline to move the extra weight.

Every time you slow down, you pay a price in more wearing of your brakes.

 

Kind of similar to people who always leave their pizza stone in the oven.

 

dcarch

 

 

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