One full-sized, on its last legs such that only the freezer can be effectively used for refrigeration. It keeps the food at 34F, and the refrigerator portion is turned all the way down (or up in terms of temp) to limit wasted energy. Ice forms in the back of the freezer, and reforms quickly if chipped away or defrosted.
The other fridge is a small cube, which is taking up valuable counter space, but is handy to have since the original refrigerator’s freezer isn’t that big.
I suggested that the best place for the small cube fridge would be in the unused lower (refrigerator) section of the old fridge. It fits fine, but I’m not entirely sure about the thermodynamics of my suggested setup.
There is very little cold air being diverted from the freezer into the lower fridge portion. I’m thinking of covering that spot with tape to further prevent cold air leakage into the lower fridge.
The small cube fridge will be generating heat, so venting into the room may be helpful. On the other hand, it won’t need to operate as much if the lower (big) fridge is somewhat cool. This is where a small amount of doubt comes in.
My inclination is to remove one or more of the rubber door seals on the big fridge to allow the heat generated by the cube fridge to escape into the room, rather than heat up both the small fridge’s immediate environment, and the body of the old fridge and its freezer. I’ll probably just run the cord out the door of the big fridge rather than drill a hole - shouldn’t be a problem with the flexible rubber seal, which I don’t want to seal well anyway.
So the questions are:[ol][li]Is my plan energy-efficient and feasible?[/li][li]Is there any safety issue with this plan?[/li]Any other points I should consider?[/ol]
What you’re doing is putting a heat source in a cool area, opening the cool area, and hoping that all of the heat you’re producing will escape the cool area, while leaving it cool. This won’t work. You’d be much better off just leaving the small fridge outside the big one entirely, to let all of the heat from the small fridge directly into the room.
Those who know Chronos know that he needs no validation, but just in case you don’t; he’s right.
Now, if somehow you could cut out the back of the large fridge so that the small one could vent all it’s heat out into the room, then there’d be a small savings. But hardly worth it.
The key issue is not saving money, but saving counter space. Assuming it’s safe to do so, I was just wondering how to go about it.
Venting out the back doesn’t seem practical, since I think there are coils there and probably some wires. So at this point I’m trying to figure out the most energy-efficient way to accomplish something that is not energy efficient.
Can you be more specific - do you believe it would be unsafe simply due to overheating? What if I put a stopper in the big door so that it would be always ajar?
Most fridges do not have strong insulation between the freezer and the fridge section. Covering the opening with tape is better than nothing, but it’s still not great insulation. It may seem like the fridge part doesn’t work, but measure the temperature in it. I bet the air in the fridge is significantly cooler than the ambient temperature. If you leave the door of the fridge open, the freezer section is going to have to work much harder to keep things cool. This would be very wasteful of energy. If you put the small fridge inside the big fridge, you’ve just added a heat source to that space, which will be even worse than just leaving the door open in the first place.
This is a good point. I’ll have to measure the temp and report back. As it is, the big fridge is running almost constantly anyway, so I’m not sure there’d be that much increase in energy wastage. The owner is simply not ready to spring for a new fridge just yet, and willing to live with a higher energy bill in the short term.
You say the main fridge sucks and is turned off, how bad is it? If the main fridge works to some degree but keeps food a little warmer than you would like, you could leave it running while you have the little fridge running inside it. This way the main fridge removes the heat generated by the small fridge. In order to work right the main fridge doesn’t have to keep its interior cold, just room temperature. If the main fridge can keep its interior even slightly below room temperature with the little fridge inside, than the little fridge will be operating more efficiently, though the full system will be much less efficient.
You may want to fill in a lot of the remaining space in the main fridge if you do this to limit the energy waste caused by opening the doors and letting the cool air out.
For heavens sake, just buy a new refrigerator and throw away both the old one and the old small one.
A modern refrigerator will be vastly more energy efficient than either of these antiquated ones that you have now. The electricity savings (since refrigerators are ‘on’ constantly) will soon pay for itself.
When I read that the freezer works fine while the fridge doesn’t, it makes me suspect that dust has clogged the coils. Pull it out from the wall and vacuum behind and underneath, and I’d wager that it’ll work much better. That’s a much cheaper solution than buying a new fridge, and it solves the problem of counter space by making the smaller fridge unecessary.
It’s theoretically possible that there would be an energy savings from putting a the small fridge inside the large one even if the large one isn’t all that efficient. After all it only has to provide an environment that will help the smaller fridge as much as possible. Since it has more power to start with (since it has to cool a larger volume, right?) the extra “boost” it gives the smaller one might be enough that two compressors operating at “peak” efficiency might be better if not just as good as one fridge struggling at max output.
But I wouldn’t put my money on it. I’d bet that it’s exactly the opposite case when you take into account waste of energy of the small fridge plus the leakage that comes from letting the power source in.
Even that really wouldn’t be adequate. Notice the big mass of tubes and fins on the back of your fridge? That’s what radiates away the heat collected by the refrigeration cycle. (Early refrigerators actually had a big radiating coil on top.) It needs to have open flow to convect away that heat; enclosing it in a chamber which prevents flow will make it more inefficient. As Chronos says, you’re better of just throwing away the big fridge and leaving the little one set out.
If you’re willing to pay for this, my friend would happily go along. Otherwise, I’m just trying to solve the problem put to me.
One step at a time.
Already been done.
I hadn’t considered that possibility until you mentioned it, but I think this is correct. However, it would require the small fridge to be pretty inefficient relative to the big fridge. This is usually the case, but I doubt to the degree required. Still, if you had a small fridge that did a truly wasteful job of refrigerating, say using 10 x the energy of the large fridge, then throwing it inside the hypothetically ultra-efficient big fridge could lower the total system energy required.
Since the small cube fridge has about the same volume as the freezer, this would bring us back to the problem of not enough space.
I went ahead and removed all the rubber seals from the refrigerator door, and the door shelving plastic as well, which was bumping into the small fridge. I placed identical digital thermometers in each space, and used the house thermostat for room temp. This last resulted in some variation, since the kitchen gets less heat than the thermostat area. Ideally I would have maintained the house at a constant temperature, but comfort and energy efficiency of the house took priority over the experiment.
Data is as follows
In each example below, temperatures recorded are in order: Room temp, internal temp of Big Fridge, internal temp of top Freezer, internal temp of Small Fridge.
63 - 58.5 - 30 - 63 ~~ Before insertion (small fridge hadn’t been plugged in yet)
64 - 65 - 34 - 25 ~~ After sitting 2 hours
At this point, small fridge temp was adjusted upward
70 - 71 - 35 - 42.5 ~~ After cooling 5-lb bag oranges 30 minutes
66.5 - 67.5 - 34.5 - 45.5 ~~ One hour later
67 - 67.5 - 34.5 - 36 ~~ Eight hours later
Later I recalled that I had no baseline with the small fridge outside on the floor, so I removed it from the big fridge.
64 - 61 - 33.5 - 32 ~~ After one hour outside
65 - 58.5 - 30.5 - 31 ~~ After four hours
67 - 62 - 30.5 - 27 ~~ After eight hours
My assessment:
Refrigerator (without rubber door gaskets) is cooling the room air by about 5 degrees by itself, and maintaining a temp only 1 degree or so above ambient when the small fridge is inside.
Freezer appears to go up about 4 degrees when the refrigerator section has the small fridge inside.
Small Fridge data is a bit more squirrelly, but looks like its steady temp goes up between 8 or 9 degrees when it is inside, although it responds rather slowly to a temperature load.
I’m open to further analysis of the data, and requests for specific measurements, tests, or repetitions.
but just in case you don’t; he’s right.