How about a chimney on the back of the fridge?

[gasstingy]

I've had some minor experience with a fridge not cooling down as well as it should in a rental house, while at the same time the freezer was doing just fine. Since I have a neighbor who works at an appliance repair shop, I asked him to go fix it. He said no, it wasn't worth his time and told me how to correct it. Maybe this will help you.

There is a flapper between the refrigerator part and freezer part. All of the refrigeration takes place in the freezer section. The cold control in the freezer determines how much total refrigeration goes on. The cold control in the refrigerator controls the amount of opening of the flapper. Convection moves the air from freezer to refrigerator. So, if you need the refrigerator part colder, you might consider turning the refrigerator control to about the mid-range (at most) position and turn the freezer control up higher.

You may already know all this, but I sure did not. I bought a small thermometer from the auto parts store and took it with me when I did the cold control adjusting. In just a few minutes the refrigerator was heading for the right temperature.

[Piwoslaw]

I've been thinking about this today: If the temperature of my refrigerator's coils is only 10°C above ambient, then is this enough to produce a noticeable chimney effect behind the fridge? If I left the coils exposed then there is a chance that drafts in the kitchen would go over them and carry the heat farther away.

I know that some fridges' coils get pretty hot (like the coils-under-floor units I saw in the US, which would blow very warm air over my toes), these would have a much more pronounced chimney effect.

Originally Posted by AC_Hacker

Here's a photo of a 1930s monitor top, not mine, but the same type.

Looks like the engineers from the 1930's were smarter than today. Same goes for the automotive engineers

[Phantom]

Something that might work to help cool the coils more is to actually paint them. On a car forum I visit they did this to a super charger with Krylon Wrinkle paint it increased the surface area and allowed for quicker cool offs. See Wrinkle finishing engine parts for Performance : PontiacBonnevilleClub.com for details.

[strider3700]

at my old house I had an older fridge (early 90's) that had exposed coils on the back. It seemed to run a lot and I noticed it at night when the rest of the house was quiet. Since I had no money what I did was unscrew the coils and slide some of that foil covered bubble wrap radiant barrier between the coils and the box then I made a small hood for the compressor to "direct" the hot air out to the back not under the fridge. I then used some plastic to make 1/2" stand off's at the bottom and 1" standoff's at the top to move the coil out of vertical. Over all the fridge run time dropped by roughly half but this was all done with me watching a clock, I didn't own a killawatt at that time so take it with a grain of salt.

[Piwoslaw]

Originally Posted by strider3700

what I did was unscrew the coils and slide some of that foil covered bubble wrap radiant barrier between the coils and the box then I made a small hood for the compressor to "direct" the hot air out to the back not under the fridge. I then used some plastic to make 1/2" stand off's at the bottom and 1" standoff's at the top to move the coil out of vertical.

This is exactly what I did yesterday, but didn't get a chance to post pictures.

This is the original set-up. As I noticed a few posts back, my fridge's coils were already slightly sloped (2cm/0.8in from the rear wall at the bottom, 4cm/1.6in at the top).

I increased the distance of the coils to 3cm/1.2in (bottom) and 7cm/2.75in (top). Then covered the rear wall with 3mm stryrofoam with foil on one side (often used behind central heating radiators to reflect more heat to the room instead of to the wall).

I also squeezed a piece of wood between the coils and rear wall to keep the radiator from bending inwards:

Since the freezer is at the bottom, with the compressor under it, this makes a very large temperature differential across the rear wall and floor: When running, the coils are around 30°C/86°F, while the compressor is at 45°C/113°F (side) and 50°C/122°F (top). The freezer's temp is -22°C/-8°F, and its evaporator is around -28°C/-18°F, so that's a difference of almost 80°C/140°F across only a few cm of insulation. This part also got a layer of styrofoam with foil. Before:

After:

The last picture is before I replaced the plastic 'cap' on the compressor. It collects (via a tube in the back) the water which condenses inside the fridge, which quickly evaporates because of the compressor's temperature.

The next step may be a small (5-6mm) computer fan at the top of the coils to suck air upwards whenever the compressor is running. It will probably be run at a lower speed to reduce noise, so the power draw shouldn't be more than 2-3W, which hopefully will pay for itself by reducing the compressor's on-time.

[Daox]

Nice mods Piwoslaw! Hopefull you can measure the power savings. I know its difficult because there is much variation in fridge power usage.

I will ask though, why put foil/foam on the wall behind the fridge coils?

[Piwoslaw]

Originally Posted by Daox

I will ask though, why put foil/foam on the wall behind the fridge coils?

The insulation is on the rear wall of the fridge, to reflect heat from the coils. I hope my post didn't suggest that I put it on the kitchen wall behind the fridge?

I have some data from an experiment I did during the winter, with ambient kitchen temperatures, so I'll try to repeat that when the right time comes. Maybe by then I'll have the small fan hooked up and will test the difference with/without the extra draft.

I just checked that the compressor takes its sweet time to cool down, I measured 32°C over an hour after turning off. It probably nevers cools down to room temperature before cycling on again. And during all that time it is radiating heat back there...

[Daox]

Ah, ok. That was my mistake.

I'm quite interested to see how this works out! That compressor is horribly hot. Now I want to go take a look at mine. As I recall, your fridge is already pretty efficient too.

[Piwoslaw]

It is, so I'm not expecting a big difference. But if I get an improvement of ~5%, then others should see even more I'll have the numbers by mid-winter.

[Phantom]

Piwoslaw have you thought about replacing the plastic cap with a metal one? If it was replaced with a metal dish and had some thermal compound for computer heat sinks it would allow it to passively cool quicker, or even adding an old spare CPU heat sink to cool it faster.