[Piwoslaw]

Sorry for the wait, had a busy weekend.

Originally Posted by Cd

So what are the coils buried within the walls of refrigerators and freezers ? Is this the same type of coil that you are talking about ? I notice that the sides of my mini-refrigerator get very hot. I insulated the walls of my minifridge with 1.5" thick styrofoam, yet it did nothing - it even seemed to increase the power useage at one point. I guess I was just sealing in all that heat.
Since coils can be mounted outside of the walls of the refrigerator, would it help the efficiency to rip out the coils within the walls and place them on top of something like my mini-fridge ? I was under the impression that the coils need to wrap around the walls of the 'fridge to extract the heat.

A refrigerator is a heat pump: it pumps heat from inside the unit to the outside. Inside is one set of coils which pick up heat, outside is another set which radiates heat to the surrounding air. Between the two is the compressor, which can get pretty hot itself.
Most new refrigerators have plastic lining inside, with the 'cold' coils behind the lining, so you don't see them. Often there is also a fan circulating air from behind the lining to the food area. Some fridges also have the external radiator coils covered, for aesthetics I guess. Sometimes the coils are under the unit, allowing you to push the fridge up against a wall. In both cases there should be fan, since airflow around the coils is hindered by the cover. In all cases the coil area should not be covered up, as you found out with your mini-fridge. You can add insulation to those walls which don't get warm.

Originally Posted by Cd

With a more powerful compressor, the on-time may even be below a minute, which isn't too healthy for it.

Can you please explain that last statement further ? So if I have the compressor kicking on for less than a minute, this might damage it ?

I read somewhere that compressors shouldn't cycle on and off too often. It's more efficient to have a weaker compressor that stays on longer. Once it does switch on, however, it should stay on for at least a few minutes. I believe this is like with an IC engine: it needs to warm up so the lubes can start to work properly. Also, the gasses in the coils need time to start working properly.

As Christ said, there are things (like ice cream) that are no good when barely frozen. The box of ice cream I'm attacking at the moment states that it should not be stored above -18*C (0*F). Meat should also be frozen hard if you don't want it to start moving after 1-2 weeks.

Originally Posted by Cd

Another thing I am considering trying is placing my freezables inside of a couple of those insulated bags that you see at the grocery store. ( And then place the items at the bottom of the fridge where the coldest air falls. )
Usually items that are frozen at the store stay somewhat frozen and firm if you can get them home fast enough, so I wont have to worry about freezing them - only keeping them that way.

Those bags will keep a lower temp only for a certain time. They impede heat transfer, but do not stop it. So, if you put 0*F ice cream into the bottom of your eco-fridge where it's 30*F, then after maybe 12 hours the ice cream will also be at 30*F. If you put it in one of those freezer bags, it might take longer, but after 24-30 hours the ice cream will be at the same temperature as its surroundings. Heat transfer ALWAYS happens, its speed depends on temperature difference, surface area and mass.

If you do go ahead with the chest freezer to fridge conversion, you may have a problem with water condensation inside. Since the inside coils get cold, water from the air condenses on them. In a normal fridge there should be a small drain at the bottom of the coils which drains the water through the back wall into a plastic container on top of the compressor. When the fridge is running, the heat from the compressor evaporates that water. In a freezer, the coils are at a much lower temperature, so instead of water you get a layer of ice. If the freezer has auto defrost, then every-so-often a heater will melt this ice and the water will drain out. (A heater inside a freezer, isn't that just sooo efficient?) If you have manual defrost, then there might not be a drain, so the bottom of unit may get wet if it is used as a refrigerator. This is something you will want to think about when picking a unit.

Another note: If you want to put the unit in a closet, then other than making sure that there is adequate air circulation, you can also add extra insulation to the walls and even the top, since it will be out of view. You can even insulate the wall with the coils: use a thin (5-10mm) piece of styrofoam with foil on one side, between the wall and the coils. Just make sure it's not touching the coils and that they have air flow.