Quote:
Originally Posted by Christ
Also - CuFt and SqFt are two completely different measurements.
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Cd: cu ft are
volume, sq ft are
area. (I'm assuming you know that, but I'll write it out just in case.)
Suppose you have a box which is 1 ft x 2 ft x 3 ft. The volume is 1x2x3=6 cu ft, while the surface area is 2x(1x2 + 2x3 + 1x3)= 22 sq ft.
The volume of a fridge/freezer tells you how much stuff you can put in. It also tells you how much air you will have to cool down after closing the door (upright fridge case). If you use a chest freezer, the door is the top, so you don't lose cold air when opening (that's one of the reasons it's more efficient). This means that you should look at heat transfer through the sides. The amount of heat gain (or cold loss) is proportional to the surface area. So, what you want is a unit with the smallest surface area for a given volume. This would be sphere, but since they don't make spherical fridges, the closest thing is a cube, i.e. height, width and depth are the same.
Next are the coils (the radiator, as Christ called it, since that's what it really is). A lot of new refridgerators have coils at the bottom,
under the unit. This is bad, since the warm air rises off of the radiator straight onto the fridge. A radiator on the back of the unit is much better. (Recently I read a thread on convection, conduction, radiation, either here or on EcoRenovator, but I can't find it now.)
All other things being equal, pick the compressor which draws less power. This may mean that each cycle will take slightly longer before switching off, but this is good for efficiency. Especially if you want to a freezer-to-fridge conversion, since then the compressor will only turn on for a very short time. With a more powerful compressor, the on-time may even be below a minute, which isn't too healthy for it.
Next is insulation. Thicker walls don't always translate into better insulation, but a freezer is always better insulated than a fridge.
Last, placement. Make sure the unit isn't placed in a warm place, like next to a stove, oven, heating vent, or where the sun will shine on it. A basement with year-round cool temps is ideal.
Hope that helps.
--Adam