E-Star freezers - how so efficient ?

[Piwoslaw]

New fridges and freezers (and A/C, heat pumps, etc.) use a scroll (spiral) compressor, which is more efficient than the old piston type. Also, wall thickness doesn't always determine insulation efficiency. Some materials insulate better than others of the same thickness. Compare mineral wool, styrofoam and vacuumpacked foam.

[hondo434]

Refrigerators and freezers have evolved over the years. Refrigerators used to be a box with fiberglass insulation and a huge compressor. They went to better insulation ( foam insulation) to increase efficiency. Then they reduced the size of the compressor so it used less electricity but had to run longer, which is one key to better efficiency, the fewer times a motor cycles the more efficient it becomes, due to reactive energy. Then capacitance was added to balance the load. The capacitor retained the reactive energy produced by the motor and held it until the motor needs it on the next cycle. This process recycles the reactive energy so it doesn't have to get from the power company. An energy star appliance will usually sound very quiet. The refrigerators have started using two thermostats, one for freezer and one for refrigerator to keep a close tolerence on temperature.
Refrigerators and freezers should not be turned on there sides or backs. They have oil in them which can move. Any compressor that has been laid on it's side should stand upright for up to 24 hours before turning on to let oil drain back into compressor.

[JacobAziza]

I don't know about energy star rated specifically, but modern fridge/freezers still waste a lot of energy for minor conveniences.

Fridge/freezers made for off-the-grid homes are much superior to even energy star rated models.
They will tend to do things like:
-Put the cooling coils on the top (because heat rises - many modern fridges put them on the bottom so it looks better, but since heat rises, it just goes right back into the unit)
-Have thicker insulation
-Manual defrosting every so often (modern fridges don't need to be defrosted because they actually put tiny heaters on the cooling coils!!!!!!!!

Some (like mine) don't use a compressor at all. They use the ammonia gas-absorption cycle to transfer heat. No moving parts at all, and can be run on either 120v electricity, 12v, or propane.
They can use less than 1/10th the electricity of a standard energy star rated fridge/freezer.

The ones made for off the grid solar houses tend to be pretty expensive up front, but if you can find one made for an RV big enough for your needs, they are the same design but cheaper.

2nd to what Honda said - don't turn a fridge on its side, you can damage the compressor if gravity drains the coolant the wrong way.

[NiHaoMike]

Originally Posted by JacobAziza

Manual defrosting every so often (modern fridges don't need to be defrosted because they actually put tiny heaters on the cooling coils!!!!!!!!

I think some of the newer ones run the fan for the refrigerator side to defrost. On mine (a new LG), I can sometimes hear an internal fan running while the compressor is off.

[JacobAziza]

I don't understand - how can a fan melt ice?

[Who]

Originally Posted by Christ

Heat rises, cold settles...

Originally Posted by JacobAziza

-Put the cooling coils on the top (because heat rises - many modern fridges put them on the bottom so it looks better, but since heat rises, it just goes right back into the unit)

Quibble Mode [On]

This is officially quibbling but I feel that it is important to always keep in mind, especially on a site like this.

Warmer air (or water) rises, but heat itself travels in whichever direction it can to get to something that has the least amount of heat.

Heat can move through conduction, radiation and convection. With conduction and radiation heat travels the easiest path regardless of direction.

Quibble Mode [Off]

[JacobAziza]

Originally Posted by Who

Heat can move through conduction, radiation and convection. With conduction and radiation heat travels the easiest path regardless of direction.[I]

Technically accurate, but since the primary method of heat leaving cooling coils is convection, I stand by my original statement.

In a truly efficient system the heat from the coils should vent straight to the roof, where it can't travel back to the inside by any means (as it does in an RV where power is at a premium)

[hondo434]

Standard refrigerators use compressors to circulate freon through coils located in the freezer comparment and under the unit near floor. The freon absorbs heat in the freezer compartment and sends it by tubing to the coils near the floor where it releases heat. The thermosat tells the compressor when to turn on. The freezer comparment will be cooled down to about zero degrees. The refrigerator gets its cold air from the freezer.Their will be a dial in the refrigerator which will open and let in a certain percentage of cold into the refrigerator. The air is moved by a fan. The coils in the freezer will collect moisture from the system and frost will collect. To increase efficiency the coils should be defrosted. Self defrost refrigerators will have heater elements to melt this frost. When this happens you will hear a faint dripping noise and maybe a popping noise. This will cycle on and off with a defrost timer. Fans you hear are recirculating air in the box.

[Christ]

Originally Posted by Who

Quibble Mode [On]

This is officially quibbling but I feel that it is important to always keep in mind, especially on a site like this.

Warmer air (or water) rises, but heat itself travels in whichever direction it can to get to something that has the least amount of heat.

Heat can move through conduction, radiation and convection. With conduction and radiation heat travels the easiest path regardless of direction.

Quibble Mode [Off]

So what happens when things heat up?

They become less dense. Less density compared to the surrounding material, in fluid dynamics, suggests that the less dense material should move upward on a measurement scale.

If heat radiates into something else, all things equal, the overall effect will still be heat rising.

According to physics, all things will take the path with the least resistance. This is a given. This is also why, when you want to keep heat in your house, you insulate the ceiling, not the floors. This makes it more difficult for heat to rise directly out of your home, and into the airfield surrounding your home. This, however, does not prevent the physical net effect of heat rising, for after it radiates through the walls, (the next apparent "easy" path), it will still rise into the atmosphere until there isn't sufficient energy to keep it heated beyond the temperature (and thus, less dense than the surrounding) fluid. This means that as it's rising further away from a heat source, which keeps the heat energized, the heat dissipates, cools, and returns to the heat source. This is what causes convection currents.

Once again, the net effect is still that heat rises and cold sinks.

[JacobAziza]

That doesn't contradict what Who wrote.
What you said (Christ) is true of fluid dynamics (ie the air around the coils)
Heat a metal bar, and the other end will get hot whether its above or below, because it is not a fluid, and the heat is traveling via conduction.
If you have an infrared lamp (like in an aquarium for reptiles), you can put it above because it gives off radiant (light energy) heat, which goes in every direction.

However, none of that is really relevant to a discussion about refrigerators.