WonderFridge

[JimiQ]

Hi, during last september I've modded my refrigerator with aluminium-styrofoam foil. I've attached the foil between compressor and freezer part. I also added the foil between refrigerator and back coils.
Refrigerator is whirlpool, cca 12 cu ft (220 liters refrigerator and 110 liters freezer). It's rated for 0.9 kWh/day.
Before mod it used 0.9 kWh/day in the summer and 0.45 kWh/d in the winter (both are averages during one week).
After mod it's under 0.4 kWh/day in winter (lowest was 0.35 when wife was away for week :-)) and 0.6 kWh/day in summer (highest 0.75 kWh/day).

I recommend this mod to everyone.

[Daox]

Wow, impressive reduction in energy usage there.

How thick was the foam insulation you used?

More pictures would be great if you have them.

[JimiQ]

Foam is 3 mm (1/8th of inch) thick. It's the cheapest one I could get. Mod cost around $4 and already (in 319 days) saved nearly $8.

Average consumption is 514Wh/d, before mod I have no complete numbers, just the two values (summer + winter). If I average them, it's 670Wh/d. So savings are around 23%. Although this year has a bit colder summer, so that must be taken in account.

This morning (there's already 7 AM :-) ) I've realised that compressor isn't room temperature before starting a new cycle. So that's something to work on.

Picture is a bit blurry, I don't have proper camera, just ****ty phone :-)
The plastic container is for condensated water drained from refrigerator. As you can see I've made few small mods, but I don't know if they have any impact, or even if they don't harm the consumption. I just hated that cold and hot pipes were so close together and uninsulated.

[jeff5may]

A warm compressor actually is a good thing. This ensures there is no condensed refrigerant in the compressor. The amount of heat stored in the shell is not huge. Having a warm compressor on start-up actually helps the condenser hx start doing its job earlier, shortening capacity ramp-up from equilibrium.

The best easy thing you can do after insulating the box is to insulate the suction line. I use armaflex closed cell foam pipe wrap. The heat not gained by the exposed piping helps the compressor run cooler by reducing superheat.

[JimiQ]

I'm not completely sure, but I guess compressor isn't warm during winter (we usually don't heat much, so there's like 21°C (70°F). Also my refrigerant is R600a, which has boiling point -11.7°C, which to me loks pretty warm, since freezer should be cooled to -18°C. That means suction line can still contain liquid refrigerant, am I right?

I am no expert in refrigeration, so I don't know if my assumptions are correct.

Also I thought that condensator is doing best job when it's end is room temperature (which in my case it's not during cycle, only at the beggining).

[jeff5may]

r600a is a little lower pressure than r-134a on the pt curve. When the freezer is freezing, there is actually less than atmospheric pressure in the evaporator and suction side of the circuit. As box temperature falls, so does evaporator pressure. At design minimum freezer box temperature, the evaporator may be operating with half a bar of vacuum.

The condenser side of the circuit follows room temperature. At normal room temperatures, the high-side pressure is usually in the 2 to 3 bar range during operation. This relatively low pressure is the reason most refrigerators last many decades before they develop a refrigerant leak. Even a badly fatigued or corroded run of tubing will hold this amount of pressure until it literally crumbles apart.

The condenser has one main purpose: move heat to ambient air. As long as it is warmer than room temperature and airflow is not obstructed, it is doing its best. Even if airflow is somewhat blocked, it still does a good job, as manufacturers routinely oversize this hx.

Trying to improve condenser performance is challenging with refrigerators. Due to the low compression ratio the compressor works against (2 to 3 bar), lowering condensation temperature doesn't have much energy saving effect. On large, commercial walk-in freezers, the most common upgrade is a txv, which matches up evaporator temperature and flow rate of the compressor to save energy. On residential iceboxes, the txv is considered an unnecessary extra moving part that can fail.

[JimiQ]

So will anyone else try this? I'd like to know if my results are repeatable

[Piwoslaw]

Originally Posted by JimiQ

So will anyone else try this? I'd like to know if my results are repeatable

I did more or less the same (foiled insulation between the back wall of the fridge and the hx coils, all the way down to insulate from the compressor's heat), and additionally moved the coils farther away (by 2-4cm), improving ventilation. This was 5 years ago and still going strong, the only issue I once had was condensation between the fridge wall and the insulation.

Originally Posted by ecomodded

The majority of the savings will be saved from the insulation on the bottom of the fridge , it gets way to warm down there to not be insulated. A design flaw really.

One of the downsides of the bottom-freezer design - the temperature difference between the compressor and freezer is greater than if the freezer was at the top.

[JimiQ]

I don't really know where to put this and I didn't want to start a new thread, so there it goes.

I stumbled upon an article about cooling fridge compressor by condensation drip from freezer coils.

https://www.sciencedirect.com/scienc...14157X17300813

I thought it would interest someone. They managed to loweer the consumption by nearly 10%

[u3b3rg33k]

Originally Posted by JimiQ

I don't really know where to put this and I didn't want to start a new thread, so there it goes.

I stumbled upon an article about cooling fridge compressor by condensation drip from freezer coils.

https://www.sciencedirect.com/scienc...14157X17300813

I thought it would interest someone. They managed to loweer the consumption by nearly 10%

AFAIK virtually all modern (American) frost-free fridges/freezers dump the condensate to a drip pan with some condenser piping in said pan. this serves to mange condensate without a pump/drain, and also boosts the efficiency of the system (notwithstanding poorly managed evaporator defrost strategies).