Proper ventilation of the condenser and compressor
is pretty vital to fridge performance. The single
best way to increase efficiency is to make sure the condenser is not bathed in recycled heated air that it itself has heated.
The Danfoss compressor
controllers have a fan output which can handle 0.5 amps of computer fans.
I have a c51is Vitrifrigo fridge which came with a 72 CFM fan that was located to pull air through the finned condenser. I added extra insulation
to the side of the fridge, and this extra thickness allowed me to relocate the fan to the other side of the condenser and so it can PUSH air into the condenser rather than pull it through.
I also used the Noctua Fan shown a few posts above in place of the vitrifrigo provided fan. The VF fan rated at 0.24 amps, actually pulls .12 amps, and is quite loud. The Noctua fan is only rated at 53 CFM, but it has a high static pressure rating, meaning it has good performance when pushing air through a restriction, and it is very quiet too!
When I installed this Noctua NF-f12 fan, which only draws 0.05amps, so that it pushed air into the condenser, performance increased. Duty cycle dropped, and noise
was considerably less than the VF provided sleeve bearing fan, and it draws 70% less electricity than the VF fan as well!
I'd made a Stainless steel shroud
over the cooling
unit so that all the air moved by the Noctua fan went across the compressor and compressor controller. I also added some sound dampening material to this protective shroud
. This single
fan pulls in cool filtered air from the floor below the fridge, pushes it once through the condenser, across the compressor and controller and is forced out the side of the cabinet and cannot be recycled.
This Modification was quite noticeable to both noise
and efficiency of the fridge.
I've also added a small 40MM fan to the interior
of the fridge which runs 24/7 and blows into the small freezer
compartment. I took 12v from the interior
light. While this aids in cooling
the fridge faster, and items placed within faster, it does not reduce energy consumption
. The fan itself adds a very small heat load to the fridge, and for this reason, I found the lowest amp draw fan I could, at 0.03 amps.
The use of this fan allows me to use a setting of ~2.2 out of 7 to maintain sub 35F everywhere in the fridge. With this interior fan turned off, a setting of 4 of 7 is required, and the floor of the fridge will be 31f and the back of the fridge below the compressor will be 44F.
So the internal fan evens out internal temps nicely, and allows for faster cool down of items placed within and allows a lower thermostat setting. When I have a Solar
power surplus, I crank the dial to 4, and then at sundown back to 2.2, and for several hours afterward, the duty cycle is reduced, saving some battery
power. Smetimes I forget to turn down the thermostat to 2.2 and My milk is slushy in the morning
I can also turn the front loading fridge into a freezer
at a setting of 5.5 where without the fan a setting of 7 will only freeze some sections of the fridge box.
Since the Danfoss controller can handle 0.5 amps of fans, one could in theory add 9 of these fans to the one on the condenser to evacuate heat from the cabinet in which the fridge is mounted. Of course this is overkill. But one could also use the Danfoss controller fan output, to trigger a relay to power fans rated at more than 0.5 amps, when the compressor is actually running.
My airflow system does not need more than one fan, and these upgrades, along with the extra insulation
mean that ambient temps must exceed 90 degrees before this 1.8 cubic foot, 50 liter fridge exceeds 1 Amp hour per hour in my average usage. In 75 F it uses about 0.75 amp hours of battery
capacity per hour, and in winter time average of 55F, it will take 3 days before it consumes more than 24 amp hours in my usage.
And my cheap
American swill beer
is 33F and gets there quickly!