Normalize fridge temperatures by installing a PC fan | Hacker News Reader

Normalize fridge temperatures by installing a PC fan

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26 pointsweinzierl20 comments

This looks cool (haha). Is it apparent to anyone how it's powered? The article says "The fan’s power cables are soldered on to the step-up converter. The step-up converter is powered by the USB power supply.", but it's not clear to me where the power supply gets the power it supplies.

Maybe the wires just go in thru the door seals. I did this once for a project, and was surprised how the seal just filled around the wires.

Check out my kickstarter: https://youtu.be/uAkJjJEljks

That's exactly it.

Most fridges have a lamp where you may be able to draw power from, however that's probably 12v.

The lamp is mains AC, and is only powered when the door is on.

I'm the author. I've updated the article to clarify.

It's powered by a 220/110V USB power supply outside the fridge, USB micro cable in through the door seal, and then the 5V/12V-converter lives inside the fridge. The converter is also used to adjust the speed of the fan.

Pre-made, if you're lazy: https://www.campingworld.com/camco-rv-fridge-airator-109170....

We use one in our RV fridge, since it often has to go from ambient to whatever we set it to, and a little circulation helps, especially if the fridge is packed. I keep a battery charger and some rechargeable D-cells. I'm extrapolating that the batteries last about a week-ish.

If the author's fridge is old enough to not have a fan for the interior, it probably doesn't have a fan on the exterior coils. Again, based on camping fridges, a quiet PC fan on the coils can make a noticeable difference.

Author said the fridge was 10 years old - it should have a fan on the bottom coils - but if the coils are on the back, then that'll take more than one PC fan (I'm not even sure what you could use - maybe a couple of box fans?).

Also - for everyone else - be sure to keep your coils clean (there's a special brush you can buy that looks like an oversized q-tip mated with a pipe cleaner), and make sure there is proper space on the top/sides/rear of the fridge for proper airflow (usually 3-6 inches of room - varies based on the fridge, and sides - some sides need more room than others, usually back side and top need 6-8 inches of room or thereabout; sides less).

The article discusses an internal fan in the cooling box to circulate the air inside the fridge.

It's interesting that heat from the fan appears not to matter.

Do newer fridges have fans built-in? I've never heard one going; even if it's shut off when the door opens, I'd expect to hear it slowing down.

Frost free fridge freezers have a fan built in, or at least some do - that's as well as the large fan to pass external air across the heat exchange. The fan was near the freezer heat exchange coils on the one I dug into.

The fan turned off when you opened the door, so you couldn't detect airflow, but operate the door switch and you could, but not where you might think, and it was barely audible. Opening the freezer door made it much clearer. The visible vent in the fridge was the passive air exit, the fan assisted entry vent was hidden amongst the bulge that contained electronics, thermostat, and a flap that shut off the entry vent from the freezer section. Presumably to shut off fridge cooling when freezer was still calling for more.

Edit: I should add it was moving a pretty low volume of air, nothing like you might expect from various CPU and case fans.

> Do newer fridges have fans built-in?

How much did you spend on your fridge? Cheap fridges likely don't have such a fan...

Zero dollars. I rent a furnished place with such a POS fridge it sounds like distorted electric guitar. But I've had the pleasure of using some very nice ones. Will listen more closely next time.

The fan does generate some heat, yes. It should be no more than 15 kW/year (it uses well under 2W but the converter is a bit inefficient). The savings are expected to be around 226 kW/year (including the added heat from the fan.)

Those units should be kWh/year, not kW/year (and kWh/d in the article).

(Though personally I'd just use Watts exclusively, and ignore the per day and per year figures.)

With decent circulation evening out all temperatures, it should be possible to have a fridge set at 1C rather than the customary 5C.

Is there any data in how much longer that would make my food last?

Maybe? Most foods are labeled that they should be stored somewhere between 4-8C.

I store insulin in the fridge so that would be too cold.

This is pretty common in the homebrew world where people have kegs in fridges/freezers.

Late to the thread, but the author mentions that the fan runs when the door is opened; perhaps a relay that is opened when energized by the interior light would be a good solution to that issue?

A simple light sensor would also get the job done. However, this would increase the price and complexity of the project. There’s a risk the electronics might be damaged by the cool moist environment, so starting out with as little stuff as possible.

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