# Ghetto Fridge Circulation Fan - approximately 7 watts



## Coxy (20/11/14)

I was having some pretty major issues with my fermentation fridge maintaining a consistent temperature from top to bottom. It is an upright freezer with a straightforward temperature controller hooked up. There are two issues that an upright freezer poses to consistent temperature that may not exist for other fermentation fridge solutions:

Being upright (as opposed to a chest) means that you have significantly longer distance from top to bottom, allowing greater temperature differences to exist.
Being a freezer, as opposed to a fridge, means that the compressor cools down the area a bit quicker, which means that the existing circulation fan is not circulating for very long each time the fridge needs to cool down, so the cold air at the bottom doesn't have much of a chance to circulate to the top.
I was doing a cold crash/lagering at 5 degrees for one of my recent brews, and when I went to pull it out to rack into the keg, I noticed that some small icicles had formed in my beer (don't worry, it was still delicious to drink, no permanent harm had been done). My temperature probe was situated slightly above the centre of the fridge, and the temperature there was a perfect 5 degrees. I measured the temperature at the top and bottom of the fridge, and found them to be 8C and -4C respectively. That's a 12 degree difference in the space of one small fermentation fridge!

Enter the ghetto fridge circulation fan. Made from a regular case fan you can get from any old computer lying round your house (or about $10 online), a piece of PVC pipe from bunnings, any old AC adapter which you have in your house that outputs 12V (the lower amperage the better, as the case fan will only draw about half an amp), some silicone and some zip ties. You will need a drill to put holes in the pipe for the zip ties. I put a heap of holes in the side at the bottom of the pipe as well and then just sit the pipe on the fridge floor. The only electronic work you need to do is to wire the +/- from the AC adapter to the +/- on the fan (red/black). Case fans often have other wires than the red and black, but these are generally to do with variable speed control and can safely be ignored. The wiring is at 12V, not 240, as you are on the low voltage side of the AC adapter, so there is no need to be worried about doing DIY electrical work.

I now have this thing running in my fermentation fridge 24/7 during fermentation. The temperature difference from top to bottom is now approximately 0.5C and the power usage is approximately 7 watts (0.48A @ 12V @ about 80% efficiency)

As I already had the case fan and the AC adapter, this came to under $20 for me (the PVC pipe was $12 at the big green shed, but I'm sure you could get one cheaper elsewhere).


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