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Maintaining Temp with Aquarium Heater in Water

I’m using a heavy duty storage bin filled with water, heated with an aquarium heater, and circulated with a small submersible pump.

I expected the temp of the beer during active fermentation to be a few degrees (2 to 4) above the temp of the water bath, but what I’ve noticed is the temp in my fermentors remains nearly exactly the same as that of the water, or commonly even a degree less. Is this normal?

I’m pretty sure the stick on thermometers are accurate, as I recently tested them against my calibrated thermometer and they where close to dead on.

I also use this technique for fermenting my ales and my results are consistent with yours (although I don’t circulate with a pump). My admittedly unscientific guess is that the greater mass of water surrounding the carboy/bucket (which is constantly being regulated by the heater) somehow keeps the wort temperature in line with the buffer water in a way that air does not. Just a guess…

Dan you’re right on, the extra water spreads out the heat of fermentation and makes the rise much less than it would be without the swamp cooler.

I use an aquarium heater on occasion in my swamp cooler, never saw the need for a pump. I’ll hang a cheap thermometer into the swamp cooler to monitor the temp.

Thanks guys - makes sense.

re: the pump - I figured it would help maintain even temps throughout the water but it’s probably unnecessary. It was cheap though.

I also use the aquarium heater method without a pump. My rubbermaid incubator (incuMaider!) container is large enough for two buckets, and works great. I even put my bottles in there after bottling; this has given me nice even temps for carbonation. The bottles seem to carbonate evenly regardless of position in the incuMaider without a pump.

The only problem I’ve had with this method is that the bottles get a sediment line at the water level that I have to scrub off before I label.

Yes. The heat transfer coefficient for water is much higher (40 times higher) than air.

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