It's well known that temperature is a critical variable when it comes to fermentation - the magical process performed by brewing yeast that turn wort into beer. The process of fermentation is exothermic - a fancy word meaning it creates heat, so for most homebrewers the simple solution to control the temperature during fermentation is to purchase a new or second hand fridge that the fermenter can be placed into, and then controlled with a temperature controller like an Inkbird or RAPT device. The temperature controller will cycle the fridge on which will cool down the fermenter and fermenting wort inside as required.
The Problem
Simple, effective and efficient as this is, what if the ambient temperature is well below our target fermentation temperature, causing our fermenter temperature to drop below the recommended temperature range for the yeast being used?
In this scenario, we need to add a heat source to help raise the temperature of our fermenter within the fridge instead of reducing it.
This is the situation we face for a brief period each year during the colder winter months where temperatures are constantly below the typical ale fermentation temperature of 18-20°C. We were about to embark on the maiden brew on our recently purchased Cheeky Peak Nano-X Fermenter and knew we needed a heat source to maintain our target fermentation temperature.
Fermenter Heating Options
There are plenty of options for heating fermenters - heat pads, heat belts, glycol chillers/heaters, light/heat lamps, space heaters - the list goes on and on. Since our fermenter was made of stainless steel, we weren't comfortable wrapping a heat belt around it. Glyocol chillers/heaters are expensive, and sitting a space heater inside a fridge really didn't seem like a great idea either.
Our Solution
We opted for a heat pad which appeared to be a relatively safe and gentle method of warming the space inside the fridge. A bit of research and we settled on the Morgan's Heat Pad - offering 25W of heating power.
Installation
We sat it inside the fridge and situated it in between the legs of the fermenter and actually had it resting on the legs. This way the heat would radiate directly up and onto the conical bottom of the fermenter. It could be situated just about anywhere inside the fridge, and doesn't get hot enough to melt or cause any damage to any surfaces it may be resting against.
Performance
Raising the temperature in a full size fridge with a relatively low heat source like this can be slow, but it does work. We also used the insulating jacket from our FermZilla as an additional layer of insulation to help trap the heat in and around the fermenter as you can see from the photo below.
Sure, the insulating jacket doesn't fit perfectly but it certainly helped and we were able to reliably maintain a temperature of 20°C, even when the ambient temperature outside was well into the single digits.
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| Our Cheeky Peak Nano-X with Morgans Heat Pad |
At the end of fermentation we were also able to raise the temperature to 22°C for a diacetyl rest with no problems at all.
Conclusion
For those who haven't used a heat pad before, we'd best describe it as getting warm at best, and not hot. So the heat it produces is gentle, and safe. It can comfortably be touched without any risk of burns whilst being powered. That being said, it means it works somewhat slowly, so anything you can do to assist in the retention of heat is going to help with the heating efficiency. Simple things like adding a jacket or any other form of insulation around the fermenter is a great start. The other obvious thing is to resist the temptation to constantly open your fermentation fridge to check how things are going which let's all the warm air out!
We're happy with this current setup being safe, effective and reasonably efficient to help us warm our fermenter. It's certainly beneficial to be able to dial in your exact fermentation temperature, regardless of whether the ambient temperature is particularly hot or cold, and to also have the ability to raise the temperature a few degrees for things like diacetyl rests.
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