Yeast stress is likely caused by one of two things- an un-viable or inappropriately sized pitching colony or poor fermentation control. Sidestepping the first issue (if you’re brewing 5 Gall. batches at less that 1.060 SG use a packet, if not make a starter), fermentation off-flavours very likely have a lot to do with a temperature that is either too high or too low. Fortunately there are a few fixes to this problem at home. The simplest involves just using a wet towel and relying on evaporative cooling to control the temperature of your carboy. This is actually surprisingly effective, and just by being aware of fermentation temperature you are likely to make better beer (those stick on thermometers are really handy and cost almost nothing.) The next step from here costs a bit more and takes up some space, but is the obvious progression, especially if you live somewhere with very high/low temperatures. This is to build a fermentation chamber to give ideal temperature conditions year round.
To build a fermentation chamber you need a couple of things: most obviously an insulated, air-tight space and a means of cooling the air inside it. It seems to me that a fridge or freezer fits this criteria pretty well, although a lot of people just use a polystyrene cooler attached to a smaller fridge, which is probably cheaper. As far as which fridge/freezer- if you want to lager under 4ºC, get a freezer, if not get whatever is cheapest. The good people at homebrewtalk have made this comparison of pretty much every new fridge or freezer on the market which shows how much you can actually fit inside them, although this project will work just as well with the old fridge you have sitting in the far corner of the garage. The guide covers both carboys and kegs, which brings me to another advantage of a fridge/freezer- you can also convert it into a part time kegerator when you aren’t using it to ferment.
The last thing you’ll need is a means of regulating the temperature of the fridge/freezer. If you have a fridge, you might be able to get away with just using the thermostat on the appliance. If you have/buy a freezer like I did, you’ll need a separate temperature controller. These work by turning the appliance on or off based on the reading from a probe, which you can put near or even in your fermenting beer. Here you have another two options: buy a ready built temperature controller, which range in price from about $60-200 depending on specification, or build your own which is a bit cheaper. I took the second option, picking up an STC-1000 from amazon.ca for $27 (about 15 quid). These controllers come highly recommended by both homebrewers and aquarium/reptile tank owners, and funnily enough are almost identical to the ones supplied my many brewery engineering firms.
One thing that’s really cool about these controllers is that they are tiny. So if you are more handy than me it’d no doubt be quite easy to build the controller into the appliance you are intending to use as a fermentation chamber/kegerator. As it is I’m not that handy, and didn’t want to start hacking apart a new freezer, so I built mine into an external housing. This does have the advantage of being easier to take apart if it breaks or lend to a friend if you’re nice, but isn’t quite as neat a solution.
The downside of going the DIY route is obviously the DIY itself, and the controller basically needs to be wired to a power source and two power outlets. I don’t really want to do a ‘how-to’ guide to assembling it here, as I’m really not the sort of person you’d want to take electronics advice from. And my advice if you’re not confident of wiring a socket into a mains supply would be to get help from a professional electrician. However, I’m pretty much a total electrical novice and didn’t find the wiring all that tough. If you do want to do the project you’ll need a few things other than the controller- some wire, a project housing (I used the box my GoPro came in) and a duplex wall receptacle.
Once you’ve collected these bits the first and probably most difficult part of the whole project is cutting holes in the housing to fit the controller and power outlet. I had to drill a load of holes and then file down the holes for bloody ages to get them smooth. If you have access to a rotary tool though you’ll find things much easier. The other thing you’ll need to do is strip your cable down and cut some lengths of wire from it. If you plan on wiring both the cooling and heating loops from the controller (you may as well) you’ll need 5 lengths of ‘live’ wire and one length of ‘neutral’ (in Canada 5 black bits and 1 white).
Again, I don’t want to give a step by step on the wiring, but the wiring diagram I used and lots of other useful stuff can be found at the Mostly Harmless Brewing blog, and there’s tonnes of other STC-1000 how-to’s. Here’s a few pictures of mine going together though:
One piece of advice that I didn’t read anywhere is that you’ll need a really thin flat-head screwdriver to tighten the contact screws on the controller itself (above left), or else they are really hard to access and your wires will end up falling out all the time.
Once that’s done you’ll end up with a controller with two output relays, one for cooling and one for heating. The device works by measuring temperature with a probe and sending power to either the heating or cooling outputs depending on whether its reading is above or below the set-point you choose. You can also set a differential and delay on the unit so that it doesn’t turn on and off with every fraction of a degree change and wear the compressor of your fridge/freezer out. It’s also worth mentioning that you don’t have to connect both a heater and cooler- I only use my cooling loop, but may have to use the heating loop attached to a brew belt or lamp when it gets very cold in the winter.
I mentioned I bought a freezer. Again, this project will work with pretty much anything, but for various reasons (mainly space) I picked up a 5.5 Cu ft. freezer from Home Depot, which cost $250, about £130. This will only fit one fermenting carboy without adaptation (or 2 standard and 2 small corny kegs), but I’m unlikely to be fermenting more than that at any given time or want a bigger kegerator. You might want to look at the 7.2 version, which is $50 more but fits twice as much. You may also want to look at upright freezers, which cost more but take up a bit less room and are easier to get stuff in and out of. Again, you may just want to use the busted up fridge already in your garage.
Anyway I’ve put some pictures below of the final project, which is keeping an IPA I just brewed happy at about 15ºC. The real test will come in a week or so when I crash cool to 1-2º. It doubles quite well as an overflow beer fridge too, so I’ve got the remainder of the SMaSH brew I did a few weeks ago waiting to cool down too. In other words, I may not be too far away from that park bench at 10 o’clock on a Tuesday morning, but by the Gods the beer will be glorious when I get there.