Last night I completed my first 5 gallon batch and have two LBK’s that I’ve used US-05 Ale Yeast. This is my first go around with US-05. I know that for best results, I need to keep my fermentation temps in the 60-64 range. My basement provides an air temperature at a steady 69. I’ve put the fermenter in a tub and have added some ice to keep the temp down. My question is simple, if I’m shooting for 62 inside the fermenter, what temp should I aim for in the cooled water surrounding the fermenter? I want to keep the temp cool but I don’t want to lock up the fermentation either by being too cold. Any experienced help?
Fermentation temps will easily climb 5* over ambient temp. So I would shoot for something around 58*.
You will get even better cooling if you place a t-shirt or towel around it with the bottom in the water and a fan placed on it.
If you put 5gal of beer in a swamp cooler with 5gal more water in it, the temp increase in that beer is going to be halved simply due to the doubling of thermal mass as the heat exchanges between the liquids. I would keep the water in the low 60’s, that is plenty cool enough for US05. It’ll perform well anywhere in the 60’s, you just don’t want to be upper 60’s ambient and then see a 5-10F spike in the fermentor.
Mostly I’m concerned with the 5 gallon Oktoberfest I just made. It has a decent amount of malt so I’m really focusing on those temps to help the US 05 yeast as much as possible. I started with an OG of 1.048 and am looking to end at 1.012. All of my previous batches have hit that mark but they didn’t contain the malt that this Oktoberfest does. I rehydrated the yeast, pitched properly, and allowed the fermenter to sit at room temp (69*) for 12 hours to give the yeast a head start but I’m trying to pull those temps down in the low 60’s over the rest of the next 3 days. So far I’m at 12 hours since pitching the yeast and I’m just starting to see some action. I just got the fermenter in the tub with about 3 inches of water, ice, and a water temp of 58*. Again, the Ambient temp is 69* consistently. Fingers crossed…
I’d add water to get as much contact with the fermentor wall as possible. Then I’d let the temp come up into the low 60s and just add an ice bottle maybe twice a day. 1.048 isn’t considered a big beer so you won’t see that huge of an explosion of activity. One thing, quite a few of the esters are produced early in fermentation, so people generally recommend pitching a little below the ferm temp you want to run. 12hr is a good time for seeing activity with dry yeast, you did good rehydrating. Should be a fine brew, and time in the bottle counts as lagering even at warmer temps.
@Tomsawyer, how much water do I need around the fermenter? Currently I only have a few inches but I can definitely add more if that’s better overall.
I’d put as much as the tub will safely hold, the more it touches the sides of the fermentor the better the heat transfer will be. I use a red tub with rope handles and I cen get 4 or 5gal in it. I freeze 1L water bottles and reuse them as my ice bombs.
There are two things working to cool a fermenter in a swamp cooler, convection and evaporation.
If you submerge a carboy or bucket so water is in contact with most of the vessel, you’re cooling mostly by convection. In other words, the heat from the carboy is flowing directly into the cooling water because they are in contact. If you can keep the cooling water temperature stable, at the temperature of your choice, this is a great option.
On the other hand, if you cover the carboy with a T-shirt and add only enough water to keep the water wicking up the shirt and not evaporating completely away, you are cooling mostly by evaporation. This can knock 5–10 °F off your fermentation temperature and the nice thing is that you don’t need to keep adding ice to the water. To maximize your cooling with this method, add as little water to your cooler as you can get away with (to keep the surface area of the wet T-shirt at it’s maximum) and have a fan blowing over the carboy to push humid air away.
Chris Colby
Editor
I feel like I’m looking good on controlling the temp the best I can. The US 05 has shown little action in the first 18 hours but I understand it can be slow.
Chris’ post highlights an important point. With the fermentor mostly submerged in a tub of water, the beer will stay quite close to the temperature of the water in the tub. But using a wet t-shirt and relying on evaporation, you can actually get the wort to a few degrees lower than the temperature of the water. Cooling towers on power plants use the same principle to operate.
That said, if you have the the ability to control the ambient air temperature around the fermentor (for example by using a fridge with external controller), that gives very good results. Set and forget.
I guess everyone is overlooking MY point… 
