[kramerog]

I see that there are two designs for swamp coolers:

1. A true swamp cooler generally has a carboy sitting in a shallow pool of water with a a t-shirt covering the carboy and wicking water from the pool of water.  A fan blows on the t-shirt causing water to evaporate thereby cooling the carboy.

2. A carboy sits in a container full of cold water. Generally, the level of water matches the level of beer. Generally, ice packs are thrown into the water once or twice a day.

What are the pros and cons of both designs?  I'm interested in throwing something together so I can brew over the July 4 weekend.

Add: I'm doing a wit that I want to ferment at 70-75 with T-58.  Ambient temp in my basement should not exceed 75.

[morticaixavier]

I think with an evaporative cooler design you are only going to get a few degrees below ambient. It might account for the exothermic rise in temp but that's about it. With the full water bath with ice you can chill to whatever temp you can keep the water at as long as you have enough ice. Both present possible mold issues.

[tom]

Just throw a little sanitizer into the water and you'll be fine.

[euge]

I would combine the two and use the "wick" method and ice-packs. Since you are using a carboy/closed fermentation mold issues are not as concerning, but still something to be mindful of.

The major asset to the second approach is the thermal mass of the water. It will resist temp swings better as the beer heats up and the ambient temp of the cellar shifts throughout the day.

[kramerog]

Here's my report:

I didn't account for the difficulty in cooling wort in the summer - I rarely brew in the summer - so I pitched the yeast at 78 F.  So I ran out to the store and bought a large rubbermaid container.  I put two carboys in there and filled the thing with water at 63 F.  The next morning the beer was fermenting at ~72F (PET Better Bottle) and the surrounding water was a few tenths less at ~71 F and my basement was at 74F. 

I really like the bath over the swamp cooler.  1. Ease of temp control by measuring the bath water and adding ice packs as necessary.  2. Large thermal mass avoids temp swings.  3. Importantly here but wouldn't be a big advantage generally was the ability to cool the beer overnight predictably. 4. The system is compact.

I still don't care for brewing in the summer, but the bath works in a pinch, when I run low on beer.