Swamp Cooler Temperature Estimates

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meteorbrews

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Hey there,

Does anyone have a rule of thumb for estimating their fermentation temperature in a swamp cooler?

I have my carboy wrapped in a towel inside a large bucket filled with water and a fan blowing on it(only one side). I have a stick on thermometer on the side of the carboy, which has since been submerged in the water, and no longer gives me readings and I would like to estimate my fermentation temperature. The water is at 66F, i'm not too sure of the extent of cooling I am getting from the fan. Any rules or personal experiences out there?

Thanks,

Brad.
 
We were just having this discussion a few days ago... the difference is going to be the same as any ambient temp to fermenter difference, about 3-5 degrees or as much as 8 on a really vigorous fermentation. Id ditch the whole swamp cooler thing, and just put your fermentor in a rubbermaid chest full of water that you chill with ice cubes initially, then swap out frozen gallons of water to keep the water around 60. Your just a tad too warm for many yeasts in my humble opinion but not by much
 
I actually did some experiments in this area to see what the difference was. I had a waterproof wire probe thermometer inside the fermenter and also monitored temps on the outside to compare them.

They are generally extremely close unless the temperature on either side is rapidly changing. e.g. if you add a bunch of ice to the swamp cooler, it will take a few hours for the colder temps outside of the fermenter to propagate inside. Even during active, vigorous fermentation, I didn't get huge temperature differences.


To be clear, I use a cooler filled with water, with the fermenter submerged in that. Not the style where you just wick up water with e.g. a wet t-shirt and blow a fan on it. IMO that method is not very reliable. You may get a consistent temperature drop from ambient, but ambient temp changes all day long so it's not very effective at controlling temperature.
 
I've always read on here that the temperature inside the fermentor will be pretty close (+2 degrees) if not the same as the water temperature on the outside.

I have no personal experience to back this up though but this is the rule of thumb I'm using as I currently have a batch sitting in a swamp cooler as well.
 
I second the opinion on just filling up a bucket with water so it's above the level of the wort in the carboy. I tried the swamp cooler thing last batch, and for whatever reason, I wasn't able to keep my temps low at all. Instead of using a t-shirt draped over my carboy this time, I just filled my bucket up, put my better bottle in there, and filled the bucket until the water was higher than the wort. By swapping frozen water bottles every 8 hours or so, I'm able to keep my water level around 62-65 and my beer temp at about 65-68. Also, my fermometer got wet, and by that I mean it's fully submerged, yet it's still reading the temps fine. Weird, because last time one of my fermometers got wet it went crazy and turned all different colors.
 
Im not sure how the temp would be the same... fermentation is always going to create at least some extra heat, and although the water outside the fermenter is absorbing it, the yeast are still creating heat in an enclosed environment. The only time the temp is the same is after the first 3 days of active fermentation in my experience. But I think we all agree, the towel method is kind of an electricity consuming waste of time
 
FWIW you can still use the towel or T-shirt to wick cold water up the sides of the fermenter without a fan. I gave up on the fan because when I tried it in the past, I actually saw my fermenter get warmer - my theory is the fan was blowing the cool vapor away from the fermenter.

So now, my surefire method is water in the tub almost up to the wort level, a T-shirt over that, and about 4-6 frozen water bottles. I swap out 2 bottles at a time every few hours (I'm lucky enough to work from home so I can monitor it all day, I realize not everyone can). I don't have a thermometer in the fermenter, but the probe I have taped to the side of the fermenter consistently reads 66-67°F.
 
Im not sure how the temp would be the same... fermentation is always going to create at least some extra heat, and although the water outside the fermenter is absorbing it, the yeast are still creating heat in an enclosed environment. The only time the temp is the same is after the first 3 days of active fermentation in my experience.

I am just reporting my experimental results. The temperatures were nearly the same (within +/- 1F) all of the time, unless I was cold crashing, in which case it would take a few hours for the temperatures to equalize. I used a thermapen to check temperatures on the outside of the fermenter, and a thermoworks MTC with a waterproof wire probe to monitor temps inside the fermenter.
 
Fermenters sitting in WATER tend to be closer to the water's temperature, as water is a good thermal conductor.

Fermenters sitting in AIR (refrigerator) have the opportunity to build up more heat as air a better insulator than conductor.

To make the water bath even better, drop a pond pump into the water to circulate it.
 
I am just reporting my experimental results. The temperatures were nearly the same (within +/- 1F) all of the time, unless I was cold crashing, in which case it would take a few hours for the temperatures to equalize. I used a thermapen to check temperatures on the outside of the fermenter, and a thermoworks MTC with a waterproof wire probe to monitor temps inside the fermenter.
Sorry bottlebomber, I'm with weirdboy here. If I hold the water bath at a constant temperature the wort temperature never gets much above the bath temperature. Two things I have are a large bath and a cheap low volume submersible pump in the bath. The pump is aimed horizontally so that all it does is keep the water in the bath in constant motion so that the temperature is even throughout the bath.

If you chill your wort to your planned fermentation temperature and put it in a bath that stays at that temperature it will never have the chance to vary more than a degree.
 
Sorry bottlebomber, I'm with weirdboy here. If I hold the water bath at a constant temperature the wort temperature never gets much above the bath temperature. Two things I have are a large bath and a cheap low volume submersible pump in the bath. The pump is aimed horizontally so that all it does is keep the water in the bath in constant motion so that the temperature is even throughout the bath.

If you chill your wort to your planned fermentation temperature and put it in a bath that stays at that temperature it will never have the chance to vary more than a degree.

good to know, I use both swamp cooler with submersed in water carboy and temperature controlled freezer for fermenting lagers, I think I will try combination of both :D to control my temperature more precisely, always wondered about temp differences but never actually measured.
 
AnOldUR said:
Sorry bottlebomber, I'm with weirdboy here. If I hold the water bath at a constant temperature the wort temperature never gets much above the bath temperature. Two things I have are a large bath and a cheap low volume submersible pump in the bath. The pump is aimed horizontally so that all it does is keep the water in the bath in constant motion so that the temperature is even throughout the bath.

If you chill your wort to your planned fermentation temperature and put it in a bath that stays at that temperature it will never have the chance to vary more than a degree.

Im not trying to argue for right or wrong, just stating what my experience is. It seems both of you guys are using pond pumps, and that's probably where the difference lies. Im using a rubbermaid tub with some ice and nothing more, so its probably the case that your carrying the heat away from the fermenter a lot faster than I. That's an elaborate set up you've got. What is the secondary tub for?
 
That's an elaborate set up you've got. What is the secondary tub for?
It's mostly re-used stuff I had laying around. Bought the Ranco and the tub. The box on the left is an old dorm fridge. Instead of swapping bottles, I pump cold water from the the fridge and gravity feed it back into the fridge. The Ranco controls the pump. Differential set at 1 degree holds temperature stable. Sounds elaborate but really pretty simple.
 
Considering I'm using this method right now and switching frozen water bottles a few times a day, your pump is definitely the difference that is preventing the wort from getting warmer than the water around it. I don't have a pump, and even while changing frozen water bottles to keep my water temp around 61-64, my fermometer is reading 66-70. Is there an easy way to put a simple pump in to keep the water circulating, or do I need to get something elaborate like in AnOldUR?
 
kyle6286 said:
I don't have a pump, and even while changing frozen water bottles to keep my water temp around 61-64, my fermometer is reading 66-70.

That's what im talkin about.... those are my temps exactly
 
I use this setup in my garage.
IMG_0038_1_.JPG


I only have to change out my frozen coke bottle once a day even though it's been 100+ all month. The probe next to the carboy stays around 64 all day and all night.

Keep in mind this is an attached garage with a second-air-conditioned-story above it. A detached or one-story garage would get a lot warmer.
 
Is there an easy way to put a simple pump in to keep the water circulating . . . ?
The submersible pump I use for circulating in the bath came from eBay. I paid less the $10 including shipping 3-4 years ago. At the time I thought I'd use it for my IC, but it didn't have enough pressure. Finally found a good use for it after all these years. It was something like this with suction cups. It's stuck to the inside of the tub with no hose attached. No matter how you keep the bath water chilled, it's important to keep it moving.

31kUvDlQbCL._SL500_AA300_.jpg
 
I dont use a pump and the temp inside the fermenter (glass carboy) is the same as the temp in the tub. It's simply a function of the mass. If you are getting significantly different readings it is probably because you are using 2 different thermometers to check the bath temp vs the temp in your carboy or maybe if you are using a plastic fementer it is more insulating. One other possibility is maybe you don't have a large enough water bath.
 
Its big enough... its probably 7 cubic feet. The reason could also be that I brew big beers almost exclusively, (1.085-1.105), and I pitch proper yeast quantity and my FG is usually obtained in 3 days. Glass carboys. Also im going off the fermometer on the side of the fermenter not actually probing the juice, but when I put my hand in the water and feel the carboy I can feel that it is warmer... like I said it might be a fermentation thing
 
I use a set-up very similar to Ravenshead. My 48 qt Igloo Ice Cube mash tun doubles as my fermentation chamber. I don't use a pump and the temp of the wort is equal to that of the water bath.

Interesting to see all the different results.
 

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