How rigorously do I need to control ferm temperature?

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md20_20

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I am getting ready to put my first ever batch together. I have a chest freezer that I will eventually turn into a kegerator, but for now I'm going to use it as a fermentation chamber while I get better organized for the conversion project.

I have one of the Johnson Controls temp controllers. It seems to be doing a good job of holding temperature below the setpoint (which I have at 64 F for testing purposes), but when it's cooling it runs down to 58 F. Part of that is the differential value I have set in the controller (which is 5 F by default) and part of it is thermal momentum (just turning off the power doesn't take the cool away from the coils).

I can adjust the differential to something smaller, but it looks like I will still be faced with a cyclical variation of about 5 degrees. Will that be a problem for an ale fermentation? (Say, if it cycles between 63 and 68 F repeatedly.)
 
Put the temperature probe into a small jar of water. This will make it so it doesn't cycle as much which could cause problems with the condensor.
Once your fermentation vessel is down to your desired fermentation temperature it should hold. This is because there is a lot more volume at a certain temperature, so its going to take longer to go up/down in temperature than your small jar of water. Once you figure out where your temperature differential from your yeast doing their thing, you'll see pretty solid ferm temps.
I usually count on my yeast being +6-+8f over ambient. So if I want my fermentation temp to be 68f I set it for 60-62.
 
5 degrees is a big difference. Plenty of people still ferment without temp control but it makes repeatibility of the recipe harder plus some yeasts need to stay in a certain range. I would say as long as you stay in that range your probably going to be fine.
 
I usually count on my yeast being +6-+8f over ambient. So if I want my fermentation temp to be 68f I set it for 60-62.

Just to make sure I understand - you're saying the fermentation process is going to liberate enough heat to raise the temperature in the vessel to 6 - 8 F over ambient, right? How long will that hold true?
 
Just to make sure I understand - you're saying the fermentation process is going to liberate enough heat to raise the temperature in the vessel to 6 - 8 F over ambient, right? How long will that hold true?

i find that true for when fermentation is most active. Either way your really only worried about the temperature during the first few days because its usually then that all the esters and funky flavors are kicked off....
 
Just to make sure I understand - you're saying the fermentation process is going to liberate enough heat to raise the temperature in the vessel to 6 - 8 F over ambient, right? How long will that hold true?

Yes. The glass of water in a jar in your freezer is going to be the "corrected ambient" temperature so the unit isn't always on for every temperature drop of ambient.
Yeast while reproducing or fermenting is exothermic, some strains more than others. Most standard yeasts like Cali or Dry London are about +8 over ambient, whereas big highly attenuative alcohol resistant ones (slower) seem to be about +6 over ambient, and crazy ass belgian ones are about +10 over ambient.

Stick a temperature strip on your fermentation vessel and you can dial it in pretty easy.
When the temperature starts dropping after the first 4-5 days you can raise your temp up quite a bit to get the yeast a little more active for final cleanup and to squeeze those last gravity points out.
 
Load up your freezer with water. In gallon jugs, in spare buckets, whatever you have that will hold water. The fuller the better. The thermal load in your freezer will keep it from temperature swings. Put your fermenter in the middle of the water if you can. If you can adjust your controller, put it to 2 or 3 degrees delta.
 
Put the temperature probe into a small jar of water. This will make it so it doesn't cycle as much which could cause problems with the condensor.
Doing that will reduce the number compressor cycles BUT the temperature swings will be larger...because the temp probe is somewhat insulated from the air temp.

Adding stuff to the freezer will also reduce compressor cycles but the temp swings will be the same (just less of them).
 
Doing that will reduce the number compressor cycles BUT the temperature swings will be larger...because the temp probe is somewhat insulated from the air temp.

Adding stuff to the freezer will also reduce compressor cycles but the temp swings will be the same (just less of them).

True, but if the jar of water is relatively small, it will change temperature a lot quicker (both heating and cooling) than your 5g+ of wort you have in the fermenter, acting as a buffer for your fermentation temperature range.
 
Adding stuff to the freezer will also reduce compressor cycles but the temp swings will be the same (just less of them).

Less-frequent compressor cycles are always desirable.

I guess the basic question is, will the temperature swings over that interval have an adverse affect on the fermentation? I'm sort of gathering that the answer is "not really" provided you stay within the good range for the yeast you're using.
 
I just wrap the temperature probe with a couple of paper towels, and then tape plastic wrap over that. Basicly it just insulates the probe to delay cycling the freezer. I found this easier as well as all probes are not water resistant. (ranco)

The temperature swing of a large volume such as a fermenter or keg will most likely be very small and of little concern.
 
I agree that the temp of the beer will remain fairly constant with a fairly wide temp swing. Hell, just a little jar of water will stay relatively stable...that's where I put my temp display probe and it doesn't budge.
 
I think the best method is to tape the probe to the fermenter with a bit of bubble wrap taped over the top. This gives me almost exactly the temp of the beer, the freezer doesn't cycle much at all since it is measuring the temp of the 6.5 gallon carboy.

I'd rather do this then try to figure out how much hotter my brew will get than ambient temp. This way when it is really going strong the ambient will adjust to keep the beer at the right temp.
 
If you have your fermenter inside a container that harnesses a compressor you are running ahead of 99.44% of homebrewers with 50 brews in their log.

Yeast are competitive, hungry critters.

Carry on.
 
I just wrap the temperature probe with a couple of paper towels, and then tape plastic wrap over that. Basicly it just insulates the probe to delay cycling the freezer. I found this easier as well as all probes are not water resistant. (ranco)

The temperature swing of a large volume such as a fermenter or keg will most likely be very small and of little concern.

I suppose one could place the probe on the side of the fermenter and duct tape it there with lots of foam insulation too.... ??
 
True, but if the jar of water is relatively small, it will change temperature a lot quicker (both heating and cooling) than your 5g+ of wort you have in the fermenter, acting as a buffer for your fermentation temperature range.

I used to do appliance repair. We always checked food temperatures, not ambient. I'd go with the probe in a quart or so of water. It will still track much faster than the carboy. I've toyed with the idea of drilling a very small hole in the stopper and putting the probe through it and wrapping it around a stainless steel washer. Seal the hole, sanitize...
 
Even with the probe in the water the the beer can be getting hot during fermentation. If the probe is on the fermenter it will pick up the temp increase much quicker than when in a quart of water. Once your past the active feremntation the jar of water will be fine, but why worry then.
 
+1

The key is getting the temp probe in water. Also, the swings in the air temp will be greater than what's actually happening to the fluid temp. You are on the right track!
 
I've done temp controlled fermentations for the past two years and have tried it all. The best results have come from simply duct taping the probe halfway down the fermenter.

Sometimes simpler is best.
 
Basically once the feremntation starts there isn't a swing, well its on the up side of the swing. Thats why wildwest and I are saying to smack the probe to side of the fermenter. I insulate the probe to keep ambient air away and get as accurate reading of the feremnter as possible. With all the mass from the beer the outside of the ferementer will be close to the acutal temp of the beer.

The temp is going up and the time it will take to warm up a box that is already cool, then to warm a jar of water that is cool and not generating any heat may allow the ferementer to get too hot.

Each feremntation is going to be slightly different. If it were the same I might be on the side of keeping the air temp at a fixed temp 5-10 degrees below what the you expect the beer to be at and calling it good.

I'm specifically talking about the first day or 2 of active feremntation. For some that might be 4 days after it is in the feremnter, or it might be 6 hours like the Dunkelweisen I did last wekend.
 
Sure, measuring and controlling the surface temperature of your carboy will provide some level of control of the fermenting wort temperature. A little insulation on the probe doesn't hurt either. Trouble I found was that this still does not provide a great indication of what is occurring inside those thick glass walls. With a stopper thermowell and digital temp recorder I found a +3 degF rise during the exponential phase that was not detected by the surface probe. I think this is why some of my beers still get that "homebrew" flavor - fusels and esters. Here is a link to my latest effort to improve control, enjoy,

https://www.homebrewtalk.com/f11/water-jacketed-fermentation-chamber-145194/
 
With a stopper thermowell

I had considered drilling a hole through the stopper and forcing a probe through and sealing it up, but this makes more sense. I immediately pictured some old capillary tubing I got years ago at a refrigeration supply house. It will be more than stiff enough to force through without worrying about having to use sealer if I drill a slightly undersized hole.

Anyone ever drill the stuff they make stoppers out of? I know an old machinist trick is to freeze rubber before machining it. Will that be needed here?
 
Yep, you gotta freeze the gum rubber stoppers in order to drill them. And regular old freezer temps are not cold enough. You need to use dry ice or liquid nitrogen. I have had pretty good luck using a torch and heating the end of tube to cherry red and then pushing it through the stopper - a little stinky and sticky mess but it worked.

IMHO, an easier way to control fermentation temp is to submerge carboy in water and temperature control the water - using either your freezer/ fridge or some sort of water chiller unit (I am using an Ice Probe). I have found that the fermenter temps will stay within 1 degF of the temp of the surrounding water. This is because the heat transfer rate from the glass carboy into water is 10x greater than it is into air.
 
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