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Old 12-18-2013, 02:13 AM   #11
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Originally Posted by FuzzeWuzze View Post
....If your using a STC-1000... your best bet is to measure the AIR temperature inside of your chamber and set it a few degree's below your expected fermentation temperature......
Why measure and control the AIR temperature, which we are NOT trying to control, when we CAN measure and control the wort temperature by attaching the probe to the outside of the carboy or bucket?

Attaching the probe to the outside of the fermenter, under a layer of insulation, has performed flawlessly for my brews.
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Old 12-18-2013, 02:23 AM   #12
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+1 to raouliii

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Old 12-18-2013, 03:48 AM   #13
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You have that backwards, in the thermowell the freezer will kick on for a long time because it will take it a long time to move the beer even half a degree...by then your freezer is at 0F.

If your using a STC-1000 and not something like BrewPi with a PID controller your best bet is to measure the AIR temperature inside of your chamber and set it a few degree's below your expected fermentation temperature.

You should only really use a thermowell if you have a PID mechanism that will compensate for overshoot and shut the freezer off early so that your freezer coasts in to the set temperature.

For example this is what my BrewPi setup results in using nothing but a Lasko personal ceramic heater and a thermowell in my 8 gallon bucket, its about 30-45 in the garage where the freezer is. The worst temperature swings were after fermentation ended on the 15th and it was still overcompensating only about .5F as it figured out the new settings it needed.


Your beer will always be pulled towards ambient, if you set your chamber to 62, the beer will get to 62, start fermenting and be around 64-65 most likely, this can be monitored with a separate probe or just one of those thermometer stickers you stick to the side of carboy/buckets. It should only take a few brews to figure out what this delta is and set your chamber accordingly.

To keep your freezer at 62 it should only have to turn on every once in a while...honestly i wouldnt use both a heater and a cooler. If its too cold(which it likely is by now in VA) just use the heater instead of having them combat eachother. Save the cooling for spring/summer.
Ha, nice chart and all, but the point is to control the beer, not the air. I use a thermowell and ferment in Sanke kegs with an ST1000... works perfectly.

On the other hand, If I forget to put the probe into the thermowell, it cycles constantly with wild temp swings.

Why would you control the air and guess at what is actually happening?
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Old 12-18-2013, 04:15 AM   #14
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Ha, nice chart and all, but the point is to control the beer, not the air. I use a thermowell and ferment in Sanke kegs with an ST1000... works perfectly.

On the other hand, If I forget to put the probe into the thermowell, it cycles constantly with wild temp swings.

Why would you control the air and guess at what is actually happening?
I guess it depends how bad your overshooting...if by measuring the side your wort is overshooting +-2F then you'd have better precision measuring the air because the beer will naturally gravitate towards that temperature.

Even if the wort starts fermenting, your chamber is going to be at a set temperature and resisting your wort from warming up.

It also likely depends on how powerful your heater and or freezer are. My chest freezer goes to -20F when its on. If its even on for 15-20 minutes the entire thing is super cold..sure my beer may be 70F to start moving towards my set point of 62, but because its so ridiculously cold in the freezer and it holds temp so well its going to take hours for it to warm up to even freezing inside even when its turned off..and as a result the beer goes way below the set point.

If your using a fridge it might not be as much of a big deal than if your using a modern chest freezer. Those damn things get super cold super fast.
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Old 12-18-2013, 04:33 AM   #15
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My STC-1000 temp probe is taped to the side of the fermenter bucket and insulated with some bubble wrap. My tolerance is set at the default of +/-0.5*C. I've not had overshoot problems even when I have to use the paint can/light bulb heater inside.

I would certainly not recommend having the probe measure the air temp. You'll get lots of fluctuation. With the other two STC-1000 units I use (one on the lagering chamber, the other controlling a keezer), I put the probes in a jar of water to buffer the temp swings. Those stay pretty stable as well.

The thermal mass of 5 gallons of liquid is tremendously greater than the thermal mass of the air inside my fridge. When the temp on the bucket gets down to the set point and the fridge turns off, the fermenter temp stays pretty steady even though the air is temporarily cooler. I've observed the same thing when using a chest freezer and an upright for fermentation.
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Old 12-18-2013, 05:05 AM   #16
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Actually, if you look at the graph, you'll see a lot of fluctuation in the air temp. In fact there's so much that it ends up pulling the fermenter temps wild toward the end.

The graph is a perfect piece of evidence that the probe needs to be insulated and measuring the wort, not the air.

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Old 12-18-2013, 05:35 AM   #17
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Quote:
Originally Posted by FuzzeWuzze View Post
You have that backwards, in the thermowell the freezer will kick on for a long time because it will take it a long time to move the beer even half a degree...by then your freezer is at 0F.

If your using a STC-1000 and not something like BrewPi with a PID controller your best bet is to measure the AIR temperature inside of your chamber and set it a few degree's below your expected fermentation temperature.

You should only really use a thermowell if you have a PID mechanism that will compensate for overshoot and shut the freezer off early so that your freezer coasts in to the set temperature.

For example this is what my BrewPi setup results in using nothing but a Lasko personal ceramic heater and a thermowell in my 8 gallon bucket, its about 30-45 in the garage where the freezer is. The worst temperature swings were after fermentation ended on the 15th and it was still overcompensating only about .5F as it figured out the new settings it needed.


Your beer will always be pulled towards ambient, if you set your chamber to 62, the beer will get to 62, start fermenting and be around 64-65 most likely, this can be monitored with a separate probe or just one of those thermometer stickers you stick to the side of carboy/buckets. It should only take a few brews to figure out what this delta is and set your chamber accordingly.

To keep your freezer at 62 it should only have to turn on every once in a while...honestly i wouldnt use both a heater and a cooler. If its too cold(which it likely is by now in VA) just use the heater instead of having them combat eachother. Save the cooling for spring/summer.
I've tried several methods, and found that the greatest overshoot was when measuring the air temp. Not only that, but measuring the air temp can often cause excessive cycling, which is hard on the compressor. This is pretty obvious when looking at Dec 12-13th on your graph. People on this forum have killed brand new freezers within days because they were measuring the air and didn't have enough thermal mass in there. I agree that using a thermowell can cause some overshoot issues, but dangling the probe can be even worse, and can be damaging to your fridge or freezer. IME the best results ore obtained by taping the probe to the exterior of the fermenter.

Quote:
Originally Posted by acidrain View Post
Ha, nice chart and all, but the point is to control the beer, not the air. I use a thermowell and ferment in Sanke kegs with an ST1000... works perfectly.

On the other hand, If I forget to put the probe into the thermowell, it cycles constantly with wild temp swings.

Why would you control the air and guess at what is actually happening?
FWIW I also ferment in sankey kegs and use an STC-1000 to control temps. I've tried using a thermowell for the probe, but found that it had significant overshoot when there was much differential between the beer temp and set temp. It worked fine when it finally settled, but there was a definite yo-yo effect when bringing it down to pitching temp, or cold crashing, or ramping temps up near the end of fermentation. I've since switched to taping the probe to the outside of the keg, and find that the exposure to the ambient shuts the fridge or heater off a little earlier, which prevents the overshoot, and the temps are significantly more stable. A thermowell is better than measuring the air temp IMO, but still not as stable as taping to the exterior of the fermenter. As always, YMMV.
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Old 12-18-2013, 06:31 AM   #18
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Let's say your basement held a steady temp of 62°. You pitch your yeast at 68° and place your fermentor in the 62° basement. We know that the temperature of the fermentor will want to adjust to ambient, but yeast activity will raise the temp around 6° so with the basement at 62°, and the heat from active fermentation raising the wort temp it will ferment at 68°. If my basement gets cold in the winter and drops to 59° the 6° increase in the fermenting wort would mean I would be fermenting at 65° That's not to bad right?

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Old 12-18-2013, 03:32 PM   #19
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like many have said you can set the margin of error. I think 0.3 is as low as it gets. you can also set the compressor delay, the max is 10 thats where I have mine set. I also unplug which ever device I wont need so that they arent constantly fighting each other. like I'm making lagers right now and they probably wont need to be heated. if the freezer chills too far past the margin of error I have set the heater wont get turned on because I have it unplugged.

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Old 12-18-2013, 03:39 PM   #20
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Quote:
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Let's say your basement held a steady temp of 62°. You pitch your yeast at 68° and place your fermentor in the 62° basement. We know that the temperature of the fermentor will want to adjust to ambient, but yeast activity will raise the temp around 6° so with the basement at 62°, and the heat from active fermentation raising the wort temp it will ferment at 68°. If my basement gets cold in the winter and drops to 59° the 6° increase in the fermenting wort would mean I would be fermenting at 65° That's not to bad right?
that's not bad IF those are the correct figures and the temps ramped up at the end of yeast activity preventing them from going dormant too early. but in all honesty that's fine.
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