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Home Brew Forums > Home Brewing Beer > DIY Projects > Fermenters > Poll: Fermentation chamber temperature probe placement
View Poll Results: Where do you place your probe?
Hanging in the air 79 22.83%
Insulated against the fermenter wall 162 46.82%
Submerged in a separate container of water 52 15.03%
Inside the fermenter utilizing a thermowell 53 15.32%
Voters: 346. You may not vote on this poll

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Old 07-10-2010, 03:02 AM   #21
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Quote:
Originally Posted by RDWHAHB View Post
With all due respect, only if you do it wrong. Use a properly tuned PID to take care of overshoot/inertia problems in your cooling loop.
Yes, obviously it would if one were using a PID controller. No one that I know uses a PID controller on their fermentation chamber fridges or freezers. Most home brewers I know use a Johnson, Ranco or Love non-PID type thermostats. IMO, a PID for this type of application would be major overkill. A simple totally dumb digital or analog switched thermostat works just fine for me.
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Old 07-10-2010, 03:07 AM   #22
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PID with refrigeration equipment is bad... Will kill the compressor in no time.
That's certainly good to know and now that you mention it, I can clearly see why.
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Old 07-10-2010, 03:41 AM   #23
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Just add a delay cycle timer to save the compressor from short cycling.
I've used defrost time delays from Safeway store refrigeration systems that I worked on they're great. Being free also helps matters with the desire to test wild ideas.

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Old 07-10-2010, 04:02 AM   #24
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Just add a delay cycle timer to save the compressor from short cycling.
I've used defrost time delays from Safeway store refrigeration systems that work great. Being free also helps with the desire to test these ideas.
But would that not defeat the purpose of using a PID in the first place. The idea was to minimize the overshoot/undershoot with the PID. You toss a delay cycle into that mix and you would be back to a large temp swing. Perhaps I'm missing something though, as I have only a very rudimentary understanding of PID's and how they operate and it's likely to stay that way for at least a while longer.
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Old 07-10-2010, 04:20 AM   #25
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The longer times between compressor cycles the more stable the temps in the fermenter's temp well i've found. Granted a wider temp swing within the keezer, who cares about air temp swings it's the fermenter's contents I want constant. I adjusted and tuned to the system at hand. This with a Johnson control kicking a relay for the compressor load. Granted a 30 year old POS keezer it still maintains a rather constant temp for fermenting is all I ask. No PID control here plus no short time internal keezer air temp swing worries.

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Old 07-10-2010, 05:00 AM   #26
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1) PID doesn't kill cooling equipment, short cycly times do. Short cycles should be avoided with t-stats as well.
2) PID is not overkill if you are experincng wild over/undershoots with your temp control. A good PID can be had for the same $$ as a ranco/johnson.
3) you want to cntrl the fermentation temp, not the air temp. Measuring anything other thanthe fermenting beer's temp introduces error.

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Old 07-10-2010, 08:08 AM   #27
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Quote:
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1) Measuring anything other thanthe fermenting beer's temp introduces error.
I've had my share of errors on my own without adding ideas from others.
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Old 07-10-2010, 06:39 PM   #28
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With due respect, I couldn't disagree with you more as to how to control fermentation temp. The ONLY thing you can directly control is the air temperature within the chamber. Keeping that as near to your set point temp is the only way to minimize the ferment temp swings which is the primary thing you want to avoid anyway. With the probe monitoring the fermenting wort the control will not kick on until there is a warming of the wort and then a big delay until it once again falls to the set point temp. However, with the control probe monitoring the chamber temperature the wort has a much greater chance to remain stable as the chamber quickly returns to set point temp.

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Old 07-10-2010, 07:18 PM   #29
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In my experience controlling the ambient air will eventually get you to the correct temps but it can take a lot longer to do so. Thermowells in my set up work better and while I might overshoot slightly, this tends to dissipate as I get close to desired temps. I can't explain it in scientific terms, it just works for me. As to sanitizing the thermo, it takes a minute.

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Old 07-10-2010, 07:56 PM   #30
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I've tried it all of those ways and having the controller probe touching the wall of the fermenter is the best compromise. It is affected by both the inside air as well as the fermenting wort. If it's in the center of wort in a thermowell, you'll undershoot the temp. The fridge will become a brick of ice before 5 gallons reacts. Putting the probe in a glass of water is the worst because it is as isolated from the wort temp as you can get. If the ferment is very active, it will be hotter than you want and take a long time for that heat to register in the satellite liquid.

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