Poll: Fermentation chamber temperature probe placement

[ILOVEBEER]

How about using a piece of pottery sponge (the green stuff they use to hold fake flowers up in a pot) It is very porous, easy to penetrate and cheap?

 

[SankePankey]

It is very porous, easy to penetrate and cheap

like a ... a.....oh nevermind.

 

[ILOVEBEER]

haha I knew it!

 

[Catt22]

IMO, having a fan in a serving freezer is a major improvement. The air in the freezer will be much warmer near the top where the beer lines and taps are typically located. The temperature differential can be as much as 10-15 deg F from top to bottom. I get much less foaming when I keep the beer lines and taps chilled. I think a fan is more important in a serving freezer than in a fermentation chamber, but they work very well for both. Most fridges have already have a fan to move the air from the freezer compartment to the refrigerator section. Not all, but most do. Without a fan, the only air movement would be through convection currents. When a freezer is used as a freezer, the entire box is usually at sub zero temps so the air circulation is of no concern. It's a much different situation maintaining uniform temps at fermentation, serving or even lagering temps which are considerably above zero. I was never happy with my serving freezer performance before the fan installation. It was a very big improvement. I'm surprised that using a fan this way is not universally embraced. It's a dramatic difference.

 

[Catt22]

How about using a piece of pottery sponge (the green stuff they use to hold fake flowers up in a pot) It is very porous, easy to penetrate and cheap?

Yes, that would probably work, but for best results you only want to insulate the side away from the fermenter. IOW, you would only half embed the probe. I've used lots of different stuff including a piece of cardboard, a wash cloth, bubble foil insulation and styrofoam. Just about anything will work to some degree. I settled on the bubble foil stuff as it is impervious to moisture, insulates well, it's cheap and I had some laying around.

 

[ILOVEBEER]

So the best place to put the probe is taped to the side of the freezer, but insulated between the probe and the freezer wall?

 

[Catt22]

So the best place to put the probe is taped to the side of the freezer, but insulated between the probe and the freezer wall?

No. That does not work well as the cooling coils are embedded in the wall of the freezer. Attach it to the side of the fermenter or mount it away from the walls in the air. I have mine mounted in the air and use a separate thermometer to measure the fermetner temp. I cover the thermometer probe with some insulation (any type will work. Foam rubber, bubble foil, etc). I don't cover the controller probe with anything at all. You can also do it Bobby's way with similar results by attaching the controller probe to the fermenter and covering it with insulation the same way.

 

[RDWHAHB]

Haven't visited the thread in a while. Cat22-Yes, I do have real experience. I have a ferm chamber that fits 2 carboys. I use a thermowell. Over shoot isn't too much of a biggie for me because the thermal capacity of air (6ft^3?) is so much less than 5 gal of beer (~.7ft^3). Even if I shut the glycol pump off when the chamber (air) is overshot by 20*F, and the thermal xfer between beer & air was perfect, the beer would not overshoot much (1*F?). If interested, I'll run some actual calcs. Those numbers are a guess. I also do industrial controls for my day job.

I am looking at a rebuild which will log both carboy & ambient temps. I am excited to see that.

Cheers, Jeffro

 

[Catt22]

Apparently you have a rather unique fermentation chamber with the glycol chilling etc. I'm sure that it operates much differently than a chest freezer would. With your expertise, I would think that your numbers would be more than just a guess. With the freezers, it's not so much the thermal capacity of the air inside as it is the thermal capacity of the freezer walls and evaporator coils which continue to cool the air for quite a while after the compressors shut down. IMO, the lag in the response time of a thermostat would increase with a probe in a thermowell and this would result in wider temp swings of both the air and the wort. I suppose this could be mitigated if you maintained a very tight differential, but I suspect the swing would exceed the one degree variance I am able to maintain with the controller probe in the air. I don't care what the air temps in the freezer is or how much it swings. I am only interested in maintaining stable fermentation temps and plus or minus a couple of degrees is plenty good enough for my purposes. I actually have my controller set to a fairly wide 5 degree differential. The compressor typically runs about 1/3rd of the time. This is with the fan running continuously. I think I could improve the efficiency a lot by adding some insulation to the inside of the wooden collar and the lid. I'm not sure what kind, if any, insulation is inside the lid behind the plastic liner. I know for sure the 2 X 6 wooden collar has a low R value and it's a major source of heat gain.

 

[patrck17]

Sorry to bring the thread back from the dead but...

I wish somebody would get something like this and do some profiles. Would be interesting to see some comparisons of the wort temp vs thermowell temp vs chamber air temp etc etc etc. Tempted to buy one myself but I don't want to have to drill anymore holes in my keezer.

http://www.pcsensor.com/index.php?_a=viewProd&productId=29

(I link this product cause it seems far more affordable than the alternative thermocouple DAQ's I've seen which typically range into the hundreds.)

 

[vincemash]

Sorry to bring the thread back from the dead but...

I wish somebody would get something like this and do some profiles. Would be interesting to see some comparisons of the wort temp vs thermowell temp vs chamber air temp etc etc etc. Tempted to buy one myself but I don't want to have to drill anymore holes in my keezer.

http://www.pcsensor.com/index.php?_a=viewProd&productId=29

(I link this product cause it seems far more affordable than the alternative thermocouple DAQ's I've seen which typically range into the hundreds.)

I just brewed a hefe on saturday and wanted to keep it at 65, I have my controller probe insulated against the fermenter wall, and a separate temp probe in the air. I probably should have written down the readings daily but I did take note that during the first couple days of aggressive fermentation the air temperature was around 52 to keep the fermenters at 65....the air temperature slowly goes up as fermentation subsides....today its hovering around 61

 

[patrck17]

I just brewed a hefe on saturday and wanted to keep it at 65, I have my controller probe insulated against the fermenter wall, and a separate temp probe in the air. I probably should have written down the readings daily but I did take note that during the first couple days of aggressive fermentation the air temperature was around 52 to keep the fermenters at 65....the air temperature slowly goes up as fermentation subsides....today its hovering around 61

This is very informative feedback. Thanks for the info. I currently have my probe mounted between a paper towel and the carboy wall. I don't imagine the insulation is as good as it could be but I imagine it is getting the job done.

 

[mthompson]

I voted for "insulated on the side of fermenter", and here is why...

I set up my fermentation chamber with a Ranco controller (b-day present) and put in the first batch on Jan. 1. I set the controller to 65*F with 1*F differential and made an insulated 'pouch' for the thermistor out of a few layers of cotton roll and a paper backing, then loosely duct taped it to the side of the bucket, as to not squish the cotton and reduce insulation properties, with thermistor in direct contact to bucket.

I have been tracking temps in each of four locations with two of these traceable thermometers -

1. ambient air temp as soon as I open door,
2. inside tub of sanitizer next to fermenter for blow-off tube,
3. inside the fermenter (sanitized from second measurement, remove air lock, test, replace lock),
4. inside the insulated pouch next to the thermistor

Today, at the height of fermentation (judged by the copious amounts of CO2 continually bubbling in the sanitizer and the fridge cycling on once every 20-30 minutes), the four measurements read (as soon as cycle turned off):

1. ambient air temp - 58.2*F,
2. inside sanitizer - 64.1*F,
3. inside the fermenter - 65.7*F,
4. inside the insulated pouch - 65.2*F
5. Ranco controller - cycles on when it displays 66*F and turns off when it displays 65*F

**each thermometer read the same temperature each time at each location

I will test the same temperatures after fermentation subsides a bit more....and maybe other can take similar readings using the various methods and post up the results. It's the only real way to settle on the "best" way to measure and control fermenter temperatures

 

[SpanishCastleAle]

I think it's worth mentioning that any container full of liquid, whether it be a carboy/corny full of beer or a jar with water in it, will always tend to be more towards the outside temp than the middle of any 'differential'. So if your controller turns ON at say 64* F and OFF at 68* F and the temp outside the fridge is significantly warmer than that; the middle of the differential is 66* F but a container of liquid in the fridge will be warmer than 66* F. The reason is because as soon as that controller shuts OFF at 64* F, the temp immediately starts to rise (and relatively quickly). As the temp gets closer to 68* F, the temp is rising quite a bit slower so the container of liquid spends way more time above 66* F than below it.

I only mention this because not all of the increased temp inside a fermenter is always due to the heat of fermentation, some of that is often just due to what I described above.

 

[Randar]

Not to restart the debate, but I originally voted for the thermowell option. Since that time I have seen the light and taping to the side of the container works marvelously for me. It is not really measuring ambient air temp. Since I ferment in Sankes there is some decent thermal conductance so while the center of the keg may be a couple degrees warmer during highly active fermentation, I can choose to adjust for this (or not) and control the temps very accurately, even in a shoddily-insulated fermentation chamber. I think this is also very similar to a glycol jacketed fermentor. The thermowells in 30 BBL fermentors do not reach to the perfect center of the tank, nor would that give extensive benefit (since the wort/beer closest to the walls that is absorbing the thermal transfer from the glycol system could be many degrees cooler).

 

[EarthBound]

Thanks to all for the tips. I was about to install a thermowell and was immediately stopped dead in my tracks after reading this thread.

"Insulated against the fermenter wall" for me!

 

[hollywoodbrew]

I'm using a thermowell for my controller probe. I get a swing of about 3-4 degrees every 8 hours or so. The freezer turns on 3 times a day so I like how its really easy on the compressor, and uses less electricity.

Is a variation of 3-4 degrees okay or will that make off flavors?

 

[Salmonhouse]

I believed that the air was the most appropriate place for the temp probe when i first hooked up my controller and was shot down by opinions in the 'ebay diy controller' forum. I then went to a thermowell. Now that i have a thermowell i find that my heater does overheat the wort to where my compressor has to kick in. I don't think i should be needing my compressor at all since its colder outside than in my chamber. Maybe my chamber is too well insulated or my heater is over sized.

I think i'm going to try to use the thermowell initially for active fermentation and then use the air. Either that or use the air entirely and monitor the temp in my thermowell with a separate thermometer and compensate my controller accordingly.

 

[Catt22]

Either that or use the air entirely and monitor the temp in my thermowell with a separate thermometer and compensate my controller accordingly.

That's exactly how I do it. I also have a muffin fan running continuously which circulates the air around the fermenter cooling it more effectively (or heating). I use an ordinary indoor/outdoor digital thermometer with min/max memory. The min/max readings tell you what the actual temp swing is. Running with a 4 degree differential the min/max variance is only 1.3 degrees.

 

[Salmonhouse]

I think i'm also going to play with adjusting the thermostat on the heater.

 

[ozonefirefighter]

is it really that important where you put it? As long as you keep it in the same place shouldnt you get consistant results?

 

[Catt22]

is it really that important where you put it? As long as you keep it in the same place shouldnt you get consistant results?

No, but much depends on how tight you want to hold the temperature range and what it is you are cooling (ie fermenters or serving kegs etc). There are more variables involved than you might guess. How these variables interrelate and what happens when you change any of them can make comparisons difficult. You have all different sizes and configurations of refrigerators and freezers. Some with fans, some without. Some with collars, some without and on and on. All with varying contents and varying ambient conditions.

 

[brewfreeordie]

Sorry for dragging up an old thread but it's really good info here.

I use a blow-off tube on every brew, and feed the probe into the starsan bucket, through the tubing, down the airlock and into the wort. After a few brews I got paranoid that I was poisoning myself from the plastic probe (stupid, I know) so I got some food/medical grade shrink wrap and put about 15" on the probe.

I converted a commercial Pepsi fridge with a Love controller. I wired the fan for continuous operation and use the controller (along with a SSR) to cycle the compressor. I tried taping it to the bucket w/ insulation but wasn't convinced I was getting an accurate number so I too various readings around the fridge and inside actively fermenting wort. Vigorously fermenting wort was a full 8 degrees away from the probe reading (I calibrated before experimentation) and fell off as the yeast settled down.

I think a lot has to do with my choice of chambers, and that the commercial unit was a poor choice, but hey the price was right. Because it's a beverage cooler it's cooling power is way, way oversized for my application, and was leading to short-cycling. I compensated by increasing the differential to 3 degrees but even this was giving me 3-4 cycles per hour and the outside temp was not linear with the actual wort temp.

Long story short, with the probe in the wort the compressor cycles 1-2 times/hr for about 12-15 minutes and the wort temp stays within 2 degrees of target.