Lager chamber

[hubie]

While it is true that the thermal mass of the carboy/bucket with liquid is much greater than the surrounding air and that their temperature should dominate, this is true only if you have good thermal contact between the probe and the carboy/bucket.  Unfortunately, unless you’re using some sort of thermal grease or other goop between the probe head and the carboy, you don’t have good thermal contact.  In my case, which is using the thermal sensor that came with my temperature controller, I have to try to get a hard cylinder (temp sensor) to make good contact with a curved hard surface (carboy).  Even in an ideal setting, that is a very tiny surface contact area, so thermal transfer needs to occur using the air trapped under the tape and/or through the tape itself.

BrewQwest’s observations make sense to me.  From a thermal engineering standpoint, you’d never attach a temperature probe to a surface unless you used some sort of thermal transfer material, like grease, along with it.  If you really want to know and control the temperature of the liquid in an absolute sense, you really need to use a thermowell or attach the probe better thermally.  I don’t have a good feel for whether putting bubble wrap over the probe before taping it is better or not.  To me, making sure air cannot exchange between the ambient and below the tape is more important, and using bubble wrap in my opinion makes that much easier to achieve.

[blatz]

@brewqwest

@hokerer

While it’s true that ambient can be much warmer than actual wort temp, when you place your probe in contact with fermenter and insulate it, you’re not measuring ambient - you’re within no more than +/- 1 degree of the wort temp.

I used to think the same as your quote above, but I am one who questioned it the more I thought about it…So I performed an experiment placing three thermometers inside my fermentation chamber.  T1 was placed in a thermowell at the center of the glass carboy. T2 was taped to the outside of the glass carboy half way up its height and then insulated from the surrounding ambient air in the fermentation chamber. T3 was placed inside the chamber only to read ambient temps. Throughout the fermentation process all probes were within a degree of each other until the yeast activity began to really ramp up. At that time, T1 would follow the increase in yeast activity. T2 would lag behind a couple degrees and T3 would continue to read the ambient which was nearing 1.5 degrees lower than T2 which was 1.5-2 degrees lower than T1 which was reading the interior of the vessel. So at max yeast activity, there was a 3-3.5 degree spread between ambient and internal temps. Now if I want my yeast to ferment a lager at 52F, I want my yeast to ferment at 52F…not 55-55.5F…Ergo, the temp controller is hooked to the probe reading the internal vessel temp, not the other two… YMMV…If you have not performed this test on your own fermentations you may want to give it a try… cheers!!!

not as rigorous as your tests, but when I got my first conical, I tested the actual wort temperature versus the temp read by the probe velcro-ed to the side of the cone at various points during fermentation (i was seeing if it was worth it to get a thermowell), and even at high krausen the dead center of the wort was within a degree (as measured by my 24" SS thermocouple probe and Palmer Wahl reader) of the probe affixed to the side.  It was enough to make me forgo the thermowell - I always ferment on the lower side of the range anyway, so even if its 1df off, no biggie.

never tested ambient - figured it was irrelevant.

[wort-h.o.g]

@blatz

@brewqwest

@hokerer

While it’s true that ambient can be much warmer than actual wort temp, when you place your probe in contact with fermenter and insulate it, you’re not measuring ambient - you’re within no more than +/- 1 degree of the wort temp.

I used to think the same as your quote above, but I am one who questioned it the more I thought about it…So I performed an experiment placing three thermometers inside my fermentation chamber.  T1 was placed in a thermowell at the center of the glass carboy. T2 was taped to the outside of the glass carboy half way up its height and then insulated from the surrounding ambient air in the fermentation chamber. T3 was placed inside the chamber only to read ambient temps. Throughout the fermentation process all probes were within a degree of each other until the yeast activity began to really ramp up. At that time, T1 would follow the increase in yeast activity. T2 would lag behind a couple degrees and T3 would continue to read the ambient which was nearing 1.5 degrees lower than T2 which was 1.5-2 degrees lower than T1 which was reading the interior of the vessel. So at max yeast activity, there was a 3-3.5 degree spread between ambient and internal temps. Now if I want my yeast to ferment a lager at 52F, I want my yeast to ferment at 52F…not 55-55.5F…Ergo, the temp controller is hooked to the probe reading the internal vessel temp, not the other two… YMMV…If you have not performed this test on your own fermentations you may want to give it a try… cheers!!!

not as rigorous as your tests, but when I got my first conical, I tested the actual wort temperature versus the temp read by the probe velcro-ed to the side of the cone at various points during fermentation (i was seeing if it was worth it to get a thermowell), and even at high krausen the dead center of the wort was within a degree (as measured by my 24" SS thermocouple probe and Palmer Wahl reader) of the probe affixed to the side.  It was enough to make me forgo the thermowell - I always ferment on the lower side of the range anyway, so even if its 1df off, no biggie.

never tested ambient - figured it was irrelevant.

So I ran the test- thermowell vs. probe attached to outside of carboy, insulated. The Johnson control probe is in my thermowell, and does not register decimal temp…just whole numbers(52f)My probe on outside of carboy runs decimals(51.5f). so the difference seems to be about 1 to max 1.5f ,as I would have expected.

[brewqwest]

@blatz

…not as rigorous as your tests, but when I got my first conical, I tested the actual wort temperature versus the temp read by the probe velcro-ed to the side of the cone at various points during fermentation (i was seeing if it was worth it to get a thermowell), and even at high krausen the dead center of the wort was within a degree (as measured by my 24" SS thermocouple probe and Palmer Wahl reader) of the probe affixed to the side.  It was enough to make me forgo the thermowell - I always ferment on the lower side of the range anyway, so even if its 1df off, no biggie.

never tested ambient - figured it was irrelevant.

If you are using a conical… all bets are off with my experience, as I have no experience with conicals only with fridges and other low-level fermentation chambers which the majority of home brewers have access to…If you are using pails or glass carboys then I suggest you best perform the tests yourself and I doubt there would be much difference in your findings…if there are I personally would doubt them after the many tests I have conducted on this matter… Yet, if there are, please pm me and let me know your particulars as I am preparing notes, experiences, to publish…thank you…

[brewqwest]

@wort-h.o.g

So I ran the test- thermowell vs. probe attached to outside of carboy, insulated. The Johnson control probe is in my thermowell, and does not register decimal temp…just whole numbers(52f)My probe on outside of carboy runs decimals(51.5f). so the difference seems to be about 1 to max 1.5f ,as I would have expected.

Please pm me the particulars of your test…as a 1.5 degree temp swing (especially with a johnson controller) between actual and ambient, does not seem to follow the test curves plotted by many of the home brewers…especially since you just started a fermentation about a week ago and my posts are only a couple days old…thank you and cheers!!

[corkybstewart]

@brewqwest

@hokerer

While it’s true that ambient can be much warmer than actual wort temp, when you place your probe in contact with fermenter and insulate it, you’re not measuring ambient - you’re within no more than +/- 1 degree of the wort temp.

I used to think the same as your quote above, but I am one who questioned it the more I thought about it…So I performed an experiment placing three thermometers inside my fermentation chamber.  T1 was placed in a thermowell at the center of the glass carboy. T2 was taped to the outside of the glass carboy half way up its height and then insulated from the surrounding ambient air in the fermentation chamber. T3 was placed inside the chamber only to read ambient temps. Throughout the fermentation process all probes were within a degree of each other until the yeast activity began to really ramp up. At that time, T1 would follow the increase in yeast activity. T2 would lag behind a couple degrees and T3 would continue to read the ambient which was nearing 1.5 degrees lower than T2 which was 1.5-2 degrees lower than T1 which was reading the interior of the vessel. So at max yeast activity, there was a 3-3.5 degree spread between ambient and internal temps. Now if I want my yeast to ferment a lager at 52F, I want my yeast to ferment at 52F…not 55-55.5F…Ergo, the temp controller is hooked to the probe reading the internal vessel temp, not the other two… YMMV…If you have not performed this test on your own fermentations you may want to give it a try… cheers!!!

I always use a thermowell for my fermenters.  I’ve tried the insulated probe on the side of the fermenter and it was always several degrees different from what my temp controller showed.  Plastic is a poor thermal conductor compared to stainless so on my buckets I had the biggest difference.  A thermowell is so imple to make and use I never understood why more people don’t use them.

[wort-h.o.g]

@brewqwest

@wort-h.o.g

So I ran the test- thermowell vs. probe attached to outside of carboy, insulated. The Johnson control probe is in my thermowell, and does not register decimal temp…just whole numbers(52f)My probe on outside of carboy runs decimals(51.5f). so the difference seems to be about 1 to max 1.5f ,as I would have expected.

Please pm me the particulars of your test…as a 1.5 degree temp swing (especially with a johnson controller) between actual and ambient, does not seem to follow the test curves plotted by many of the home brewers…especially since you just started a fermentation less than a week ago and my posts are only a couple days old…thank you and cheers!!

My fermentation started Saturday…3 days ago .  Using a Taylor probe thermo and my Johnson controls. When both were strapped to outside of carboy, they registered no difference ( 51 and 51.5f…)As I stated, Johnson controls probe temp is whole numbers, and Taylor is decimals. I’m not sure if the Johnson controls turns off at my set temp of 51f at 51.0’ or 51.9f…there lies the unknown differential between the two test probes. I watched my probe attached to outside off carboy drop to 50.5 before my freezer kicked off, and Johnson control registered 51f.  So I’m figuring about 1.5f differential between the two.  If I’m reading your post correctly, you indicated 1.5-2f difference between thermowell and insulated probe…so I’m basically stating my results are the same at about 1.5f difference.

[brewqwest]

@hubie

While it is true that the thermal mass of the carboy/bucket with liquid is much greater than the surrounding air and that their temperature should dominate, this is true only if you have good thermal contact between the probe and the carboy/bucket.  Unfortunately, unless you’re using some sort of thermal grease or other goop between the probe head and the carboy, you don’t have good thermal contact. I don’t know why I never thought of using this information before… I recently built an all-electric system with two 30 amp circuits feeding it in order to easily do back to back sessions or to reheat the HLT for hot rinse water while the boil continues…My SSR’s use the very same thermal grease to thermally connect to the heat sink… I don’t know why I never drew the same correlation you just mentioned, prior to now… thank you!!! In my case, which is using the thermal sensor that came with my temperature controller, I have to try to get a hard cylinder (temp sensor) to make good contact with a curved hard surface (carboy).  Even in an ideal setting, that is a very tiny surface contact area, so thermal transfer needs to occur using the air trapped under the tape and/or through the tape itself.

BrewQwest’s observations make sense to me.  From a thermal engineering standpoint, you’d never attach a temperature probe to a surface unless you used some sort of thermal transfer material, like grease, along with it.  If you really want to know and control the temperature of the liquid in an absolute sense, you really need to use a thermowell or attach the probe better thermally.  I don’t have a good feel for whether putting bubble wrap over the probe before taping it is better or not.  To me, making sure air cannot exchange between the ambient and below the tape is more important, and using bubble wrap in my opinion makes that much easier to achieve.

cheers!!–BrewQwest

[davidgzach]

OK, been thinking about this as I have fermented in my chest freezer using all three methods:  thermowell, taped to carboy/bucket inside styrofoam and ambient.

Now in this thread the discussion has been around the difference in wort temp for the three methods.  My question is, could different methods be better for different phases of the fermentation?  My thought:

When fermentation is starting, I think you want the probe in the wort so the machine is reacting to the raising in temperature due to the yeast activity.  It’s constantly keeping the wort from raising in temp and stable at fermenation temps.

The same goes for bringing the wort up for a diacetyl rest and on the way down to lagering temps.  The best way IMO is in a thermowell.

However, once the wort is fermented and you bring the beer down to lagering temps, wouldn’t the probe be better suited in the ambient air?  If you leave it in the thermowell, then you are guaging when the thermal mass of the beer raises/lowers temp.  However if you keep the ambient temp +/- 1 degree, then the beer is maintaining a consistent temperature as there is not enough time for the thermal mass to change while the ambient air is being maintained.

Or am I just nuts?

Dave

[wort-h.o.g]

@davidgzach

OK, been thinking about this as I have fermented in my chest freezer using all three methods:  thermowell, taped to carboy/bucket inside styrofoam and ambient.

Now in this thread the discussion has been around the difference in wort temp for the three methods.  My question is, could different methods be better for different phases of the fermentation?  My thought:

When fermentation is starting, I think you want the probe in the wort so the machine is reacting to the raising in temperature due to the yeast activity.  It’s constantly keeping the wort from raising in temp and stable at fermenation temps.

The same goes for bringing the wort up for a diacetyl rest and on the way down to lagering temps.  The best way IMO is in a thermowell.

However, once the wort is fermented and you bring the beer down to lagering temps, wouldn’t the probe be better suited in the ambient air?  If you leave it in the thermowell, then you are guaging when the thermal mass of the beer raises/lowers temp.  However if you keep the ambient temp +/- 1 degree, then the beer is maintaining a consistent temperature as there is not enough time for the thermal mass to change while the ambient air is being maintained.

Or am I just nuts?

Dave

I think you are on to something. Core temp during fermentation is important. However when lagering, perahaps the ambient air temp helps maintain a contestant temp vs. thermowell…think we have an experiment to do!

[wmlindel]

I have experimented with both the probe on the outside and insulated and with a thermowell. Monitoring temps at the same time, they were within 1 degree. People have commented on “hot spots” during fermentation and said that the themowell should be more accurate, but I have found essentially no difference. I think the convective movement of the wort durning fermentation distributes the heat evenly.