How to measure temps in ferm chamber

[martinlarosa]

Hi guys, what is the appropriate way of measuring the temp of the beer?
For what I've been researching it would be to make the stc-1000 work with the chamber temp, but set to a temp that makes the beer be at the desired temperature?

For example, I have the stc-1000 set at 18° C but the beer I think it is at 20° C ( The sticker themometer and a temp of a sample I took read that temp). So let's say that if I want to ferment at 20° I have to make sure the average temp of my fermentation chamber is 18°, making the tem controller to act on the chamber air and not the beer temp as that would cause lots of swings in temps right?.

Although I would imaging that this would be a problem if fermenting different yeasts or beers at the same time, as some might get hotter than others?

 

[FVillatoro]

Hi guys, what is the appropriate way of measuring the temp of the beer?
For what I've been researching it would be to make the stc-1000 work with the chamber temp, but set to a temp that makes the beer be at the desired temperature?

For example, I have the stc-1000 set at 18° C but the beer I think it is at 20° C ( The sticker themometer and a temp of a sample I took read that temp). So let's say that if I want to ferment at 20° I have to make sure the average temp of my fermentation chamber is 18°, making the tem controller to act on the chamber air and not the beer temp as that would cause lots of swings in temps right?.

Although I would imaging that this would be a problem if fermenting different yeasts or beers at the same time, as some might get hotter than others?

The only sure way to measure beer temperature is by getting a thermowell into the beer.
Inside the thermowell goes the temperature probe and you're getting an exact reading and you can control fermentation temp that way.

I personally use a 1/4 thermowell which goes through a very tight-fitting grommet that's wedged on a hole that I drilled on my bucket lid. Inside the thermowell I use a 1/4" Johnson Controls temp probe which turns my little cooler on and off depending on what I set my temp to (depending on yeast).
With my setup I stay within 2 degrees of what I set my temp to and it works great.

Highly recommend it!

Here's a pic so that you can see what i'm talking about:

 

[HollywoodTK]

I agree with FVillatoro, I use a thermowell in the heart of the beer to control temps.

Get your wort down to fermentation temp before inserting the probe as that will help ensure you don't overshoot by too much initially. After the initial cool, I find that my fridge runs only 10 or so minutes every few hours (which is a pretty good cycle time for the condenser) and my temps stay within +1/-2 degrees of target.

I'll generally set my controller (Johnson) to 1 degree above my actual target for the first few days. The fermentation will try to raise the wort temp, which will mean more action required by the fridge. This period is where the overshoot is most evident.

After initial fermentation, I I set it to my desired rest temp exactly and let it ride.

Edit:
If you decide to control to the temp in the chamber, you'll have to do some trial and error to see how your system reacts, but generally I'd say during the first few days you'll need to have the chamber a few degrees below the desired wort temperature. Fermentation is an exothermic reaction, and will cause the wort to heat up, if your fridge is at your desired temp, your actual temp during active ferm. will be higher.

 

[thereverendmaynard]

I am using a brewpi and it works great. According to the temps measured in my thermowell I am within .1f of my set point. There is a thread on building a brewpi with all the instructions on how to build.

You also get some nice features like Beer setpoints, Fridge setpoints, or timed programs (eg, hold x temp for x days then increase etc)

 

[jddevinn]

+1 for using a thermowell

 

[martinlarosa]

Thanks everybody.
My concern is the overshot when measuring with a thermowell.
I just saw that the BrewPi handles that with an algorithm, do you know if there is a way of building a brewpi over a raspeberry pi instead of using an arduino?

 

[jddevinn]

When I used carboys I didn't see any noticeable overshoot directly measuring the wort temp. The thermal mass of the liquid is many many times larger than the thermal mass of the air surrounding it.

 

[DurtyChemist]

I take a blue shop towel and fold it about 4 times and put the probe on the carboy and cover it with the paper towel then tape all 4 sides of the towel. It will keep the air temp from influencing the temperature the probe reads and it's simple and works for glass, pet carboys or buckets.

 

[thereverendmaynard]

The brewpub requires both a raspberry pi as well as an arduino. The actual process code runs on the arduino, along with the physical connections to the sensors and relays. The pi is just the Web server

 

[Nagorg]

The BrewPi has been deprecated by the BrewPi Spark. https://store.brewpi.com/featured/brewpi-spark-v2 I think you can still build the BrewPi though if you're so inclined... . I've personally been considering a Fermostat: http://ohmbrewautomations.com/

EDIT: And use a thermowell too!

 

[Natdavis777]

Thermowell or taped to the side of the fermentor... Use one either way. Just dont rely on ambient temp. Best way to fry a compressor smack

 

[martinlarosa]

Why would measuring freezer ambient temp fry a compressor?

 

[Natdavis777]

Subtle changes like opening the door or just the air dropping 1-2 degrees will kick on the compressor. There is a chart floating somewhere that should compressor activity while measuring ambient, and the compressor was turned on around 100x a day. Compare that to the probe in a thermowell or taped to the side of the carboy with some insulation on the outside, the beer itself would have to change that much that frequently to keep the compressor running all the time. Well, this doesnt happen. Instead, the compressor runs a lot less and the temps in the chamber stay stable at whatever your setting it.

I fried my first freezer this way, and it wasnt very old.

 

[martinlarosa]

I'm still worried about the inertia in the temp change. What range do you set the temp controller to start working on? I currently have it at +/- 1.5° Celsius. I guess if I do that with the sensor in the beer I would greatly overshot the target temp

 

[Natdavis777]

Mine is set to stay +1/-1 of the set temp. It then has a 3 min compressor delay. I have no statistical measurements to provide, but on brewdays when I am in the garage for a good while, the compressor only runs a hand full of times during a 6 hour period.

 

[martinlarosa]

I'm not worried about it running too many times. I'm worried about it running for too long until then beer gets the cold it needs.... And then keep getting colder because the air is really cold because it gets cold much faster than the beer

 

[HollywoodTK]

The same inertia that makes the beer take a long time to cool will prevent the beer from over-cooling significantly once it does reach it's temperature. Refrigerators/freezers can only get so cold, and if you have one with a temperature dial, even better. As I said in my first post, I usually set it to about 1 or 2 degrees above my desired fermentation temperature during active fermentation, then drop it down to the desired temp after that. This usually keeps me in a good range.

The air will get cold, but the amount of energy that amount of cold air will be able to transfer from the warmer volume of beer isn't as significant as you might think.

 

[martinlarosa]

Alright I guess after two pages I have to give up an give it a try
Thank you all for your inputs!

 

[HollywoodTK]

Note that some people do successfully measure the ambient temp. Some people also tape the probe to the outside of the fermenter (after insulating to ensure proper readings). There are many ways to go about it; I find that using a thermowell results in accurate temp control and minimal compressor cycling, so that's what I use.

 

[devils4ever]

I never bothered with the thermowell.

I take the temperature probe and wedge it between the side of the carboy and some bubble wrap inside the wall of the refrigerator. This takes a combination of air and wort temperatures. It works great for me.

 

[stratslinger]

Until just a couple months ago, I've been in team "tape the sensor to the outside of the fermenter." Then I recently picked up a thermowell and I've used that for my last two brews. Never had a problem where the brew cools too much... Remember, there's a heckuva lot more thermal mass in the fermenter and its contents than there are in the ambient temp in your chamber. That's a big part of why they cycle so much less when you're managing the fermenter temp than the ambient temp. The fridge cuts off when you hit your desired temp, and I may have seen mine coast another 0.1C, but never more than that (I have an unmodified STC1000 that only operates in Celsius, and I've never had a problem maintaining a range of +/-0.5C, and never noticed any significant overshoot in either direction.

 

[trav77]

I'm still worried about the inertia in the temp change. What range do you set the temp controller to start working on? I currently have it at +/- 1.5° Celsius. I guess if I do that with the sensor in the beer I would greatly overshot the target temp

I use a thermowell in conjunction with a rigged up dual stage STC-1000 switch and a brewbelt. The brewbelt keeps the internal beer temperature from dropping too low as a result of inertia from the freezer kicking in. I noticed the OP is also already using an STC-1000 so that might be a way to go.

I get very precise control this way and I don't find the condenser kicking in very often at all (also there is a delay on the STC to prevent this).

No fermenter in the chamber at the time of this pic but I generally set it up with the brew belt around the actual carboy while fermenting. It does work well to simply control ambient when you pull the thermometer out of the thermowell and the brew belt is just left in the freezer basket.... say for cold crashing, etc.

 

[SleepyCreekBrews]

I use a couple layers of reflectix taped over the sensor, similar to Durtychemist's method.

 

[martinlarosa]

Excellent. So what delta are you setting the STC-1000 to operate in when measuring the fermenter's temp?
Right now I sensor freezer's ambient temp and use a 1.5° Celsius delta. I'm guessing you guys go for a narrower margin as you are sensing the fermenters?

This morning I put a Golden Ale to cold crash and put the tip of the sensor touching the wall of the fermenter. No tape or insulation yet. And it was already measuring hotter temps than the freezers ambient. Which doesn't surprise me, but I'll leave it like that until I tape a towel around it or find a cord/belt.

Also thinking about purchasing those little heaters as we are already in Autumn here in Argentina. It was 13° Celsius outside this morning.

 

[kombat]

Another thermowell advocate here. I use a dual-stage STC-1000 controller with a 0.3°C variance and a 10 minute compressor delay. I have a heating belt exactly like the one shown in the photo in the previous post, connected to the heating circuit. "Overshooting" temperatures is not a problem. As mentioned, in practice, the beer has far more thermal mass and will remain very close to the target temperature. Thermowell is the "correct" way to do. All other methods are hacks or workarounds to try and get as close to a true thermowell profile as possible, without spending $20 on the thermowell. Just get the right tool for the job. Heck, they're so cheap, get 2 and save on shipping. It's one of the cheapest pieces of homebrewing equipment, and it doesn't get any better than a true thermowell for optimizing reading the temperature of your beer.

 

[trav77]

Excellent. So what delta are you setting the STC-1000 to operate in when measuring the fermenter's temp?
Right now I sensor freezer's ambient temp and use a 1.5° Celsius delta. I'm guessing you guys go for a narrower margin as you are sensing the fermenters?

I set mine at +/- 0.5 C and it holds that quite steadily without much freezer cycling. As mentioned, there's a lot of thermal mass there to mitigate rapid temp swings if you have the probe in the thermowell/beer as opposed to ambient in the freezer.

 

[stratslinger]

I set mine at +/- 0.5 C and it holds that quite steadily without much freezer cycling. As mentioned, there's a lot of thermal mass there to mitigate rapid temp swings if you have the probe in the thermowell/beer as opposed to ambient in the freezer.

Same config here - and I've done that successfully now with both the probe strapped to the outside of the fermenter and with the probe in a thermowell.