Am i overthinking this?

[Scout]

Im getting a refrigerator set up for fermenting, and like many others, I have a small space heater inside for heat. As a test, I put a small cup of water inside with the probe in it and turned everything one. The result was some pretty wild temperature swings. I figured it had to do with the delay of that water heating to the air temp, and once the heat shut off the water temp would continue to climb until the fridge would come on to cool it, rinse and repeat.

My thoughts are to get a reptile heat mat to stick on the fermenter (a keggle) which would prevent the wort from over temps. The other thought is that since the fridge is in my garage, I should just leave the heat off during the summer and fridge off in the winter. Maybe both the heat mat and unplugging?

 

[AlexKay]

My recommendation is always to use a small fan in place of a heater, and to leave it on all the time. I find the motor on the fan generates enough heat, and you can just let the temperature controller handle cold. The fan makes the temperature within the freezer pretty constant everywhere, which is a big plus. Also, it gets enough of the CO2 out of the freezer right after opening it that you have less of the pass-out-and-fall-in hazard.

I hang my temperature probe in air. This undoubtedly cycles my compressor on and off more frequently, but I haven't had a freezer break on me yet. If you can't bring yourself to do this, try a smaller amount of water -- basically, fiddle with the thermal mass until you've got the behavior you want.

 

[jambop]

In an ideal world you would want the probe in the centre of the fermenter and instant heat transfer... you won't get that though but the centre of the mass of beer is where you want to know the temperature... other wise why bother heating it at all? If you have it in the surface layer the rest of the beer is not being heated to the correct temperature . In summary though I honestly thing you can chase your tail thinking about these matters because there is not an ideal answer because of heat transfer issues. I have a very low wattage heater so I am hoping that because of this the heat supplied is so low there is less issues with surface over heating .

 

[eric19312]

I think a space heater is going to produce way too much heat and likely drive temperature swings. I agree with @AlexKay ... a small fan, always on, is a good way to go. I put mine on top of a ducting tube so that it pulls air from the bottom of the freezer, past my repile bulb, and pushes it up. I use a 60W bulb as a heat source, it provides more than enough heat.

I also use a dual probe temperature controller which considers both the temperature of the fermenting beer (thermowell in the conical) and the air temperature inside the freezer. The dual probe controller's logic looks at temperature of the beer and if it is too cold it then looks at temperature of the air inside the freezer. If the air inside the freezer is below the limit I set (usually 75F for a ferment I am controlling at 66-68F) it will listen to the call for heat and turn on the bulb when requested. Burt if the air temperature is at or above that set limit it will ignore a call for heat.

 

[Bobby_M]

Im getting a refrigerator set up for fermenting, and like many others, I have a small space heater inside for heat. As a test, I put a small cup of water inside with the probe in it and turned everything one. The result was some pretty wild temperature swings. I figured it had to do with the delay of that water heating to the air temp, and once the heat shut off the water temp would continue to climb until the fridge would come on to cool it, rinse and repeat.

My thoughts are to get a reptile heat mat to stick on the fermenter (a keggle) which would prevent the wort from over temps. The other thought is that since the fridge is in my garage, I should just leave the heat off during the summer and fridge off in the winter. Maybe both the heat mat and unplugging?

The best compromise is fixing the probe to the side of the fermenter with a small patch of foam rubber (2" x 2") over the probe. This will isolate the probe from the ambient temp in the box for short periods of time. During active fermentation, the probe/surface of the fermenter will always be a little colder than the core of the liquid, but it's close enough. Putting the probe in a separate buffer fluid is unrealistic because it is almost 100% disconnected from the temp of the beer. Putting it into the core via a thermowell would cause huge swings unless the beer was being stirred.

 

[doug293cz]

The best compromise is fixing the probe to the side of the fermenter with a small patch of foam rubber (2" x 2") over the probe. This will isolate the probe from the ambient temp in the box for short periods of time. During active fermentation, the probe/surface of the fermenter will always be a little colder than the core of the liquid, but it's close enough. Putting the probe in a separate buffer fluid is unrealistic because it is almost 100% disconnected from the temp of the beer. Putting it into the core via a thermowell would cause huge swings unless the beer was being stirred.

This is the best way to proceed. Plus a reptile mat, or similar for heating. I used a small space heater for a while, but it caused too much cycling because it provided too much heat.

There is a fairly long explanation of why this is better than a thermowell or temp probe in a jar of water, but I don't feel like typing it right now (I've typed it many times in the past.)

Brew on

 

[JohnSand]

I think part of the reason for your temp swings was the small volume of your test liquid.
I tape the probe to the side of the fermenter, the volume of liquid buffers any changes.

 

[agentbud]

The best compromise is fixing the probe to the side of the fermenter with a small patch of foam rubber (2" x 2") over the probe. This will isolate the probe from the ambient temp in the box for short periods of time. During active fermentation, the probe/surface of the fermenter will always be a little colder than the core of the liquid, but it's close enough. Putting the probe in a separate buffer fluid is unrealistic because it is almost 100% disconnected from the temp of the beer. Putting it into the core via a thermowell would cause huge swings unless the beer was being stirred.

This is interesting. I guess I always just assumed that using a thermowell would be more accurate than the side of the fermenter. Would love to hear the logic behind this. I find the thermowell gets in the way a lot so any valid reason to get rid of it is good by me.

 

[Scout]

The best compromise is fixing the probe to the side of the fermenter with a small patch of foam rubber (2" x 2") over the probe. This will isolate the probe from the ambient temp in the box for short periods of time. During active fermentation, the probe/surface of the fermenter will always be a little colder than the core of the liquid, but it's close enough. Putting the probe in a separate buffer fluid is unrealistic because it is almost 100% disconnected from the temp of the beer. Putting it into the core via a thermowell would cause huge swings unless the beer was being stirred.

Thanks, my next plan is a reptile mat and the probe stuck to the side of the vessel. I'll put the heat wrap on the side opposite the probe, so the mat doesn't heat the probe, and add a fan as others have suggested.

This is interesting. I guess I always just assumed that using a thermowell would be more accurate than the side of the fermenter. Would love to hear the logic behind this. I find the thermowell gets in the way a lot so any valid reason to get rid of it is good by me.

I think the issue is, if I understand right, that its going to tak e alot of time for the temp of the beer along the outside to reach the inside, and by the time the inside reaches temp the outside has overshot, hence why he siad it would work if it is being stirred.

This is the best way to proceed. Plus a reptile mat, or similar for heating. I used a small space heater for a while, but it caused too much cycling because it provided too much heat.

Brew on

Thats the same issue I'm having, crazy temp swings. At least its just plain water to work out the bugs first.

I think part of the reason for your temp swings was the small volume of your test liquid.
I tape the probe to the side of the fermenter, the volume of liquid buffers any changes.

Part of the issue isn't that the test water is too small, its that I'm heating the air and using the air to heat the water. the water will get to temp, the heater shuts off, but the air is still hot and the water continues to warm up.

 

[agentbud]

This conversation is bringing up a lot of things I had not thought of. If the best way is to tape the temp probe to the side of the fermenter instead of using a thermowell, it would seem that you could not attach a heat mat directly to the side of the fermenter, even if on the other side, as that would heat the temp probe directly through the fermenter wall. But if you just have the heat mat loose in the chamber, then (like OP says above) the air gets too hot? Maybe I am overthinking this too! Time for a beer.

 

[jambop]

Thanks, my next plan is a reptile mat and the probe stuck to the side of the vessel. I'll put the heat wrap on the side opposite the probe, so the mat doesn't heat the probe, and add a fan as others have suggested.

I think the issue is, if I understand right, that its going to tak e alot of time for the temp of the beer along the outside to reach the inside, and by the time the inside reaches temp the outside has overshot, hence why he siad it would work if it is being stirred.
Thats the same issue I'm having, crazy temp swings. At least its just plain water to work out the bugs first.


Part of the issue isn't that the test water is too small, its that I'm heating the air and using the air to heat the water. the water will get to temp, the heater shuts off, but the air is still hot and the water continues to warm up.

Use a very much less powerful heater. I use a 25 W heater for my fridge and in conjunction with the inkbird it works great. Yesterday I kegged and bottled 25 L which I put in the fridge the next morning it was up to 20C. The heater kicks in when the temp falls to 19C and switches off at 20C . It takes about 20mins heating to go from 19 to 20 C depending on the outside temperature and the quantity of stuff in the fridge. Thermodynamics only works one was cold things get hotter and hot things supplying the heat get colder. If you use a less powerful heat source you will have less over shoots when heating. Whatever way there is no easy way to solve a heating problem it takes time for the heat to transfer... in my book heating slowly is better than trying to do it faster. Just my opinion though. My fridge is constantly cycling from 19 to 20 to 19C over the course of about an hour or so and I can live with that. For what it is worth I have never seen the fridge kick in if you have the inkbird set right it is a continuous 19 -20-19-20C cycle. Of course you may be using different temperatures which make my system useless to you

 

[day_trippr]

^agreed^, going big with a heating element just causes problems with control. I use 40w reptile bulbs in my ferm fridges but if they came in 25w size I'd have gone with those...

Cheers!

 

[Gthurner]

I ferment a 50L barrel that is in a refrigerator. The control of the fermentation temperature is done by an Inkbird. The stainless steel sensor rod is placed in the middle of the wort.
On the surface of the wort also floats my "Float" (similar to the Tilt) which records the course of density and temperature. Heating is done with an infrared heating mat that heats the fermenter from 3 sides without contact. The air circulation is done by a PC fan.
Despite all the effort that is driven the problem with the poor heat distribution within the wort remains unsolved. Who has an agitator in the fermentation barrel? It is therefore recommended to shake the fermentation vessel well at the start of fermentation to accelerate temperature equalization. This recommendation also applies to any planned temperature increase, e.g. for a diacetyl rest.
In the picture you can see that on the 1st fermentation day the heating was switched on too long. The reason was that the sensor of the Inkbird was accidentally positioned at the (cold) bottom of the fermentation vessel. After positioning the sensor correctly and shaking the barrel, the problem was solved.

 

[superiorsat]

TLDR Skipped most of this thread because there is a way to use your set up as is. Don't put your probe in water or against the fermenter. Try to get it centered away from the space heater somewhere. You won't get drastic temp swings in the fermenter when you do a over and under shoot of 2 degrees on the ambient temp. When the heat shuts off it climbs a touch but not enough to trigger cooling and vise versa on cooling. The down side to this method is you have to monitor your fermenter temp independently from the fridge ambient temp. If your fermenter is getting to warm you have to turn the temp down or if you want warmer turn temp up. You have to keep any eye on things, as an example maybe you put your wort into the fermenter at say 61 but you wanted 64. Well you might have your ambient temp at 64 to bring the temp up but over night your yeast gets rocking and by morning you may have 70+degree temp in the fermenter. Definitely not ideal way of doing things but it is easy enough.

 

[Henbrew]

My recommendation is always to use a small fan in place of a heater, and to leave it on all the time. I find the motor on the fan generates enough heat, and you can just let the temperature controller handle cold. The fan makes the temperature within the freezer pretty constant everywhere, which is a big plus. Also, it gets enough of the CO2 out of the freezer right after opening it that you have less of the pass-out-and-fall-in hazard.

This works for me. In fact, when I need to actually raise the temperature of my beer I just use a larger fan.

 

[eric19312]

View attachment 764534

This overshoot on day 1 is pretty similar to what I experienced trying to control 60L spiedel tank in a fridge with a single probe STC controller. My heater (reptile bulb) stayed on too long because the the thermowell was in middle of the beer and it took a long time for the middle to warm up. Once fermentation takes off the beer is well mixed and the over/undershoot issue goes away. The solution I found was a dual probe controller that would not let the air in the chamber go more than a few degrees over my target temperature. This increased the amount of time needed to reach my target but avoids the overshoot seen here and the difference was very noticeable in the finished beer.

 

[Gthurner]

This increased the amount of time needed to reach my target but avoids the overshoot seen here and the difference was very noticeable in the finished beer.

Interesting. What difference in taste did you see?
But back to the overshoot problem. If you don't do an additional control measurement of the temperature (in my case, via the Float), you don't notice the problem, because the Inkbird only displays what it sees, so it doesn't counteract.
We are here already in the area of fine adjustments and thus with the question of whether further measures (2nd sensor, stirrer...) are proportional to the effort.

 

[Scout]

Wow guys, this thread kinda took off without me realizing it. I just looked at my heater, its 400 watts. I wasn't sure if such a small (in size) heater would be enough. Attached is a picture of my setup as it currently sits. I havent touched it since I first posted, other than to dump out the cup of water the temp probe was in. Yes the cup and probe were on the bottom of the chamber.. I am thinking I am going to add a small fan for circulation, plus I will move the probe up towards the top of the keggle where the heat would be if the fan fails.

 

[MaxStout]

400W is way more than you need for most sizes of chambers. My 7 cu ft ferm chamber is in an unheated garage. A 50W infrared ceramic heater provides plenty of heat, even in Minnesota winters. I use a small computer fan inside, to distribute the heat.

 

[renstyle]

The best compromise is fixing the probe to the side of the fermenter with a small patch of foam rubber (2" x 2") over the probe. This will isolate the probe from the ambient temp in the box for short periods of time. During active fermentation, the probe/surface of the fermenter will always be a little colder than the core of the liquid, but it's close enough. Putting the probe in a separate buffer fluid is unrealistic because it is almost 100% disconnected from the temp of the beer. Putting it into the core via a thermowell would cause huge swings unless the beer was being stirred.

This is the best way to proceed. Plus a reptile mat, or similar for heating. I used a small space heater for a while, but it caused too much cycling because it provided too much heat.

There is a fairly long explanation of why this is better than a thermowell or temp probe in a jar of water, but I don't feel like typing it right now (I've typed it many times in the past.)

Brew on

I do exactly this with a 23L corny fermenter. Temp probe on one side and the reptile mat on the opposite.

I had enuf of the probe insulation to also give the reptile mat a "blanket" as well, but its prolly not necessary.
I must have read one or both of you saying similar in the past

It's all run off an inkbird with a 2 C temp swing, which is ok for me.

A fan for recirc is next.

 

[Dr_Jeff]

I find that the beer generates enough heat in a well insulated fermentation chamber, and I only need to control the cooling, even in the winter.
The only times (3-4 in ten years) that I added any heat was with a droplight like one uses in the shop.

 

[Scout]

I find that the beer generates enough heat in a well insulated fermentation chamber, and I only need to control the cooling, even in the winter.
The only times (3-4 in ten years) that I added any heat was with a droplight like one uses in the shop.

I'll be brewing in an unheated detached garage, so I can't imagine I'll need heat unless its winter. Still though, I'd like to work the bugs out now.

 

[Bobby_M]

I'll be brewing in an unheated detached garage, so I can't imagine I'll need heat unless its winter. Still though, I'd like to work the bugs out now.

It's just better to be equipped for unseasonably cold nights in the fall and spring as well.

 

[superiorsat]

Inkbird does both heat and cooling so unless you remove the heater for some reason the work is done for you. I never pull the heaters out of my chambers whatever the season but to each his own.

 

[Scout]

I added a fan up high to blow downward, and used some elastic band to hold the probe against the side of the fermenter. Initial tests are pretty good now.

 

[balrog]

Smaller heat source.
Big fan always on.
Tape to Fermenter and covered to be invisible to chamber air temp.

That'll get you most of the way home.

 

[Scout]

Smaller heat source.
Big fan always on.
Tape to Fermenter and covered to be invisible to chamber air temp.

That'll get you most of the way home.

Thats pretty much what I've got now.

 

[cgriffith]

So it sounds to me when I get around to buliding my ferm chamber controller, I should have a probe in the center of the fermenter and one on the side (isolated from env) and avg the two temps to get the best idea of wort temp.

 

[SanPancho]

design guidelines for conical brewing tanks with thermowells are 1/3 the diameter of the tank. not the center.
you want to split the difference of the convection currents. if you had a tank with internal coils then i guess you'd split the difference between the coils and the vessel wall. thats just an assumption, but the principle is the same.

 

[McMullan]

My fermentation chamber is in an unheated room in the basement, which gets pretty cold during winter and sometime warm during the summer. I control wort temperature via a thermowell. Generally, a 50w heat cable comes on during winter mainly and the fridge mainly during the summer. I usually opt for unplugging either the heat cable or fridge, depending on ambient temperature, to stop fermentation temperature ping-ponging back and forth. I do try not to giggle when graphed temperature profiles get posted, though.