Fermentation Chamber Temperature Probe Location

[Edison]

For those of you who have a temperature controlled converted fridge/freezer, what are your preferred positions for your temperature probe?

I used to put the probe directly into a thermowell in the FV but I was finding sometimes I had problems with hysteresis with the delay between the temperature at the centre of the wort and the air temperature in the chamber. I was concerned that as a beer was actively fermenting the freezer would kick in and by the time the centre was at the correct temperature the outer would be much colder. Possibly as active fermentation was beginning to slow it could cause the yeast to go dormant prematurely an result in a slightly higher than expected FG.

This brew i have been monitoring the temperature in the FV thermowell but controlling the air temperature in the chamber with the probe hanging free. This seemed to handle things more smoothly with less fluctuations in wort temperature, but this morning my wort temperature had fallen from 19.1c to 17.2c, possibly because I noticed one of the door seals was catching last night and corrected it before bed (and air temperature was set to 15c to compensate for active fermatation)!

I'm hoping at may have been close to FG anyway as it has gone from 10.7 OG to 5.9 on the refractometer (in a day and a half!). It is still bubbling, only slower than last night.

 

[foxy]

For those of you who have a temperature controlled converted fridge/freezer, what are your preferred positions for your temperature probe?

I used to put the probe directly into a thermowell in the FV but I was finding sometimes I had problems with hysteresis with the delay between the temperature at the centre of the wort and the air temperature in the chamber. I was concerned that as a beer was actively fermenting the freezer would kick in and by the time the centre was at the correct temperature the outer would be much colder. Possibly as active fermentation was beginning to slow it could cause the yeast to go dormant prematurely an result in a slightly higher than expected FG.

This brew i have been monitoring the temperature in the FV thermowell but controlling the air temperature in the chamber with the probe hanging free. This seemed to handle things more smoothly with less fluctuations in wort temperature, but this morning my wort temperature had fallen from 19.1c to 17.2c, possibly because I noticed one of the door seals was catching last night and corrected it before bed (and air temperature was set to 15c to compensate for active fermatation)!

I'm hoping at may have been close to FG anyway as it has gone from 10.7 OG to 5.9 on the refractometer (in a day and a half!). It is still bubbling, only slower than last night.

The thermowell is the best place for readings and control if it is in the centre of the wort. The next best place is insulated on the side of the fermenter, on the understanding it will be 1-2 C cooler than the centre.

 

[fury_tea]

I've got thermowells, I sometimes use them but often just stick it to the side under some bubble wrap. I've noticed absolutely no difference in the end product whatsoever. As long as your temps aren't swinging wildly and you are in the general area you want to be, it should be just fine.u

 

[Banbeer]

Thermowells for me (3 FV's). not had a problem at all.

 

[dalecek]

Thermowell for me. I used to put the probe (properly sanitised) straight in the wort through the blow off hose. That worked fine, never had any problem or infection. Thermowell is just a bit more convenient.

 

[Edison]

Thanks for the input all.

I was finding with the STC-100 set to 19C for example (+/- 1C) it would rise up to 20C, the chiller would kick in, switch off at 19C and the wort would continue to drop to close to 18C before beginning to climb again. This would be a continuous cycle of 2C which didn’t feel a great solution and feels like it could stress the yeast and/or cause high FG if the yeast gets chilled before it’s properly finished up.

This is with only a 19L batch volume, setting the variance to less than +/-1C results on the compressor and heater constantly cycling.

I have a conical SS fermenter and if the yeast is beginning to fall into the bottom of the cone towards end of fermentation, it is likely to get chilled more than the centre of the whole volume and shut down early.

Controlling the sealed air temperature around the FV has smoothed out the temperature fluctuations measured in the centre of the wort significantly. While primary fermentation is happening there’s maybe +/-0.1C fluctuation, but there’s definitely a point at which the exothermic part of fermentation tails off and the temperature surrounding it has to be switched from -2C desired temperature to +2C.

I‘m thinking there is maybe a middle ground of fixing the probe to a 100ml bottle of water to smooth things out.

 

[Mayor of Simpleton]

The best solution I have found is to put the temperature probe in 500 ml water. I am able to keep the temperature +/- 0.5c of the set point and the three brews I have done since I got my brew fridge and started with this set up have resulted in my best ever beers

 

[foxy]

The best solution I have found is to put the temperature probe in 500 ml water. I am able to keep the temperature +/- 0.5c of the set point and the three brews I have done since I got my brew fridge and started with this set up have resulted in my best ever beers

Problem there is, there is no exothermic activity in the water, its the temperature of the wort which has to be monitored.

 

[Mayor of Simpleton]

Problem there is, there is no exothermic activity in the water, its the temperature of the wort which has to be monitored.

True. It's not perfect; but tests I did showed it gave me the best results for my set up. Fridge + greenhouse heater + inkbird

 

[foxy]

True. It's not perfect; but tests I did showed it gave me the best results for my set up. Fridge + greenhouse heater + inkbird

I think you will find you will get better results with a thermowell.

 

[honeymonster]

I used to use a bottle or glass of water with the probe in it when I was doing kits, but moving to AG and doing no chill, it became an issue.

Cool overnight as far as it will go, stick it into the FV and put it into the fermentation fridge to get it the rest of the way before pitching. Without the probe being taped to the side of the FV I wouldn't really know the temp of the wort.

 

[Mayor of Simpleton]

I used to use a bottle or glass of water with the probe in it when I was doing kits, but moving to AG and doing no chill, it became an issue.

Cool overnight as far as it will go, stick it into the FV and put it into the fermentation fridge to get it the rest of the way before pitching. Without the probe being taped to the side of the FV I wouldn't really know the temp of the wort.

I have a separate temperature logger that I fix to my fv

 

[foxy]

https://byo.com/article/fermentation-temperature-control-tips-from-the-pros/

 

[Edison]

https://byo.com/article/fermentation-temperature-control-tips-from-the-pros/

Interesting read that.

Yes theoretically the thermowell is the best route, it accurately reads the wort temperature in the centre of the FV. Unfortunately the problem with controlling temperature by heating/cooling in a fridge/freezer is the small surface area of the outside of the FV. By the time the centre of the wort is at the set temperature, the air around the vessel is many degrees colder/hotter. Even after the chiller/heater has switched off the air temperature will continue to influence the wort temperature and overshoot the set point. In my experience this is close to 2C fluctuation during fermentation.

Managing the air temperature around the FV this time definitely resulted in a smooth, slow climb from 18C to 19.2C, but there is a point where active fermentation tails off and the temperature of the wort can suddenly drop off due to the much cooler temperature around the vessel.

My FV has an immersion coil for pumping chilled water through to cool the wort, the higher surface area might work better to control wild temperature fluctuations. I may have to dig this out for next time!

 

[foxy]

Interesting read that.

Yes theoretically the thermowell is the best route, it accurately reads the wort temperature in the centre of the FV. Unfortunately the problem with controlling temperature by heating/cooling in a fridge/freezer is the small surface area of the outside of the FV. By the time the centre of the wort is at the set temperature, the air around the vessel is many degrees colder/hotter. Even after the chiller/heater has switched off the air temperature will continue to influence the wort temperature and overshoot the set point. In my experience this is close to 2C fluctuation during fermentation.

Managing the air temperature around the FV this time definitely resulted in a smooth, slow climb from 18C to 19.2C, but there is a point where active fermentation tails off and the temperature of the wort can suddenly drop off due to the much cooler temperature around the vessel.

My FV has an immersion coil for pumping chilled water through to cool the wort, the higher surface area might work better to control wild temperature fluctuations. I may have to dig this out for next time!

Are you not using the thermowell to control the temperature? The movement in the fermenter will keep the temperature in the wort fairly stable. the insulation properties of the fermenter body is what will give the difference in temperature to the outside.

 

[SteveM]

With all the excess amazon packages I’ve got in the garage since lockdown I just used a piece of polystyrene stuck against the fermenter and wedged the temp probe between the bucket and polystyrene.

seems to have worked.

 

[Edison]

Yes, l usually have the SC-100 probe (which controls the freezer compressor and the tube heater) in the thermowell, but it is the thermal inertia of the wort which is causing the swing.

I believe some (if not all) large commercial breweries control FV temperature through water/glycol pumped through an immersion coil or water jacket built into the FV. Controlling the temperature of air in contact with the skin of the fermenter doesn’t seem the most efficient way of doing it.

Just exploring other ways of doing it!

 

[Edison]

So as an update, I think I have found a solution. My thermowells extend into the fermenter by 10cm, I have found that by inserting the probe only 8cm into the thermowell I am better able to control temperature swing to the extent I have been able to set my controller to +/- 0.5c. In my setup this has enabled me to keep the wort temperature as measured from a second thermowell much more stable.

My original concern relates to the geometry of my SS cylindrioconical fermenter. It was my hypothesis that as primary fermentation begins to naturally slow down, so will the convection currents in the wort allowing the outer extremities to cool down more than the core of the wort if the ambient air temperature in the chamber is significantly lower than the core. As the yeast begins to drop into the cone it falls into cooler wort and this puts it into premature dormancy and results in higher than expected FG and less yeast byproducts cleaned up, that’s the theory anyway.

This setup has behaved itself, even during my first ‘ballon-assisted’ FV cold crash to 3c, with no chiller/heater cycling as would have happened before.

In short, other thermowell setups may benefit from not inserting the temperature probe fully in.