Fermentation frig temp. control question

[WoofdogABC]

Hi, I have searched and didn't see anything obvious relating to this, though I have seen it discussed in other threads (who knows which ones) in the past.

I have a dedicated frig for fermentation, with a digital thermostat. I keep the probe in a glass of water inside the frig at 65 or so. I think what is happening is that during active fermentation temps the wort is getting substantially higher than that, possibly into the 70's, because I am running into taste problems, some of which definitely meet the profile of hot fermentation. I can put FV's on two levels in the frig. The one time I used the top level (random reasons) the beer was excellent, all others have been on the bottom and several batches have been off taste-wise, to the point of not being enjoyable. One thing that really clued me into the temperature issue was a pale ale gravity sample I tasted actually making part of my tongue numb (no peat-smoked malts in it).

I will note that the taste problems are while in the FV all the way to bottling, most batches have never even gotten recognizably close to the style profile. I do have the fermometer strips on the FV but they are apparently not properly insulated, I just get the temp rage of the thermostat/water.

Thinking about it from a thermo-dynamic view, I can see how a FV in a frig that is usually off (no fan) will not have much cooling impact from the frig most of the time to offset fermentation heat. I obviously need to both cool the FV and at the same time speed up the rate at which the water glass warms from the warmer air from the same.

I am thinking of putting a separate fan inside the frig which will always be on, and directing it towards the FV and the water glass/probe, with the hope that it will help keep fermentation temps. within a few degrees of the thermostat setting.

I do not have a thermowell for the next batch but I will after that.

Is this a viable plan, or is there another way i should approach this? Is there any specific equipment that works very well with this? Any other thoughts on this appreciated.

 

[MalFet]

Why are you measuring the temperature of a glass of water? Just tape the darn thing to the carboy, and then tape a sock on top of it. You'll be within fractions of a degree of the temperature you'll get from a thermowell.

 

[WoofdogABC]

I could certainly do that on this batch, I didn't realize the probe would be so accurate outside the carboy.

What if I have 2 FV's at different stages of fermentation in the frig?

 

[MalFet]

I could certainly do that on this batch, I didn't realize the probe would be so accurate outside the carboy.

What if I have 2 FV's at different stages of fermentation in the frig?

Well, if you saw that your two carboys were at significantly different temperatures, what would you want the fridge to do anyway?

Realistically, if the two carboys are at significantly different temperatures due to exothermic yeast, the fridge can only be set to accommodate one of the two temperatures, no? Temperature control is more important in the early stages of fermentation, so keep the measurement there, I suppose.

If you get more ambitious, get a second probe and a couple of fermwraps. Keep the fridge slightly colder than you need and maintain a more precise temperature control to each by nudging them with a bit of heat. If you wrap some insulation around the carboys and the fermwraps, you don't lose much energy efficiency.

 

[WoofdogABC]

Well, if you saw that your two carboys were at significantly different temperatures, what would you want the fridge to do anyway?

Realistically, if the two carboys are at significantly different temperatures due to exothermic yeast, the fridge can only be set to accommodate one of the two temperatures, no? Temperature control is more important in the early stages of fermentation, so keep the measurement there, I suppose.

If you get more ambitious, get a second probe and a couple of fermwraps. Keep the fridge slightly colder than you need and maintain a more precise temperature control to each by nudging them with a bit of heat. If you wrap some insulation around the carboys and the fermwraps, you don't lose much energy efficiency.

This is something I may try later on - what kind of insulation is appropriate for wrapping the fermwrapped FV's?

 

[MalFet]

This is something I may try later on - what kind of insulation is appropriate for wrapping the fermwrapped FV's?

A high end solution would be a neoprene carboy jacket. More DIY could be as simple as a towel.

 

[WoofdogABC]

A high end solution would be a neoprene carboy jacket. More DIY could be as simple as a towel.

thanks again. I have looked into this and do have one set-up question - do you just set the frig for whatever its high temp range is (I think mine is 46F) and leave it on all the time, and let the fermwrap/probe handle heating the carboy? Can the wrapper/parka offset a 20-degree +/- difference?

 

[MalFet]

thanks again. I have looked into this and do have one set-up question - do you just set the frig for whatever its high temp range is (I think mine is 46F) and leave it on all the time, and let the fermwrap/probe handle heating the carboy? Can the wrapper/parka offset a 20-degree +/- difference?

If well insulated, probably, but it wouldn't be particularly efficient. Ideally, you might want to bypass your fridge's thermostat and run it just a few degrees below the cooler temperature you need, and then use the fermwraps to nudge things up as needed. You could bypass the fridge's inline thermostat with a cheap bimetal thermostat if you're handy with electricity, or with another Johnson (or the second stage of a 2-stage Johnson) if you're not. If neither of those are options, it'll probably still work okay. Test it out first though.